Vmax7 connecting rod problem
08-25-2004, 10:55 PM
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Vmax7 connecting rod problem
Does anyone know if Norvel has solved their connecting rod problem on the Vmax7? Mine broke off the top of the rod right after startup for the first flight of the day on mine today and its' only had something like 20 flights on it (maybe). Havnt contacted LMH yet.
08-27-2004, 05:29 AM
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RE: Vmax7 connecting rod problem
I'm on my 3rd right now. I don't hold much hope for the one I'm currently breaking in. It siezed up the other day and there is a big scratch along the cylinder, I think from the wrist pin coming loose. I'll probably end up running it until it breaks all the way... I got it last week and it has about 15 minutes of run time on it so far.
The last one lasted just over 20 minutes, and the one before had worked beautifully for about 20-30 flights and broke suddenly in flight.
When I received the current engine, it was extremely tight at TDC and I couldn't even turn it over. I let it soak in oil for a day, and that didn't help too much, but then I heated the engine with a heat gun and it expanded the cylinder so the engine could turn freely. After it was expanded I would run backwards on an electric starter for a few seconds, drip some oil in it, and do it again. I would repeat that until I felt it was cooling off and getting tighter. After some time of this it got loose enough where I could flip the engine through TDC without it jamming up...
It has been talked about before, where the wrist pin is insufficently held in the piston because the piston isn't coined properly. I think that's what has happened to my V-7 now. Perhaps when the piston expands the wrist pin is free to drift out a bit and then snags on the transfer ports. If this engine ends up FUBAR, I'll probably take the next one apart and check the indents to make sure they're good enough.
The last one lasted just over 20 minutes, and the one before had worked beautifully for about 20-30 flights and broke suddenly in flight.
When I received the current engine, it was extremely tight at TDC and I couldn't even turn it over. I let it soak in oil for a day, and that didn't help too much, but then I heated the engine with a heat gun and it expanded the cylinder so the engine could turn freely. After it was expanded I would run backwards on an electric starter for a few seconds, drip some oil in it, and do it again. I would repeat that until I felt it was cooling off and getting tighter. After some time of this it got loose enough where I could flip the engine through TDC without it jamming up...
It has been talked about before, where the wrist pin is insufficently held in the piston because the piston isn't coined properly. I think that's what has happened to my V-7 now. Perhaps when the piston expands the wrist pin is free to drift out a bit and then snags on the transfer ports. If this engine ends up FUBAR, I'll probably take the next one apart and check the indents to make sure they're good enough.
