Will be posting a blog update shortly describing my trials and tribulations with brushless motors. By using the "softest" start programmable ESC settings have found the squeal is largely eradicated. If you have not tried them, it is worth the trouble. The slipping coupling will not help, but am sure that will be corrected. I am using solid universal joints, which although noisy, give a positive drive. Your boat looks to go well, but hard to judge from onboard pictures.
Thanks, plenty to look at! Will work though the system and see where improvements can be made. Right now the squeal is intermittent and can be lived with. Once it happens returning the lever to neural and trying again seems to resolve it.
Adjusted the transom flaps and reprogrammed the ESCs to the softest start settings, retested. Until now, the test runs did not have the duration or stability to really examine what was happening. Using 3 S batteries acceleration is rapid and a is plane quickly achieved. However, as the acceleration continues and speed increases, the bow digs in. A cloud of spray then surrounds the model as the plane is lost. Brushless motors do not modulate as smoothly as brushed and adjusting power tends to be erratic or exaggerated. This is a scale model and the propeller shaft angles are per the plans. The thrust from the propeller has two components, horizontal and vertical. The horizontal propels the vessel forward. However, the vertical component forces the stern upwards and, correspondingly, the bow down. Have moved as much weight as possible towards the stern to counteract this, limited by maintaining the correct displacement and waterline. The easiest solution is to reduce motor power, decreasing both speed and the lifting component. Decided to retry the 2S batteries as they give reduced power. A plane is again achieved, but as the motor response is more docile, it can be controlled. If the speed gets too high the bow lowers, as before, but the motor output can be more easily adjusted. Spent a pleasant half hour or so with the vessel accelerating onto and off a nice, controllable plane. Much less spray and drama than with 3S and much more controllable. Have now decided to revise plans and use 2S rather than 3 batteries. A further advantage is the motor noise is muted and now sounds more like a gas turbine than a dental drill! Finally feeling comfortable with the model. Will thus shelve further building until the late fall when sailing in Canada concludes. Want to enjoy the rest of my fleet in the meantime! Will summarize my experiences with brushless motors in another blog shortly for the benefits of others contemplating their use. After restarting the model will resurrect periodic build blogs to advise progress.
Doug, Am sure it can do both of those! So far, have not had a high speed run long enough to really test the brass shafts. I hope to only need to use it for a couple of test runs shortly before will dismantle, make those upgrades and then finish the model over the winter. Rowen
Thanks Colin, will check as intent to strip down and lubricate this winter as the build progresses. Plans are to replace the two outer shafts with Stainless steel, currently brass rod anyway. Not holding out much hope though as have been been through all the obvious mechanical issues already. Rowen
Been researching the squeal and stutter on other websites and conclude RFI is probably not the major contributor. Others attribute it to a mismatch in the ESC / motor timing, which seems more likely. Whatever caused it, resulted in the affected motor failing. Which came first, the failure causing squeal or squeal causing failure is open to conjecture. Much to my surprise the manufacturer has decided to replace the motor under warranty. In the meantime, the motors I had planned to use originally (2800kV Outrunners) came into stock, so purchased a couple. Until now have had to use the ESC default settings as did not have a programming card. This also arrived with the motors. Following advice from another contributor reprogrammed the motors with “softer” start and acceleration settings. Fitted and tried the new motors and settings. On the bench, the squeal and stutter have almost gone. The motors are also more tractable. As the brushless motors are now going to be used for high speed operation only, with slow on the centre brushed, thought could simplify the controls by putting the brushless ESCs on one control system using a “Y” lead. However, this introduced inconsistent and erratic motor responses. Reverted to the two previous separate controls, port and starboard. On the water the performance is fine, as is the reliability. The 2S battery gave almost half an hours operation. The bow lifts nicely with both 2 & 3 S Batteries; plenty of spray. Hopefully resembling a 50 knot vessel! Another adjustment is needed to the transom flaps to try to hold the bow down later as she accelerates. Feeling now to finally be making progress with this model. The squeal has not gone, nor has erratic motor operation. The squeal is high pitched screech, rather like treading on a budgie! When it happens, bringing the control back to neutral and advancing it again almost always overcomes it. The erratic operation happens also when starting and is rather like the motors are not getting a signal to react to the control. Again, returning through neutral briefly seems to correct it. The revised motors and ESCs have increased the weight to 6lbs for the hull including all running gear, excluding batteries and superstructure. Whilst still trying to control weight have concluded this figure is satisfactory as the performance certainly is.
