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Spring Claws SP1/1

A_HRD

Well Known and Active Forum Website User
VOC Member
OK guys, let's have some honesty here. Am I the only one who always has a hell of a time trying to fit SP1/1 bronze spring claws to the springs properly and get them both snug and parallel? I have just spent a small fortune on buying a set of 4 new ones and I have tried them on a variety of different springs - early slimline Comet ones, Standard Rapide ones, Pettefords and sidecar Pettefords. As most will know, I am not averse to a little fettling, but the spring claws seem to me to be unfit for purpose. They don't even get close to parallel! More material needs to come off the claws than is already on there to get them anything like close to correct.

Interestingly, the larger claw ID is machined 11/32 dia and the smaller one 1/4 dia: why would this be? And why are they machined parallel to the face when the spring has a helix angle around 5 to 6 degrees?

Now turning to the springs. Should not the first/last coil have been softened and bent to reduce the helix angle to zero before grinding it off flat? None of mine are (just a small ground flat).

It seems to me that the only way to get these right is to make my own; and make them much thicker so they can be machined parallel after being fitted to the spring; the last operation being to drill and tap the 7/16 BSF thread. There again, who's tried machining a lump of metal attached to a spring? Interesting ain't it!

All of a sudden, Thorntons seem to be a better bet despite the price. If only Laney and Dave Molloy could come up with a proper solution to prevent 'cocking'. And that's another story for another time.... Sigh!

What we need here is an expert. Frank, where are you?

Peter B
Bristol, UK.
 

Bill Thomas

Well Known and Active Forum Website User
VOC Member
Hello Peter, It sounds like your the Man for the job !. You have worked out the problem, I gave up years ago, I sent off for rear boxes, Which I was told had plactic inside, But it was only done for the front spring boxes, Clev Trev said he does something to stop scraping the inner rear boxes ?. Could you Grind the claw flat after fitting to the spring ?. All The Best Bill.
 

Tom Gaynor

Well Known and Active Forum Website User
VOC Member
John Emanuel has a Rapide with the suspension seriously modified. He altered the pivot points on the Girdraulics so that they worked the way they are claimed to work (no change in wheelbase with deflection), but don't. He told me that the key to improving the rear suspension was to allow the wheel to move through the maximum arc, which meant getting rid of the claws, and allowing (presumably) the damper to act as stop. This gave about 3" more travel. (The conversation was a while back, so this is what I remember. He must also have converted to Series D, which is probably a good idea anyway.)
What I remember particularly well was someone who went past me at Braddan Bridge in IoM in 2007, going like a rocket, perfectly stable until he went rapidly out of sight. This, it transpired, was John. He was first back after the lap. The memory that remains was of both speed AND stability, quite evidently in a different class from anything else that came past.
I tell a lie: Patrick Godet sailed past on his Prince coming down the mountain. It was like being overtaken at 90 mph by a square-rigged ship under full sail.
As to your direct question, it won't help you to recount that mine went on nae bother, with Petteford springs.
I have Thornton dampers fore and aft.

OK guys, let's have some honesty here. Am I the only one who always has a hell of a time trying to fit SP1/1 bronze spring claws to the springs properly and get them both snug and parallel? I have just spent a small fortune on buying a set of 4 new ones and I have tried them on a variety of different springs - early slimline Comet ones, Standard Rapide ones, Pettefords and sidecar Pettefords. As most will know, I am not averse to a little fettling, but the spring claws seem to me to be unfit for purpose. They don't even get close to parallel! More material needs to come off the claws than is already on there to get them anything like close to correct.

Interestingly, the larger claw ID is machined 11/32 dia and the smaller one 1/4 dia: why would this be? And why are they machined parallel to the face when the spring has a helix angle around 5 to 6 degrees?

Now turning to the springs. Should not the first/last coil have been softened and bent to reduce the helix angle to zero before grinding it off flat? None of mine are (just a small ground flat).

It seems to me that the only way to get these right is to make my own; and make them much thicker so they can be machined parallel after being fitted to the spring; the last operation being to drill and tap the 7/16 BSF thread. There again, who's tried machining a lump of metal attached to a spring? Interesting ain't it!

