Forum

Propshaft Lubrication

I have always used wheel bearing grease. I have a brass tube fitted to the prop shaft which is the same diameter as a grease nipple so slides into the grease gun Yours Brian

5 years ago by scout13

Blog

1-35 Scale Schenllboot By TeeJay

Hi all for the second blog report on the schnellboot I am going to go over the rudder a propeller shaft assembly in more detail. The first stage was to make the rudders which were made of brass ,and having taken note of what has been said about the increase in size needed for the kit by other members I have increased the size of the rudders by 50% so that they have more effect and hopefully the boat will be more agile .I fitted 3mm treaded rod on to the rudder and in a 4mm flanged tube to reinforce the brass rod. The second stage was to make and fit 5mm flanged tube in the location for the rudders in the boat, these were made to be above the water line and will be sealed in place to reduce the possibility of leaks. These were fitted to a rudder platform inside the boat which was fitted to the kit moulding for the rubbing strip that runs the length on the boat and secured by making resin blocks which were fitted with computer extension nuts. which were then superglue in place to secure the rudder platform. The rudders were then fitted in place and held in position with the tiller collars which were made from 8mm rod and fitted the tiller arms and locked in place with 3mm computer screws and ni-lock nuts, a connecting plate was then fitted to connect the three tillers together, I also fitted rubberised washers to seal the rudder tubes. The third stage was to make the propeller supports. The centre support was a direct copy of the kit part made of brass and fitted to the kit with a plate and screws (this plate and the rudder plate were made from galvanised steel) and will sealed with resin after the I test the boat for leaks. The port and starboard supports were made by taking the kit parts and cutting them in have along the joint line or mould seam this gave me a template ,which I used to make cross-section segments but I did alter the template by increasing the boss diameter to 10mm and extending the support legs so that the finished support could be fitted through the hull (the picture of these show the mk1 version where I forgot to allow for the 4mm prop shaft which has a 6mm tube) any way the boss of these segments were drilled out with a 7mm drill and a length of 7mm brass tube fitted through the boss to assemble the segments, all of which were coated in soldering flux at this stage of the assembly which were riveted at both ends to hold it all together during soldering, after soldering the supports were then filed to the size and shape to resemble the kit parts as close as possible and fitted to the hull using a superglue and talcum powder mix and then I cast resin around the extensions to secure the prop supports in place. The fourth stage is the propeller shaft housing for the centre propeller housing I place a brass rod in a plastic straw and place in position in hull and using resin I sealed the hull with the rod in place this gave me a pilot hole for the centre prop shaft after I removed the brass rod. For the port and starboard shafts I used the kit parts which had hole place when assembled, this when I reinforced the housings ,the centre housing I glue 2mm of plasticard on each side and for the port and starboard I made a brass tube shroud which covered the housings which left gaps between the kit part and the brass which was filled by casting resin in the gap this increased the diameter to 10 mm so that there were little chance of breaking throw with the drill and finished these off by fill-in the outside with body filler and sanded to shape and finish . I then drilled through the pilot hole in the housings using very long extended drills and a wheel brace ( if I had use a power drill the heat would have melted the plastic of the kit and may have caused problems) I drill the shaft housings out 6mm them filed them out with 6mm file so that I could insert a length of 6mm brass tube. After all this was done I fitted a flanged bush made from 7mm tube and 2mm brass plate turned to 11mm to the ends or the propeller shaft housings. And now it is time I must ask for some help could anyone advise me on the length of propeller shafts, I know I can use a 300mm shaft for the centre shaft, but port and starboard will have to be longer. and I also need advice on selecting the motors, I want to use 4mm prop shaft with 35mm propellers. Any opinions welcome.

6 years ago by teejay

Forum

Smoke generator

Hi Rowen, Looks very similar to what I fitted to my Sea Scout. I bought it from Krick here in Germany. They ship round the world and very fast👍😉 https://www.krickshop.de/Accessories-Spare-Parts/Accessories-for-Ship-Models/Shafts-Couplings/Stegkupplung-kpl-3-17-auf-4mm.htm?shop=krick_e&SessionId=&a=article&ProdNr=63902&p=192 Copes with my Propdrive 1000kV on a 3S very well 😊 You can buy the basic coupler and inserts for various motor/prop s separately to mix and match as required. Copes with the power, is silent and slop free 😊 Cheers, Doug 😎 PS I turned up a rigid alu coupling in a few minutes on the lathe to do the setting up and alignment, much much quicker than faffing about with the 3D printer. Yes I do have one, but seldom used. The lathe and miller are quicker for one-offs.

5 years ago by RNinMunich

Forum

Boat shaft connectors (which stuffs to use and which is good)

1 - I concur with figtree7nts. You don't want a long length of unsupported floppy tube transmitting power. You will see that my illustrations show the unsupported tube to be very short. 2 - You also want thick tube to transmit power. if you have thin 2-3mm tube that will easily kink. I make my own connectors at the ends of each shaft to bring the internal tube diameter up to about 6-8mm. 3 - if you want to try a quick fix for what you have, I would suggest putting a small piece of wood or plastic inside the unsupported section of your tube, which will stop it collapsing when it is twisted. This may work if the torque is not high. And it's a quick, cheap thing to try. 4 - if you want to try making your own, you could get something like this - check the correct shaft size - https://www.ebay.co.uk/itm/Brass-Hexagon-Flexible-Coupling-Coupler-Connector-Motor-Model-Car-Boat-3-8mm/302549582190?_trkparms=aid%3D555017%26algo%3DPL.CASSINI%26ao%3D1%26asc%3D20170221124951%26meid%3Ddc345e0eff7a498aaf6d1efe0039d818%26pid%3D100643%26rk%3D1%26rkt%3D1%26%26itm%3D302549582190&_trksid=p2045573.c100643.m3226 or this: https://www.ebay.co.uk/itm/Coupling-Inserts-for-RC-Models-Various-Sizes-available-RC-Model-Boat-Fittings/322996589219?_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D1%26asc%3D20170920101022%26meid%3D7c9c41e4b98047af9227e21aef42a96e%26pid%3D100010%26rk%3D4%26rkt%3D9%26sd%3D191479721852%26itm%3D322996589219&_trksid=p2047675.c100010.m2109 and then buy a length of something like this - https://www.ebay.co.uk/itm/1M-Food-Grade-Clear-Translucent-Silicone-Tube-Beer-Milk-Hose-Pipe-Soft-Rubber/253549582415?hash=item3b08bb984f:m:mLOWX25B4-LemH4pL11iYfA:rk:12:pf:0 checking the diameters that you need, of course... Here is a similar Eezebilt to your craft. it's the OSA Missile boat. You can see that the unsupported length of silicone is short, and this boat at 32 inches takes quite a lot of power...

