Swing Arm Spindle Fix - different way, am I nuts?

Why not turn the whole spindle tube/transmission plate into a clamp?

That is clamp the swing arm tube with the spindle tube and the transmission plates.

I'm thinking of making a single long cut at the rear of the transmission plate unit; it would go from one transmission plate and on across through one side of the spindle tube and through the other transmission plate. The cut will be at 90* to the chassis to turn the transmission plates and the spindle tube into one big clamp for the swing arm spindle.

I'd weld a pair of steel bushings to the inside edge of each of the transmission plates but not to that Reynolds 501 spindle tube. A pair of pinch bolts, residing inside each pair of the bushings, one bolt per side, would then clamp the swing arm spindle inside the transmission plates' spindle tube. I've got some used 12 point ARP rod bolts that are about the right size.

The questions are . . . . first, will the bolts/bushings and clamped swing arm spindle maintain the integrity of the transmission plates? The swing arm will be torqueing on those transmission plates, on those new bolts, and right up to the isolastic tube above, and . . . second, without disassembly, will I be able to get in there and make a clean cut and good welds?

xbacksideslider said:

Why not turn the whole spindle tube/transmission plate into a clamp?

That is clamp the swing arm tube with the spindle tube and the transmission plates.

I'm thinking of making a single long cut at the rear of the transmission plate unit; it would go from one transmission plate and on across through one side of the spindle tube and through the other transmission plate. The cut will be at 90* to the chassis to turn the transmission plates and the spindle tube into one big clamp for the swing arm spindle.

I'd weld a pair of steel bushings to the inside edge of each of the transmission plates but not to that Reynolds 501 spindle tube. A pair of pinch bolts, residing inside each pair of the bushings, one bolt per side, would then clamp the swing arm spindle inside the transmission plates' spindle tube. I've got some used 12 point ARP rod bolts that are about the right size.

The questions are . . . . first, will the bolts/bushings and clamped swing arm spindle maintain the integrity of the transmission plates? The swing arm will be torqueing on those transmission plates, on those new bolts, and right up to the isolastic tube above, and . . . second, without disassembly, will I be able to get in there and make a clean cut and good welds?

Click to expand...

There is nothing stopping you from cutting and welding to your heart's content. That being said the spindle clamps have seem to proven themselves highly effective and very cost effective. It doesn't seem like your proposal has that much advantage over the clamps, other than killing off an afternoon or three. :mrgreen:

In fact it sounds more like the MkIII solution.

Dave -

Good point about the MKIII assembly. I can see where the MKIII design prevents the swing arm spindle pin from moving side to side laterally, but does it clamp the pin inside the spindle tube? I have not seen those parts, are the bolts also wedges? If so, then yes, they clamp the pin.

I got onto this idea because while the spindle clamps provide two threaded holes to deliver two more bolts to the swing arm spindle pin, they do not clamp the extremities - at the point of greatest leverage, or do I mis-understand them?

For that matter, you could just drill two holes and put bolts through them . . . . the swing arm pin would prevent the spindle tube pin from crushing, would it not?

xbacksideslider said:

Dave -

Good point about the MKIII assembly. I can see where the MKIII design prevents the swing arm spindle pin from moving side to side laterally, but does it clamp the pin inside the spindle tube? I have not seen those parts, are the bolts also wedges? If so, then yes, they clamp the pin.

I got onto this idea because while the spindle clamps provide two threaded holes to deliver two more bolts to the swing arm spindle pin, they do not clamp the extremities - at the point of greatest leverage, or do I mis-understand them?

For that matter, you could just drill two holes and put bolts through them . . . . the swing arm pin would prevent the spindle tube pin from crushing, would it not?

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I'm really comfortable that the way I did my spindle is probably the most effective for the effort which was just drilling two holes in the tube and not through the hard spindle [edited]. I was told that I couldn't use the flats on the spindle but I used shorter bolts and they clear the swingarm just fine.

not-another-spindle-thread-t5978.html

ludwig,
That's exactly what I had done to mine. Since it was already beaten oversize, I had it bored out and the .005 over spindle put in and 2 allen bolts like yours. Nithburg in Canada did it for me, don't know if they still do. Cost me about $175 plus shipping back in 03. But if the spindle is still good, you could probably do it on the bike taking the rear wheel off.




Dave
69S

xbacksideslider said:

The questions are . . . . first, will the bolts/bushings and clamped swing arm spindle maintain the integrity of the transmission plates? The swing arm will be torqueing on those transmission plates, on those new bolts, and right up to the isolastic tube above, and . . . second, without disassembly, will I be able to get in there and make a clean cut and good welds?

