Silent block bushings again

[coater87]

 Does anyone know of a supplier that makes these correctly? I am sending back another set of these because the inside diameter is too large. That's the second set, both sets could have been the same maker, I just don't know.

 I can fix a too large outside diameter, but not to big on the inside.

 I am thinking 1 should end up with a .002 thousandths press fit into the swingarm, and the hollow Spindle should have about .001 when finished.

 It's hard to get that when the inside is already .007 too big.

[RichardL]

Lee,

I don't know about 0.007", being too much, but 0.001" seems a lot closer than needed. I think it pretty unlikely that you would get the bushes to line up with eachother within 0.001" at the middle of the tube. By the time I got mine in place (using a profuse amount of sweat for lubricant), the bushes were not aligned and I had to use a reamer to make way for the spindle. By the way, considering you are basically local, the reamer is availble for loan if you need it.

Richard L.

[coater87]

 Richard,

 Maybe I am not understanding how the bushings work.

 I thought the outter tube should be a press fit into the swingarm. I figured 1 to 2 thousandths of an inch oversize (on the bushing) would be a tight enough fit into the swingarm.

 Then I thought the hollow swingarm shaft needed to be a press fit into the inner bushings, I figured one thousandth of an inch or a little less would be tight enough for this.

 I envisioned that when everything is together correctly, that the rubber in the bushing works like a hinge, and there is no metal to metal rubbing anywhere.
Maybe I am not understanding how this all fits together....

 There will be no sweating here, have a 30 ton hydraulic press available by appointment.

 Lee

[RichardL]

Lee,

This has sent me looking for the big discussion where I had to be convinced, kicking and screaming, as to the design intent of the Silentbloc bushings. You were in that 2009 discussion. There are a lot of places in that discussion where one could drop in, so I just picked one and you can peruse whatever parts you wish.  http://www.a7a10.net/forum/index.php?topic=1185.msg8396#msg8396

I think the most telling thing you mention in today's post is the part about no metal to metal rubbing. So, if you have 0.001" clear or 0.007" clear it wouldn't really matter, as long as the system is working as designed. If it's not, and the inner sleeves slip in the frame plates, then it would seem that minimal spindle clearance would help. If you read around the topic at the above URL (I had to), you can see (at least, I read) that the spindle is not really intended to be a press fit in the Silentbloc, but a slip fit.

Funny thing, I had also offered the loan of my reamer in the 2009 discussion. At least I'm consistent or, maybe, just have a one-track mind.

Richard L.   

[bsa-bill]

I have bought bushes that were to big, they did the rounds some years ago maybe they are still around, people did turn them down in a lathe but I have no lathe, the trader I bought them from sold them as original  but defo they were not as I bought a proper set from C&D autos.
They should be a press fit into the S/A.
your about right with your surmising except the hollow tube does not need to be pressed in, the inner metal tube of the bushes should protrude enough from the swinging arm that they get clamped when you tighten up the nut on the end of the hollow tube, sound like a bad idea but it works, think about the amount the S/A actually twists at the pivot and it's not a lot

[RichardL]

So, if you have 0.001" clear or 0.007" clear it wouldn't really matter, as long as the system is working as designed.

Maybe I read you wrong. Were you implying a 0.001" interference fit? In any case, I believe slip fit is correct.

Once again, and as always, I will bow to the more experienced answer, if it's out there. [After 10 years on the forum and 43 years of A10 ownership  (30+ of which were completely without a clue) I might one day start to trust myself.]

Richard L.

[Clive54bsa]

I bought mine from C&D Autos in Birmingham, they fit perfectly, I pressed them in with all-thread, washers and Vaseline.

[coater87]

 Thanks Richard for the reminder of that thread, it answered my question. I think with the new shop (much better equipped) I should be able to turn up something to keep the bushes in line, or at least close enough to get the spindle in. If not I will certainly remember who owns the right reamer, so thanks for the offer (again).

 This bike has taken forever and a day. If its not moving jobs, or moving houses, or some other thing bringing it to a halt its another. So the stopping, and restarting, and being stopped again and restarting again....makes everything seem like Ground hogs day (an American reference for you ). The only good thing about it is going through the new parts I have bought over the years, and finding something I had forgotten I bought way back when.

 The bushing I mentioned back in 09 was killed last week. I removed the old bushes (big press and a welder) and began pressing in the new bushing. About half way in on the first bushing, the press really started to grunt, then it let loose. The outer tube of the new bushing had flared way out and was ruined. I did some careful measures and found it was almost a 10 thousandths press fit, way too big.

 Ordered a brand new set, and they are also too big, but by 8 thousandths. Then I started to compare the three good bushings I have left, and none are the same. Thats when all the confusion started again. Very poorly made reproduction parts, but what choice do you really have with an isolastic bushing??

 Lee

[bsa-bill]

Very poorly made reproduction parts,

Very possible, however could also just be wrong, these bushes were used in other applications, do any of them have a scroll on the outer tube, the ones I had that were wrong did and were too big

but what choice do you really have with an isolastic bushing??

As has been said  - a dealer who knows BSA inside out

[coater87]

 Here is the long and short of it.

I had to buy 2 sets, got the job done.

 Diameters were wrong on every one. Be it inside or outside, of both.

 I ruined 2 of them trying to press them in. I found 1-2 thousands max oversize was a go. They were all 8 - 17 thousandths overside when i recieved them. Knocked them down with a draw file in the lathe.

 The inners wete too tight by 2-6 thousandths. Used a 3/8 inch boring bar to make them round and bring them to size.

 Used the first bushing to help line up the second bushing, and pressed them in. The hollow tube lines up great, and is a stiff press fit by hand.

 If the parts were made right, I figure I could swap a set out in about an hour. As it was I had almost 8 hours in it. It takes a long time to draw file 15 thousandths off with my crappy files. Plus having to remove 2 new bushings because they mushroomed over when 7/8 the way in.

 Lee

[duTch]

 I just have to say, I appreciate my Plunger frame so much more when I read of these headaches

[muskrat]

Me too dutch.
 I made greeseable brass bushes for my swingarm.

[Triton Thrasher]

 I just have to say, I appreciate my Plunger frame so much more when I read of these headaches

The rubber system does wear well, though.

I ride around on 59-year old Slientblocs.

[coater87]

 I just have to say, I appreciate my Plunger frame so much more when I read of these headaches

The rubber system does wear well, though.

I ride around on 59-year old Slientblocs.

 I would have also, but someone had started the job long ago, and left the hard stuff for the next poor ba$+@&).