5 years ago by DodgyGeezer

Forum

Boat shaft connectors (which stuffs to use and which is good)

Hi Sakibian, Why can't you use couplings from Cornwall Model Boats! https://www.cornwallmodelboats.co.uk/acatalog/Universal-Joint---Red-MA5000.html#SID=737 Maybe you can take a picture of your project to show us. What you are working on! I think the shaft should be close to the motor. Or the rubber hose will tear! Try looking for plastic tubing. Of the diameter you need! Or harder rubber tubing.... Regards, Ed

5 years ago by figtree7nts

Blog

1-35 scale S100 schennllboot

Hi all for the second blog report on the schenllboot I am going to go over the rudder an propeller shaft assembly in more detail. The first stage was to make the rudders which were made of brass ,and having taken note of what has been said about the increase in size needed for the kit by other members I have increased the size of the rudders by 50% so that they have more effect and hopefully the boat will be more agile .I fitted 3mm treaded rod on to the rudder and in a 4mm flanged tube to reinforce the brass rod. The second stage was to make and fit 5mm flanged tube in the location for the rudders in the boat , these were made to be above the water line and will be sealed in place to reduce the possibility of leaks. These were fitted to a rudder platform inside the boat which was fitted to the kit moulding for the rubbing strip that runs the length on the boat and secured by making resin blocks which were fitted with computer extension nuts .which were then superglue in place to secure the rudder platform. The rudders were then fitted in place and held in position with the tiller collars which were made from 8mm rod and fitted the tiller arms and locked in place with 3mm computer screws and ni-lock nuts, a connecting plate was then fitted to connect the three tillers together, I also fitted rubberised washers to seal the rudder tubes. The third stage was to make the propeller supports. The centre support was a direct copy of the kit part made of brass and fitted to the kit with a plate and screws (this plate and the rudder plate were made from galvanised steel)and will sealed with resin after the I test the boat for leaks. The port and starboard supports were made by taking the kit parts and cutting them in have along the joint line or mould seam this gave me a template ,which I used to make cross-section segments but I did alter the template by increasing the boss diameter to 10mm and extending the support legs so that the finished support could be fitted through the hull (the picture of these show the mk1 version where I forgot to allow for the 4mm prop shaft which has a 6mm tube) any way the boss of these segments were drilled out with a 7mm drill and a length of 7mm brass tube fitted through the boss to assemble the segments, all of which were coated in soldering flux at this stage of the assembly which were riveted at both ends to hold it all together during soldering, after soldering the supports were then filed to the size and shape to resemble the kit parts as close as possible and fitted to the hull using a superglue and talcum power mix and then I cast resin around the extensions to secure the prop supports in place. The forth stage is the propeller shaft housing for the centre propeller housing I place a brass rod in a plastic straw and place in position in hull and using resin I sealed the hull with the rod in place this gave me a pilot hole for the centre prop shaft after I removed the brass rod. For the port and starboard shafts I used the kit parts which had hole place when assembled, this when I reinforced the housings ,the centre housing I glue 2mm of plasticard on each side and for the port and starboard I made a brass tube shroud which covered the housings which left gaps between the kit part and the brass which was filled by casting resin in the gap this increased the diameter to 10 mm so that there were little chance of breaking throw with the drill and finished these off by fill-in the outside with body filler and sanded to shape and finish . I then drilled through the pilot hole in the housings using very long extended drills and a wheel brace ( if I had use a power drill the heat would have melted the plastic of the kit and may have caused problems) I drill the shaft housings out 6mm them filed them out with 6mm file so that I could insert a length of 6mm brass tube. After all this was done I fitted a flanged bush made from 7mm tube and 2mm brass plate turned to 11mm to the ends or the propeller shaft housings. And now it is time I have to ask for some help could any one advise me on the length of propeller shafts , I know I can use a 300mm shaft for the centre shaft but port and starboard will have to be longer . and I also need advice on selecting the motors , I want to use 4mm prop shaft with 35mm propellers. Any opinions welcome.