Decided to separate the two power systems; one to the port ESC and motor and the other the starboard. Hope this will reduce interference between the motor systems. Have also reverted to a remote battery powered Rx rather than the BECC system, again to reduce possible interference. The modifications did not resolve the problems. The squeal and stutter are still present, but much reduced. Sounds rather like a slipping coupling, but as these have been checked many times they can be eliminated. Apart from the squeal and the stutter, everything works well. The squeal /stutter occurs at start up, when it happens the control is returned to neutral, If the motor is immediately reselected, usually the problem goes away and the motor runs up cleanly. It only occurs when both motors are selected at the same time. Either runs up cleanly when selected individually. Interestingly enough, did some research on various Model Boats site and found some references to RF interference, no specific solutions though. Also examined some Aero modeling sites as they use powerful brushless motors with ESCs. There is some history of the problem there. Evidently when the mosfets (?) of the ESCs convert DC to AC, RF interference is generated. It can often be addressed by using ferrite rings on the ESC control leads. My latest ESCs actually have ferrite rings, so the problem must have been anticipated. This might account for the latest reduction in squeal and stutter levels. Am at a loss to think of any other modifications, so decided to conduct a water test. Maybe it is a characteristic of brushless motors, but their control response seems “ragged”, not smooth as with a brushed. Anyway, the squeal and stutter seemed reduced yet again, perhaps the water load damped them down. Was able to start exploring both the performance envelope and the viability of the brushed centre shaft motor. First impressions are that on a 2S battery the performance is fine, but it sparkles on 3S. On 3S the stutter and squeal are more pronounced though. Intend to do further trials but, unless something unexpected occurs, now plan to use 2S power. The centre brushed motor idea works well, this layout seems a good compromise. Will design a simple switching circuit to ensure the brushless motors can selected separately. This will avoid the inadvertent operation of both brushed and brushless unintentionally as they are on the same control stick. The brushed can then be used for low speed operation. Returning to the problem of squeal and stutter – has anybody else experienced this and how was it resolved?
Blog 4 update – Adjustable transom flap using metallic tape did not work. Think the vibration caused flexing and fatigue, so it finally split. Fortunately had established the correct angle, so reproduced the flap arrangement with a fixed thin alloy plate. Much more robust. Have installed the new brushless motors and ESCs. The current layout is brushless motors on the outer propellers and brushed on the centre, all powered by a single 3S Li-Po battery and Rx. Am hoping to commence water trails this week, but have found an issue which was also present with the original brushless motors. When either brushless motor is powered up it operates nicely, however, as soon as the second motor is started either motor “stutters” and a pronounced “squeal” can be heard. The brushed motor is unaffected. Have now tried several ESCs but to no avail, the issue remains. It can be cured though by powering each brushless motor with it's own battery. When this is done everything powers up cleanly and quietly. The obvious solution is to use two Li-Po batteries and abandon the single battery approach. Am reluctant to do this as the model weight will increase yet again. Has anybody experienced this when using twin brushless motors and, if so, how was it resolved?
