Hi, Any tips to help get a stuck seat post out? It's jammed fast and I doubt any of the WD40 I'm spraying on is getting anywhere inside either. Also, I am not the only one with trouble as it has so many marks on the post where the previous owner has had a go Thanks in advance IMG_2827 by Sooper 8, on Flickr
Lots of ice on the seatpost and a rag soaked in boiling water briefly on the frame. Clamp the seatpost in a steel vice and pull on the frame
By the way, there is evidence of a hacksaw cut at the bottom of the clamping split and someone has put a tack weld to hold it together. Using a sharp chisel or a careful angle grinder you could split that weld which would no doubt release the seat post. Welds contract as they cool which is probably why its holding the seatpost so tightly.
Al
Last edited by al_yrpal on 4 Dec 2012, 10:19pm, edited 1 time in total.
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Quite a few methods for this. If you don't want the post then cut it off level with the seat tube and then cut down the inside of the remaining post with a hacksaw blade, try to keep it level so you go through all of the metal together and avoid cutting the seat tube inner wall, do a few of these cuts in various places and then try to peel the cut seat post sections out with the help of a bit of levering.
Another option is the good old fashioned caustic soda down the bottom of the seat tube, bit more hazardous though.
Thanks of those answers. I don't want the post, so might go that route Trigger. Yes, now you point it out Al, I can see what you mean about the tack weld Cheers
I somehow missed Al's post first time round...I missed the tack weld, too....but what is going on right next to the other seatstay? I can see a line, or a Vee....but I can't turn it into anything logical.....?
531colin wrote:I somehow missed Al's post first time round...I missed the tack weld, too....but what is going on right next to the other seatstay? I can see a line, or a Vee....but I can't turn it into anything logical.....?
I should explain I didn't see it at first either and edited my post. I think it was done while the seat post was out and someone forced it in after welding.
You have pm
Al
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- I would not recommend putting the seat post in the photo in a bench vice; it looks thin-walled and has a round top. All you will do is crush it.
- the tack weld and other marks on the frame are IMHO red herrings; the seat post slot on this frame appears to have been cut before the frame was assembled or painted, and a tack weld has simply spilt over it during manufacturing (edit- possibly to secure the burr remaining from the slotting wheel). It most likely has absolutely nothing to do with the seat post being stuck.
Removing this kind of seat post without collateral damage can be difficult. It is straighforward enough I suppose if you decide to sacrifice the seat post, but beware the length remaining in the frame.
If you want to have a go at saving the post and you think the post will turn if only you can get enough purchase on it, one route is to open the hole at the top of the seat post (ie. so the rolled edge is removed so that the bore at the top is paralell sided), degrease, and bond in (using epoxy resin) something that you can clamp onto hard/drive (like a steel socket ground down to size). You can remove the socket afterwards by heating to about 140 deg C which will soften the adhesive. Do be aware that if the seat post is weakened already (often the saddle clamp makes a groove) then it will simply shear off regardless of how it is held. A bonded in steel socket about 1" long should allow about 200Nm of torque to be applied, which is comparable to the likely strength in torsion anyway. You will need to grind to the chrome plate off the socket in order for it to bond; a rougher socket is better than a smooth one for bonding.
A lot of the other heating/cooling or chemical methods have merit, but any of them will require some purchase to shift the post, so bonding in a plug might be worthwhile in any event.
I think its pretty clear that there has been bother with this seatpost in the past. That little blob could be weld or possibly a blob of brazing spelter, welds or brazing don't spatter like that as anyone who is experienced as those skills will know. I would carefully grind or file it away and the hacksaw split can then then be opened up a bit and the seatpost can then be more easily withdrawn. If the seatpost is clamped in a machine vice the frame can be carefully twisted and pulled to release it. A little oil might help, its a better lubricant than WD40.
Al
Reuse, recycle, thus do your bit to save the planet.... Get stuff at auctions, Dump, Charity Shops, Facebook Marketplace, Ebay, Car Boots. Choose an Old House, and a Banger ..... And cycle as often as you can......