6 years ago by teejay

Response

Rudders and Propellers

BTW; I copied your above massive text block into a document file and split it up into paragraphs so I could see where you're at! My conclusion: so far so good BUT! You made the one classic mistake of many model boat / ship builders 🤔 You continued the prop shaft tube right back to the propeller and hence you had to make oversize struts to support them. This is fundamental wrong and creates unnecessary work.😉 On real ships, including the Schnellboote, the so called 'stuffing tube' is JUST THAT, it 'stuffs' the shaft through the hull and includes stuffing glands to prevent the ingress of sea water. Outside the hull ONLY the rotating shaft itself continues on through the bearing in the support strut and to the prop. See attached pics of my HMS Belfast as an example. There was actually no reason for you to make oversize strut bearings, simply bushes to match your prop SHAFT not the tube would have been correct. Inside the real ship there is also NO TUBE, only bearings at suitable intervals. They look like gigantic versions of the big ends in your car. Imagine on really big ships, carriers, container ships, bulk tankers etc, with s of 1metre or so how big the 'tube' would be, how much weight that would add and how difficult it would be to service and maintain! I've often noticed in posts here that folk confuse shaft and tube, often referring to the whole assembly as 'the shaft'. For convenience we modellers use prop tubes, who wants to fiddle about making a row of internal shaft bearings no one will ever see and will most likely never be really concentric? The downside is that continuing this 'convenience' outside the hull is wrong, adds weight and detracts from the scale appearance of the model. 😭 OK, it's 3am here now so - orf me 'obby 'orse and up (in my case down!) the wooden stairs to Bedfordshire, G'night all, cheers, Doug😎 Re shaft length: What fits fits, what don't don't! Such a question is like asking 'How long is a piece of string?'! If all three motors abreast won't fit you have to decide if the central motor should / will fit fore or aft of the outer motors. Then measure / adjust the shaft length accordingly. Before you start fitting the centre motor check what length shafts are commercially available and adjust your motor fit to suit. Otherwise make your own shafts and tubes to fit as required, as I've started doing cos I got fed up with 'standard sizes' wot don' wanna fit my ship. 🤔 G'night All, cheers, Doug 😎

6 years ago by RNinMunich

Forum

VOSPER 46'' Crash Tender

Actually 4 pole , "Graupner HPD 2920-4000 High-end brushless motor Particularly suitable for: MiniMono, MiniHydro, MiniCats, MiniHydroplanes, aircraft with wingspan up to 1 m, off-road and on-road 1:12 Features ?Special CNC-machined housing for maximum heat dissipation ?High-efficiency 4-pole 12-slot brushless motor ?High-performance rotor with Kevlar reinforcement ?High-purity copper coils for optimised conductivity ?Extremely strong sintered neodymium magnets ?Intense torque at low weight Specification Operating voltage range : 4,2-16,8 V No-load speed: 29600 U/min All-up weight, approx. : 90 g Free shaft length: 10 mm Recommended controller: Navy V75 G7257 Output : 650 W Number of poles: 4 Permissible motor direction : R und L Nominal voltage: 7,4 V Case length: 30 mm : 4 mm Case diameter: 29 mm Revolutions/Volt: 4000 " Taken from one Google, first response at Cornwall Models Boats!😉 Note. 650W, Nominal voltage 7.4V. No wonder it's a bit quick on 11.1V 😲 Cheers, Doug 😎

6 years ago by RNinMunich

Forum

replacing propshaft

Hi all I have taken the bull by the horn and removed the 4ba prop-shaft, which was remarkably easy first using a stanley knife on the keel each side of the shaft and then as I was advised by a forum member to use mole grips, which I did, wallah out came the shaft, now as can be seen by the photos the new one, ( it is too long by an inch, Doh I ordered the wrong one) is a smaller diameter than the old one. What is the best way to refit it? Also using the keel as my straight edge, the shaft is at 9 degrees, is this going to be OK, also I am replacing the 54mm 3 blade prop for a 40mm so with the 850 motor I hope this will be sufficient.

6 years ago by RichardSReade

Forum

Taycol Supemarine Resurrection

Evenin' Colin, Thanks for the offer. I'm going to use some stuff the Martin sent me, called Chrodite apparently, although I can't find any description or reference to Chrodite anywhere! Looks like brass with an extra ration of tin. Supposedly harder wearing. Anyway, stator and frame spacers etc are now finished.👍 So after feeding the inner man I'll start measuring up for the bushes and see what I can do about tidying up the drive shafts. Have just sorted out a 'Live Centre' for the mini lathe which should help. I want to hide the bushes inside the original Paxolin cards and the external end plates which contain the felt oiling pad. So ball races are out of the question unfortunately; too large diameter and too thick 🤔 Needle roller bearings would be nice, but I ain't got none that small😭 (Nah, admit it Doug you ain't got none at all, they're way too expensive😭) Amused myself today polishing up all the brass nuts and bolts! Confucius he say "Polishing nuts - very painful" 😁 Weather should be good for spraying tomorrow so I might fire up the compressor and give my PTB a blast of Pacific Green. 😊 Cheers All, Doug 😎 BTW: where are the pics of your Avanti? Harbour posts without pics are pretty dead 🤔 Cheers, Doug 😎 Oops! This doesn't belong here!🤔

6 years ago by RNinMunich

Forum

54'' long Cervia tug.

My Cervia was ready built. I have replaced the Electric motor with a large servo motor (Brushed) .Direct drive and being heavy helps with ballasting. lead acid gel cells are power source. Motor rated voltage24 v but run it on 12v . low rev high torque no load current 1 amp. 0.5 in. Gives some idea of power out. Being servo motor (ex computer drive 30 years old) well balanced no vibration. Photo near shore shows power of motor.

6 years ago by tysonyoung

Forum

Help with a 4BA prop

Hi all, just measure the shaft in my Chris-Craft and blowed if it ain't 4BA thread on a 3.5mm shaft. Can't change it as it's well buried in the hull, but I don't have any props with a 4BA thread. Does anyone have any spare 2 or three blade props of about 30-35mm diameter with a 4BA thread. I'm sure somebody must have one tucked away somewhere and I could always do a bit of modelmaking by way of a swappsy. Cheers, Martin

6 years ago by Westquay

Forum

Chinese props

Just received a prop for my outboard motor from China as I couldn't find one for dog drive and the right over here. It wasn't the cheapest, but ye Gods, somebody has seriously specced up this baby. It is superb, light as a feather, completely CNC machined, sharp as a razor. Couldn't be happier with it for an ebay purchase. Now, with brushless and prop, I suppose I will have to get the boat finished! Cheers, Martin

6 years ago by Westquay

Forum

Cheap motor for a quick fit, but what prop gents?...

