Electric conversion

[PeteC]

I've just picked up an old balsa model of a Tiger Moth (48" wing span) which appears to have been flown using an Irvine 40 Mk. II motor (I say "appears to", as the motor is separate to the model).

 

If I wanted to convert to electric power, what motor size and ESC should I be looking at ?

 

I'm new to this sort of thing, so any advice weould be appreciated.

[Alan Hilton]

Talk to George at 4 max he is clued up It’s also worth looking on. the recomended set up section on the same web page

[John Lee]

I've built the RBC Tiger Moth which is that size & used the power train from one of the Chris Foss Foamy Wots that I had lying about, it is more than enough & I never use full power.

 

If you look at the RBC kits specs Link and that of the DB Sport & Scale version which is the same size Link it should give you a good idea, but I found the set up is not critical.

[Murat Kece 1]

Hi assuming your plane will be about 5.5lb, Eflite Power 25 870kv or its equivalent 4Max 3547x800kv should be more than enough.

[Murat Kece 1]

TigerMoth48-Electric.pdf

[kc]

There is already an electric setup for the DB Sport & Scale 48 inch Tiger Moth .   Yours could be heavier of course.  Get the Lipo as far forward as possible to save having to use lead.

[kc]

I also noticed that DB Sport & Scale sell a vacformed cowl as a spare for their electric Tiger Moth  which might be of use to you.

[MattyB]

1 hour ago, Alan Hilton said:

Talk to George at 4 max he is clued up It’s also worth looking on. the recommended set up section on the same web page

 

Sorry, but I'm not a fan of the "just ask George" approach. Sure, he is knowledgeable on sizing powertrains, but shouldn't a newcomer really develop some knowledge of how their model is powered and why we size stuff a certain way? Without developing this they will be forever reliant on others and/or are much more likely to have an escape of magic smoke?! Far better to teach the man to fish...

 

25 minutes ago, Murat Kece 1 said:

Hi assuming your plane will be about 5.5lb, Eflite Power 25 870kv or its equivalent 4Max 3547x800kv should be more than enough.

 

Hmm, suggesting a motor isn't terribly useful either without a prop or cell count recommendation - remember, the OP appear to have no experience of electric flight.

 

@PeteC, here are some resources that should help you to pick up some of the basics - get a brew on and spend an hour or so leafing through them, then come back with questions and we will try to help: 

• Crib sheet on powertrain selection from 4-max
• Another decent article on core concepts and sizing kit (the example at towards the bottom is useful)
• Threads on ESCs. motors and batteries in the beginners e-flight forum:

 

Edited February 16 by MattyB

[MattyB]

PS- Playing with the variables on eCalc can also be a good way of learning the relationship between prop size/pitch, motor Kv, cell count, and motor mass. They also have a setup finder tool as well, though not all the services are free...

 

https://www.ecalc.ch/

[Geoff S]

Wasn't it Biggles Elder Brother who suggested starting at the propeller and working back - certainly when converting from a glow engined design?  Say the original power drove a 12x6 prop at 8k rpm then that's what you might aim for with an electric motor.  I tend to go for a much bigger, heavier motor when doing a conversion because you'll need the weight anyway and the motor will be very underused and stay cool.  The next thing to take into account is the likely all-up weight and that will give you an idea of the power you need (100 watts/lb is a common assumption but something like a Tiger Moth might be OK for scale flying with less (say 80 watts/lb).  One advantage of fitting a much bigger motor than you need is that it gives you the option of increasing the prop pitch or diameter to increase power.

 

Just look at the suggestions at 4Max for various models similar to yours and go from there.  I tend to go for a 4S LiPo set up on medium-sized models because there's less current for the same power and the weight is often useful.