It is impossible to be 100% certain of the manufacturing sequence from a picture but I think it must have gone thus;
-tubes prepped for welding -tubes welded -seat tube slot cutting using a slotting wheel, cut direction upwards. (NB the slot clearly passes through the weld fillets) - de-burring -paint.
In this case the deburring operation would have included dealing with a long end burr cast into the seat tube from the slotting wheel. This burr would be the full width of the slot. The normal approach of drilling a hole at the slot end would be difficult in this case because the hole would have to be drilled through the welds, and the slotting wheel would likely clip both sides of the hole at the same time anyway, because of the angle of attack which is constrained by the other parts of the frame. In addition to the end burr, there would be (much smaller) side burrs. Dealing with the side burrs would be easy enough using a flap wheel or similar; however dealing with bigger burrs such as the end burr is a PITA as anyone who has done such can testify. In this case I think they simply pushed the burr back flush, and tack welded it into place, where it can do no harm; a novel solution....
I have had troubles with this kind of seat post getting stuck unexpectedly and the single biggest problem is getting a firm hold of them without crushing them or tearing them. Very often once you have a secure hold of some kind, you find they were not that tight or seized in after all. Second best to bonding something in would be a collet gripping the outside and a plug up the middle to prevent crushing. But this is more work than bonding something in and furthermore requires special tools. Using pretty much anything else to grip the outside inevitably risks the thin material of the seat post deforming and tearing, local to the jaw contacts, even with a plug up the middle.
BTW having removed the seat pin, I'd have the frame reamed to size, and purchase a new seat pin to fit the reamed size properly. It has been my experience that un-reamed frames (which is most mass produced ones) have slightly undersize pins (which 'fit' despite the weld distortion). However these pins move slightly in use and have a small gap all round in places. This makes it easy for anti-seize to be displaced and and then for water to get in. Thus loosely-fitting seat posts, even if treated with antiseize, are more likely to seize in the frame than closely fitting ones IME.
It's obviously bets to try the gentler methods first and get progressively more aggressive as each attempt fails!
I've found it pays to bear in mind that what you are currently trying might fail and you ought to try to leave the means for the next attempt. One of my efforts started with gentle easing and progressed through penetrating fluids; widening the clamping slot with a screwdriver; using hot water; clamping the post in a vice and twisting the frame - crushing the post and regripping it, eventually crushing it at seat tube level; until I finally resorted to cutting vertical slots in the remaining post and separating it from the frame with a hammer and slim chisel (OK, it was an old screwdriver!). Of course, I had to finish by reaming the frame. The moral of the story is if I'd thought further ahead and put something inside the post to stop it collapsing (or bonded a socket - wish I'd thought of that) I might have avoided the saw blade and chisel work.
Happily, the frame now has a smooth and snug fitting seatpost and is in use as the basis of my "new" winter bike.
A lot of the other heating/cooling or chemical methods have merit, but any of them will require some purchase to shift the post, so bonding in a plug might be worthwhile in any event.
despairing of anything else, I used the caustic soda (sodium hydroxide) method. I didnt shift the post, i dissolved it! It took several goes, and filled my garage with hydrogen, but it worked when al else failed. It knackered the paint though, but it was getting a respray anyway.
If you do try it though, just be careful. i wore goggles gloves etc throughout and made sure it was well out of the way of the kids/cat/mercian...
This might be covered in the previous post (too good to lose), but here goes...
When I've encountered this problem and others like it before, I've used Plus Gas. Pour some in around the top of the post and leave to work it's way down overnight. If you are not going to use the post again, drill a hole straight through just above the seat tube. Then using a long screwdriver or similar, poke through the holes and start the freeing process by very gently tapping it sideways with a mallet first left, then right. Sooner or later, it will start to budge. Eventually you'll get to a point where you can also twist the post gently upwards with each swing and then, right out.