OK, found one, 'discontinued product' 🤔 Seems Tower pro only make gas engines these days. https://hobbyking.com/en_us/towerpro-brushless-outrunner-2408-21.html Specs "TP 2408-21 The most widely used towerpro motor available today. the 2408-21T is often used in GWS (means Grand Wing System, USA apparently!) upgrades. Paired with just an 18A besc, this motor is an excellent and cheap way to upgrade small planes to brushless. An RD1047, RD9070 or 8040 size propeller are the best choice, with the RD9070 and 8040 giving the best thrust and amp draw balance. For 2-3 Li-Poly Cells (7.2-12.6V) 31 mm diameter x 62 mm length Maximum current: 13A Weight: 50.2 grams / 1.77 oz Comes with stick mount plastic frame Firewall mount capable Comes with two prop nuts and one washer 3mm 10mm x 10mm stick mount Kv: 1750 9 Stator Poles, 12 Magnets" So it's OK for a 3S LiPo, which will give about 19.400rpm OFF LOAD. Max current 13A ON LOAD. No way of finding the other little one without at least a hint🤔 Looks like an Outrunner plane motor as well. Suck it and see! Probably similar specs to the Tower motor. The two brushed ESCs should be good for your Taycols as none of them should take much more than 10A or so. Use 15A fuses, as I have already fitted to your converter boards.😉 Bon chance mon ami, Cheers, Doug 😎 Re GWS; https://www.google.com/search?q=GWS+models&client=firefox-b&tbm=isch&source=iu&ictx=1&fir=Yy9FOffyN9znOM%253A%252Cm55UYJTjtHfuaM%252C_&usg=AFrqEzdcX_L57leaM37UXLA9kg6sVLbSag&sa=X&ved=2ahUKEwiyo8mUnO_cAhUkB8AKHc_UDNEQ9QEwAnoECAYQBA#imgrc=Yy9FOffyN9znOM: Pic is a typical GWS small plane, called 'Slow Stick'. if I had one I would name it 'Spindle-shanks' 😁

6 years ago by RNinMunich

Blog

20th Scale ELCO 80ft PT boat part 5

After some calculations I find I need to extend the reinforcing for the port & starboard shafts forward towards the bow. Created some wooden guides when drilling the prop-shaft holes and glued them in position temporarily, as you make expect the drill needs to be rather long, so I made one out of an old brass shaft basically sharpening it so it could cut wood. Next job will be to cut out for integrated shaft support brackets (2mm wide and minimum of 35mm long slot) and the tube shafts are 8.5mm in diameter.

6 years ago by CB90

Forum

Brushless outboard...

As Doug suggests, a new topic for this. The Motor is a 2845 of 2600Kv. I have no idea what the is so may have an adaptor to turn there. The guys what makes the rules for 152VO say 2 or 3 S, but there is a formula that takes in S number, prop size and Kv and it should all add up to some magic figure which escapes me. If anyone's interested, I'll look it up. The website, a very good one, is in German and really doesn't translate well! Martin

6 years ago by Westquay

Forum

Lifeboat plans

Doug, the outboards are made to take a 28mm brushless. There's an angled pre-drilled plate comes with it, to which I assume a 28mm brushless screws. They tend to use 2S LiPos on their boats with 23-2800KV, so about 18,5oo revs or a bit more. Can a brushed motor do that? I have a speed 400 from an aeroplane. Not sure what the is. I want it to go well, although, no I won't be racing it. As far as I know nobody does 152VO in England. I just need to fit a usable motor that I can build the Godiva casing round it. I don't want to HAVE to spend 30 quid on a motor, when I have one here, but I don't know what the performance would be. Martin

6 years ago by Westquay

Forum

Brushless motor selection

Hi robhenry What volt battery are you running at present ?? 12 or 24 volts. If 24 volts those motors spec at 24,000rpm. Power is 511 Watts on 24 volts. 24,000 divide by 14.8(4S Lipo batteries) equal 1612 kv. So the closest motor would be 1700kv, eg water cooled 3660SL-1700kv which has a 5mm shaft and 44mm diameter with a length of 60mm( from Hobbyking). Power rated at 1800 Watts on 6S, so it would be lower than that. But if you are running 12 volts on the Graupner motor it would be about half the rpms. These brushless motors are far more powerful so check out the specs on the motors you are looking at !!! Canabus

6 years ago by canabus

Forum

Sea Queen prop shaft

Hi Andy I have been working on a barn find old Sea Queen kit in very poor condition. The restoration required fitting a 5mm prop shaft as the old shaft supplied was a little short, I ordered a new 5mm shaft 19inches long from Model Boat Bits uk and when I tried to fit it it would not fit. Not realising the old shaft was 3/16inch. I had to ream the bushes to take the new shaft of 5mm. this proved a little difficult as the shaft was already fitted. I finally did it and everything works as expected. Fitting the motor which is a 700 ?. The shaft was 1/4 inch diameter. Boring out the brass insert did not leave much meat and I am hoping it does does not let go under power. So far so good. I hope there is some info there that you can use. Regards Sid

6 years ago by sidley70

Forum

Sea Queen prop shaft

I'll second that MT 👍 I'm gradually replacing all old and 'suspect' shafts with silver steel. Bought a small stock of 1m lengths of 1,2,3,4mm diameters from Conrad here. Checking with a micrometer the tolerances seem better;

6 years ago by RNinMunich

Forum

Too Powerful Brushless ?

Hi Graham If we are talking about the Graupner Brushless Speed ​​500 ECO no 7295 https://www.graupner.de/Brushless-Speed-500-ECO/7295/ then yes the Kv is 500 which equates to 7500 at 14.8v. it's 50mm x 80mm with a 6mm shaft so really a heavy duty motor and in a Aeronaut Queen 36" still much too big and powerful. You really need to resolve the drive train and shaft problems and this will be easier if you choose a motor of smaller diameter and power. A 36xx or very similar size motor at about 1000Kv or less (500Kv with 14.7v) will be ample. The prop should be less diameter than the motor. There are many examples of 36" model boats on this site and I do believe the majority of our members have used similar set ups, to those we have suggested, in their models with a large degree of success. It could be we are talking about a different motor as you refer to " the small outrunner motor". if so please post a link to a pic of the motor.

