UN1 Gearbox Issue

Shaun

Supporter
Likewise I thought they were made that way with the slope on them, could I ask one more favour, on the new one could you measure A and B in the image below?
Can they be welded and tempered insitu or is it a strip dpwn job
Cheers

1646926573040.png
 
View attachment 121382

Example of shafts. (Forget the rust, these are just shafts for waste). On right, a new one, on left a used one. You can see that one side of the slot of the used shaft is shaped. This comes from the lack of control of an H pattern in the UN1 conception for shifting. As the finger is only cable driven, it can move in diagonal and then shift after shift eats the slot. This gives bad shifting as the finger is not at the right place.

Best
Blimey, mine are obviously very well worn too, it really makes you wonder what constitutes a gearbox “rebuild” then doesn’t it….

I was certainly not informed of any issues with mine either
 

Shaun

Supporter
Shaun, are you sure you have it positioned correctly to the spigot shaft ? Frank
Hi Frank it's in the crank right up to the stop but think I have the bearing carrier in back to front as the needle bearing seems too far back
Will check bolts good spot
Cheers
 
Likewise I thought they were made that way with the slope on them, could I ask one more favour, on the new one could you measure A and B in the image below?
Can they be welded and tempered insitu or is it a strip dpwn job
Cheers

View attachment 121383
Hello Shaun, I have 10.00 mm for A and 14.00 mm for B.

No, you have to strip the gearbox to do this kind of job (adding metal through MIG/TIG)

These shaped shafts brought some vehement talks at my club...Some saying that they saw gearboxes with these shaped shafts (45° cut) but not everytime when new other not....
From my side, new gearboxes I saw were unshaped.
If we give credits to everybody, and from a technical point of view, the V shape, whatever its origin (worn or manufactured) allows a diagonal move of the finger. From the basic driver point of view, it makes things easier to shift, from the gearbox view, it introduces lack of precision as the contact surface is smaller. The "no shape" needs the driver to make a straight H pattern to shift but makes the gearbox more precise.
Also, as there is no axial guide for the finger in the UN1 conception, if shaped , the finger can place itself partially on the shape wich is wrong as the travel of the shaft will not be the one necessary to move correctly the shift sleeve on hub.
Personnaly, all the gearboxes I built or rebuilt (UN1/UN5) went out of my bench with the "no shape" and I would recommend this for the use we have of these in our GTs.

Best regards
 
Last edited:

Shaun

Supporter
Thanks will check what I have, 14 I think mine is much wider than that and interesting note re the shape being on some and not others, cheers
 
Top