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That's possible but the top cover distorts and beraings pinch cams. Check out what racers used to do back in the day to modify those valve covers. The problem is not necessarily the combined yield point of the screws. In this case the cover could distort and/or chunks could be torn out of it.

Is there a way to fit longer studs at each side and uses a frame bracket bolted to those longer studs. I think it was Tony Foale that did that with a Z1.
 

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Discussion Starter #42
not on the 750, the gs models are nice because the outer 4 studs are clear, lots of race bikes use a steel bracket that goes directly onto those studs. the top cover would have to distort the head itself to move the bearings, they're not attached to the cover like the 550, I'm going to try to design the mounting points to avoid the unsupported section of the cover and keep stress areas close to the screws
 

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not on the 750, the gs models are nice because the outer 4 studs are clear, lots of race bikes use a steel bracket that goes directly onto those studs. the top cover would have to distort the head itself to move the bearings, they're not attached to the cover like the 550, I'm going to try to design the mounting points to avoid the unsupported section of the cover and keep stress areas close to the screws
My guess is (depending on how the mods were done) the cover would indeed be ripped off the head, but most of the rim (especially at the screw locations) would remain in place, broken off from the cover itself.
 

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Discussion Starter #47
well as long as you've got a good sense of humor about the whole affair. personally I'd never experiment like this on a customer bike, but this one is mine and you learn a lot by experimenting and testing your theories, frankly the motor was another theory, built in a way that almost no one said was do-able
 

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well as long as you've got a good sense of humor about the whole affair. personally I'd never experiment like this on a customer bike, but this one is mine and you learn a lot by experimenting and testing your theories, frankly the motor was another theory, built in a way that almost no one said was do-able
Sense of humor aside, I have to give you credit for being far more adventurous than me; then again, I know I can't weld, so that's the FIRST of several of my limitations.
 

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also did some figuring, it would take 38 thousand pounds of force to pull the valve cover off a cb750 if all the screws were installed.
Is that peak shock load, shear, radial load or tangential stresses you have calculated of the screws? Or a combination of all that I've mentioned?

Mr Whitworth would be impressed with your diligence, and the appliance of science.

Danger, is my business."
 

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It's a metal and mental issue here. I doubt you realise that you will be making anywhere from 3 to 6 frames before you have a viable sohc race frame.

You have to wrap your head around the mental, and then tubing around the motor.

How do you plan to align the frame after welding it up? Bear in mind having three or four useless 'prototype' frames hanging up on the works wall, will only add to your engineering cred.

Danger, is my business."
 

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finally getting around to starting the frame for my cb750, "sketched" it out in 1/4 rod, any thoughts? the top tubes are going to be 1-1/4" along with the two tubes going down to the front engine mounts, the rest will be 1", the black foam is where mounts will be welded to the valve cover. the subframe will either be aluminum tube or possibly carbon fiber, in which case the whole seat/tail section would be one piece of carbon. the swingarm will possibly be connected to the shock through a linkage where the shock is mounted to the underside engine mounts

View attachment 12736
How about getting a spare pair of rocker covers, bond on something to form the shape of the lugs you need, fill the joints & bolt holes smooth with bodyfiller and get a pair cast in alloy. Heat treat them, and there`s little machining to do. Get them cast in green sand and a decent foundry guy can tap the pattern oversize to allow for the contraction.
 

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Discussion Starter #54
I had thought about that, I've actually got a foundry and could cast them myself, but I couldn't figure out how to tap the tappet cover holes, I mean, I could figure it out, but it would involve a shit ton of money to make or buy a large tap, so it was that or redesign the tappet covers to use machine screws, I'll try welding for now and if it's not the right way to go, consider other options
 

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If you're going to cast a new cam cover, go with this style of inspection port:



You could really mess with peoples' heads with a custom designed cam cover.
 

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The other thing I've seen is using the exhaust studs to bolt a plate to use as a frame mount, but admittedly that was on a water-cooled engine where the area is quite flat and airflow not an issue.
 

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I had thought about that, I've actually got a foundry and could cast them myself, but I couldn't figure out how to tap the tappet cover holes, I mean, I could figure it out, but it would involve a shit ton of money to make or buy a large tap, so it was that or redesign the tappet covers to use machine screws, I'll try welding for now and if it's not the right way to go, consider other options
So after you have welded on the rockerbox mounts, then you find out the cylinder studs are too weak to cope with the extra stresses. What then? Or when you find out the rockerbox mount makes the bike vibrate like hell, and then have to rebalance the crank to suit the bike?

Reinventing the wheel - Wikipedia, the free encyclopedia

Can of worms - Wikipedia, the free encyclopedia

It's not rocket science, to built a bike frame.

Aerospace engineering - Wikipedia, the free encyclopedia

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Danger, is my business."
 

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So after you have welded on the rockerbox mounts, then you find out the cylinder studs are too weak to cope with the extra stresses. What then? Or when you find out the rockerbox mount makes the bike vibrate like hell, and then have to rebalance the crank to suit the bike?
Stronger studs would be step one.

Step two would be to ignore you.

Oh - he's made that step one.....

 
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