Going Straight

I am doing this post only to share a cheap, easy, and very accurate tool for checking wheel alignment. I have searched this forum for wheel alignment and have read about fluorescent light bulbs, strings, boards, etc.
My business requires us to have a sheet metal shear and brake. We use it to make trim for metal buildings. The sheet metal shear produces a clean cut which is very straight.
I made two tools. One to check sprocket alignment and one to check wheel alignment.
They are just a piece of sheared 29 gauge sheetmetal with some bends on one edge for stiffness and ease of handling. It can be built to work on either side of bike. Right side would be best as chain guard would be in the way on a bike that was not stripped down. Then anything that would be in the way of bringing the tool to the wheels is cut away. You could even cut around the tires.

I thought that you folks may be interested in what I found. It is a great deal straighter than I thought it would be.
It's an 850 Commando, build date June 1973. Wheels are true. Forks have been rebuilt. Rear axle is all the way to the back of the axle slots. Rear axle center is the same distance from swingarm pivot center on both sides.
Bike is still being torn down, hence the grime.
The front rim is rusty , so is being replaced with a 19" WM3 Excel and SS spokes.
Although I would like to replace rear rim with an 18", the rim and spokes are too good so I am just having it re-torqued. I figured that this was a good time to check things out in case I wanted to move right or left with the wheels, the re-lace guy could do it with the spoke set-up.
The front wheel is 1.5 mm further to the left than it should be. That is close enough although I will ask the wheel builder to try to get that out.
The first thing I did was a visual sighting of the front sprocket from the rear sprocket.
From this It looked like the rear sprocket should move 9 mm to the right. The tool I made proved this to be wrong. Sprocket alignment is pretty good with the front of rear sprocket just 1 mm or so too far to the right.
With the wheel alignment tool pushed up against the front and back of front wheel and the back of the rear wheel. There is 5 mm space between the front of rear wheel and the tool. If I adjust rear axle to bring this to the tool, the wheels will be aligned and the sprockets will be very close too.
I am actually impressed as to how close it is. I did not expect that.
Most heating contractors and steel building producers would be able to make something like this.
Note the wood shock. Pine for solo, and hardwood for 2 up, eh?

neato, good job

Congrats on making a useful tool!
Although the front rim is centered in the forks, the rear rim is slightly offset to the right with respect to the hub, 1/8-3/16, IIRC.
To get wheel alignment on my bike, the right side of the rear axle sits about 3mm farther to the rear in the axle slot. I believe this is due to the slightly asymmetric swingarm.

Great tool!

Thanks for posting.

It’s good to hear that some Norton’s were made straight after all !

I don't think this alignment method guarantees straightness. You can turn the bars and make the wheels parallel. Ludwig posted about this years ago and had a nice picture of what happens. I think whatever method has to reference the backbone of the frame. Also the wheels might not be not aligned in the vertical plane so check with a plumb bob.

You turn the bars so that the wheels are parallel anytime alignment is checked.
That's a must.
With the wheels parallel and the alignment tool above, or a string, or a straightedge, one can see if they wheels are both in one plane or if they are parallel but offset to one another. If offset then change things until the wheels are parallel and in the same plane. You also want the rim centres to be on the frame centreline at the same time, that's where it sometimes gets a bit tricky. The tool shown above doesn't necessarily help with that, although it could have frame centre marks offset and dropped down on it to give that reference.

Glen

I think that with a bit of care, and a plumb bob (as already suggested) this tool would show if the wheels were central to the frame quite well. Because it is so long, any error will show as quite pronounced.

If the front wheel is centralised in the forks, and the tool applied as shown, a plumb bob, or vertically placed spirit level placed at the rearmost point and viewed from behind with a half decent eye would show whether or not it was in line, certainly to an accuracy that’s good enough for most of us to care about !

As it sits, unless I'm missing something, it would work well to align the wheels in one plane.
All that would be required to see if the wheel centreline is on the frame centreline would be reference marks made at a chosen offset and dropped off the frame spine onto the body of the straightedge.

I was too lazy to build a frame jig for my one off Egli monoshock frame, so I used a similar straightedge with reference marks when building frame and swingarm.
It worked just fine.

Glen

Well, I didn’t like to say Glen, but I always thought you were pretty lazy building your hand built, 1360cc, monoshock, Egli Vincent too ...

batrider said:

I don't think this alignment method guarantees straightness. You can turn the bars and make the wheels parallel. Ludwig posted about this years ago and had a nice picture of what happens. I think whatever method has to reference the backbone of the frame. Also the wheels might not be not aligned in the vertical plane so check with a plumb bob.

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If the wheels are parallel but not inline (in the case of 2 equal width 19" rims) there will be space to the straightedge at the front (or vice versa) until the back wheel is brought true. I use a similar method on machines with 3.5" front rims and 6" rears. When the wheels align, the space to the front and back of the front rim will be half the difference (1.25") in the wheel sizes. Plumb should be checked before you start because if something is bent, all bets are off. The most accurate place to check alignment is at axle height.

If we are lucky maybe Christ on an allotment parellel bike will be along to advise soon!! Cheers

Fast Eddie said:

Well, I didn’t like to say Glen, but I always thought you were pretty lazy building your hand built, 1360cc, monoshock, Egli Vincent too ...

Click to expand...

It was one of those " this won't take long" deals that turns into a year and a half of workplay.

Glen