6 years ago by Dave M

Forum

Too Powerful Brushless ?

Graham, I have attached the same table that Doug sent me. This has the relevant information you seek. According to the table attached the Graupner 500 kV ECO has a specified output of 1440 watts and 80Amps. Strangely the 400 kV ECO has a specified output of 2010 Watts. So the 1440Watt output is questionable and may be a typo based on the other entries in the table. more likely to be 2440Watts In any case you need a 5mm diameter propeller shaft. For shaft alignment i use a brass tube that slides snugly on the propeller shaft and then on the motor shaft. When the tube rotates/slides well on both then the shafts are aligned. I then fit the motor mounts, check and tweak the alignment if necessary, remove the tube and replace with a universal coupling. if the motor or propeller shafts are a different diameter then I insert the relevant size smaller tube inside the larger of the tubes. This method is simple and has served me well, including for larger IC engine powered boats belonging to friends. Haig

6 years ago by reilly4

Forum

Too Powerful Brushless ?

Hi Graham Now we can see the actual prop shaft and motor it is clear that the shaft is not supported inside the hull close to the coupling. At the high revs your motor achieves I am not surprised you have had problems. I do agree with all the comments and help you have been offered and agree a 5mm shaft would help as well as a different motor. I use 3 blade brass props with brushless and have no problems but do keep the prop size to a diameter no greater than the motor diameter, as Mark advises. It's difficult to see how much space is in the hull to allow the motor coupling and shaft to be closer, but if you are replacing the shaft it may be a good time to reposition the motor and the shaft with the prop attached to a slightly different angle. This will mean opening the slot and perhaps enlarging the outside skeg but you can easily repair any damage with plastic padding to make good. Even if you keep the existing arrangement I suggest you provide support for the prop shaft close to the bearing as I suspect this is where you have experienced the problem with the vibration. A simple 2" block of wood attached to the keel and shaft would suffice. Model looks very good and I look forward to seeing some on water shots.

6 years ago by Dave M

Forum

Too Powerful Brushless ?

Hi Traiderman, How long is the propshaft and tube???? The reason for asking is that if the shaft is more than 6 - 8" and of small diameter, 4mm, it is likely that the shaft is whipping inside the tube, a 1000kv, ish, motor with if needed some support bearings inside the tube, what model is being fitted??? Mark

6 years ago by jarvo

Forum

replacing propshaft

Chris, the boat is the Sea Commander, a boat my late father started in the 60's and I got to grips with it in 2015 but only floated it this year. Mark, I have just got in from the workshop and saw your comments, well guess what, after shortening the new shaft by an inch and running a 4mm die down the inner shaft and trimming it to suit, I had a brainwave, why don't I try to fit the new shaft inside the old tube which would solve the problem with the hole in the hull and keel, so I cut the old one to the required length and tapped the brass bush from the end, the inner diameter of the old tube was too small, so on the lathe with it and fed a drill down it from both ends, as I did not have a drill long enough, so the old tube is in place and the new shaft assy is fitted, all I have to do now is epoxy the whole set up. Mark have I measured the shaft angle correctly, using the keel as the flat line?

6 years ago by RichardSReade

Forum

Sea Queen Prop Shaft

Am in process of building a Sea Queen, but not with supplied motor, will be fitting a brushless. Based on the motor and the voltage it is likely to be about 400 watts output, which is about 5 times the supplied output. My concern is the supplied prop shaft which is 18" long and 4 mm dia. is there likely to be 'whip' in a shaft of that length ? Was considring a larger diameter, but that brings in the problem of obtaining propellors M4 and M5 are common. Or can one get prop shafts with centre bearings. What have other people done ? Or are my fears unfound, I remember the days when prop shafts were mild steel not stainless and bent easily.

6 years ago by AndyG009

Forum

Matching motor to Propellor

HI Scotty, First of all, Shaft, the length is the critical bit, the roller bearing shafts are superb, so , probably 4mm would suit your needs. Coupling, the center is a U/J, with inserts of the correct size, 5mm plain for the motor, 4mm threaded for the shaft. Prop. 60mm, Raboesch from Deans, 4mm thread. Contact Deans, they will sort all the right bits you need into a package. Mark

7 years ago by jarvo

Forum

Motor problem

Hi Richard, Good morning, Prop first, if the blade to hub is 30mm, it is a 60mm diameter prop, think of the circle of sweep, twice the size that your 550 motor can take. As the shaft is free running, we can discount drag, simply the motor working to extreme, so we need to prop down considerably, If you are staying with the 540 motor in the pics, a 35mm 3 blade prop is the maximum, a rough guide is no bigger than the motor diameter. I would save myself a lot of problems in the future and fit a larger motor, Canabus is right a watt meter will save its readings so you can get a proper idea what the motor is doing. I would swing towards the 850, or the 700. Not expensive but safe to run with a smaller prop. The 700 might fit your mounting but the 850 will need a new one, usually supplied in the box. The Sea Commander will serve you well as a great sailing model, once you are past the teething problems. Just looked back, your first post said the hull was built in the 60's, it might have a 4ba thread, not many ba props available these days, a 4mm prop will fit but it will be tight, don't forget the locking nut (to many props at the bottom of the lake) also a thrust washer to protect the motor bearings. Mark

7 years ago by jarvo

Forum

Motor problem

Richard, If as you said each blade from shaft centreline to tip of blade is 30mm then it would not matter if you had two blades or ten. if the radius (your measurement) is 30mm then the diameter is 60mm. Perhaps you can remove the prop and place it on a flat surface so you can see the swept circumference when rotated.

