40 trainer or electric conversion

[Steve Hargreaves - Moderator]

Maybe you tune 'em extremely lean Peter.....have you noticed the cylinder head glowing red hot occasionally....

 

Your post raises another interesting point as well Peter.....you talk about the weight of your tank as its capacity & that is fair enough as tanks are often sold in "ounce" sizes but (& I really am speculating here) is that how they are measured? Methanol is much lighter (over 20% lighter) than than, say, water so a tank that holds 10 oz of water will only hold 8oz of methanol.

 

To put it another way does a 10 oz tank hold 10 oz of methanol or does it hold 10oz of water.

 

Obviously we need to factor in that the fuel is 15% or so oil which will affect the overall SG of the liquid but you take the point....

 

The only way to be sure is to physically measure it & get the volume of the tank in cc or cu in....

 

I think quoting oz for fuel is a bit misleading.....its the volume of liquids we should consider not their weight....

[Eck]

I always thought that oz. for fuel tanks referred to fluid ounces, a measure of volume - but I sit at the feet of the learned and listen!

[Steve Hargreaves - Moderator]

You could be right Eck, you really could....I don't know....it only occured to me last night when I was trying to find out how big the tank in my model was so I could respond to Peter....its not easy to see so I thought...I know I'll weigh the model...then fill the tank & weigh it again.....

 

So I did & it only weighed 7 oz more which surprised me as I though the tank was much bigger.....

 

I dug it out & thought, yeah that looks like at least an 8 oz tank to me. I measured it & it was 5.5cm x 5.5cm x 8.3 cm which multiplied together gives me 250cc. Now an ounce to me is 28grams & as 1cc weighs 1 gram so 250 divided by 28 is 8.9 ounces so call it a 9 oz tank

 

But this is where it falls down because 1cc of methanol doesn't weigh1g...it weighs 0.8grams so 250cc of methanol weighs 200g......which is just over 7oz which is what I measured originally...

 

So have I got a 9 oz tank or a 7 oz tank......

 

Confused? I most certainly am.....

 

I think I have a DuBro tank in the drawer with the size moulded into it.....either 12 or 14oz I think it is.......maybe I need to fill it & weigh it!!!

[Eck]

Just out of curiosity, I pulled a tank marked 4oz from my spares box, the others either being marked in cc or unmarked. It held about (i don't seem to have an Imperial measuring cylinder) 3 FlOz of water, and on weighing it empty and full, it held 3.55 oz. by weight of water. Could it be

a) incorrectly marked

b) a reference to (possibly) American FlOz (their system of volume measurement seems to take Imperial names but be different just to confuse us)

or (c) poor experimental technique?

[Steve Hargreaves - Moderator]

Or d) all of the above.....

 

I'm not sure Eck.....you've just managed to chuck another brick into the muddle puddle though haven't you........US fluid ounces are different to ours!!!

 

Fluid ounces

 

1 Imperial fluid ounce = 28.4130625 mililitres or cc (approximately...)

1 US fluid ounce = 29.5735295625 millilitres or cc (give or take a bit either way)

 

So 1 imperial (US in brackets) fluid ounce of water would weigh 28.41g (29.57g) but 1 imperial fluid ounce of methanol would weigh 22.48g (23.42g) given that the SpG of methanol is 0.7913...

 

Obviously this is at room temperature of 20C....if we were to take the typical temperatures we have today then (contd on page 94)

[Eck]

Cheers Steve, my brains have just oozed out of my ears and are pulling faces at me from the other side of the room!

[Peter Beeney]

Steve, - as I said in the first post, I was only trying to draw a comparison between i/c and electric, in terms of the power output of each, i.e. looking at an i/c motor and finding an equivalent electric substitute.

I’m afraid I can’t really agree that our engines and motors don’t really produce “Power”, I will agree that power is a rate of working though, and in my view this is exactly what we are looking at.

So I will try and define power as I see it. Starting with energy.

Energy is the capability of doing work. If we run a motor without a prop on, it has kinetic energy, when we put a prop on it’s doing work. When it is doing work, though, we don’t know at what rate the energy is being used at, so to give it a rate we have to divide it by time. Thus we can simply say, or define, power as energy divided by time, or the rate of doing work. Using the familiar horse power as the unit of measurement, we can say this is given to be the energy required to lift 33000 lbs through 1 foot in 1 minute. Thus 1 BHP is 33000 ft lbs per minute. Without the time factor it could be in one minute or one day.

