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Author: Subject: Bike engine orientation in a 7
OliilO

posted on 9/8/21 at 07:08 PM Reply With Quote
Bike engine orientation in a 7

What is the current thinking on orientation of bike engines in a 7? My carís engine is currently aligned with the chassis putting it an angle to the prop tunnel. This hasnít been an issue over 10k+ miles but wanted to check the current thinking as I will be building a new engine cradle to upgrade to a CBR1000rr engine shortly.

Is it worth aligning it with the prop, bearing in mind I will then need a new manifold, or just keep things simple and leave it as it is? Iím currently inclined to replicate the existing angle however Iíve noticed quite a bit of variation across peopleís various cars.

Thanks,
Oli

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adithorp

posted on 9/8/21 at 09:26 PM Reply With Quote
Ideally you want the front and rear prop flanges parallel to each other. That means the engine being inline with the centre line, not the chassis rail.





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40inches

posted on 9/8/21 at 10:03 PM Reply With Quote
quote:
Originally posted by adithorp
Ideally you want the front and rear prop flanges parallel to each other. That means the engine being inline with the centre line, not the chassis rail.

That's how mine was.
Description
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feckn7

posted on 10/8/21 at 05:39 AM Reply With Quote
I had my engine aligned with the side chassis rail so that the output from the bike engine was almost central to the gear tunnel.
I used a prop shaft with a CV centre joint - Both front and rear UJ's were pretty much parallel to the shaft (not to each other) as the CV joint doesn't introduce any speed differences during rotation, this meant that the UJ's were effectively parallel to each other.
I was told by the engineer that built the prop shaft that the Holden Commodore CV prop shaft CV joint could handle ~350hp at all sorts of crazy angles - the bike engines torque wasn't going to cause it any issues whatsoever.

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adithorp

posted on 10/8/21 at 09:21 AM Reply With Quote
CV centre joint makes sense to overcome the phasing issues with miss alignment. I think space is more of a packaging issue on a 7 than my Fury so sometimes being at an angle isn't easily avoided. I guess in that case a conversation with someone like Dunning and Fairbank about props is useful.





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pigeondave

posted on 10/8/21 at 01:10 PM Reply With Quote
like someone said as long as the faces are parallel you wont have problem.
This video shows what can go wrong
https://youtu.be/gmV4qwLfOMY

I always though it was best to have a slight 5deg offset so that the joint is articulated, but I'm probably talking rubbish.
Having an off set somehow buggers the torque delivery. I think I saw a video where they said about the XR2 fiesta and how the dropped the drive shafts 25mm and it made a difference in the losses (they were less).

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DavSki153

posted on 10/8/21 at 01:26 PM Reply With Quote
You would still need to phase the propshaft UJ's if it has a Centre UJ though wouldn't you?
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feckn7

posted on 13/8/21 at 05:28 AM Reply With Quote
Yes - still have to phase the front and rear UJ's. The centre CV (being Constant Velocity) can be at any angle as it's effectively not there (or a straight tube) as far as the UIJ's are concerned.
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adithorp

posted on 13/8/21 at 09:25 AM Reply With Quote
Yes you'd still want the front and rear joints phased but the flanges can be misaligned as the CV joints ability to slide reduces the vibration.

As Pigeon Dave says a slight angle between joint and shaft is desirable as that means the needle rollers move and that reduces wear (rather than constantly being in the same spot). Don't know about the torque thing; XR2 was front wheel drive so 2 unequal length drive shafts so not a direct comparison. Ford played with diameters to reduce torque steer AFAIK.





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OliilO

posted on 13/8/21 at 10:15 AM Reply With Quote
Thanks everyone.

While the current set up has worked fine, it seems a good opportunity to make an improvement on the original builderís design so will aim to improve the alignment when I install the new engine.

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pigeondave

posted on 13/8/21 at 10:31 AM Reply With Quote
quote:
Originally posted by adithorp

As Pigeon Dave says a slight angle between joint and shaft is desirable as that means the needle rollers move and that reduces wear (rather than constantly being in the same spot). Don't know about the torque thing; XR2 was front wheel drive so 2 unequal length drive shafts so not a direct comparison. Ford played with diameters to reduce torque steer AFAIK.


Yeah, I can't find the video right now and it looks like YouTube only keeps History for a year. Give me the weekend to have a rummage.
I'm 80% sure it was the XR2

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