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Alan - 22 Jun 2004 19:01 GMT

Here's one for all you engine gurus.

My mate Rick has cooked his TT 50:-(

It's about three months old, (about 20 tanks) has been running on Prosynth
5% nitro and up until last weekend was fine. Sunday it sounded a bit harsh
and due to operator error, spat out a glow plug at some altitude, not a lot
of height, just enough to make Rick glad he'd been practicing autos on the
sim! (Reflex XLR, awesome graphics!).

A new plug was screwed in, this time tightly, and all seemed to be well.
Yesterday he went out on his own and after a short while phoned me to say
he'd had an impact with the hard bit at the bottom of the sky, bad enough,
all the usual damage, but when he tried to turn the engine over by hand, it
wouldn't. The backplate came off and there was the con-rod in two bits. NO
sign of overheating, nice and clean inside. At the time the engine was
running at more than three turns on the main needle and producing smoke.

The other factor was that he'd changed to Prosynth 10% and had mixed half a
gallon of 10% with the remains of the 5%, thus making approximately 7.5%
Nitro mix.

The motor came from Cyber and they have suggested by mail it was probably
due to a lean run........;-)

Any thoughts......he's going to borrow my Webra 52 in the short term.

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Beav - 23 Jun 2004 00:23 GMT

> Here's one for all you engine gurus.
>
[quoted text clipped - 13 lines]
> sign of overheating, nice and clean inside. At the time the engine was
> running at more than three turns on the main needle and producing smoke.

So was the engine running when it decked Al? It sounds very much like it was
(all that "usual" damage doesn't happen if the heli's in autorotation, no
torque from the motor turning the blades see?) and if it WAS, then it's
blown up post decking which isn't in any way unusual. A motor driving
bollocks all but a rotor shaft doesn't last long:-)

> The other factor was that he'd changed to Prosynth 10% and had mixed half a
> gallon of 10% with the remains of the 5%, thus making approximately 7.5%
> Nitro mix.

I don't see the link unless the engine crapped itself in the air. Mind you,
I like to KNOW how much oil my fuel has.

> The motor came from Cyber and they have suggested by mail it was probably
> due to a lean run........;-)

It might also be due to revving it's leg off doing a nice shaft run

> Any thoughts......

See above.

he's going to borrow my Webra 52 in the short term.

Oh f.ck me. Don't ring me up:-)

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Paul McIntosh - 23 Jun 2004 23:53 GMT

Conrods don't usually break while running normally. I also doubt that a
lean run would do it as clearances normally get bigger as the engine heats
up. Most likely the quick stop at the bottom of the drop caused it.

Only other thing I can think of if it was REALLY lean, the big end might
have siezed on the crankpin. That would be very obvious on disassembly.

--
Paul McIntosh
http://www.rc-bearings.com

> Here's one for all you engine gurus.
>
[quoted text clipped - 28 lines]
> Remove the dots to reply
> http://heliweb.users.btopenworld.com/

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Beav - 24 Jun 2004 16:57 GMT

> Conrods don't usually break while running normally. I also doubt that a
> lean run would do it as clearances normally get bigger as the engine heats
> up. Most likely the quick stop at the bottom of the drop caused it.

Actually Paul, I've discovered that the engine was running at the "end of
the flight" at which point all load was removed but the motor couldn't be
shut down. No load and with the throttle stuck open, it revved itself to
death like ANY engine would in those circumstances.

This thread should really be re-titled to "Engine death" without naming the
engine in question. (IMO)

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Beav

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Paul McIntosh - 24 Jun 2004 22:28 GMT

That clears it up! Thanks. I was going on the assumption that the engine
died upon impact as there was no other facts presented.

--
Paul McIntosh
http://www.rc-bearings.com

> > Conrods don't usually break while running normally. I also doubt that a
> > lean run would do it as clearances normally get bigger as the engine heats
[quoted text clipped - 16 lines]
> Beavisland now lives at
> www.beavisoriginal.co.uk

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Beav - 25 Jun 2004 00:08 GMT

> That clears it up! Thanks. I was going on the assumption that the engine
> died upon impact as there was no other facts presented.

As I first heard about it, I was assuming the engine died and THEN the heli
followed it which would've put the engine under suspicion. I talked to the
owner (he rang me last night) and that's when I learned the heli developed a
glitch (mechanical or radio I don't know yet) which resulted in the heli
dying first:-)

The heli rotated violently to the left indicating a loss of tail drive, but
it could easily be an electronic failure, but one thing it wasn't, was an
engine failure. That happened while it was killing itself to death lying on
it's side.

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Beav

Please note my E-mail address is "beavis dot original at ntlworld dot com"
(with the obvious changes)

Beavisland now lives at
www.beavisoriginal.co.uk

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Model Forum / Radio Controlled / Helicopters / June 2004

TT 50