The watt is slightly more obtuse, this is given as one joule per second, a joule being as the energy expended when a force of 1 newton is exerted through a distance of 1 meter. Or alternatively, as a current of 1 ampere that flows in a resistor of 1 ohm when connected to a p.d., potential difference, of 1 volt for 1 second. So from this we can say that power = the energy supplied in joules divided by time. We can see from the little statement this equals volts by amps by time, divided by time. The time element in the equation cancels out, leaving us with the very well know watts = volts times amps. So it fits nicely in the SI units of measurement.
Actually, strictly speaking, watts are volts times amps times power factor, but we’ll leave that for another day.

Or conversely, we can also lift 1 lb through 33000 ft in one minute. Let us use the i/c engine as an example, and because power is a derived function we can’t measure it directly, however we can measure the revs per minute, and the torque or twisting action, that’s applied to the crankshaft, so then we can calculate the power from this. Torque is a product of the magnetising strength, or force, F, and the radius, r, that’s the distance from the centre of the drive shaft to the magnets in the rotor. So an outrunner will be said to have more torque because r is longer, the magnets outside the coils, than on an inrunner, with the magnets turning inside the coils; so it has a greater moment arm.

When a Torque Reaction Beam was used to measure the torque, the twisting action of the engine lifting a weight at a given point along an arm bolted horizontal to the engine, the result given in oz-inches, it can be shown that the Brake Horse Power can be calculated by simply multiplying the torque by the revs per minute and dividing by 33000. Or in this case, 1, 008, 000. This is because we need to convert ft-lbs to oz-ins, so multiplying by 12, inches in a foot, and 16, oz in a lb. As with all these little calculations, you need to calculate in all the same units, otherwise you can seriously confuse yourself, I’ve got that stack of T shirts!

Now we can plot two graphs, one of torque, in oz-in against rpm, and another, the calculated BHP against the same RPM, by multiplying the torque at any given point, by the rpm’s at the same point. In very general terms the torque graph will slowly fall away, so the BHP curve will rise to a peak and then fall away. The max BHP is shown on this curve at the highest point on this graph, so you can prop your engine to get these revs in the air for maximum power. You could prop it to go faster, or slower, of course, but the power will soon start to fall off. The torque curve falls away because it gradually takes more power to overcome the steadily rising inertia of the moving parts due to the increasing revs. But as I said, this is in general terms, there are exceptions.

 

[Peter Beeney]

PART TWO

The TRB as a torque measuring device was not very successful though, it tended to give erratic results, but I’m sure a modern dynamometer is; this might consist of a flywheel on the shaft whizzing round in a stationary drum which has coil attached and an electrical supply. The flywheel then calls up our old friend Eddie Current who sets up a magnetic reaction between the drum and the flywheel and that causes a drag on the engine which gets progressively greater and then by manipulating the old abacus beads and the electrical supply to the coil the torque can be very accurately calculated in a trice; and then by virtue of it’s electric chips chicanery one millisecond later it can produce an output of RPM, Torque, Power and BHP results in any old unit you like.

The same applies to an electric motor. If we had a shaft sticking though a brick wall, and no means of knowing what was driving it on the other side, the result would be just the same. The same torque and the same rpm would give the same power output, in watts, in HP, in PS or what ever takes your fancy. I think some knowledge of the working arrangements of an electric motor would help, but I’d consider that the maximum torque is reached when the magnetic circuit reaches saturation, or possibly just before, and that’s not when it’s stationary. I found a very good website at one time, a gentleman had done much research and testing work and had produced some excellent graphs for many motors, containing all the information you could wish for. Unfortunately it seems to have disappeared and I can’t remember the name. Certainly there can be a lot of torque produced by electric motors, but there can be a price to pay as well, as Gordon R said, by stuffed batteries and ESC’s; and motors, too, at times, I wouldn’t be so wondered.
I’ve never ceased to be really impressed by the power of really concentrated magnetic circuits, they can, at the limit, bring the biggest of engines driving them to a shuddering stop; and with no obvious physical connection!

I’m not trying to dispute the 100W/lb rule, simply comparing it with i/c engines. I think, also as Gordon Rigg said, you can generally have loadsa power and short duration, or low power and long duration. An i/c can have power and duration, too, simply because it’s much easier to store the potential energy in the liquid fuel than in the batteries. But I have seen many electric planes flying really well. Once we can get back to a spot of flying I will make some enquires at the patch, we do have a few electrics, of all sorts.

