RCMF

Level 1 => IC Engines => Topic started by: NickK on June 12, 2020, 18:21:29 pm

Title: Inverted 2 stroke ????
Post by: NickK on June 12, 2020, 18:21:29 pm
Evening Chaps.

Some years ago I bought a 2nd hand Gangster 52 airframe. My second ever model was one of these back in the early 80's and I always wanted another one.

The previous installation was obviously an inverted engine. Unfortunately I'm a bit of a half wit with glow engines so its going to need all the help it can get to start and run reliably. My only other glow model is a DR1 with an ASP 90 4 stroke which runs fine inverted but I'm not confident about an ancient Super Tigre 51 which I intend to fit in the Gangster.

I just want to get it flying with the minimum of messing about although the captive nuts appear to be imperial (very close to M4 so according to Mr Google PROBABLY 4BA  but not necessarily.) Have found some on Ebay if they fit.

So my question to you experts on the infernal combustion engine is will it be OK inverted or would I be better off chopping it about and installing the engine the right way up. Please take into account my incompetence in your answers  ::)  ;D

I would actually prefer to convert it to electric but the engine mount holds the nose wheel in place and whilst this is by no means beyond the wit of man to solve its a bit more messing about than I really want.

Thanks in advance for any advice
Title: Re: Inverted 2 stroke ????
Post by: PDR on June 12, 2020, 18:35:34 pm
It's up to you, but an ST51 is rather excessive in a Gangster 52. I've had several over the years with a range of engines (Merco 35, HP40 (silencer and pipe), OS40-FSR (piped), Irvine 40 (piped), Super Tigre X45 (silencer and pipe in two different aeroplanes) and with the more powerful set-ups you had to be sensible with the throttle in dives or the tailplane bailed out.

Pretty well all my FAI-F3D pylon racers had inverted engines, and (remembering that you have to be able to reliably start the Engine within a 10-second window to be able to peak it at the right time for take-off) the recommended technique was to have your caller hold the model at waist height with the left wing resting on his foot. You could then have full access to the plug, the exhaust and the fuel pipes for easy starting with the engine now effectively a sidewinder (so it doesn't flood) for starting.

PDR
Title: Re: Inverted 2 stroke ????
Post by: NickK on June 12, 2020, 19:11:16 pm
Thanks, Pete - Duly noted. I know the ST is probably a bit much but I do like plenty of power. Have to say the more I look at it the more I'm tempted to do the extra work and go down the leccy route.

Had an OS 40 in my old one all those years ago.

Good advice on the starting technique - it was flooding on starting that was worrying me
Title: Re: Inverted 2 stroke ????
Post by: PDR on June 12, 2020, 21:09:30 pm
Well the lecky power would be something like an Axi 2826 on 4s prop'd for about 50-55A. If you want serious speed then it's a 2826/8 on a 9- or 9-8(ish) or a more tractable setup would be a 2826/10 on an 11" prop. The /8 will be a bit noisy, because it wioll probably be doing more than 15,000rpm - this motor on 4s/3300s is what I have planned for a Sport40 Midget Mustang I hope to start building shortly (I've found an untouched kit).

While the Midget Mustang wasn't the fastest Sport 40 racer it was a really nice flyer. I won many races and the odd race meeting with my two (one irvine powered and one Rossi powered), got into the finals of the British Nats and placed second in the scottish nationals. I think the lecky version will carry more pitch, so I'm hoping it will be nearly as fast...

PDR
Title: Re: Inverted 2 stroke ????
Post by: PDR on June 12, 2020, 22:01:44 pm
I should stress that this is my intended power system. It feels right, but I haven't tested it yet. I'll let you know when I have.

PDR