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MVVS 45 IRS MG - Prop Drilling

Old 02-01-2008, 03:08 PM
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Airial
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Default MVVS 45 IRS MG - Prop Drilling

Not another question about how to drill props?!??!

This engine has three peripheral bolts equally spaced around the crankshaft, however the propdriver has six holes.

The instructions do not explain how the three bolts should be orientated on the prop hub or if all six holes (per the prop driver) should be drilled.

The manufacturer obviously thinks that this engine does not need six bolts (unless I'm missing three) and that three will be enough, what i don't understand is how the prop will be balanced with two bolts one side and one bolt on the other.

Someone put me out of my misery and tell me I'm not being stupid (or that I am)?!?!

Eitherway works for me!

Thanks
Old 02-01-2008, 05:43 PM
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pe reivers
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Default RE: MVVS 45 IRS MG - Prop Drilling

They shoot horses don't they?

Jest aside:
Put a bolt in every other hole. They will be perfectly balanced.
I just conducted a complete series of tests with only two bolts + the central bolt. That is enough to keep on compressing a wood prop, so you will have to know when to let well enough be good enough. Tighten evenly, and do not use full muscle force. 6 bolts is way too much, because the central bolt takes most of the load, and there is only so much crush load that wood can take. Light wood, AKA blond wood because of it's lighter color, compresses more easy.
Old 02-01-2008, 08:10 PM
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Airial
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Default RE: MVVS 45 IRS MG - Prop Drilling

Pe,

You are a pretty scary guy - to joke in another language is one thing but to get that kind of reference is....well.... scary! and it makes me very humble.

Thanks for the response - this is my first Petrol engine and I'm a little daunted by the choice (range) of Props available, the motor is going into a 2m Extra with a KS 4 chamber cannister on a swan neck header- I was planning to go with a Mejzlik 24x10 prop.

What do you think? at £50+ each I'd like to get it right (or as close as possible) first time.

Would there be any benefit in trying wooden props (would this give any indication of the optimum Carbon size)? If so where to start 23x10?

Thanks again
Old 02-02-2008, 04:36 PM
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pe reivers
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Default RE: MVVS 45 IRS MG - Prop Drilling

A wooden prop is very cheap, and the perfect way to try out the best combo with plane/engine/prop/muffler
I would suggest a 22x8 or 22x10 for initial trials. The MVVS will pull a 24x10, but if you use the 3207 side muffler, slightly higher rpm will perform much better.

Use the three bolts provided. It is more than enough. With wooden props, check for tightness often, and do not over-tighten.

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