I think all the fluid oz stuff is just a red herring; a diversionary tactic, no less. I just ignore it. As long as everyone uses the same units then we get the same results; and in this country most people will use imperial or metric scales, unlikely American. I use a squeezy bottle, ex. bath foam, so I filled the tank, full, as I always do, emptied the squeezy, weighed it, 50 grams, sucked all the fuel from the tank back into it and re-weighed it. 290 grams. So there is 240 grams of fuel in the bottle. Now I need to fly it, for a time check, but I’m sure I will get the same result, around 23 minutes. So then I think I can confidently assume that my Irvine has a fuel consumption of 0.37oz per minute. And it’s difficult to see how any other Irvine 53 will be very much different, if it ran with the same sort of performance.

So now the umpire has decided to uphold his original decision, and declare “Not Out”.

PB

[Steve Hargreaves - Moderator]

All good stuff there Peter & I wouldn't really take issue with any of it in part 1.....

 

I do notice that in all your examples of "power" an element of "time" has sneaked in there as well..."33000 lbs ft per minute"....."joules per second"...this just underlines the point that Power has a time element in it....it isn't really a force at all.....

 

This is the problem when we play fast & loose with physics terminology......these are closely defined but terms fall into general use & their precise meaning becomes lost.

 

With regard to the torque/BHP thing then you are right.....the torque curve will fall away as revs increase...this is due to frictional losses but also due to the engines porting beginning to restrict the flow of fuel gas. Maximum torque occurs when the fuel flow through the engine is at its maximum. Of course the torque falls away quite slowly so the loss in power is compensated by the increase in rpm.....as we get higher up the rev range this fall off becomes more noticable until the increase in rpm no longer compensates for the reduction in torque.......the engine is now af maximum power.

 

The trick is to get peak torque & peak BHP as far apart as possible to get a flexible engine.....getting them close together is the key to high power but makes for a very peaky engine that isn't very flexible.....not good

 

Part 2 I will have to come back to when I have more time....

[Peter Beeney]

Steve, just to try and make my point, this is the definition of power. Whenever you say ‘watts’ or ‘BHP’ or ‘PS’ this is exactly what you will be talking about. I’ve just checked, and it’s still the same meaning as the textbooks of before yesteryear, - ‘ The dimension of power is energy divided by time. The SI unit of power is the watt, (W), which is equal to one joule per second.’ When you say ‘100 watts per lb.’ this is exactly what it means. What you are actually saying is - 100 joules per second per lb. If you wanted to use the term ‘force’ I’m not sure what units you would use.

Perhaps you are talking in the general term, as in “I have a powerful car” or “The president is a powerful man”?

I’m not sure that I’m playing fast and loose with terminology, just trying to get it straight so that I can do some comparisons.

I’m still thinking that maximum engine torque occurs around start-up and tapers off from there. I only have some examples on paper of some small engines, but if I can find them I will try and scan them in, to illustrate what I mean. Although I’ve not even tried this laptop on the printer, as yet!
BHP is a product of the torque and rpm, i.e. torque multiplied by rpm, so I’m not sure you can juggle the curves, one with the other. To make the engine flexible might mean making all the operations, such as valve timing and compression ratio, bore and stroke, etc. a bit ‘softer’, to so that it has a more even range. But this might mean some top end losses, so as always, it will be a compromise!

PB

[Steve Hargreaves - Moderator]

Morning Peter.....a whole new week ahead!!!

 

I'm not sure we are disagreeing at all now...merely saying the same things in different ways.... I wasn't implying that you personally were playing fast & loose with terminology...just making the general point that specific terms fall into general use & their meaning becomes a little blurred.

 

Regarding engine torque then this occurs when the filling of the cylinders is at its most efficient. This can occur.....pretty much wherever the designer wants it to depending on the use of the engine.....if we take car engines as an example we would see that a typical 2litre diesel engine will churn out around 140bhp at 4,000rpm & maximun torque will occur at around 1800 rpm....a typical 2 litre petrol motor will chuck out around 150bhp at 6000rpm but peak torque will be around 4500 rpm....you will know that the diesel engine is the more flexible....