Click to expand...

I think the answer to both of your questions is probably no. The cradle plates are pretty weak but it seems to be sufficient, if you do anything to weaken it you might be asking for it.

You wouldn't believe how thin the swingarm tube is until you cut one in half and its not the tube that actually stretches. When parts like the cradle are stressed by something like the swingarm spindle it isn't the tube that is going to show the strain, its the furthest outboard edges that bear the load and cave first. That would be the plates. I cut the old tube out and made up a tube from bar. I make it as big as I could till I ran out of plate to weld to, it's very thick at the clamp points. I wouldn't recommend going that far but my cradle was pretty far gone at that stage. Truth be told, just running a bead around the tube at the plate will shrink everything down pretty well and buy one years of use.

Yeah, ludwig. I don't have a machine shop here, so I have to get people to do things for me and I find the closer they are the more expensive they are. I had a local guy chase a 3/8-20 thread for me and it cost me $40 and the item was only $5. However he is not getting any more of my busines since I told him not to hurt me. I don't happen to have a friend with a complete machine shop either. That's the price I pay, but only once.

Dave
69S

swooshdave said:

xbacksideslider said:

Dave -

I have not seen those parts, are the bolts also wedges? If so, then yes, they clamp the pin.

Click to expand...

Click to expand...

They are wedges.

Ken

Bob,
Your bike has so many surprises. I love it.

Scott

Well, now I don't know what I'm gonna do. Guess I'll pull it apart and see how bad it is. I know it's pretty bad, based on the amount of slop she has. Tapping the pin for cap screws is looking good. Some washers with a radiused surface to bear on that thin 501 spindle tube seem like a good idea. Or, maybe build up a pad . . .

I'm hoping that I can rotate the pin 45* or flip it end to end together with a 45* rotation, to present unworn surfaces on the pin to the swing arm bushing. I imagine, as I have seen in other bikes, that the bushings in the swingarm will be "OK" having picked up grit that got embedded into the bronze bushings of the swing arm and then that grit cuts the bearing surface of the swing arm pin/spindle.

The bushings like mine were may be good, but the hole in the cradle may be worn past just rotating the (rusty) spindle. You may need to bore it and get an oversize spindle, which means boring the bushings too. I wouldn't try to fudge it, it will only get worse, just my opinion.

Dave
69S

I just rebuilt my swing arm. When I first built the bike up, I simply drilled the extra two holes, at the out board extremities as shown. That worked pretty well for 10,000 miles. But this time I decided to make an oversize spindle, approximately 5thou and reamed out the tube to make a nice drive fit, still using the extra bolt trick. This works really well I think, and if you thread into the spindle, it makes for a pretty sturdy set up. If you have a lathe it is a pretty easy project, I even used the original swingarm bushes, just bored em to suit the pin. Ream can be purchased for about $20.00.
I do like the set up shown in pictures on this post with the rod link. However after fixing my swing arm spindle, the handling is rock solid.

Cheers Richard

Here how Less Loudin did an alloy cradle that ended up in Peel. Top blocks 3/8" allen head bolts clamp spindle not to rock in its bushes.


Rock steady is a relative term Richard. My experience is the more ya rigid up the chassis the stabler it gets until next threshold is reached for a harsher crescendo.
Trixie has late Heinz's collars and large spindle in new bushes, can't see-feel any slack in the joint, one to one transmission of rear patch tug thru rear iso pivot to the front iso. I can still induce hinged handling limits in sweepers before traction becomes a concern. I don't hear much descriptions of riding in and out of hinged handling states. So its scary to read about rock steady w/o some idea how hard
the rocks pressed on. My safe way to judge the improvement or lack of, is low air in one or both tires then zig zag in lane till bike or me can't take it. Finding out while eagerly leading or following sport bikes in 80 mph above sweepers is the scary way to me on non linked isolastics. Below the nutzo onset, factory Trixie with collars and greased bushes feels like flying carpet on rails.
Until the carpet ends starts flapping, weehoodoggydoo!

Hobot, my term rock steady was relative to the feel of the bike before tightening up the old girl. Granted I am not a racer, but the first ride, the bike felt different than I remember, even though this was a while ago. My Australian winter rebuild included engine, iso's and new tank and side covers. I first thought the bike felt a little ressistive to turning, kind of stiff. I am running 4.10 avons front & back. But I was okay with the handling before, but now she feels more planted, once initiated into a turn. So much so it shows up the dampening or lack of it in the front end. I might even try modifying the damper pistons in the forks to control the springs better?

