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Prop hub type for 25 cc two stroke.

Old 11-14-2018, 02:31 AM
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Jim.Thompson
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Default Prop hub type for 25 cc two stroke.

I am converting a Chinese 2 stroke 25 cc engine. I plan to machine the prop hub. However, I don't know what type is suitable for this size engine.
By that I mean, is it customary to make and fit a 4 bolt type with a centre spigot? Or just a single threaded shaft to retain the prop.
Can someone advise please?
I am planning on trying a 17 x 6 wood prop for starters.

Jim.
Old 11-14-2018, 07:45 PM
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speedracerntrixie
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Jim, I would lean towards the single bolt hub. It will secure the prop just fine and you may find that the use of a 4 bolt hub would greatly reduce your prop selection. I don't think there are too many props that small that would have a large enough hub for 4 bolts. The only challenge may be getting it to run true but based on other projects I have seen you take on here and on RCG I confident you are up to the task.
Old 11-14-2018, 09:20 PM
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Jim.Thompson
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Originally Posted by speedracerntrixie View Post
Jim, I would lean towards the single bolt hub. It will secure the prop just fine and you may find that the use of a 4 bolt hub would greatly reduce your prop selection. I don't think there are too many props that small that would have a large enough hub for 4 bolts. The only challenge may be getting it to run true ........................
Thanks Speedracerntrixie,

That more or less confirms my thinking. I am confident about the centreing for true running. We how have a good dial gauge and stand for the old lathe in our local "Mens Shed".
I will purchase the prop first to get the boss outside diameter and the centre hole size before doing anything about it.
Thanks for the reply.

Jim.
Old 11-15-2018, 12:56 AM
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Jim.Thompson
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After a quick discussion with a engine rebuilder buddy of mine, I/we came up with this possible configuration for the manufacture of a prop hub for this little motor.
I will attach a quick draft. Mainly for discussion purposes.
And if alternative design concepts are in popular usage, I hope someone will post details etc.

Jim.

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