Brompification springs - sizes?

[chagzuki]

Does anyone know what size/type of spring will work as the Brompification ones do? There's a very small clearance between bolt and frame and the spring has to clear the bolt threads, a little too large and it'll scratch the frame paint. I'd prefer a DIY solution than to buy the Brompification versions.

[rogerzilla]

I googled it but I'm still not sure what springs you mean.  Can you explain what they do?

[chagzuki]

Ooops, should have been clearer:

http://www.brompfication.com/17-hinge-clamp-plate.html

They push the hinge clamp plates off the frame as the wingnut thingies are unscrewed. Their version of the hinge clamp plate, as they call it, is a little longer on one side and I think slightly shorter on the other (compared to the Brompton version).

[nobby]

I've modified mine by making new bolts up and I took them to a spring maker in Tipton. He found me two that are a sliding fit on the bolt and made off thin gauge wire.

[chagzuki]

Did you file/cut down one side of the original clamp plate? Or perhaps somehow lengthen the other side?

[nobby]

Did you file/cut down one side of the original clamp plate? Or perhaps somehow lengthen the other side?

No, I didn't need to.

I started off with the modification to make the original bolt captive; I used a washer and a split pin. I didn't like the look of the turnkey heads so I made new bolts to length from threaded rod (8mm, if memory serves correctly), with the washer and split pin again to make them captive. At the end for the turnkey I used an acorn headed nut (bought from a motorcyle shop) and secured it to the threaded rod by drilling part way through both and epoxing in a short piece of steel rod. I decorated that by gluing on bamboo as the lever.

Where the threaded rod passes through the alloy hinge clamp I shimmed the hole for a closer fit with a piece of brass tube (available in B&Q or model aircraft shops) and peened each end over to keep it in place. Then I bought springs that were a close fit over the threaded rod and adjusted the length of the rod until it locks open against the captive washer at just the point where the clamp clears the hinge. The pressure of the spring is sufficient to stop the alloy clamp from turning.

It has worked fine so far but I do not have to fold my B so very often, so cannot say how long it will last although I'm not expecting it to wear out, or fail.





Hth

[chagzuki]

That's one of the most unusual mods I've seen.

I've got the same sort of result using a circlip to hold the clamp plate in place. I think a spring would work better though.

[nobby]

That's one of the most unusual mods I've seen.

I've got the same sort of result using a circlip to hold the clamp plate in place. I think a spring would work better though.

Is that unusual as in good or ok, or unusual as in "oh dear"? 
The spring helps to push the alloy clamp away from the hinge as you undo the screw which idea I think I stole from a fancy Japanese mod.

[Pickled Onion]

Sorry, I don't get it. I fold my Brommie 6-8 times a day and have never thought there was an issue with the clamps being out of line. Does this really make a big difference?

[chagzuki]

It removes the step of having to position the clamp plate over the hinge plates which can sometimes be a faff, and lessens the number of rotations of the wingnut thingies, i.e. it just makes it faster and less fiddly.

[chagzuki]

That's one of the most unusual mods I've seen.

I've got the same sort of result using a circlip to hold the clamp plate in place. I think a spring would work better though.

Is that unusual as in good or ok, or unusual as in "oh dear"? 
The spring helps to push the alloy clamp away from the hinge as you undo the screw which idea I think I stole from a fancy Japanese mod.

yeah. A circlip that's tight enough to remain buttressed against the clamp plate, keeping it in position by the wingnutty things does work, however it'll probably gradually move and need adjusting. . . a spring would be preferable.
I think the spring needs to be <9.5mm OD and slightly larger than 8mm ID. I can't find anything online so far.