All of a sudden, Thorntons seem to be a better bet despite the price. If only Laney and Dave Molloy could come up with a proper solution to prevent 'cocking'. And that's another story for another time.... Sigh!

What we need here is an expert. Frank, where are you?

Peter B
Bristol, UK.
 

Ken Tidswell

Well Known and Active Forum Website User
VOC Member
The other route is to attack the springs with Vee Blocks and make the ends parallel. Spring makers do this to extend springs to their correct lengh after retempering. At least they do in Rochdale. But that is in Lancashire. Ken
 

davidd

Well Known and Active Forum Website User
VOC Member
Peter,

I put a lot of thought into redesigning the rear springing system, but as you know I ended up building a coil over with a Works Performance damper, which is now available from Thornton. I did so because the when the spring boxes cocked, I noticed that on one box, the inner had worn through the outer and thus created a serious stiction point. I had made springs for the rear which were cylindrical and "closed and ground" which is the usual "end." The springs you mention do not sound as if they were closed before grinding.

I had intended to take some springs that were closed and ground and trim the end back until is was an "open" end. I was then going to turn my own claw which would be an aluminum plug with a groove to match the pitch of the spring. If you are interested in some cylindrical springs I could come up with some.

The damper moves roughly 3.25" to its limit. When I was designing the short front springs I found that there was no practicable way to utilize a progressive spring through a 3 inch stroke. As a result, I was not wedded to the barrel shaped stock springs in the rear.

David
 

clevtrev

Well Known and Active Forum Website User
VOC Member
Peter,

I put a lot of thought into redesigning the rear springing system, but as you know I ended up building a coil over with a Works Performance damper, which is now available from Thornton. I did so because the when the spring boxes cocked, I noticed that on one box, the inner had worn through the outer and thus created a serious stiction point. I had made springs for the rear which were cylindrical and "closed and ground" which is the usual "end." The springs you mention do not sound as if they were closed before grinding.

I had intended to take some springs that were closed and ground and trim the end back until is was an "open" end. I was then going to turn my own claw which would be an aluminum plug with a groove to match the pitch of the spring. If you are interested in some cylindrical springs I could come up with some.

The damper moves roughly 3.25" to its limit. When I was designing the short front springs I found that there was no practicable way to utilize a progressive spring through a 3 inch stroke. As a result, I was not wedded to the barrel shaped stock springs in the rear.

David

The springs are barrel shaped for a very good reason. Trying to move an unsupported spring through an arc, leads to its moving away from its centre line in an outward direction. The spring boxes are there to give it support and contain this deflection, hence the wear you have found, the barrel shaped spring keeps this contact area to a minimum.
 

davidd

Well Known and Active Forum Website User
VOC Member
Trevor is correct and I would add that I have talked to Laney Thornton regarding the springs and I think that the replacement springs did not undergo sufficient development. Cocking is a problem with the new springs and the originals work fine, but do not offer much in a range of selection for differing loads.

David
 

Peter Holmes

Well Known and Active Forum Website User
VOC Member
I purchased a complete set of Thornton rear springs before the spring over dampers became available, so I sort of feel compelled at sometime to give them a try, with regard to cocking, if the spindles are nice and free to oscillate in their bushes with the movement of the spring box eye bolts how bad is the cocking and is it further increased by the fact that that the springs are smaller in diameter than the original springs. I note in the kit that I purchased there are supplied a couple of small angle iron brackets with self adhesive velcro strips to overcome the problem but with best will in the world I simply cannot see how this could be strong enough to work. I did consider getting made by my friendly metal fabricator some reduced diameter spring boxes with the added advantage that it might enable me to get one of the very slightly taller black Westco batteries of more less the correct dimensions in place of the original battery, but is really worth all the bother, I have been using Petterford sidecar springs fully sprung with a Koni since time begun, but when I read about John Emanuel's silky suspension I does make one wonder what I am are missing out on. Is anyone out there using the new coil over device and if so does it fit in the center and if so are relatively slim studs up to job when I guess with the original set up the stress the springs inflict on the stud was supported right next to the UFM and the rear frame. Questions, Questions
 
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