Brushless equiv.

[Terence Lynock]

 

What would be the brushless equivelent of a Mills .049 glow? converting a Mills Beam to lecky with slight modificatashuns,

 

regards,       Terry

[Klippy]

Hi Terry, excuse my ignorance, did Mills ever make a glow?

[Frank Skilbeck]

I put one of these in an Estes Canard instead of a Cox 049 http://www.brchobbies.co.uk/?page=shop&item=193. Plane didn't fly with the Cox, not enough power, but went well on this with a 3s lipo and 7 x 7 prop. To get 049 power you could prop down to a 6x4 or 7x5.

[Tim Mackey]

Yeh, 100 Watts + will be fine.

Heres the "live" link that lazy old Frank couldnt be bothered to insert correctly

[Terence Lynock]

Not sure on engine type thinking on it but the Mills Beam was designed for the replica Mills .049, decided to build a modified version that has a fuselage about as crash proof as it can get, dont mind making new wings as long as the fuse survives intact.

The wing for the Mills Beam is simple to build and doesnt take much material., I have plenty od spare 2812, 2822 and so on sized motors which I think should do,

 

regards,      Terry

[Simon Chaddock]

Like you Tony I was puzzled by the reference to a "Mills 049 glow" except of course that 0.75cc is near enough 0.049 cu ins but to the best of my knowledge Mills never made a glow. 

[Steve Hargreaves - Moderator]

I think that rather than try & replicate the power of an engine with an electric motor you should go back to first principles & look at the watts per lb rule PLUS the type of model you are going to fly. Electric motors & glow motors are very different in their power delivery & torque characteristics & this can really show up with smaller designs.

 

In a fit of nostalgia I recently built a DB Mini Tyro (32" R/E model) which I used to fly on a DC Sabre 1.5cc diesel swinging a 9x4 prop....I reckoned it would weigh about a pound so went for 100watts....sure enough it weighed 17oz ready to go & I had 110 watts available. It was a complete animal to fly & tried to roll over every time I opened the throttle above half. I propped down to achieve 50watts & it flies nicely now...just like its earlier ancestor........all of which leads me to ask...does a 1.5cc diesel turning a 9x4 prop really only produce 50watts of power??

[Tim Mackey]

Thats a very good point Steve - and I think reflects the fact that model type / flying style can have a big influence over the 100Watt per lb "rule". This should be considered a guideline only, and many models I have, fly perfectly well on much less than 100 WPlb. Of course, just like with IC, there are people who actually want to fit grossly overpowered motors into their models, but almost always these are not scale type models, which do IMO, fly, and look far better if flown at proper scale speed and in a scale manner. This includes a 'plane which needs a full length of strip to get away, gently rises to a reasonable altitude, and will never do a loop as long as it lives !

[Bert]

Posted by Steve Hargreaves on 16/07/2009 09:39:39:

........all of which leads me to ask...does a 1.5cc diesel turning a 9x4 prop really only produce 50watts of power??

 

Yes, it probably does, you have to let IC engines reach the top of their curve to get full power - try it on a 7x5

 

Bert

Edited By Bert on 16/07/2009 10:23:34

[PatMc]

Even with a 7x5 it would still only produce about 75 watts. Of course that's at the shaft not power input but electric props are more efficient in both shape & useable size so the difference comparisons can't be all that much.

 

BTW Steve, 1.5 diesel seems big for a 32" Tyro one of my first rc models was a 45" Tyro - started as single channel later changed to 2 function with my first Futaba set. It had a Frog 1.49 which was just about enough power until I fitted a silencer. Then it got upgraded to a Fox 15. AUW was about 50 oz.

[Steve Hargreaves - Moderator]

It might have been an 8x4 Bert....it was about 20 years ago & long since gone from the hangar but off course you are right...IC engines need to rev to give of their all where as with electric you get full torque at.....er...zero revs but my basic point was that IC & electric are different & rather than try & replicate one or the other we should go back to first principles & use the watts/lb rule whilst taking note of the model type & the sort of flying we want to do.....fewer blind alleys that way in my opinion.....

[Steve Hargreaves - Moderator]

I've always been a bit power mad Pat......!! Of course you are right...I think the stated power source was 0.5-0.75cc but I wanted speed & performance so I stuck a big engine in it & upgraded the spars to spruce!!!!!

 

Ah.... there was no stopping me in those days!!!!