7 years ago by reilly4

Forum

Motor problem

Hi Richard, if each blade is 30mm from the shaft centre, it is a 60mm diameter propeller and is far too big for that size motor. For performance you need a larger motor say a Graupner 700 and I would still recommend a smaller propeller.

7 years ago by reilly4

Forum

Crash Tender Shaft Tube Poistion

Hi Neil, the pics look good 👍 You have 11/16" from keel to shaft centre so your max prop diameter is 32mm. You might squeeze a 35 in if you flat off the keel to hull behind the shaft. The fillet is a triangular piece of ply (or hardwood if you have some scraps) fitted between the top of the tube and the hull bottom (keel plate in your case) and reaching from the end of the tube just in front of the prop to the hull exit point and completely filling (hence the name 😉) the whole gap. Min 6mm thickness would be good. Cheers Doug 😎

7 years ago by RNinMunich

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Crash Tender Shaft Tube Poistion

Standard Saturday Mrs Mac decided I had other things to do before being allowed out to play but I think I've got there, just need to check it's right before gluing up. OK so I lied that I wouldn't be asking more questions on this topic😁😁 The hole has been opened out enough to achieve 3/4" but the photo doesn't really show it. it took some time to achieve it as well more time than I thought, even used my dremel at one point😁. But pmdevlin's tip on using a disc was a great help. The position of the outer tube on the hull needs a slight adjustment but nothing major and still achievable as no glue. I did have a check fit of the motor and came across another issue as there was no way I could achieve alignment of the shaft and motor which was made easier by Doug's universal coupling idea😁. I went for removing the last remaining piece of the old motor mount (should have listened to Dave a year ago) which took about an hour as it was glued in good and proper.😤😤😤😤😤 There is some clearance on the hull from the prop so think I'll be going for a 30mm prop as suggested by Dave as to my surprise mine is 40mm diameter. Hopefully the arrangement is all good and I can use Dave's and Doug's tips on getting it secured. I still need to blank off the water pick up and fit the new rudder tube. Also I think the motor alignment will still be interesting as after removing the last bit of the old mount the motor was interfering with the bulkhead behind it so removed so it. Also will possibly need to take some out of the hull centre piece to achieve a perfect alignment. Hopefully tomorrow will go well as will also fitting the oiler as seen on Robbob's Build Blog.

7 years ago by neilmc

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Crash Tender Shaft Tube Poistion

Hi To you all thank you for the continued advice it is making life so much easier and I do like it when the thinking is done by experts. Paul The disc idea is an absolute bonus and will be using it for sure as it takes away the need for continued measurements. Dave The water scoop is going as like you and Doug say I don't need it no working monitors for me, just a working boat would be good. I'll be using measurements given to achieve shaft positioning as at the moment I have a 2 blade prop which I think is 30mm diameter so disc to suit will be used. Doug I like KISS it's worked for me loads of times in the past but I can't help buying shining things 😁😁😁 The shim idea on the prop tube is a good one but may still go for a support even though not needed it shines 🤣🤣🤣🤣. But it may still go back to the filler piece as all depends on how difficult it is to fit the A frame support. I purchased one at 8mm for the tube and not 4mm for the shaft. I'm looking forward to the weekend to get started and even set an alarm for an early start which is unusual for me. Im off to HMS Alliance as I do volunteer guiding there otherwise id be starting now. Will keep you all posted hopefully with good news and no more questions - well on this bit anyway 🤣🤣

7 years ago by neilmc

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Crash Tender Shaft Tube Poistion

Ill chip in! Pictures tell a story. Ok, a twin shaft, but the principle is the same. Imagine the angle of shaft you have, then propeller is pushing up, get it a shallow angle, and its now pushing forward. On the 34" fireboat, largest prop you will end up with is 50mm, so cut a dics 50mm, attach to your shaft, with a flat on it so it sits on the hull, viola, here is your prop angle👍 Prop support, use a strip of brass, heat it, and bend around same diameter rod (as your outer shaft, not on the shaft as the heat could damage the bearings), clamp together and either solder or use a small nut and bolt, fit through a slot in the hull, and then bend the side over, like wings, inside the hull, and epoxy. Paul Fit a water pick up, its easier at the build time, than regretting it later, you don't have to use it if its not necessary

7 years ago by pmdevlin

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Crash Tender Shaft Tube Poistion

Hi Neil, while you're on that site get one of these shaft alignment couplings http://www.modelboatbits.com/UNIVERSAL-ALIGNMENT-TOOL Check the diameters of your prop shaft and motor shaft before you order. They are a great tool for lining up the motor with the shaft. (I make my own on the lathe😉) Cheers

