Thornton for Bramptons

Oldhaven

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I'm getting to the tail end of a decades long project of resurrecting a '48 B Rapide, and thought I would share photos of the Thornton setup for Bramptons I will be using. This was the initial fitting before I disassembled the forks for repaint and Patzke taper bearing installation. The spring preload is not done yet, so ignore the position of the adjusters. I want to thank Dave Molloy and Ted Leno for their help in getting me the information I needed to fabricate the top and bottom mounts. Dave has to modify this shock for the B front by adding an internal spacer to limit travel, and the mounts have to be just right as the space is quite limited. Ted had gone through this before me and provided a source for the clevis's, though they still need to be modified considerably to work.
Ron
 

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Albervin

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That is very similar to my set-up. I used a screw mount at the top like you to find the correct position then brazed it. Clearance is "minimal" but the ride is superb. Well worth the effort. I tried a couple of springs and then played with pre-load. Get the static sag sorted and then ride it to obtain final settings. Keep a diary so you can always go back a step or two if necessary.
 

roy the mechanic

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Albervin, I make you right on the diary. In racing circles it's called "the record book" The memory plays tricks!
 

vincenttwin

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Ron
Can you let me know where the Clevis came from. also a rough idea of the mods you had to do. Just got back from a week in Ireland and the bumps bottom out the old std spring.
 

Oldhaven

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Sure. http://www.midwestcontrol.com/ They have a distributor in the UK. I used these rather pricey SS items, and still had to modify them extensively, so if you are good with a lathe and milling machine, you could do them from scratch. Midwest has other plain steel parts that will work for less cash. You will need the shop machines and the services of a SS welder to even use these. I had to plug the bottom 12mm hole and re-drill and tap for 3/8. I am not near the bike right now so if you don't mind waiting until next week I can list the modifications required. I used metric 12mm since a 12mm stud fit the top spring mount nicely. I welded the stud into the clevis. You also need to make an adapter for the clevis to the bottom Thornton spring plate. As I mentioned, Ted Leno in the Pacific Northwest helped me out a lot and there is a drawing that describes the required parts and dimensions, but it needs to be corrected for what I did. I'll try to get that done when I get home. As you know, the contact for Dave Molloy is in MPH. He may even have the complete setup or a more complete drawing available now, but did not when I bought the shock. Nice guys both.

Qty Part Unit Price Extension
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MTC-12L-SS
Clevis, DIN Metric, Stainless Steel USD $26.67 USD $53.34
 

vincenttwin

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Ron Thanks, I am very interested in the bottom mount , did you leave where the std spring is attached to on the forks and just moved the new mounting point foreword to the bottom mounting point for the bottom head light stays, Just looked at my A single (I keep my B in Ireland) and it looks like the back of headlight bucket might hit the unit.
You could make longer top stays F85/1's and rotate the headlight foreword , what are your plans , If I do this I will need a full kit so when I go back to Ireland it will be a simple bolt on job.
 

Oldhaven

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No hacksaw required for the spring claw. I have not put a headlight on yet, since the whole machine is apart right now, but here is another picture of the installation and one of Ted's with the headlight. (Note the essential equipment on the workbench. ) I don't think he had to modify the stays, but as you can see, it is a tight fit. You should be able to do the machining here and take it back complete. I should be able to get the correct dimensions from my setup if Ted and Dave's prints are not done yet.
 

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