electric to oily motor conversion

[thunderstreak.keith]

Hi just a quicky, I have an old glider used to run on 540/50 size brushed motor 8.4v nicd. I want to put a cox 049 on the front. would this be ok? Its just to get it in the air from a flat field. once up and the motor shut down this old plane stayed flying for ages. just wondering if the rpm of the cox minus weight of heavy nicd batts and speed controller would compensate for the substitution af a small engine such as a cox. i have a texaco and 3 other o49 motors

cheers keith

[Piers Bowlan]

Some information about the model might help; span, weight, model name if you know it? Perhaps a conversion to a modern brushless motor/LiPo battery conversion might be better?

[Cuban8]

Having cut my 'flying teeth' on a Graupner Dandy with a pod mounted Cox back in the 70s, yes, you could go down that route. However, from a purely practical and convenience standpoint, a small brushless setup will be far superior IMHO. If you fancy noise, an oily model and oily hands, high nitro fuel and all the prop flicking (mine had a spring start) and a dose of nostalgia, then a Cox will do nicely. Whatever floats your boat, naturally.

Edited By Cuban8 on 05/03/2020 13:26:33

[Shaun Walsh]

If it had a brushed motor/Nicad power system originally then I would hazard a guess that there should be room for a brushless/ Lipo setup which would be cleaner and quieter and would also allow you to regulate power and go through a number of power/glide cycles rather than climb until you run out of fuel then glide down.

[Piers Bowlan]

I think a Cox .049 motor would weigh just a fraction of the weight of the old brushed 540 motor and 8.4v NiCd battery. I think you would need a fair bit of additional lead in the nose along with the Cox motor to get the c of g in the right place.

[Old Geezer]

One ( minor? ) issue with a lil' Cox on your glider is the noise they can make. Such a high pitched, penetrating noise might draw unwelcome attention to your activities. Unless you've already spent the money and have committed yourself to i/c power I think you couldn't do much better than follow Shaun's advice above. (LiPo Outrunner & Folding Prop'.)

[Old Geezer]

One ( minor? ) issue with a lil' Cox on your glider is the noise they can make. Such a high pitched, penetrating noise might draw unwelcome attention to your activities. Unless you've already spent the money and have committed yourself to i/c power I think you couldn't do much better than follow Shaun's advice above. (LiPo Outrunner & Folding Prop'.)

[Solly]

Typical of the electric brigade. Someone wants advice on i/c conversion and all he gets are biased reasons why he shouldn't do it.

[Tim Kearsley]

Posted by Solly on 05/03/2020 18:09:42:

Typical of the electric brigade. Someone wants advice on i/c conversion and all he gets are biased reasons why he shouldn't do it.

No, he's getting advice that a modern brushless setup is far more practical, not "biased reasons". Don't start yet another " I.C. versus electric" diatribe for goodness sake.

Tim.

[Solly]

Keith, I'm sure the Cox engine will be fine. You might have to use some lead in the nose for balance. Cox engines are very well made and last for years.. please don't be put off about getting oil on the model . Contrary to rumours it's easily wiped off with a wet rag and is not highly poisonous.

[Trevor Crook]

Was the original power plant in the nose? I had an electric powered glider many years ago with a brushed 500 and 6-cell nicad pack under the canopy. That lot was very heavy, so would have needed a lot of lead if a small glow motor had been used.

Personally I too would recommend a modern electric powertrain with a bit of ballast if needed, but if you are set on piston power, what about a small diesel? No glow battery to carry, it will swing a bigger prop at lower rpm and make less noise, and the smell is lovely!

[brokenenglish]

OK, my bit of input:

I'm an i.c. engine fan and always have been. However, there's no doubt that on a powered glider type of aircraft, an electric setup would be a lot more convenient to operate, not to mention the possibility of switching the power on and off at will. Even being an i.c. man, I would go electric in a powered glider.

However, if you really want to use an engine, a small diesel (PAW) would be a much better bet than a reed-valve 049. Production quality isn't the issue. A reed valve with no accessible carburettor is a recipe for inconsistent running, and that's what you get. I've never understood why so many people accepted that...

[PatMc]

A 540 brushed motor will weigh around 160 - 180 gm against a Cox 049's weight of about 60 gm. If the original battery was situated around the cg a nose weight in the region of 100 - 120 gm isn't outlandish. However the power of a Cox 049 is nothing like a 540 on 8.4v. In both power and weight a Cox is about on a par with a brushed 400 motor (typicaly 70 gm) on 8.4v.
You don't say how much the model weighs or give it's size but on the basis of original power versus proposed power I think it unlikely to give a satisfactory performance. If you are intent on following Solly's prejudiced advice then, IMO, an 09 glow or a perhaps a PAW 1cc diesel would be more practical choice.

For comparison, about 25 years ago I designed & built Henry, the power glider model in the photo, to be powered by Cox 049 Babe-Bee. It was 63" span, had a decent climb & glide performance, was capable of some loops & mild aerobatics. It was also flown as a pure glider quite a lot at my local slope site. A year or two into the Henry's life I converted it to electric using a 400 brushed motor with 7 x Sanyo AA 800 mAH cells similar to the ones used for Rx's at the time. Using the same 6x4 prop as used by the Cox or a 5" folder (as an the photo) power & performance matched that of the Cox despite the increase in weight of 3 extra cells.

[Former Member]

[This posting has been removed]

[Bob Cotsford]

It sounds as though the OP has some Cox 049s already and just wants to know whether one would do the job. I'll just say "it depends on the model". Many years ago I had a couple of powered gliders using Cox 049s, one a Graupner kit, an ASW24 maybe? 60odd inch span. The other was an Orange Box, a 72" lightish soarer. Both flew on the 049 power but climbs were very slow, on a poor day marginal. The Orange Box ended up with a 540 size motor on 7.2v which was much better.

If you want to use the 049s for a bit of nostalgia and the airframe is 6 foot or less and lightly built then go for it. If you just want rid of the 540/nicad setup either go for a small brushless/LiPo setup or just replace the Nicad with a 2S LiPo. Worked for me on a Zagi with a 540 and Jetti brushed ESC.