TT GP42 problems
09-08-2004, 01:53 AM
#1
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TT GP42 problems
The engine is a Thunder Tiger GP42 which now has about 30 minutes running and puts out plenty of power.
It was run in with a tank on the ground and the rest of the time in the air with a rich two-stroke needle setting and a 10.5 x 5 prop.
After the first run the engine seemed to have fouled the plug because it would stop abruptly about three seconds after the glow-clip was removed.
Changing the plug fixed that problem and haveing several excellent flights yesterday the engine was running like a watch with good power, transition and an idle as smooth as a swiss watch.
Today, on the first flight, all was going well with a number of idle-by passes being made without problems.
Then the engine cut and the plane was landed deadstick.
On restarting the engine it exhibited the same symptoms of a fouled plug -- stopping abruptly a few seconds after the plug clip was removed.
I've encoutered this fouling before when running in ABC/ABN engines and it seems to be caused by microscopic particles of aluminum being deposited onto the plug filiament and reducing the area of platinum catalyst.
Once again a plug change fixed the problem -- but on the very next flight the new plug fouled and another deadstick resulted.
This is leaving me a little stumped.
I usually run in my ABC/ABN engines using a cheap plug that I can afford to lose to aluminum fouling but this engine has now fouled three and I'm reluctant to put an OS#8 in until it settles down.
The fuel is 18% coolpower, 7% castor, 70% methanol and 5% nitro. The methanol is not contaminated with water because I have been using exactly the same batch in my little Norvel 061 with no problems at all. I'm using 25% oil with a castor component because this is a plain-bearing engine and I don't usually drop the oil on a new engine down to 20% until it's had at least 45 minutes running.
I will try mixing a new batch of fuel tomorrow however, and see whether this helps.
But, if anyone else has any ideas in the meantime...
It was run in with a tank on the ground and the rest of the time in the air with a rich two-stroke needle setting and a 10.5 x 5 prop.
After the first run the engine seemed to have fouled the plug because it would stop abruptly about three seconds after the glow-clip was removed.
Changing the plug fixed that problem and haveing several excellent flights yesterday the engine was running like a watch with good power, transition and an idle as smooth as a swiss watch.
Today, on the first flight, all was going well with a number of idle-by passes being made without problems.
Then the engine cut and the plane was landed deadstick.
On restarting the engine it exhibited the same symptoms of a fouled plug -- stopping abruptly a few seconds after the plug clip was removed.
I've encoutered this fouling before when running in ABC/ABN engines and it seems to be caused by microscopic particles of aluminum being deposited onto the plug filiament and reducing the area of platinum catalyst.
Once again a plug change fixed the problem -- but on the very next flight the new plug fouled and another deadstick resulted.
This is leaving me a little stumped.
I usually run in my ABC/ABN engines using a cheap plug that I can afford to lose to aluminum fouling but this engine has now fouled three and I'm reluctant to put an OS#8 in until it settles down.
The fuel is 18% coolpower, 7% castor, 70% methanol and 5% nitro. The methanol is not contaminated with water because I have been using exactly the same batch in my little Norvel 061 with no problems at all. I'm using 25% oil with a castor component because this is a plain-bearing engine and I don't usually drop the oil on a new engine down to 20% until it's had at least 45 minutes running.
I will try mixing a new batch of fuel tomorrow however, and see whether this helps.
But, if anyone else has any ideas in the meantime...
09-08-2004, 07:51 AM
#2
RE: TT GP42 problems
Mine took a long time to fully break-in. I think the sleeve bearing takes a lot longer then the piston-cylinder. I would use extra castor for a gallon or so, cheap plugs and, as someone said in an earlier thread, "run the snot out of it." They really go when broken-in.
09-08-2004, 08:01 AM
#3
RE: TT GP42 problems
I use idle bar plugs for the first gallon or so, if the engine will run on them. Not only are they cheap, but the idle bar helps to keep the aluminum of the element.