7 years ago by RNinMunich

Forum

Crash Tender Shaft Tube Poistion

Hi Neil, yes, very similar. Could be regarded to as a first step before applying Eze-Kote to give it a harder, knock and almost everything else resistant surface. Hammerite then sticks to it like the proverbial to the blanket and you have a super clean 'engine compartment' dead easy to keep clean. 😊 80 quid for a brushless !!! Do you want it gold plated or what? My Propdrive 2830 cost less than 20 knicker from Hobbyking and was delivered almost before I ordered it! Just make sure it comes from the UK or EU (still!?🤔) warehouse and not USA or Global. otherwise you might get stuck for import tax 😡 For the motor mount / shaft alignment: no one said it was easy, but Nothing's Impossible', maybe that's why I drive Toyota!!😁 back end is determined by the diameter of the prop you want to fit, which in the case of brushless motor should be roughly the same diameter as the brushless (outrunner). in my case 28mm motor and 30mm prop. This defines how far you can lift the aft end of the shaft, leave at least 1cm between the prop tip and the hull! This reduces unwanted interaction between the vortex from the prop and the lamina flow along the hull, result; more forward thrust and better rudder effect. (Didn't spend 30 odd years talking to shipyards for nowt😉) If you have plan (or at least a sketch - take some measurements if you don't have one of these and make a sketch) of the keel and existing motor mount; project back from the newly determined exit point of the shaft. Check how far forward you need to go to be able to comfortably fit the motor mount with good alignment and purchase a shaft of appropriate length. Cut a wood block to fit around the keel as the basic mount and 'fiddle' with it until your motor and mounting (e.g. the Robbe / Romarin 400 mount) aligns with the shaft line. Alignment is checked by running the motor at a fixed low speed with an ammeter showing the current it draws. Shim the motor mount up / down, and shift slowly from side to side until the current reading is a minimum. Then glue and screw everything in place quick before anything moves! Takes almost longer to describe than to do😉 The coupling type shown in my photo is called a 'Steg' coupling here in Germany (don't know the English🤔) and available from Krick Modellbau, for various motor shaft / prop s, here the link to their English page- http://www.krickshop.de/?shop=krick_e Part number for the 3.17mm (1/8") to 4.0mm version I used is 63902. part number for the motor mount I used for my 28mm brushless is 42117. Advantages (to me at least!) they are not as long as the traditional UJ and Cardan types, they are resilient but don't flop about like the UJ types so are much easier to fit and align. Cos they are shorter you can use 'em for mountings in confined spaces. And they don't make no noise!! 😉 One final tip (may not be so useful on hard plywood built boats!). When I had this problem with my destroyer I sharpened the end of an 8mm alu tube (same as the shaft tube dia) and used it to bore back from the hull exit to the last bulkhead before the motor mounts. the bulkheads though were 1/4" balsa! Nice and soft man 😉 Hope this helps more than confuses, but it all worked for me! Cheers and happy fiddling, Doug 😎

7 years ago by RNinMunich

Forum

Crash Tender Shaft Tube Poistion

Hi Dave, forgot to mention that Marin tested the calculations and computer simulations with scale models in their 250m test tank, with good agreement. Later full size measurements in sea states 5 and 6, with variable winds and drift angles also gave good agreement. One important point though; I misread a paragraph🤔 The actual distance prop tips to rudder leading edge was 1 prop radius!! So for my Sea Scout with a 30 or 35mm prop my 17mm spacing is about right 😊 Most of the tests were actually to determine the rudder's lateral position relative to the prop shaft on multi-shaft designs and vertical position relative to hull and prop diameter. Vertical position was determined as; if possible close to the hull, in the lamina flow region and 'covering the upper 47% of the prop diameter'. In this position the effects of the drift angle in a fast turn (e.g. caused by wind at an angle to the bow and the turning of the ship itself, 'skidding') are reduced to practically zero. If the rudder covers the lower half of the prop diameter it is affected by transverse water flow across the stern, reducing manoeuvrability and increasing rudder torque and stock loading! So again Sea Scout is about right 😊 The Aerokits designers knew their stuff, or were just plain lucky! For the shaft alignment I use the balsa wedges for fine adjustments then epoxy everything in place when the ammeter tells me all is OK. Filler and cosmetic to finish off. Cheers Doug 😎

7 years ago by RNinMunich

Forum

What motor have I got?

Right, I hope this works! The can length is 57mm,can diameter is 35.7mm and the is 3.18mm. Photos are attached,fingers crossed.the motor with the impeller,if that is what it is, also has a bronze(?) front bearing, different to the other two. in one of the photos of one of the terminals there is a small wire coming out from the inside, matched by a similar wire on the other terminal. Does this signify that there are internal capacitors fitted? What does the small red plastic thing on the rear signify? Chris

7 years ago by octman

Forum

Working radar

Hi Julian, don't know exactly how much room you have under the radar mount but I still think you will need a couple of pulleys! Motor mounted out of sight underneath the mast - shaft running up the mast to pulley #1 - pulley #2 mounted at end of the boom underneath the the radar mount. Choose ratio of diameter pulley 1 to 2 according to the space available and final rotation rate (RPM) you want. Strong rubber band to connect the two pulleys. Didn't need this method for my destroyer radar cos it sat right on top of the Director Tower, but used the pulley principle for gun turret rotation to connect two turrets together! 👍 One servo with extended rotation arc and two pulleys. Cheers Doug 😎

7 years ago by RNinMunich

Forum

Fairy Huntsman

As this is a refurbishment chances are it was fitted with an IC engine in which case you need to remove all the gunge and heavy mounting blocks from inside the hull as well as checking the propshaft and bearings. If you can get the weight reduced then I would expect a speed 600 motor with a 30 to 40 mm prop should suffice. A 20/25 watt ESC powered by a NiMh would also be suitable and keep the weight down. if you use racing props the current will be greater than if you use brass 3 blade props, and the bigger the prop the greater the current. As a general rule the prop should have a diameter of no greater than that of the motor. The voltage of the NiMh must not exceed the max voltage the ESC can handle. A higher voltage will reduce the current draw so a 9.6v may be better than a 7.2v and give a longer run time. if you already have batteries for other models I would use those but SLA's are heavy and may hinder planing. if you already use LiPos then make sure your ESC can stand the voltage and has a built in cut off to protect the battery.

