The swinging arm is pretty loose on my 1970 S due to the classic spindle to transmission cradle wear issue. I think the bronze bushings are still good. I've been trying to make sense out of past posts on swinging arm spindle mods-- the clamp method formerly performed by Heinz Kegler and the alternative-- two nuts welded to the rear of the spindle mount on the transmission cradle. I could do either one since 1) I have a spare used cradle, and 2) the cradle on my complete Norton will soon be off.

Do either of these work just as well? If so, who currently has the clamps, or alternatively, what size nuts/bolts are used with the welded method?

Also, do I need to get the 0.005" oversize spindle to tighten things up first or is it OK for the loose (worn) spindle to be used as is?

Ted Lang

Well mine wasnt loose but since I had it out and striped to fix the centre stand holes I welded on some round bar that I turned down to about 15mm I think, I also had a pilot hole drilled in them. They were welded as close to the plates as possible (I may have even ground some flats on the outside faces of the bar). Then I drilled and tapped to 5/16 UNF, when it goes together I will use two grub screws in each hole as I dont like the idea of the lock nut pulling the bolt back out of the hole.

The only reason I went this way was that it was easier and cheaper to make than the split shaft collars..... It is also lighter and simpler

The spindle stablizing clamps is a matter of degree in how hard and long you expect to flog you Cdo. The metal tube that nuts are welded on is pretty thin and the bigger the bolt the bigger the hole and weld to soften and distort. I'd silver soder if mine. The collars bare all the way around the tube so more beefy and leverage advantaged to the clamp bolts to bear spindle wobble loads. Both proven effective for decades. Some past collars were gun blued finish and will rust like crazy after road grit gets em. Then there's the oil resvior driooler vs grease caking mod. I'm a greaser myself knowing what happens just sitting around or putting off and putting off one of the more nasty tediums of 750 Commando-doom

Ted Lang wrote:The swinging arm is pretty loose on my 1970 S due to the classic spindle to transmission cradle wear issue. I think the bronze bushings are still good. I've been trying to make sense out of past posts on swinging arm spindle mods-- the clamp method formerly performed by Heinz Kegler and the alternative-- two nuts welded to the rear of the spindle mount on the transmission cradle. I could do either one since 1) I have a spare used cradle, and 2) the cradle on my complete Norton will soon be off.

Do either of these work just as well? If so, who currently has the clamps, or alternatively, what size nuts/bolts are used with the welded method?

Also, do I need to get the 0.005" oversize spindle to tighten things up first or is it OK for the loose (worn) spindle to be used as is?

Ted Lang

The best way to sort this problem out would be to remove the thin wall spindle mounting tube from your spare cradle, get something more substantial made, and fit that to the cradle. I would imagine the OE mounting tube is getting distorted in use, leading to the hole becoming oval.

I used the split-collars on mine and they worked out well.Just be careful where you locate centering hole so you can get
at it after the swing-arm is on the bike.There are both stainless and chrome collars,1and1/8 I.D.I centered mine 1/2 inch
in from the sides,with the pinch bolt towards the bottom.Drilled and tapped the collars using 1/4-28 jam screw as per
instructions from Heinz,who passed away about a year ago.

Carbonfibre wrote:The best way to sort this problem out would be to remove the thin wall spindle mounting tube from your spare cradle, get something more substantial made, and fit that to the cradle. I would imagine the OE mounting tube is getting distorted in use, leading to the hole becoming oval.

You're right, the metal isn't actually wearing, it's being stretched. And it isn't the tube itself, it's at the cradle plates where all the contact loads are concentrated by the spindle. The spindle mounting tube has no strength or structural function at all, it's just there to hold the oil in. If you cut one in half you'll see how thin they are.

I cut the spindle mounting tube out and made a new one out of bar stock and had it welded to the cradle plates. The guy that welded it for me said it was pretty cool and he saw what I was trying to do but it would have been almost as good to just run a bead around the original weld at the cradle which would shrink the metal back down and give it a tight fit again. It's probably true.
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Ted

PM sent.

rpatton wrote:

Carbonfibre wrote:The best way to sort this problem out would be to remove the thin wall spindle mounting tube from your spare cradle, get something more substantial made, and fit that to the cradle. I would imagine the OE mounting tube is getting distorted in use, leading to the hole becoming oval.

You're right, the metal isn't actually wearing, it's being stretched. And it isn't the tube itself, it's at the cradle plates where all the contact loads are concentrated by the spindle. The spindle mounting tube has no strength or structural function at all, it's just there to hold the oil in. If you cut one in half you'll see how thin they are.

I cut the spindle mounting tube out and made a new one out of bar stock and had it welded to the cradle plates. The guy that welded it for me said it was pretty cool and he saw what I was trying to do but it would have been almost as good to just run a bead around the original weld at the cradle which would shrink the metal back down and give it a tight fit again. It's probably true.
.

That looks a very good idea..........I would think play on the swinging arm due to movement where the spindle mounts is pretty common, and needs something along the lines you have done to rectify the problem.

Stoned hippy hayseed's rump view inspired by stoic Bob Patton lead.

Thanks one and all! If either collar or welded nut method is about equally effective, I'm inclined to go the collar route.

On the other hand, if the root cause is that the tube is effectively spaghetti (0.12" wall), wouldn't the tube itself flex under collar or nuts? What if I were to weld the split clamps on the tube, say 1/4 to 5/16" inward from the plates, with multi-pass full penetration weld to fill the gap, and a fillet weld to the tube on the other side of the clamps? That would reinforce the tube pretty far out from the side plates, perhaps shrink the tube, and tie everything together. Would this distort the plates too much?

