What engine/muffler combo, Raptor 30....

[Farmer Giles]

Hi, I'm getting seriously pee'd off with my Raptor 30, well more specifically the engine. I spent an hour yesterday up at my club with one of the experienced heli flyers try to set the mixture correctly and in the end we gave up. The only thing I have left to do is weaken the idle mixture abit to see if that helps out but if that's no good then it's replacment time. I'm not going to spend hours ****ing about with it.

The engine is a relatively new Redline TT39 with a Weston pipe fitted.

So what are other people using in their Raptor 30's ??

I've seen the OS37 on the FL website but I thought the 30 sized OS was .32 or is the .37 the latest offering.. I also have no idea on mufflers.

It will be used for sport flying, circuits and maybe the odd flip, roll, bit of inverted as my flying skills developes. Also running on 20% fuel.

any input appreciated.

cheers

[electricsceadu]

the os 37 is the new offering from os
you may be limited by the choice for the pipe as many have gone to stocking 50 pipes as the 50 size heli is more popular these days
but the mp30 (if you can find one), zimmerman or a hatori are good pipes
i have no idea on the western pipe (i've never used one) but as you have one its worth trying the new motor with it

but i would check that the fuel system is all ok on the raptor and that the exhaust isn't blocked and the pressure nipple isn't blocked

the tt39 can run well, the carburation can be tricky to sort out but once sorted it does run ok
i had a tt39 that was class as junk after a few tries at getting it going by a chap in my club, i bought the engine and spent a little time tuning it and only stopped running it when i left changing the rear bearing to late after 30 gallons of fuel and it took the piston and liner out
i did run the bottom end on the rich side to stop it hanging on the pipe when the throttle was lowered
and they do run warmer than other engines

[mark Taylor]

I use to use a os 37 with Weston one piece pipe with no probs
hope this helps
cheers

[trillian]

I have an OS37 in mine with a Zimmerman pipe and it has always run very reliably. I have been using Magnum 15%. Some days it feels like it has a bit less power but I rarely have to mess with the needle. With Magnum you get lots of smoke and this engine has always run a bit hot to the touch so I am not sure if it is at the optimum mix.

I have seen quite a few Raptors flying very well with the TT39 so I know it's possible.

[Farmer Giles]

cheers.

I am going to give it another chance by replacing all the fuel and clunk lines, adjusting the idle mixture and making sure everything is as it should be but it's on notice.

[Farmer Giles]

i did run the bottom end on the rich side to stop it hanging on the pipe when the throttle was lowered
and they do run warmer than other engines

by hanging to mean keeping higher revs when the stick is in the idle position, because that was something else is started doing yesterday but only as we were approaching a lean mixture..

[heliphil]

do a search as I recall re profiling the idle needle with a different taper at the end - after that they work well, otherwise its almost impossible to get the idle and main needle correct. Look on runryder....

http://www.runryder.com/helicopter/t...t=tt39+%3Cspan
http://www.runryder.com/helicopter/t...dle+needle+mod

[trillian]

cheers.

I am going to give it another chance by replacing all the fuel and clunk lines, adjusting the idle mixture and making sure everything is as it should be but it's on notice.

Well if it proves to be too fiddly you could always drop a .50 engine in there, change the gearing / fan and whatever and then have plenty of power even if on a rich setting (and maybe be able to run lower nitro).

[Farmer Giles]

Well if it proves to be too fiddly you could always drop a .50 engine in there, change the gearing / fan and whatever and then have plenty of power even if on a rich setting (and maybe be able to run lower nitro).

Can you run a .50 OK without turning it into a Raptor 50, bigger blades, boom etc ?


I'm sure the TT39 will be powerful enough if I can ever get it running right and , more importantly, consistant.. just want to know what I'm getting from one day to the next.

[trillian]

Can you run a .50 OK without turning it into a Raptor 50, bigger blades, boom etc ?

Yeah, you just need to change the gearing a bit because you would be running the bigger engine most of the time at lower revs, so to keep a decent headspeed it would need a lower gear ratio. The engine doesn't 'know' what size blades it is turning it only knows it is given a certain load at a certain rpm. The 50s rev a little lower than most 30's at the top end plus you'd be spending more time running it at less than max power. The only caveat being that with 550mm blades you may need to set the throttle / pitch curves so it does not reach wide open at too low pitch or use a governor (to prevent over-revving)

[electricsceadu]

by hanging to mean keeping higher revs when the stick is in the idle position, because that was something else is started doing yesterday but only as we were approaching a lean mixture..

the revs stay up due to a lean condition
its down to the needle profile
mine did sound like a bag of nails on tick over due to the rich needle setting but once the throttle was opened it was fine
i never did the carb mods to mine so i can't help you on that one

[David Drew]

I have an OS37 in mine with a Zimmerman pipe and it has always run very reliably.

Good combo

[Chris Hinds]

My TT 39 ran absolutely fine in the same model as you have, albeit with a Zimmermann silencer. I did find a few things that seemed to have an impact though -

1. Enya No.3 plug worked better than an OS No.8
2. Seemed to be easier to keep it consistent on 30% than on 20% or 15% fuel.
3. The needle settings in the book are a load of monkey nuts for my engine. I ended up about 2 turns open from stock on the low end to stop the symptoms you describe. The high end turned out to be about 4-4.5 turns open depending on Nitro content and plug.
4. The engine likes to run slower than you'd think, on stock gearing about 1750-1800rpm on the head made far more power far more consistently than running faster.

Cheers

Chris

[Farmer Giles]

My TT 39 ran absolutely fine in the same model as you have, albeit with a Zimmermann silencer. I did find a few things that seemed to have an impact though -

1. Enya No.3 plug worked better than an OS No.8
2. Seemed to be easier to keep it consistent on 30% than on 20% or 15% fuel.
3. The needle settings in the book are a load of monkey nuts for my engine. I ended up about 2 turns open from stock on the low end to stop the symptoms you describe. The high end turned out to be about 4-4.5 turns open depending on Nitro content and plug.
4. The engine likes to run slower than you'd think, on stock gearing about 1750-1800rpm on the head made far more power far more consistently than running faster.

Cheers

Chris

Well thats a couple of other things to look at then.

I am using an OS no.8 plug.

I set the head speed on my governor to just over 1700 rpm (16250 engine rpm) and when I was testing it without the governor it was all over the place but I have not idea how fast it was running, I suspect a fair bit faster..

I have a full bottle of 20% so I'll be using that for now.

At the w/e I will run it again and set the idle mixture and I'll aim for the richer side of things but I have not idea how many turns it's set to now, I presume it's still stock settings. It's certainly too rich at the moment though.

I'm also replacing all the fuel and clunk lines and removing the in line filter for now.

thanks for your post.

[Chris Hinds]

Martyn,

The biggest issue I had was with it seeming rich and not wanting to idle like you describe, but actually being a little lean hence the hanging on the pipe. I found that I needed to richen the bottom end significantly in order to get a clean mid range in the air. Unfortunately this meant the engine did tend to die at idle unless running 30% fuel due to the richness of the mix needed. If I was running on lower nitro fuel then I'd tend to blip the engine on the way out to the strip to keep it alight.

Good luck...

Cheers

Chris