Cheers Richard

bpatton said:

Truth be told, just running a bead around the tube at the plate will shrink everything down pretty well and buy one years of use.

Click to expand...

I can't see any telltale in this photo, but where is your oil filter (if you have one)?

This is probably the haunch link I'll end up with to complete the iso / linked triangulation, as it appears this one can co-exist with oil filter AND centerstand!

xbacksideslider said:

Tapping the pin for cap screws is looking good. Some washers with a radiused surface to bear on that thin 501 spindle tube seem like a good idea. Or, maybe build up a pad . . .

Click to expand...

My bike is still pretty tight so I put this mod on the back burner but plan to deal with it this winter. I have been thinking about using Ludwig's method but adding your idea of radiused washers. I have been thinking about finding a section of tubing with an inside diameter equal to the outside diameter of of the cradle tube. Then splitting it lengthwise wide enough to cover about a quarter of the surface of the cradle tube. If the diameters are not a perfect match, this is one of those places that I would use some type of epoxy as an interface thus spreading the load out. Over-engineered? Maybe, but this appeals to me and is much simpler than it sounds! It will be mid-winter before I am getting to this project.

Russ

grandpaul said:

I can't see any telltale in this photo, but where is your oil filter (if you have one)?

This is probably the haunch link I'll end up with to complete the iso / linked triangulation, as it appears this one can co-exist with oil filter AND centerstand!

Click to expand...

It's a high capacity filter. I had to loose the pocket on the inside of the sidecover but I never used it anyway. The link probably would have been better positioned further down and away from the spindle but I really wanted to keep the centerstand.
Speaking of centerstands, there hasn't been much in the way of pointless stories lately, so I'm going to throw one out.
I was in Terrace, B.C. and I needed a new rear tire, I didn't have a centerstand at the time. The dealership there was a converted furniture store or something and the shop was in the basement which was accessed from the back. It had a long wooden ramp down from the alley to the shop. The guy there could hang the back of the bike from the ceiling, but he wouldn't let me ride it down the ramp, so he took it. He forgot what I told him about the brake being on the left and managed to lock up the rear wheel by putting it in gear. He skidded down the ramp and centerpunched a Goldwing. Didn't hurt my bike but he knocked over the Wing, $$. I promised myself then never to let anyone touch my bike and not to get caught without a centerstand again.

The hard part is that I'd like to get an effective fix done now, for a BSA club ride in the Lake Isabella area of CA in a couple of weeks. With that deadline, I'm not going to get into taking the cradle out of the bike.

When the day comes that I do pull the trans and I'm looking at an oversize swing arm spindle pin and reaming (or building up the ID of ?) the spindle tube, while I'm at it, a Heim joint link will be going in too.

Might whip up a Heim joint head steady in the meantime though.

Hobot, my term rock steady was relative to the feel of the bike before tightening up the old girl. Granted I am not a racer, but the first ride, the bike felt different than I remember, even though this was a while ago. My Australian winter rebuild included engine, iso's and new tank and side covers. I first thought the bike felt a little ressistive to turning, kind of stiff. I am running 4.10 avons front & back. But I was okay with the handling before, but now she feels more planted, once initiated into a turn. So much so it shows up the dampening or lack of it in the front end. I might even try modifying the damper pistons in the forks to control the springs better? Cheers Richard

Click to expand...

OK Richard that makes perfect sense and exactly matches my own on fully fettered Commando minus the rear and other rod links. Commando ridden just short of hinged handling are wonderful delights that more than keep up with sane thrilling riding. So stable and fine it can lead ya into trouble, usually a decreasing sweeper.

Rod links do add another level of smoothness but only if the rest of the bike is up to snuff. As you state its sorta like polishing Al, the finer the grit the more the imperfections stand out, if you look that close or press than hard. Best to let some air out a tire or two and get the sense of wobble and reversed input reactions and just never ever go there in joy rides and be pre-trained to recognize a low tire before it tears the stem out blow out. You can not feel a blow out at high speed straight line, justs feel like some wind buffet, till ya lean a little, wheehooowee.

Bob's rear link is too high for oil filter. I'm going to make a center stand with a crook in it to clear Peel's lower down away from spindle and rear iso to have more leverage advantage against their distorting under loads and let offs.
I had to spend a bunch to get smaller filter to mount over the spindle d/t increasing the rear spring travel a couple more inches made swing arm brace
strike the stock oil can.

So far only two know the joys of fully fettered Commando + 'rump' linked.
Bob would you speak about any sense of ride comfort you got by the rear link beyond the handling transformation. Its so nice I often get stoned just puttering along not wanting anything to jostle the sense of no bike under me.