 

If we think about 2 stroke motorcycle engines then a 250cc motor will produce maximum torque about 500rpm before peak power.....in case you haven't ridden one of these () I can tell you that the engines are as peaky as heck & very difficult to ride well because nothing much happens below 8,000rpm

 

So what has all this to do with model engines? Well not a lot if truth be told but I try to use the examples to show how we can tell how flexible an engine is by looking at the comparative torque & power peaks. You are absolutely right to say that these values are affected by "mechanical" changes such as port/valve timing etc & therefore cannot be changed by mere mortals like us & as you say compromise is the name of the game here.....timing that works well at 5,000 rpm won't work so well at 15,000 rpm...

[Steve Hargreaves - Moderator]

So to part 2.....I've racked my brain to come up with a workable explanation for how electric motors produce their torque without resorting to complex formulae so try this for size...

 

As we know an electric motor works by producing an electromagnetic field to repel/attract the various magnets within it. Effectively this field "rotates" & drags the rotor around with it. The rotor is trying to catch up with the rotating field but can never quite make it. there is "slip" between the two.....the more slip there is the more current is drawn by the motor in an effort to catch up.....

 

This is why, when we load up our motor with a bigger propellor it slows the motor down & the current drawn from the battery increases. The ESC is still producing the same rotating field & the field is still rotating at the same speed....it has no knowledge that you've changed the 12" propellor to a 14" one...how can it know? The only thing that has changed is the slip between the rotating field & the rotor itself because the rotor has slowed down due to the greater load.

 

So having established a relationship between the slip value & the torque of the motor we can see that maximum torque will occur when the slip value is at a maximum....when does this maximum slippage occur? When the rotor is at rest...ie zero rpm....this is known as the stall torque.

 

Lets go the other way now & take the prop off completely.....the motor will speed up but it won't ever reach its kv (rpm per volt) value.... If it did then there would be no slippage between the rotor rpm & the speed of the rotating field produced by the stator & the motor would actually produce zero torque. As we know there are mechanical losses inherent in any motor...friction in the bearings etc & to overcome this requires a force...torque from the motor...hence there must be some slip to produce this torque ergo the motor will never reach its kv.

 

(I hope I've explained this adequately.....its a difficult concept to get your head around....if you still don't believe me I'll have to go & dig out some formulae & try & prove it that way.......probably be a good cure for insomnia though!!!)

 

So we can see that IC & electric motors are very different in their production of torque & power......both will fly a toy aeroplane very well though.....

 

Just a final thought on battery capacities etc that was raised earlier....yes you are absolutely right that you can opt for lots of power & a short duration or less power & a longer duration but this is also true of IC engines....its just less easy to achieve...we can draw more current & get more power (& less duration) from our electric motor simply by changing the prop.....if we took different pistons & liners & crankshafts to the field with us then we could change our engine characteristics to produce more power (& use more fuel) simply by building the engine to a different spec . We are up against the laws of thermodynamics though & can't extract unlimited power from our IC engines......just as we can't extract unlimited power from an electric motor....because it would melt if we tried!!!

[Peter Beeney]

Steve - yes indeed, as they say, a week may be a long time in aeromodelling……

Sticking with the model two stroke engine for a minute, I would say that I would really only be interested in the peak BHP because that will drive our most suitable propeller in the best possible manner. Although it’s it’s not nearly as good as looking at a graph I can quote some figures from one, this is an OS Max 29, 4.8cc, glow, circa 1950’s.
Power noted in BHP, torque comes in oz-ins. We start at 8000rpm, the torque is 37.5, BHP 0.30. Then the revs increase to the max torque point at 10000, the BHP is 0.37.5, the torque being it’s max at 38. It goes downhill from here. Winding up the revs a bit further to the max BHP point, at 14800, the torque has fallen to 32.5, but the BHP is now at it’s best at 0.48. Maxing out at 17600, the BHP drops to 0.41 and the torque to 22.5. I'll quote two propeller size examples, out of seven. A 7 by 9, turning at 13400rpm, the nearest I can get to the magic 14800rpm, and a 7 by 4 at 17600rpm.
This all looks pretty mundane, but here’s the acid test. Assuming a 10% unload in the air, then the 7 by 4 will reach 19360rpm. This equate to an air speed of 73.26mph. Our 7 by 9 figure will limit at 14740rpm, very close indeed to that 14800rpm figure, but this now represents an air speed of 125.5mph. A not inconsiderable 71.3% increase. I think this demonstrates the importance of trying to get the prop size about right for a given engine to get the maximum power out of it. Looking back at the front end, when the torque curve is at it’s highest, at 10000rpm, the nearest to this is a 10 by 4 at 12000rpm, and would equate to 50mph. Fictitiously, if a 10 by 5 resulted in 10000rpm we would see 52mph.
The fuel, back in those days, was methanol 40%, nitro 20% and castor oil 40%. I think some modern fuel might improve these figures to a degree. Certainly they seemed to like their oil….