This hobby gives countless opportunities for changing ideas! After some thought, have decided to try another approach. Whilst brushless motors give fantastic performance; so far have had poor experience of system reliability. As more information and advice from other modelers is gathered, suspect have been using undersized ESCs, accounting for many of the problems. However, whilst still waiting for the new brushless motors an idea developed. To instal a brushed motor on the centre shaft, whilst retaining brushless on the outers. My thinking is this could provide several advantages such as; a better slow speed performance more suitable for manoeuvring, lower current draw, improved fuse life and a reliable BECC output. It will also operate at below the Li-Po cut-off voltage, giving a “get home” facility in the event the brushless ESCs cut-offs operate. However, there is a slight weight penalty as brushed motors and ESCs are heavier than brushless. Fitted a brushed motor of the same O/D and mounting arrangement as the previous brushless to minimize installation issues. With a reliable Mtroniks ESC from my stock and suitable fuses, fitted these items along with the ballast and battery used earlier. Now, back to the pool. The system worked well. The vessel speed is much less than with a brushless motor on the centre shaft, but control-ability greatly improved. With the triple rudders she steers nicely. The thought of using a brushed motor on the centre shaft, with a brushless motor on each of the outers is attractive. It is hoped the additional operation of the outers in conjunction with with the centre shaft, will provide the expected performance. The centre shaft would then also provide manoeuvring and reliability with the outers shut down. If this works, think this power-train combination could be ideal. Once the new brushless motors and ESCs arrive will instal and report. On the attached pictures, the first shows the ballasted model sitting with the brushed centre shaft motor, the second with a brushless. The difference in draft is imperceptible, the bow sits slightly high in both cases. The third shows the model with the brushed centre shaft operating only at “full” speed.
Has anybody heard of, or have, a "rule of thumb" for the sizing of brushless ESCs? Am new to brushless motor powertrains and have been using ESCs that nominally exceed the current draw capacity of the motor. Have heard that they should substantially exceed the motor capacity and wonder, if that is the case, by what percentage?
Hi Doug, Certainly having fun and gaining more appreciation for the various drivetrain combinations available to us. My objective for this summer is to get a combination, using all three shafts, that works properly at all speeds. This coming winter will refine by using items such as you recommend. That item would help, so will keep the details on one side. The program would be assisted enormously if a supplier (located in Hong Kong) was able to meet back-order commitments!
Hi Doug, Am undecided how to use the centre shaft. Have had conflicting suggestions; one to use it for "boost", the other for maneuvering. Have components on order which will let me do either, once can install them think will try and see what works best. Rowen
Whilst waiting for the new motors and ESCs, reviewed videos of the vessel under power and noted that as the speed increases, the bow lifts towards a plane. However, as she gathers speed the transom flaps become effective, forcing the bow down in a cloud of spray. At this point the plane has been lost and the model becomes almost uncontrollable. Decided to temporarily ballast the hull to simulate the new motors and ESCs, then try to establish the optimum flap angle using just the centre propeller and shaft. This is the original 2838 brushless motor installation with a 30 mm propeller. With this simulated drivetrain it would also be an opportunity to determine the best battery locations for both 2 and 3S Li-Po batteries. Made up an angle template with a spirit level to get the correct deck inclination with the vessel floating at rest. From this located each type of battery statically - somewhere close to the mid-point of the hull. Which also seemed as good a place to start as any! Somewhere in the research for this model found a reference to the transom flap angle. This was at a 2 degree -ve (pointing downwards) angle. Installed the 2S battery and tried the model. The bow dug in at speed. Adjusted the flap to a straight and level position and tried again. The bow still wanted to dig in, but to a reduced extent. Readjusted the angle to 2 + ve and repeated. The bow now lifted so the forefoot just cleared the water and then remained in that position. Replaced the 2S battery with the 3S. The extra power obviously increased speed and the bow lifted slightly further. The spray was deflected by the chine rails and a level plane established. The conclusion is that the transom flap angle is critical to the correct planing of this model and that it should not be negative. Until the new motors and ESCs are fitted will leave the transom flap and battery locations as is. Once these components are installed, intend to repeat the test. Am confident that with some fine tuning the model can be now made to plane properly at a scale speed. Interesting to note that the model will just about plane with only one propeller operating – wonder what it will be like with all three?
Thanks Doug, Good suggestions. Have dropped a line to the Yorkshire Belle 2 organization and will let you know what transpires. From the picture the vessel looks very much like the one I sailed in too many years ago to want to describe! Rowen
Just been reading a book on the pleasure steamers that used to ply the Yorkshire coast from resorts such as Scarborough, Whitby and Bridlington. The Coronia and Yorkshire Belle bring back memories and am considering building a model of one. Has anybody any idea where I could find any plans?