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Hi Andy, what you might call a FAQ!! Have a look at the info here to help filter the plethora of motor specs and find something close to the MFA850 performance - or better as the brushless motors are more powerful size for size and LiPo batteries much lighter. http://www.thercmodelboatforum.com/t1234-brushed-to-brushles... As a guide here is a table of the Graupner brushless specs for you to compare with the 850 spec. There is no conversion table as such, especially since with many brushless and ESCs you can alter the performance by adjusting timing at the ESC! Turbo!! Happy hunting, cheers Doug 😎
Well today was the first chance I had to take the boat to Coate Water in Swindon to use their small boating area, which is weed free and only about 3ft deep, Video 1 shows the boat with two 7.2 volt batteries at the rear of the boat, video 2 shows the boat with the two 7.2volt batteries mid section just behind the motor, video 3 shows the baot with the 12volt L/Acid battery with the two 7.2 volt batteries in the section in front of the motor as ballast, vidio 4 shows the bat with one 7.2 volt battery mid section with one 7.2 volt battery front section as ballast. Sorry about the quality of the video's but I was on my own so had my phone on a small tripod. The motor got quite hot, so maybe the 56 mm three bladed prop is too much still and I suspect the angle of the prop maybe too great, although with the present prop I would not be able to move it much as there is only about 5 mm between it and the hull. I seem to have trouble with downloading the video's it keeps coming up with a message saying download failed, I have tried downloading just one, that fails as well, any idea's?
thanks everybody for the info .I will get 2 -6 volt batteries and fit them in the hull so that Ican work out the necessary extra ballast. I never thought of using a mixerbut will probably do this as well but nearer to when the build is complete .I am on with the drawings now scaling them from pictures /photos on the internet. I will then produce the templates -make the bits in cardboard then when they look ok finally out of plastic sheet .I have had one or two comments doubting my ability but as the bionic man said 'we have the technology we will rebuild it'
Regarding the batteries, I suspect it was 2 x 6V ?Ahr gel cells. One for each motor. 2 x ESC and possibly the Robbe mixer. I agree with Jarvo it could have been 12v from 2 x 6v in series but it was common to use 6v during this period. Could be the space was for the ESC.
Hi Andy, I have 'twined both the 34" and the 48" Huntsman, i used 600 size motors in the 34, and 850 motors in the 48. Both were very quick, but, the run time was poor, about 10 mins. With modern lipo's or big Nimh batteries they would be a lot longer especially if you used brushless motors. Props, on the 34, they were 35mm x 3 blade brass, on the 48, they were 45mm x 3 blade brass. Sad but i sold them some years ago but now have a 48" fireboat to play with. Mark
No worries mate, have the esc's got a max and min voltage??? they may not work at 6volts, if not then a set of 7.2v NimH packs will be brilliant x2 or possibly 4 packs with a Y lead for each pair, 3300mah packs are going for a good price on ebay at the moment, also have a look at component shop and hobbyking, be sure you are on the uk site to keep the postage down!!!! Wouldn't bother with lipo batteries, SLA or NimH are more user friendly. If you want the H/H superstructure try contacting Krick they now make the kit, took over from Robbe when the went bust. Are the propshafts ok??? withdraw the shafts and lightly oil them get the oil into the inner bearing as well. Mark
The motor units are Robbe EF76 with fitted gearboxes, rated at 6 - 8volts, superb units and very reliable, did you strip and clean the gearboxes as well???? were the photos taken before you cleaned the motors??? The battery space looks to have been fitted with 4 x 6v 4ah batteries, probably giving 6v drive power, might have been 12v. Is there an ESC fitted?? that would give us the final key, apart from the red and black wire in the 4th photo is there any other wiring??? Mark
Hi Alex Yes sounds like one cell has gone. You can probably feel the heat from the faulty cell after charging and discharging. If you are competent you could split the pack and identify the failed cell. A meter across each cell whilst running a small motor will show up any low voltage cells. Chances are the rest will be ok and will take and deliver a full charge. If so and you can use a soldering iron and can purchase replacement cells of the same make and capacity you could make the pack OK. I'd even consider rescuing all the good cells and making a lower voltage battery, 5 amp batteries being the price they are.
The boat is in a relaxed position for the winter. Batteries are removed for the winter here in Canada. But I shall look more closely at it and make those adjustments nowto be ready for sailing after the ice goes out. Would adding more material to the front edge of the keel hinder or help? Say 1 1/2” strip?
Hi Pilot, first of all welcome to the forum. Do you have any modeling experience?? Which kit or plan are you using??? I would recommend an outrunner look for one with about 700 - 800 watt output, 3s or 4s rated with an ESC rated at least 100 - 150 amps, as a start with a 40 - 45mm brass prop. Kit or plan, reduce the angle of the propshaft to about 15 - 20 degrees electric motors can lie lower in the hull which was designed for I/C motors with their flywheel hanging below the motor, needing extra clearance. Suppliers. Have a look at the hobbyking site, for motor and esc, once you have the basic build underway, decide on the batteries you are going to use. Hope this helps as a starter, look round the web sites get more info and we can direct you further as to your requirements Regards Mark
Thanks Jarvo for the additional info...I did Google the safety bag afterwards actually. But...given what you've both advised.......as a stepwise approach, rather than discard x2motors plus ESCs plus batteries all at once, do you think perhaps upgrade the batteries first (more power less weight) and re-assess ? Then , if still not satisfactory, change the motors and Escs ? J
Hi What type of props are you using(size and number of blades). I see your basic problem is under powered motors and a very heavy battery. I made the big switch over three years ago from brush to brushless motors and to Lipo batteries. With the help on the forum and club members it was a learning curve, but, I would not go back. A 5800mah Lipo battery is in the weight of 450 to 570 grams and would give you a good 1/2 hour run time. A good balance charger and safety bag are the main requirements, also maximum charging for the 5800mah battery is 5.8 Amps(same as the old Nicads). Also a low voltage battery alarm. Your 600 motors can draw up to12Amps !!! Replacement same size motors for your mounts would be 35mm brushless motors, but, you will require two ESCs with a Y connector to run on the same throttle channel. Replacement brushless motors are far more powerful e.g. a Hobbyking 3639-1100kv with a 60Amp ESC on a 4S 5800mah Lipo Battery is 800watts and with two in your boat is 1600 watts!!! Your old motor would in the 100 watt each mark !! I have the same size crash tender, but, with a single brushless motor. I have all the order numbers for the motors etc. and a setup the ESCs if your require. Canabus
Just a thought- The component shop does do a voltage reducer rated at 6 Amps power draw, and will drop from DC (10.5-40v to 1-9v) I thought about using one of these to run a 6v volt Marx Hectoperm motor from a 12v source, to save buying a new battery. As long as your motor speed controller setup doesn't draw more than say 4~4.5 Amps. I'm my case the tug had 4 x 6Ahr 6v batteries wired in parallel giving 16Ahr and 2-1/2 hours running time @full speed. These batteries have since all died due to age. I wanted to use just 1 x 20Ahr 12v battery instead and keep the added ballast I need anyway. This 6 amp unit is on the limit in my application. P.S i'm tight with money and I acquired the battery free from an alarm battery swap.