7 years ago by Dave M

Forum

Propshaft Bearings

I bought a bearinged propshaft from China but I'd ordered it too long, I cut it to the correct length & Dremel'd the inside diameter until the bearing was a good tight push fit. Mine is made out of stainless tube with a stainless shaft, they should be easy to make, it would all be around selecting tube, shaft & bearings that would suit each other. Cheers Wayne

7 years ago by Midlife306

Forum

2 motors 1 esc

I was looking at these as motors. using 12 volts. 3 - pole electric motor with integral cooling fan and high quality carbon brushes. Two flux rings offering high torque motor. Originally specified for Black and Decker power tools, these motors are of the highest quality and recognised as one of the most useful model motors currently available . Suitable for 6 - 12 volt applications. No Load speeds approx. 4.8V 1.7A 8500 RPM 6V 1.9A 12000 RPM 7.2V 1.9A 13500 RPM 9V 2A 20000 RPM Dimensions: L65mm, D36mm, 3.2mm Off load Current: 1.57A

7 years ago by none

Forum

raf crash tender 3ft

Hello Paul well the bent shaft is another purchase i managed to find a complete shaft on eBay which is the same dimensions as the boat so hoping when it arrives it will fit but overall length is 230mm and outside diameter of tube is 8mm 😆 George

7 years ago by georgeo5664

Forum

raf crash tender

Consider going brushless mechanically the motors are simpler ( no brushes) and they are more efficient. if you take the plunge and use LIPO batteries you can have any amount of performance. Not sure but I think an 800Kv outrunner would give you all the power you need and no gearbox needed. The torpedo motor has a recommended rating of Operating Voltage 12 volts. Current approx. 5.28A at max efficiency. RPM at 12.0v - 4289 at max efficiency. Weight 595g (approx) - 6.35mm The 800Kv has a 28A rating at 12 V so a wattmeter and a bit of fiddling you can match prop to motor and get some performance

7 years ago by Haverlock

Forum

Clamp on prop-shaft grease nipple

My part built Perkasa already has the tubes and shafts fitted. Holes have already been drilled in the tubes near the top but no oiler or grease nipple has been fitted so grease keeps oozing out. Being an old kit the is 3/8" or 9.5mm. Whilst I have been able to find the items I want, I can't find a larger diameter than 8mm. Unless anyone knows of a larger diameter I will have to try and drill out the 8mm. Any suggestions please? Steve

8 years ago by cormorant

Forum

Precedent Perkasa

Hi Steve I see the needle file couplings are nylon so should be much better than the original metal variety. Both types of Fittings on the link say they are good up to 2.5cc ic engines so I assume the advice given relates to use with ic engines where the power is not as controllable as with electric power. I refer to the fact that ic engines are often started out of the water then launched at high revs resulting in considerable shock to the couplings. My own experience is that universal are ok with electrics even high powered brushless. I believe I would go with option 3 assuming you can get the fitting with the correct thread. Re threading the shaft is not that easy and a possible better option is to re-thread the coupling. You will need a lathe to do this accurately to avoid misalignment damaging your bearings. Should the joint prove to be noisy I suggest putting a sleeve of Silicon tubing ( as used for ic engine exhaust coupling) over the joint to take up the tolerance in the ball and pin coupling. Regarding replacing tubes I usually obtain a new tube and shaft of the correct dimensions remove the shaft and bearings from the new and old fitting and replace the new in the old shaft. Only works if the old tube is serviceable and straight but usually works fine. As I have a lathe I can make new bearings should the tubes be of different diameters, but often this is not a problem. Good luck and please post how you resolved the issue. Cheers Dave

8 years ago by Dave M

Forum

ESC problem

Hi there, bit of a newbie to ESC's Need some advice on what AMP rating to get for the current setup any and all help is appreciated. Prop -> Graupner Jet Propulsion Unit 5 (2347) (G2347) Flange Diameter: 78mm 7mm Motor -> Graupner HPD 2948-3760 7.4V Brushless Motor Operating voltage range : 7,4... 24 V All-up weight, approx. : 180 g Free shaft length: 10 mm Output : 2000 W Number of poles: 4 Permissible motor direction : R und L Case length: 58,2 mm : 4 mm Max. charging rate: 105 A Case diameter: 29 mm Revolutions/Volt: 3760 Part No: G7757 Battery ------- 7.4v 2s 40c 5600mah Boat -> Weight: will be 8 Kilos once equipment fitted. currently around 5 kilos. length:1.3m I hope that this information is suitable and can help with my question. many thanks 😀 Ashley

8 years ago by sheaffy

Forum

Brushless motor control

Dimension: 27.8*27mm : 3.17mm Max Efficiency: 80% Max Efficiency Current: 4-10A (>75%) Current Capacity: 12A/60s No Load Current @ 10V: 0.5A No. Of Cells: 2-3 Li-Poly Weight: 65g KV: 1000 You need a minimum 20A ESC 30A would be better. http://www.hobbyking.com/hobbyking/store/__15205__Hobby_King_30A_ESC_3A_UBEC.html if you don't need reverse that will be ok ( just as an example) use it to look at parameters You will see it works fine on NiMh batteries if you want reverse ( and waterproof ) look at http://www.mtroniks.net/prod/Boat-Speed-Controls/Hydra-30.htm Gives reverse and is sealed

8 years ago by Haverlock

Forum

Motor selection

I am building a 14" Keil Kraft Mermaid. I have included a 9.7:1 gearbox connected to the prop shaft, cannibalised from an aeroplane gearbox, taking a 12mm diameter motor (i.e. large enough for a small brushed motor or a small inrunner). I should be grateful for views on which of two motors two use: 1. Brushless, 11,000kv, max 7V, max 49W 2. Brushed, max 7.2V, max 20-25W Both are at my disposal. I had planned to use the brushless motor, but I am experiencing misgivings that it might overpower the boat or cause some catastrophic marine conflagration (despite the heat sink). The brushed motor came with the original gearbox, and I now wonder whether it might be better suited. In case it is relevant, I plan to use a 20mm three-bladed propeller. I have a 30mm three-bladed propeller available should that be advisable. Many thanks.

8 years ago by coelacanth

Forum

Sea Commander

I removed a prop tube from an old boat that has been fixed in place with araldite. I did mine by strapping the hull onto my drill table and lining the shaft up using the old prop shaft then drilling out using a drill .5mm smaller than the diameter of the prop tube. Then using a drill the same size as the tube, but turning the chuck by hand. This worked for me, Hope you manage to remove it without too much trouble. Thanks Colin

8 years ago by Colin H