Seat tube lugs

[Anthony_]

I have an old Falcon Super Tourist, with Reynolds 531 frame. The seat tube has a couple of lugs at the back to hold a bolt used to clamp the seat post. Some while back, a bike shop fitted a too small seat post, and used a quick release to clamp it. Due to overtightening, the lugs have been ground away to the point there is no longer a flat bearing surface.
I have now found a seat post that fits. Amazingly, it is the exact size it was always supposed to be! But now I am have trouble finding something to put through the lugs to secure the post. My thinking is:
- sacrificial copper washers
- aluminium ferrule
- epoxy a bolt in place.

Any better ideas?

[531colin]

Yeah epoxy a bolt in, or fabricate a bolt head so it can't turn.

IMG_1399 by 531colin, on Flickr

IMG_1397 by 531colin, on Flickr

Tighten the nut.....that way the bolt bends ONCE to conform to the bent lug shape....if you make it so you have to turn the bolt, it won't last!

PS....those are "wrap-over" seatstays.....whats the thing in front of one seatstay?

[Anthony_]

That thing in front is the brake cable.
I don't think I can fabricate anything to fit that space so it won't turn. That's why I was thinking of crushing some copper or aluminium in there. Just enough to stop the bolt turning when tightening the nut.

[PT1029]

The mangled side of the lug has the slot for the bolt to key into.
Does the other side of the lug have such a slot (if so, turn the bolt round the other way), if not, you could file one in on the other side, then put the nut end of the bolt on the mangled side. If I was doing that, I think I try to make something triangular/wedged shape to try and square up the mangled section.

Alternative would be to grind off the back parts of the lug and get a frame builder to braze on some new parts for the bolt to go in. Rather boarder line economics considering the bike, and only then if you touched up the paint your self.

Some seat bolts have a hexagonal head, thus with 2 spanners you would not need to worry about the bolt not keying into the lug.

[mattsccm]

As a yougster the concept of making something knackered work perfectly well was almost the default. In this situation we would use a bog bolt witha washer underneath to stp it pulling through. If it did use tw or thicker one or even a nut. File out anything in the slot that stops it closing properly. Alternately I have welded a captibe bolt in from the most damaged side.
You can buy, mine were fromAliexpress or possibly some junk advert from Facebook, super duper welding rods that work with a blow torch and ging by the videos will hold a train. I don't have a train but it will hold shelf brackets together. Worth a try if you don't have a welder handy.

[Anthony_]

There is a slot, on both sides. But the bit on the seat post binder bolt that I bought is far too discrete to be stopped by it.
I think the remaining bit of lug does not have enough material to compress the tube. I am going to have to pack it out with something.
I think a brazing fix will be uneconomic. It's a shame, because the rest of the bike is fine.

[Jdsk]

Experts, please: Could you cut off the lugs and and use an external clamp? How far does the slot in the tube currently extend below the lower edge of the top tube?

Thanks

Jonathan

[PT1029]

Use of an external clamp (I guess you mean collar similar to Collin's photo up thread) might work, it would depend on how much seat tube/lug there was sticking up above the top tube on the front facing section.
Of course, trying this has no way back if it didn't work.

[Anthony_]

I can't see any way to fit an external clamp. There is no space above the top tube, and the seat post stays are in the way.

[jimlews]

If this were my problem I would first:

Attempt to carefully reshape the deformed eye by inserting a blunt drift through the L/H, undamaged eye to tap out the deformed metal to something like it's original shape - from the inside. Bicycle metal usually has enough malleability to tolerate this, unless it's a casting, which this isn't.

If that failed, a competent frame builder could remove the bolt eye and braze a "proper" item in it's place - a relatively inexpensive procedure;
IRO £60.00 for an allen key seat clamp boss C/W stainless steel bolt.

[Barrowman]

I would try a slightly undersized bolt with a washer under the head from the side you can't see in the photo.
With a bit of luck the Nut will partially engage in the bent bit and can be tightened by the bolt from the 'other side' Perhaps a nylock Nut or a shakeoroof washer.
Don't think a 'loose' clamp will work, the top of the lug is curved and the wrap over might be in the way too.

[531colin]

https://spacycles.co.uk/m9b0s84p3102/SP ... atpin-Bolt

Those are designed to fit the "un-mangled" seat cluster.......the plain shank is 8mm diameter and the head is 12mm diameter.

For the mangled seat cluster, I might look at something like these;

https://www.screwfix.com/c/screws-nails ... ge_size=20

The sleeve of the "sleeve nut" is again 8mm, and the flat head is 15mm.
I would be looking at using 2 of the sleeve nuts; in one I would silver solder (or epoxy) a bit of M6 threaded rod, for example from one of those bolts, or any M6 bolt. The other one I would drill (or file) out the thread. On both, cut off part of the flat head to seat against the seat cluster. Then, insert the special bolt from one side, insert the drilled out sleeve nut from the other side, and clamp up using any M6 nut. The bolt will bend, once, to conform to the shape of the lug.

E bay and Amazon both list M8 furniture connectors, where the plain sleeve will probably be about 10mm diameter

[Anthony_]

OK, thanks for all the helpful advice.
I think brazing is the best solution, but I'd have to find someone nearby, get the bike to them, repaint afterwards. So it is a last resort. If I knew someone nearby (Surrey) I would give it a go. But the bike is old and nothing special (except I like it!) so if it gets to that, it might just be time to replace it.
I think the problem for a bodge fix is that the lug has worn to the point that it bends instead of pulling the tube closed. So I am going to try: packing the space immediately on the lug with M6 washers; file away a bit of the outside to get a new bearing surface; put some M8 washers on that; put an M6 bolt through; epoxy it all in place; put a nut on the face of the undamaged lug. Let's see if it holds!

[rogerzilla]

Argos fixed my mate's when he had the same issue. Once you add the cost of a respray and decals it gets to £400 very easily. He loves that bike, though.

[Anthony_]

Here is what I have done. The bad replacement seat post was 26.0. By trial and error I found I could fit 26.6. The inside is bright steel apart from the top few inches, which are heavily scarred. Below that, it appears to be butted. 27.0 fits down to a hard stop, and 26.8 goes a half inch further. Only 26.6 slides the whole way in.
I have cut a shim so that it packs out only the rear of the post. Then I have used an M6 bolt and washers, starting with M6 form A washer, then lock washer, then M6 form C washer, then lock washer, then M8 form A washer. The idea is to give more bearing surface, and not just compress the weak part of the lug.
I decided against epoxy, as I think it would have simply given way when the lugs changed shape.
So far, it works on a very short ride.