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MVVS 35 IFS Gasser - Severe vibration issue

Old 06-28-2011, 08:54 PM
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Peter_OZ
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Default MVVS 35 IFS Gasser - Severe vibration issue

Folks,
doing this post on behalf of a good friend of mine.

He has a MVVS 35 IFS Gas/petrol engine part No. 30981 with about 2 hours running time.

It was fitted to a 90" Spitfire, not that it really matters.

The issue is that at high RPM it vibrates to the point that the airframe was suffering damage. If you held the model at full RPM the high frequency vibration physically hurt your hand.

He is a very experienced modeller with many years operating large scale Warbirds and Gas/Petrol engines.

Measures taken:

- balanced the prop, swapped props
- balanced the spinner, removed the spinner
- removed the engine, fitted it to the bench and the vibration is still there


It is not an airframe issue as he has now fitted a MVVS 40 Gasser and it is perfect. Same spinner and prop too.

Is this a known problem with this model engine?

Any constructive, informed thoughts appreciated.

cheers
P
Old 06-29-2011, 01:44 PM
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pe reivers
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Default RE: MVVS 35 IFS Gasser - Severe vibration issue

It is not a problem that the 35 should have. Did he balance the prop completely? same prop on the 40cc?
Prop balance basic items:
1) prop blade angle balanced?
2) prop blade shape identical?
3) prop mounting hole symmetrical?
4) tip - tip balance OK?
5) hub balance OK?
6) do the prop blades track well? (may be a bent crankshaft issue, or prop mounting face)

PS
You say not an airframe issue. I am not convinced of that. Different engine in same frame and same prop have different harmonics that they can share. Just changing one single component can make a world of difference.
If the items 1 to 6 are OK, it surely is the combination of all components that play havoc.
I am inclined to suspect item 6), but hard to tell from the other side of the pond.

Old 06-29-2011, 05:16 PM
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Peter_OZ
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Default RE: MVVS 35 IFS Gasser - Severe vibration issue

1 - 6 all done and ok.

He removed the spinner to eliminate that as a source.

He used same prop on the 40 - on the 40 it is fine. Same spinner fitted to the 40 and it is fine.

He put the 35 in a different model - it caused same vibration. Hence not an airframe issue.

He is simply perplexed as to what may be causing it. Everything he has tried points to an issue in the engine.
Old 06-30-2011, 01:57 PM
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Default RE: MVVS 35 IFS Gasser - Severe vibration issue

Are you sure the prop tracks well on the 35? How does the spark plug look? Ignition timing may be off. Too much carbon inside the head? Something is out of whack. The 35 normally is a smooth runner.
Old 06-30-2011, 02:07 PM
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Peter_OZ
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Default RE: MVVS 35 IFS Gasser - Severe vibration issue

spark plug? That is a new one! The engine has at most 2 hours on it.

It is not a propellor issue as he used same prop on the 40 and it is smooth as silk.

I would suggest you offer to take the engine and check it over for him. Would you be happy for him to send it to you? If it was me I would be looking for that as a minimum, not my engine so trying to get best outcome for him.

at present he has an expensive engine he cant use and had to purchase a new one by way of a MVVS 40 to overcome the problem.

If so please advise how he can do that as he is in Australia.
thanks
Old 07-01-2011, 04:26 AM
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pe reivers
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Default RE: MVVS 35 IFS Gasser - Severe vibration issue

I tried to guide you through a problemsolving process. I am sorry if you do not want to go along with the questions I have. I do have a reason for asking.

This is not the place to discuss warranty issues.
If you/your friend thinks it needs warranty, or a factory checkup, contact the seller directly. he will instruct you on how to proceed.

BTW, I am MVVS dealer, not the factory. If you/your friend bought from me, let him contact me directly. My contact data are on the invoice. If the invoice is lost I have back-up, send me a PM.

He also may contact https://www.petenplanes.com.au/ who seems to be dealer on Oz.
Old 07-01-2011, 01:57 PM
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Peter_OZ
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Default RE: MVVS 35 IFS Gasser - Severe vibration issue

mate firstly this is not my engine.

Secondly and you do not seem to be understanding here. He has checked all the things you mentioned and all is fine with those. The only things he did not check is spark plug and carbon, why would there be carbon build up on an engine with less then 2 hrs on it?

Obviously you do not want to help him.

I'll advise him accordingly.
Old 07-02-2011, 05:30 AM
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Default RE: MVVS 35 IFS Gasser - Severe vibration issue

Carbon and spark plug checks are needed to see if the engine has run with advanced ignition, or possibly selfignition by glowing carbon particles.

I suspect however, that the engine has seen a heavy prop strike that bent the crankshaft. Hence my question of prop tip tracking.
I do want to help, but your assistance raises questions.

having said that, The 35cc engine would at least be two years old, if not more, so it should still be under extended warranty if it indeed has only two hours running time. My advice was, and still is, to have the original seller help the guy through his paces to get the engine to MVVS for a checkup.

To be frank, I have a uneasy feeling about this mystery around "your friend". If it were my customer, the engine would be on it's way to MVVS by now unless the customer didn't want to. MVVS wants all engines with major issues to be sent to them for inspection. This is not my freedom of choice. They have an excellent, ISO9000 certified, engine repair department and have very quick return of serviced engines.

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