twybrow
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| posted on 21/2/08 at 12:53 PM |
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Engine cradle bolt size
I have to bolt my engine cradle onto my chassis. The cradle sits on top of the chassis rail. I have used 4mm plate on the ends of the cradle, that
will be bolted to the same size plate welded to the chassis. I have 2 bolts in each of the 4 legs, and wondered what size bolts people would use? I
currently have 8mm bolts in there (total of 8 bolts over the cradle). Please pic below for an idea of the arangement:
 
cradle attachment drawing
[Edited on 21/2/08 by twybrow]
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BenB
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| posted on 21/2/08 at 12:58 PM |
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If you're using 12.9 bolts 8*8mm bolts should be more than enough.....
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jacko
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| posted on 21/2/08 at 05:56 PM |
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10mm will do it
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indykid
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| posted on 21/2/08 at 06:11 PM |
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8.8 8mm bolts will do it too!
most engines are fastened in with maybe 3 M10 studs.
8 8mm bolts is more than plenty.
tom
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twybrow
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| posted on 21/2/08 at 09:11 PM |
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3 different views thus far....!? Keep 'em coming!
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jacko
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| posted on 21/2/08 at 09:47 PM |
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8mm bolts will be ok but 10mm would be better.
I have made /fitted 3 bike engines now but i put the bolts vertical if you look at roadrunners photos you will see what i mean i think thats the
best way
only my opinion 
Jacko
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twybrow
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| posted on 21/2/08 at 10:31 PM |
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I do like that method... However the frame is made, and I am not cutting it up again!
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ChrisS
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| posted on 21/2/08 at 10:39 PM |
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Well based on the size of the original engine bolts on the bike, which is 12mm, and the fact that ive use suspension bushes to mount the engine on,
and the fact that i probablyover engineer thins on the safe size, ive used 12mm . So id say 8mm was quite small, and 10 would be good.
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indykid
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| posted on 22/2/08 at 08:51 AM |
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quote:
Originally posted by ChrisS
Well based on the size of the original engine bolts on the bike, which is 12mm, and the fact that ive use suspension bushes to mount the engine on,
and the fact that i probablyover engineer thins on the safe size, ive used 12mm . So id say 8mm was quite small, and 10 would be good.
i thought R1s used m10x1.25 engine bolts?
anyway, the longer lever arm means the forces the bolts actually see are much reduced.
be a devil and stick M8 12.9 socket caps on it. they look nicer if nothing else
tom
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iiyama
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| posted on 22/2/08 at 05:48 PM |
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M10's on mine
If its broke, fix it. If it aint broke, take it apart and find out how it works!
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tks
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| posted on 23/2/08 at 10:02 AM |
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it all depends how it is fixed and torqued up.
Also the surface on the plates is an import figure...
in the end the bolt only has his normal axial load... and the plates are pressed together and that is the resistance the engine sees.
If the bolt would be loaded for shearing off then it would be another thing....
8.8 M8 will do the job. (i used 4 of them)
also i used M10 ones
Tks
The above comments are always meant to be from the above persons perspective.
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