Turning to vehicle engines, I’ll make it up as I go along so it is guesswork but I think it’s basically down to the fuel. A diesel engine has a higher compression ratio than petrol, indeed it has to have, to condense the heat sufficiently for combustion. So it can clout the piston a bit harder. Thus the moment arm, r, the distance from the centre of the crankshaft to the centre of the crankpin can be made longer, imparting a greater turning motion to the crankshaft. This also makes diesel fuel more efficient than petrol. The slight downside, maybe, of this ‘higher gearing’, plus other things, such as a heavier flywheel, makes the engine run generally slower but with as much power at these slower revs. I consider this then is why the diesel has the power low down. But, of course, some performance will be sacrificed in terms of acceleration, etc.
There is obviously much more to it than that, and I really wouldn’t have much idea about any of it, but I still think there seems to be some sort of odd correlation between my perception of electric flight power and i/c flight power, which at the moment I’m unable to put my finger on. But… I’ll keep on kicking it around, but I really need to get some practical figures from some motors to play with. I’m working on it…

PB

 

PS I've just noticed your part two. I'll read that later.

[Former Member]

[This posting has been removed]

[Steve Hargreaves - Moderator]

Gordon Riggs is a garden centre in Rochdale.....

 

Interesting figures from that old engine Peter......I'm shocked at the amount of oil used......40%....blimey!!!

 

The figures are certainly interesting & bear out the point I was making in the original post I made whilst fielding your initial cover drive ....The OS has peak power at 17600 rpm but needs a silly sized prop to get there....you aren't really going to put a 7x4 on an OS29 are you.....a 9 or 10 x 6 would be much more practical & would probably bring the revs down to around the 10,000 mark....max torque & a good bit less power (20% less) than the peak.

 

The speeds suggested are highly theoretical based on revs & pitch but it is unlikely these speeds would ever be realised in a practical model.....a Super 60 powered by an OS29 will never do 125.5mph no matter what prop you put on it....

 

And you are right about diesels too....these are essentially low speed engines....the high compression & subsequent proximity of the valves & pistons work against high revs which precludes high power......so they are tuned for high torque with turbo chargers etc to boost the air intake so they can burn more fuel. Also diesel fuel is more calorific than petrol.......you get more "bang" for the same abount of fuel, all other things being equal....

[Peter Beeney]

We have a bit to cover here Steve, so starting with your your part two, I have to say with the greatest respect regrettably I’d rather not comment at this stage on the electric motor bit, but this has absolutely nothing to do with your very good self, or your post, but it’s all to do with me. All I would say for the moment is: - could it be possible some more brain racking may be in order?

With regard to the relative duration of batteries and fuel I was actually trying to make the point that with my i/c engine I can get both the performance and the duration. As standard. Within certain limits, of course. I still feel that I can get more energy into, and out of, a fuel tank than a battery. But we do still have slightly differing views on this, the whole point of this discussion, really. I gather that my idea of electrical power maybe seen as somewhat slanted; and I have to admit, for now, I seem to be standing alone on this particular island.

But there is no doubt, the electric situation continue to improve at a rate of knots. For a whole variety of reasons the emphasis is more and more on electric power. But, from my very limited experience of watching points at our strip, it does still seem to have it’s share of problems.

On the subject of the OS 29, I’m sorry my figures weren’t that clear. It was a bit of a jumble I must admit. So to make it as clear as I can, firstly I’m only talking about the maximum power of the engine, I’d like to consider that the prop suitability for an individual model is really a separate issue. The peak power is at 14800rpm, not 17600, this is simply to indicate the engine will reach this speed. They were all an actual test runs. The torque is at it lowest point here. It you did indeed chuck a 7 by 9 on the front you would get the figures that I said, 125.5mph, at the maximum BHP at around 14740 ticks. Reducing the revs to 10000 by substituting a 10 by 5, maybe, lowers the BHP to 0.375, (not like what I put first, 0.37.5!?).

So the long and the short of it is, if you had two identical models, one with a 7 by 9 on, and the other with what ever prop reduced the revs to 1000, say around a 10 by 5, the first would go twice as fast as the second. Or put another way, the first would do 15840 foot-pounds of work in one minute, the second 12375, simply because the first is more powerful at those revs, although the second is at the max torque.

