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Flandria Maeda Perfect Weco Cross Threaded Freewheel Repair.
#1
The bike is an old Flandria with a Maeda Perfect FW on a Weco hub.

This bike had about 1/4" transverse peak-to-peak wobble in the freewheel (10-speed, "big" gear.) Everything about the wheel was so true, I figured it had to be cross threaded.

So I leaned about freewheels and removed it to find it cross threaded as expected.

I cleaned up the threads with a 24 pitch thread file and the FW spins on nicely. I don't think the threads were damaged that badly. After 1-2 thread engagement, the FW is nice and snug with no slop. I can turn it on by hand all the way. It is nice and smooth with Never Seize on the threads.

Now here is the question I need answered:

This bike had 2 thin, about 1/16" square cross-section, spacer rings stacked on the hub before the FW was installed. There was also a plastic chain guard with an ID that was nowhere close to fitting over these spacers.

These rings were badly distorted, one more than the other - the worst one is now unusable.

Further, the plastic disc chain guard ID was too small to fit over these spacers, so there was a nasty haphazard stack of the 2 spacer and the guard beneath the cock-eyed FW.

When the FW is tighened, should it bear against these spacers or a flange or should you simply bottom out the hub threads?

There is a very narrow flat on the hub that these spacers could thrust against, but one of them was already starting to roll off this flat.

Frankly, I can't see this hub flat being wide enough for any kind of spacer bearing.

If I put the FW on the hub all by itself, the threads will bottom out.

There is a definite flange on the FW that could bear nicely against spacer washers. However there is nothing like that on the hub.

There is over 1/16" clearance between the FW flange and the hub flat.

If the FW must seat on its flange, then I would think the best course of action would be to use a wider steel washer that would not "roll out of the way" or make a washer that fits outboard of the hub flat. This outboard spacer would bear against the hub flange right next to the flat. While not machined, it is probably true enough.

QUESTION: Do I need a thrust spacer installed for the FW to bear up against or should I just let the FW bottom out in the threads?

Thanks in advance,
Tom

PS. I already assume the plastic disc chain guard ID should be enlarged to fit on the spacer.
  Reply
#2
I don't think it's critical, but I would think it would be better if the FW tightened up against the flange on the hub rather than the hitting something on the outside of the threads. It may be a little hard to find specific spacers for this, but if you're able to machine something, great. One easy jury rig is to use the lockring from an old cup and cone bottom bracket. Many shops will have a few of these lying around. The threads are usually the same as the hub threads, or you could file them out if you want just a clean spacer.

I'm a little confused what you're asking on the plastic chain guard. If the guard has a metal center, it wouldn't be unusual for this to get sandwiched between the FW and hub. If it's plastic of course, this won't work well and it should have little clips or something else to keep it snug against the spokes. These guards are not "necessary", but are a secondary protection against serious damage if you derailleur is bent or out of adjustment.
  Reply
#3
Thanks for the suggestions.

The spacers I referred to being aluminum are in fact steel - the section is so small, they bend quite easily so I mistook the metal.

The plastic chain guard is a bit of a mystery.

Someone definitely had this apart and looks like they were replacing spokes.

The ID bore of the plastic was too small to fit over the spacers. It would fit over the hub threads.

So if you put the spacer on, then the plastic disk, the disk would stack on top of the spacer. Then when you installed the FW, who knows what would happen. What I removed seemed to have the plastic pinched on one side and extruded out the other side. Of course the FW was quick cocked, so nothing stacked up as it was supposed to.

Currently, I have opened the plastic ID so it fits snugly over the one remaining usable spacer ring.

It now turns out that when I tighten the FW, it is stopped by this spacer and not the threads bottoming.

I am going to assemble it like that and not use any Blue Loctite. I will keep the Never Seize on the threads.

Still, I am not sure how the FW got into this state. There were two spacers, one of which was unnecessary and the plastic guard disk had a unworkable ID bore too small for the spacers.

To my current benefit, the two spacers kept the FW from engaging all the threads so by eliminating one, I'm using at least an extra turn of good thread.

Then I'll have to line up the balls and reassemble the FW(!) I took it apart do use a vise to unscrew the FW hub. That worked nicely and frankly, I would have been a bit concerned about using a proper took with the tang. Considering how had it was torqued, I would be worried about the tang and the hub slots.

One neat footnote on the Maeda Perfect FW is that there is a conical ramp that pushes the ratchets inward so you simply slide the sprocket ring onto the hub without any worries or rubber band contraptions. What a nice feature.

Thanks
Tom
  Reply
#4
Sounds good. Yes, no loctite on FW threads. The assembly is tightened every time you pedal so there is no risk of it coming loose. The big risk is cross threading from sloppy installation and seizing due to dissimilar metals (usually a junction of steel and aluminum.) Bikes tend to have several places where steel and aluminum sit against each other for long periods (seat post, stem) and it is important to occasionally clean and recoat these areas with grease or anti-sieze to prevent electrostatic welding.

From your description, I assume you have some machining background. You may be a bit surprised how sloppily bikes are often put together and maintained. The loads are often way below the limits of the materials (at least on older bikes) and it's somewhat amazing what people will get away with riding on for years. That said, always better to do it right. !!
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#5
Yes, I'm beginning to see what passes for a bike repair can be very crude to be kind.

I'm laughing, the Wright Brothers were bicycle mechanics, right? Its a wonder they got off the ground!

HaHa
Tom

PS. OT, but #000 steel wool is like magic when it comes to getting the chrome back on non-perfect rust pitted rims! Truly amazing. And it is VERY fast.
  Reply
#6
Spacers are there to get proper chainline. You would have to check to see if chainline looks acceptable without them mounted. http://sheldonbrown.com/chainline.html
  Reply
#7
Thanks cny-man, I think you hit the nail on the head.

Since the hub threads were degraded due to the cross-threading, and since the one spacer was completely bent/curled/rolled, I think my only option is to eliminate the one spacer and keep the other. This lets me achieve virtually full thread engagement on the hub/freewheel.

I'll check the resulting alignment when I get some time.

Thanks
Tom
  Reply


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