Nobody commented on re-use of the spindle (Of course it would depend on how bad it is.) It appears that the left end of the spindle has essentially no wear, and no visible wear under the bronze bushings, either end. It does have about 0.002" to 0.003" off half the diameter (facing rear) on the right end, starting at the cradle plate going inward. Total play is much more due to ovality of the hole. Waste of money or should I just get a new spindle?

So what is the "dogbone" link mounted between Hobot's cradle and frame? Looks like it would supplement (or fight) the head steady?

Ted Lang wrote:Thanks one and all! If either collar or welded nut method is about equally effective, I'm inclined to go the collar route.

On the other hand, if the root cause is that the tube is effectively spaghetti (0.12" wall), wouldn't the tube itself flex under collar or nuts? What if I were to weld the split clamps on the tube, say 1/4 to 5/16" inward from the plates, with multi-pass full penetration weld to fill the gap, and a fillet weld to the tube on the other side of the clamps? That would reinforce the tube pretty far out from the side plates, perhaps shrink the tube, and tie everything together. Would this distort the plates too much?

Nobody commented on re-use of the spindle (Of course it would depend on how bad it is.) It appears that the left end of the spindle has essentially no wear, and no visible wear under the bronze bushings, either end. It does have about 0.002" to 0.003" off half the diameter (facing rear) on the right end, starting at the cradle plate going inward. Total play is much more due to ovality of the hole. Waste of money or should I just get a new spindle?

So what is the "dogbone" link mounted between Hobot's cradle and frame? Looks like it would supplement (or fight) the head steady?

Any sort of clamp arrangement on thin wall tube will improve things, but will not alter the fact that the tube is too thin and while it may have worked ok when the bike was new, will almost certainly have distorted to some degree over the years, which will mean excessive play in the swinging arm.

Fit a thick wall mounting tube, which has been accurately bored to suit a new spindle exactly. Assemble with copper grease, and you should have no more problems.

Id throw a couple of bits of 1/2 steel aft at ends , slotted & through tube . Drilled for H.T. aircraft grade unobtainium screws , this might CLAMP it satisfactorilly .

Better to replace with a 40 mm Min HT tube & needle roolers , Though . . . Though the Cosworth runs a similar thing dimensionally , along with many others .
Load if secured at ENDs would be ' less ' . significantly . But . but . but . Bushes ? often theres Needle Roller replacements for Std. size bushes . Which the designers
tend to use , from their ' Standard bushes catalouge . ' .

ONE THING , a bloody great PRESS ( 20 T ) can fit the pin at a reasonable interferance fit . ' Always do youre best ' , and dont put youre finger in it .

Ted Lang wrote:Thanks one and all! If either collar or welded nut method is about equally effective, I'm inclined to go the collar route.

On the other hand, if the root cause is that the tube is effectively spaghetti (0.12" wall), wouldn't the tube itself flex under collar or nuts? What if I were to weld the split clamps on the tube, say 1/4 to 5/16" inward from the plates, with multi-pass full penetration weld to fill the gap, and a fillet weld to the tube on the other side of the clamps? That would reinforce the tube pretty far out from the side plates, perhaps shrink the tube, and tie everything together. Would this distort the plates too much?

Nobody commented on re-use of the spindle (Of course it would depend on how bad it is.) It appears that the left end of the spindle has essentially no wear, and no visible wear under the bronze bushings, either end. It does have about 0.002" to 0.003" off half the diameter (facing rear) on the right end, starting at the cradle plate going inward. Total play is much more due to ovality of the hole. Waste of money or should I just get a new spindle?

So what is the "dogbone" link mounted between Hobot's cradle and frame? Looks like it would supplement (or fight) the head steady?

If you go this way I would be inclined to turn a chamfer (or attack it with the angle grinder) on the inside edge of the collar that is closest to the plates so there is as smaller gap as possible and then weld it as you have described. The plates should be fine but it will shrink the tube! I have just mocked mine up to set the ISO clearance. I had also ground back and rewelded around the tube as original they hadnt even ground off the mill scale and it had some very obvious cold laps. Long story short it now needs honing to get the spindle in.

The link on Hobots bike and rpattons bikes help transmit any lateral load to the frame instead of and in conjunction with (depending on which one) the plastic washers in the ISOs, Im sure either will clarify but I think they both have replaced the head ISO with a link and added a third to the front ISO as well

Cheesy wrote:If you go this way I would be inclined to turn a chamfer (or attack it with the angle grinder) on the inside edge of the collar that is closest to the plates so there is as smaller gap as possible and then weld it as you have described. The plates should be fine but it will shrink the tube! I have just mocked mine up to set the ISO clearance. I had also ground back and rewelded around the tube as original they hadnt even ground off the mill scale and it had some very obvious cold laps. Long story short it now needs honing to get the spindle in.

That's what I did when I was turning the tube, I cut a bevel where the guy was going to weld. Yeah, the original welds on the tube aren't great, but they only had to be oiltight. They knew that the tube wasn't structural.

They did something funny when they put the cradle together. The tube is turned down at the ends so that it fits inside the plates. They used it as a distance piece. You can just see it when you look at the side of the cradle. So when I cut out the tube and filed down the welds there was a 0.060" thick collar in a 1" hole in the cradle. These are from memory and it's been 15 years so they're approximations. I left them in and used a spindle to position the new tube for welding, but I wrote off the plates as being able to take a load directly. Yes, welding certainly does shrink things. I had to use a press to get the spindle out and needed to use an adjustable reamer to get the dimensions back.

For me, the link in the back is an attempt to stabilize the cradle vertically near the swingarm, working along with the rear iso. Then the headsteady and the front iso only have to more or less deal with side to side forces. Also, the cradle plate idea works great on the Featherbed, but hanging the swingarm off it overwhelms it. The material strength of the plates, the fasteners, and the bosses cast in the cases aren't up to it, so they get a small break too.