F: Frame Removing Comet front seat bushes

[poor1]

Picked up the following old thread in a forum search

'While the sintered bronze bearings in the seat stay end (FT111) are readily accessible and visible and thus most likely receive appropriate maintenance to keep them free, the bearing at the front of the seat is a different story. The front of the seat is positioned on a 3/8” seat pivot rod (F35/1) that passes thru a steel tube (F57/1) which itself passes thru the top hole at the rear of the UFM. There are two sintered bronze bushes (ET64), one each side, between the bore of the UFM hole and the thru tube. The intent is that the overall length of F57/1 is slightly greater than the length of the hole thru the UFM. What this means is that once the front seat bolts on F35/1 are tightened the seat frame is held securely (and unmoving) against the ends of the tube F57/1. However, because of the two sintered bronze bushes, the tube itself can readily rotate within the UFM and in turn the seat can also freely move in the vertical plane as required. Well that’s the theory! In my case I found that both ET64's were seized solid resulting in a seat that was very difficult to pivot.'

Question: when then the internal tube and bronze bushes are together seized what would be the best way of removing the tube with the least possible of damaging anything. Ideally a double diameter drift I suppose but I do not have a lathe any longer. I have have replacements to hand.

 

[Bill Thomas]

Picked up the following old thread in a forum search

'While the sintered bronze bearings in the seat stay end (FT111) are readily accessible and visible and thus most likely receive appropriate maintenance to keep them free, the bearing at the front of the seat is a different story. The front of the seat is positioned on a 3/8” seat pivot rod (F35/1) that passes thru a steel tube (F57/1) which itself passes thru the top hole at the rear of the UFM. There are two sintered bronze bushes (ET64), one each side, between the bore of the UFM hole and the thru tube. The intent is that the overall length of F57/1 is slightly greater than the length of the hole thru the UFM. What this means is that once the front seat bolts on F35/1 are tightened the seat frame is held securely (and unmoving) against the ends of the tube F57/1. However, because of the two sintered bronze bushes, the tube itself can readily rotate within the UFM and in turn the seat can also freely move in the vertical plane as required. Well that’s the theory! In my case I found that both ET64's were seized solid resulting in a seat that was very difficult to pivot.'

Question: when then the internal tube and bronze bushes are together seized what would be the best way of removing the tube with the least possible of damaging anything. Ideally a double diameter drift I suppose but I do not have a lathe any longer. I have have replacements to hand.

You could use a grindstone on a larger bolt or stud, To get your double diameter , Soak it all in WD40 ?, You have already got the spindle out ?, And the top of the Damper out of the way ?, Be careful, It is easy to bend the Lugs that the bushes are in, When you have got the bushes out , You may have bend/Reposition the lugs back a bit. Good Luck, Bill.

 

[poor1]

Thanks for the suggestion. Yes the spindle is out. I've currently got it soacked a penetrating oil and tapped the end of the clever gently from Keith ends and it doesn't move as yet. It occurs to me that if I drill out the sleeve on both ends I will have a floating sleeve between the bronze bushes and will be no further forward but if I drill one end out there is only the resistance of one seized bearing which might stand a chance of being gently tapped, or is that too much to hope for. I would much prefer to draw the sleeve out with a piece if studding but the difference in diameter would make they difficult. Heat might help. I'm open to suggestions please

 

[Bill Thomas]

Thanks for the suggestion. Yes the spindle is out. I've currently got it soacked a penetrating oil and tapped the end of the clever gently from Keith ends and it doesn't move as yet. It occurs to me that if I drill out the sleeve on both ends I will have a floating sleeve between the bronze bushes and will be no further forward but if I drill one end out there is only the resistance of one seized bearing which might stand a chance of being gently tapped, or is that too much to hope for. I would much prefer to draw the sleeve out with a piece if studding but the difference in diameter would make they difficult. Heat might help. I'm open to suggestions please

The trouble with Drawing it out is there are two lugs and if the first one goes out of line it will jam. I think if you make a rod to knock it, And knock it first one way and then the other it will shift, A thin rod through one tube for knocking outwards ?. Cheers Bill.

 

[Bill Thomas]

Sorry, I am talking about spring box fitting, I have lost the plot !!. Cheers Bill.

 

[b'knighted]

Can you screw in a stud extractor or a tapered tap? If you actually end up cutting a thread, possibly M10, you can insert a bolt then drift the bush out from the other side, failing that with stud extractor or tap tightly inserted you may be able to gently drift against it to drive the bush out.

 

[poor1]

Can you screw in a stud extractor or a tapered tap? If you actually end up cutting a thread, possibly M10, you can insert a bolt then drift the bush out from the other side, failing that with stud extractor or tap tightly inserted you may be able to gently drift against it to drive the bush out.

I like that idea thanks

 

[poor1]

I like that idea thanks

Following that I'm thinking tapping a thread into the sleeve because it's that which is deigned into the bushes. I'm assuming that because the sleeve is sitting in a bronze or oilite bush it will not take a lot of shifting

 

[Martyn Goodwin]

I used a HD precision extractor. A solid drift and a 4 Lb mash hammer! No matter what you do you will need new bushes and a new steel tube. Do yourself a favour any purchase a length of tube from a merchant then make the replacement even a tad longer than the original just to ensure its truly free when all is reassembled. Be brave!

 

[chankly bore]

Is the U.F.M. on the bike, or can you lay it on a pedestal drill table? If so, carefully creep up on the bugger in small increments up to 1/2". Once at 1/2" you should only have the Oilite bushes to drive out.