Fork 2 way damper drawing

[Tomcat]

I've just dug this old thread out to find out about two way damping. As buying them suits me better than making, I had a look around parts suppliers WWW's and have found SRM sell them but with hidden top threads. Does anyone know where I can purchase kits with the exposed acorn nuts? Thanks in advance TC

[BSA_54A10]

Paul Groff does a couple of BSA forks

[Tomcat]

Yep, spot on Trevor. Exactly what I was after, and 20 quid less! Cheers TC

[KeithJ]

Hi, just been reading the posts as I am about to re-fit my dampers.  Can someone tell me if the dampers should touch the oil when the bike is off or on the centre stand?

Thanks

Keith

[Peter in Aus]

I have just made up a set of these dampers and one of the things I though I would do is to make the rods longer so as not to have to put so much oil in to cover the valve with the forks fully extended. But I soon found out that you can't, as when I checked to see if the valve would go right down (e.g. forks fully down) the valve hit on some thing, so had to make the rods so as the overall length was as the drawing, 16 1/4", I did  creep a bit I made mine 16 3/8" that gave me about 5" of movement before it would bottom out, not sure just how much movement there is  as I did not check that when I did the forks up some time ago, but I suspect that it is about 4" some one might be able to correct me on that?
One of the things that concerns me is the fact that the oil comes so far up the stanchion to cover the valve it leaves not much space for the oil when the forks bottoms out, I put 260ML of oil in to cover the valve,  adding a bit at a time (Fork oil 10W)and the last bit took only about 20ML to raise the oil level about 3"! (without the valve in there) so that makes me think that when the forks bottom out there can't be much space left at the top of the stanchion for the displacement of the oil, the pressure must be very high at the bottom of it travel, what do you think?
Haven't taken it for a test run yet, its been a bit wet and I'm allergic to water! but on all accounts it's makes a big difference.
Peter     

[chaterlea25]

Hi Peter,
The length in the original post I wrote was 16 and 11/16in. (424mm app)
In reality the oil quantity and grade is a personal choice to some degree,
The valve does not need to be completely submerged,  once the end of it is in the oil at full extension it will work
most of the time the forks are compressed to some degree so the valve body is in the oil

John

[Peter in Aus]

Thanks John, yes that makes sense re valve not needing to be fully submerged in the oil.
And thank you for putting the post up with drawing in the first place

[Peter in Aus]

Had to take my forks out of my A7 Plunger for repairs (that's another story) so checked to see how far down the stanchion the damper valve body could go.
On my stanchions it is 19,1/4 Ins from the top of the top yoke to just above the top bleed hole of the two bleed holes in the stanchion, which is still well clear of the spike in the bottom of the slider. It could go down further but this would cover the bleed holes which may or may not affect its function? 
This adds just a bit over 2 Ins to the length so not having to put so much oil in to cover the valve body.
As far as I can see all the A from 1950 to 1962 are the same so 19,1/4 Ins should be ok for A7/A10 50 to 62.
Best to check thou.
Peter

[mikeb]

I’m eyeing up this mod – a question: the thread references making the valve out of various aluminium grades or 316 S/S whereas I don’t want to work with SS and don’t have the right aluminium lying around. As it’s bathed in oil, how about just mild steel? Any downsides (other than some weight)?

And I assume there is never significant vertical force on the valve/rod so mounting it under the fork cap hex doesn’t have to bear any load?

Thanks

[muskrat]

G'day mike.
I can't see why not use ms.
Cheers

[chaterlea25]

Hi Mike,
It depends on how you go about attaching the rod to the underside of the top nut ? A paper clip won't work 
I have seen A65 nuts used or a suitable nut brazed into the standard nut but that ruins the chrome!
(It has to be dead centre)
The rod is under tension when the fork is extending , the ball valve is closed and oil is being forced to flow around the outside of the valve body in the small gap between both parts. This is what does the damping

John

[orabanda]

It's best to have dissimilar metals rubbing against each other; less liklihood of galling.

[Peter in Aus]

I used MS on mine no problems so far

[mikeb]

thanks for the comments guys.

A paper clip won't work

i was thinking blutak or hot glue John  tho now you mention it, it hadn't occurred to me the A65 top nut would do. checking the specs it looks like the early A65 top nut will fit the A10 forks and has a 5/16 26tpi thread on the inside. I could put a 5/16 26tpi male thread on some 10mm threaded rod easy enough...

so checking the details- will the A65 top nut (41-5146) fit to the A10 forks, with similar-ish external dimensions eg across the hex?

cheers

65-5331 A10 (etc) - Thread: 1+1/16" x 20TPI
41-5146, 97-2652 – A65 66-68 Outer thread: 1+1/16" 20 TPI – CEI, Inside thread: 5/16" 26 TPI - CEI

[chaterlea25]

Hi Mike,
I am not sure which A65's nuts work,
But, if you go that way you lose "street cred"
If observers see the dome nut on top of the A10 nut,  they go "OOOH"  "double dampers"
With A65 top nuts you will be told they are wrong

 
John