Personally, I think it’s always been quite difficult to get an indication of the power from a torque graph, so that’s why the BHP graph is used.

Coming to the Super 60, and considering the aeroplane, this is obviously always going to be a gentle plane to fly, so from the beginner upward everyone is going want a relatively slow revving, fine pitch prop, so the 10 by 5 might be on the button. Even though the power is down, it probably doesn’t matter, there is still more than enough, as with many models. So, at the end of the day, everything has to be taken into account. And maybe it just comes down, as always, to the old suck-it-and-see technique, just try a handful of propellers.

Interesting discussion, lets hope that eventually we can make something of it… …I have a feeling the electric issue has further to run…

PB

[kal wise]

a year a go i converted wot4 to electric, the setup was

XYH50-55 580kv Brushless Outrunner £24

ESC 60a === £16

5000mah 4s you can use 5s or 6s for this motor

4 std servo

 

still flys very good, if you need help pls let me know.

 

[Bob Moore]

Thanks for that Kal. I've pretty much finished my Wot4 conversion now with the gear as listed in this thread here Smaller motor and only 3300 mA 4s but it seems to shift a lot of air. I'm just working out how to push some air through the fusi to keep the 80 amp esc cool. I've seen the scoop on Chris Foss's design so will do similar. With luck I may be at the flight test stage soon

[gordon rigg 1]

I was a little disappointed when the Rochdale Garden centre pushed me of the google Gordon Rigg top places

I'm the other bloke with the same name who flies various things, sometimes with me actually on them

 

Thanks for that specific info on the Wot 4 electreic conversaion. 50004s should work out similar to 4000 5s, after all its the same actuall joules in there. With 5S it'd probably just need a diffferent prop on it, and perhaps an 80A ESC - I'm guessing a cheap 60A shouldn't go near its current limit. I usually use my 5S4000 in a heli with an Align 60A ESC and that has been fine.

 

However in this case I decided to stick a .50 heli engine in this Wot4 for now. If my lad get rally interested maybe the next one will be electric.

 

Gordon

[kal wise]

Hi Bob,
I did not need any air slot as the esc and the motor barely got warm. I decided not to make any hatch/opening for the battery, instead access it through the top after removing the wings, I installed a switch to arm the plane from outside.

 

How did you balance the plane with the 3300mah 4s? when I tried 3350mah 4s I needed 90g of weight to balance it so i went for 5000mah 4s

 

Kal

[Pete B]

Posted by gordon rigg 1 on 14/02/2012 22:18:32:

I was a little disappointed when the Rochdale Garden centre pushed me of the google Gordon Rigg top places

I'm the other bloke with the same name who flies various things, sometimes with me actually on them

 

Blimey, if Google's right, you must sure breed some BIG pigeons up in Cheshire, Gordon!

 

 

Sorry, off topic - but couldn't resist it!

Pete

 

[Former Member]

[This posting has been removed]

[Bob Moore]

Hi Kal

 

I wish I'd made a similar access for the battery rather than done it the way Chris Foss suggests. Very awkward getting the battery in and out his way. And a bit late now having cut a hole in the bottom of the fusi.

 

With my battery as far forward as it will go the model is just about level balanced. It's listed weight is 380 gms. Maybe I put my motor a bit more forward than yours. I've mounted it so the prop will be in the same place relative to the cowl. The rear of the mount is 43 mm from the original engine bulkhead. I'll add just a little bit of lead to make the model slightly nose heavy as I believe it's recommended?

 

My esc does get a bit warm so I have made a cooling slot. Will possibly add a couple of small ones to the side as well for more ventilation too. I'm not sure how warm they should get?

[Bob Moore]

Kal , you mentioned you fitted a switch to arm the motor. Because of the high currents involved I didn't think switches could be fitted. What type did you use?

[Steve Hargreaves - Moderator]

Bob a Wot 4 is usually pretty tolerant of the CoG position so you may be OK with it as it is.....if you are doubtful in any way then add some weight....remember the saying..."Nose heavy, flies badly.....tail heavy....flies once"!!!

Like a motor an ESC will always get warm in use.....how warm? Well if I couldn't touch it after a flight because it was too hot I'd be concerned....

Some people use a fuselage mounted Deans connector to break the battery to ESC connection & then just before flying insert a shorted Deans plug to bridge the connection.....might this be an idea....?