swing arm alignment

[Omarttentmaker]

Anybody got a home-made way to check a tubular swingarm for alignment from left to right? Eyeballing mine from what would be the back of the bike, it looks as though the brake-side arm is higher than the right. I'm guessing that the 2 slots where the axle fits through should be in the same plane. The only way I can figure to do it would be to run a shaft through the bearing inner races and rest it on equal sized blocks, then jack the back up with jack screws and indicate the slot on either side once one is level. This seems like a tedious and time-consuming task, to say nothing of the prep, and access to a surface plate big enough to rest everything on. Any suggestions?

[joe fxs fxr]

Use a level to get the frame square then check the swing arm for level. You may need a string level to get thru the spokes.

[pan620]

Anybody got a home-made way to check a tubular swingarm for alignment from left to right? Eyeballing mine from what would be the back of the bike, it looks as though the brake-side arm is higher than the right. I'm guessing that the 2 slots where the axle fits through should be in the same plane. The only way I can figure to do it would be to run a shaft through the bearing inner races and rest it on equal sized blocks, then jack the back up with jack screws and indicate the slot on either side once one is level. This seems like a tedious and time-consuming task, to say nothing of the prep, and access to a surface plate big enough to rest everything on. Any suggestions?

I did what you said to one on a 68, can not remember exactly how much it was out of level but is was a lot, long story but figured out that is was cracked on the drive side, it was one of the early ones with out the extra gussets added. I just replaced it it instead of repairing.

[T. Cotten]

Anybody got a home-made way to check a tubular swingarm for alignment from left to right? Eyeballing mine from what would be the back of the bike, it looks as though the brake-side arm is higher than the right. I'm guessing that the 2 slots where the axle fits through should be in the same plane. The only way I can figure to do it would be to run a shaft through the bearing inner races and rest it on equal sized blocks, then jack the back up with jack screws and indicate the slot on either side once one is level. This seems like a tedious and time-consuming task, to say nothing of the prep, and access to a surface plate big enough to rest everything on. Any suggestions?

I guess it depends upon where "home" is, Omar!

It sounds like another case of sidecar disease.

My inspection equipment is naturally the same as the straightening fixturing...

SWNGRM1.jpg

The large press was used only to secure the fork square, and then a variety of means were used to force a leg upward or downward, using the cage of the large press to stabilize the other.

....Cotten

[BigLakeBob]

Looks like a nice process Tom.

[T. Cotten]

Looks like a nice process Tom.

The steak-knife shim didn't bother you, Bob?

.....Cotten

[BigLakeBob]

The steak-knife shim didn't bother you, Bob?

.....Cotten

You know a machinist, we want everything perfect, but there is also a time to be practical and get the job done. I use shims a lot especially when machining a casting.

[T. Cotten]

... I use shims a lot especially when machining a casting...

But,.. With rosewood handles, Bob?

(Forgive me, Folks! Omar asked for a home-made remedy; My point is that with a little imagination, the dumpsters offer the best resources...)

,,,Cotten

[BigLakeBob]

Tom, I was trying to compliment you on your ingenuity and make fun of a machinist like myself. My comment about being practical was to say you have what it takes to get the job done where someone as myself will sometimes go overboard.

P.S. Just curious so Omar knows where to shop. Did the press, holding blocks, machinist square, knife, aluminum flat and round bar, rebar, and all come from a dumpster?

[T. Cotten]

...P.S. Just curious so Omar knows where to shop. Did the press, holding blocks, machinist square, knife, aluminum flat and round bar, rebar, and all come from a dumpster?

I was keeping it fun too, Bob,..

Until you ask where a diver finds his trophies; Then its like asking a fisherman which pond he caught his lunker.

My point is to keep fishing.

....Cotten
PS: Yes, Folks,.. one way or another, they were ALL scrounged. No other means is practical.

[Omarttentmaker]

20210313_073619.jpg
20210313_074123.jpg
This shows leveling the frame....note cardboard shims!
20210313_074628.jpg
20210313_073708.jpg
this shows 2 different arms
20210313_074007.jpg
This is the good arm.

[Omarttentmaker]

Hope these pics show up. Thanks to all. Hey, Cotten, you really took "home-made" to heart!

[Omarttentmaker]

Here's a bubble pic of the bent arm. Of course, this is the one I prepped for assembly. New bearings, seals, paint, blah, blah, blah!
20210313_074639.jpg

[exeric]

In the frame alignments I have done, I always measure from a known datum, i.e. surface plate, and/or angle plate. In Tom's photo, it appears he is basing his measurements from a flat plate to precisely see what he needs to move, and how much. The surface plate can be upside down, hanging from a wall, or on a 33 degree angle, but all of your measurements will be based on that known, datum surface. I don't trust my eye with a bubble level, but I do trust steel rules, micrometers, depth gauges, and good dial calipers. Wow, Tom; it must have been like Kismet to find a screw press that had 'LIBERTY' cast into it's platen.

[Omarttentmaker]

In the frame alignments I have done, I always measure from a known datum, i.e. surface plate, and/or angle plate. In Tom's photo, it appears he is basing his measurements from a flat plate to precisely see what he needs to move, and how much. The surface plate can be upside down, hanging from a wall, or on a 33 degree angle, but all of your measurements will be based on that known, datum surface. I don't trust my eye with a bubble level, but I do trust steel rules, micrometers, depth gauges, and good dial calipers. Wow, Tom; it must have been like Kismet to find a screw press that had 'LIBERTY' cast into it's platen.

While I agree with you in theory, in practice I would have to say that a level is a pretty fair means of determining straightness dimensions. After all, even the manual displays 2-place dimensions for the frame straightness, which is plus or minus .015". And if you put a .015" shim under a bubble level, you can certainly determine by eye the difference displayed as opposed to level. As to point of reference, while I did shim under one side of the frame to achieve level across the motor mount surface, once that surface is level it becomes my point of reference. I figured if I followed that reference point back to the swingarm, it would align all the assemblies needed to be in line with one another. So motor refers to drive line, which refers to tranny and sprockets, and even how true the brake shoes are to the brake drum. The pic you see of the misalignment of the bent swingarm according to the bubble is .135", as I determined by shimming under the level "in situ" to move the bubble to its level position.