F: Frame Comet Frame Tie

Martyn Goodwin

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Non-VOC Member
On behalf of another VRV member - In the Comet aluminium Frame Tie F106 there is an internally threaded bush F110 that the gearbox bolt upper F48/7AS screws into.

Here is the problem. At some time in the dim dark past a dastardly dodge was performed. The steel bush F110 was removed or lost and the bodge was to simply replace it with a nut! This left the end of the gearbox bolt with room to move about causing some distortion/enlargement to the hole in the Frame Tie that was designed to accommodate the F110 bush.

So now to rectify but there are some unknowns.

1. What should the ID of the hole in the Tie Frame for the bush be??
2. It is assumed the hole (once fixed) will need to be line bored to match up with the inside of F117 ?
3. What actually should be holding the bush F110 in the frame tie F106? If interference, how much?
4. Is there anything wrong (from a structural perspective) of enlarging the existing but misshapen hole in the tie frame and fitting a made to fit bush, keeping #2 in mind?
5. Given that there is no stress in that part of the Tie Frame, could the hole be repaired with a form of Liquid metal - Loctite has a few such products in their range?

Sensible suggestions sought.
 

erik

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VOC Member
I would recommend welding and line bored to standart size .Best done on a cnc mill.Erik
 

Bill Thomas

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Morning Martyn, Just took one apart.
First thing is the " NUT " Has a Spline, So for me it's tricky to tell you exact !.
The OVERALL length is 718 thou, The top hat lip is 110 thou ish.
The Male spline is 705 thou, But that is the outside of the spline !.

The hole in the Alloy Lug is 700 thou , But again the inside of the spline ???.
The width of the alloy Lug is 625 thou.
I warmed F106 in front of the Electric fire and gave it a big wack !,
So it's tight but not too much.
As you know the Alloy Tube that slides for alignment, Is not tight, So I don't think it has to be spot on ?.
Good Luck, Bill.
 

Martyn Goodwin

Well Known and Active Forum User
Non-VOC Member
Morning Martyn, Just took one apart.
First thing is the " NUT " Has a Spline, So for me it's tricky to tell you exact !.
The OVERALL length is 718 thou, The top hat lip is 110 thou ish.
The Male spline is 705 thou, But that is the outside of the spline !.

The hole in the Alloy Lug is 700 thou , But again the inside of the spline ???.
The width of the alloy Lug is 625 thou.
I warmed F106 in front of the Electric fire and gave it a big wack !,
So it's tight but not too much.
As you know the Alloy Tube that slides for alignment, Is not tight, So I don't think it has to be spot on ?.
Good Luck, Bill.
Thanks Bill
 

Bill Thomas

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VOC Member
Just thinking Martyn, I don't think it has to be a spline ?, I would make up a nut a few thou bigger than the hole and Loctite it, Making sure the stud thread is a nice free fit, And grease the thread before fitting, To help if you have to take the Gearbox out later.
 

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vibrac

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VOC Member
I think that it will receive considerable torque on the 1/2" bolt and long term locktight may not be enough, a spline takes a considerable amount as any kickstart would tell you . My take would be entirely as above, but add either a spirol pin or a countersink cap screw of appropriate length up from the unseen underside of the boss into the plug nut since the new plug nut hole will be bigger (to remove residual spline groves?)there will be enough body. to be OK just run the tap down after.
 

Bill Thomas

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VOC Member
I don't do that bolt up too tight, I had the head come off a Stainless one, After not been touched for a long time, Trev seemed to think it was two different types of stainless, Where the nut was welded on the stud.
The old ones in steel were brazed.
 

vibrac

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VOC Member
Like most penny pinchers I make up my 1/2" bolts like front wheel spindles on racers I thread on a nut with good interference face off reduce part of plain portion to thread depth if appropriate and add a spirol pin.
 

Bill Thomas

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VOC Member
Yes I love stainless, But I won't use it there again, Funny I found the old one, I knew exactly where it was after many years !, And fitted it.
I got a BSA Cad' one I will rethread, For the new bike.
 
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oexing

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VOC Member
Not quite knowing much about this trouble why not fabricating a threaded bush and go for next size internal thread for the alu frame tie. So you´d make a bush with that oversize thread on the outer diameter that has the old size internal thread for the standard bolt. A Helicoil would be too slim but you can do your own bush instead. So no need for a flanged nut, the threads will hold the pull.
Spiral pins for locking nuts on their thread ??? Nooo, a bit of Loctite 270 and you´d be VERY challenged to undo this . . . .

Vic
 
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