Swing arm pivot tube and bearing race removal

[DucRedux]

I have almost completed a strip down of a 200-250cc narrow case frame from a ca. 1963 Ducati of a yet undetermined road model, possibly a Mach 1. The easier problem for the forum to help me with is the removal of the lower race from the steering yolk. The center tube was deformed by a metal punch securing the race to the lower collar. I've used a fine Dremel grinding wheel to smooth out the punch deformation as cleanly as possible, but the race will not spin off with moderate pressure using a pipe wrench. Before using more force, I'd like some input. Should I cut, or drill the race off, or use more force and possibly heat?

The second problem is a stuck swing arm pivot rod. This forum has some past comments on the topic including using very special internal tube wrench to apply lateral force (twist) to break the bond with the bearings and, separately the use of a sledge hammer. So far penetrating oil and pounding the tube using a socket of the same diameter to drift it out has been unsuccessful. My next move may be a hydraulic shop press, but before I clutter my garage space with a heavy piece of orange floor metal, any ideas from the forum members are welcome

[StewartD]

Hi DucRedux,

I posted some suggestions for removing the bearing race in the topic 'Disassembly of forks on 68 Mark III' on the 16th of May. I think using a pipe wrench will crush the bearing race and rotating it is not desirable.

Cheers,

Stewart D

[Ventodue]

The problem is the removal of the lower race from the steering yolk. Should I cut, or drill the race off, or use more force and possibly heat?

Decription of one 'Time Honored' method below:

1. At a convenient location, carefully grind away part of the vertical face of the (inner) race until you're almost at the stem - you should see a line appear up the middle that changes colour.

2. Stop grinding and with a hammer and cold chisel, give a stout whack on one edge of the now flat section of the race.

3. The race will crack up the thin bit. Prize it off with a screwdriver. Don’t dilly dally with the grinder either - it's good to get some heat into the race.

HTH

Craig

[DucRedux]

Thanks Craig and Stewart. The race is off. After a long week of soaking in penetrating oil, I scored the edge of the race and shocked the bond free with rapid blows of a hammer on chisel. The race was still on very tight and even high heat would not get it to move around the stem and not at all upward. Since the part was previously marked up, I got a Dremmel grinding wheel and cut into the race at about a 60 degree angle to avoid cutting the stem. The cut was about half through when a cold chisel and hammer opened up the inner diameter it so that it could spin free.

The swing arm pivot tube is next. (I haven't gotten any hints yet.)

Thanks.

Dan

[StewartD]

Hi Dan,

I am quite surprised the bearing took such drastic measures to remove.

Here's a suggestion for the swing arm pivot. You say pounding with a socket has not had much effect. Before going to the trouble of using a press, can I suggest pressing it out with an easily made screw press.

The inside diameter on the pivot tube is approximately 21mm. Buy a metre length of M20 fine pitch (or 3 foot of 3/4" UNF) 'all thread' and 2 nuts to suit. Also get some heavy series washers. The outside diameter of the pivot tube is approximately 28.5mm and the outside diameter of the swing arm bosses is 40mm.

An 'outer sleeve' can be cut from 1-1/4 nominal pipe. 1-1/4” Schedule 40 pipe is 42.16 outside diameter and 35.05 inside diameter. Schedule 80 or XS pipe is the same outside diameter and 32.458 inside diameter. Both could be used for an outer sleeve. Make sure the ends are cut square. The swing arm pivot tube is about 215mm long so the sleeve can be about 250mm long

Assemble the ‘allthread’ through the swing arm pivot and the outer sleeve. Put one washer and nut on the end of the ‘allthread’ that protrudes through the outer sleeve.

Now note that a standard washer and M20 or 3/4” nut will not go through the swing arm bushes when the pivot tube is drawn out. You can either turn a standard nut down on a lathe to a bit less than the pivot tube outside diameter (<28.5mm), or use a 250mm length of 3/4” nominal schedule 40 pipe which is 26.67 o.d. and 20.93 i.d. to make an 'inner sleeve'.

Assemble the inner sleeve onto the allthread that protrudes through the pivot tube and put on the standard washer and nut. Alternatively put on a turned down nut without the inner sleeve.

You can now rotate the standard nut, at the outer sleeve end of the allthread, and hopefully draw the pivot tube out with no drama. If it doesn't come, then try hitting the end of the allthread, when it is tensioned up as much as you dare.

Cheers,

Stewart D

[DucRedux]

Hi Dan,

I am quite surprised the bearing took such drastic measures to remove.

Here's a suggestion for the swing arm pivot. You say pounding with a socket has not had much effect. Before going to the trouble of using a press, can I suggest pressing it out with an easily made screw press.

Stewart D

I tried half hardheartedly last week with a screw press of 1/2 inch rod with no success, but what I needed was the stubbornness of my brother-in- law to try again. The "piston" on the screw press was a 13/16 in. impact socket with about a 28 mm outer diameter to mate with the swing arm tube and fit within the frame tube. The "receiver" was a 30 mm impact socket to mount on the opposing side of the frame tube and catch the protruding pivot tube once freed. Many a good strong turns on the bolt of the screw rod extracted the tube with the aid of WD40 while the tube was sliding past the bearings. Success!

Thanks