Dismantling the bogies.

[Adrian Harris]

One of the hardest tasks so far in this strip down has been the removal of the radius arm pivots.

For those that don't know the Sherman suspension, the radius arm holds the wheel in place and connects to the bottom of the main bogie housing:

WheelAsFound.jpg (29.45 KiB) Viewed 1408 times

This photo shows the rust on the axles but unfortunately gives a somewhat false impression of how corroded the radius arm pivots had also become.

I should have realised when Mark and I pushed the Sherman off the mound and onto the driveway and I noticed that none of the bogies flexed at all

Adrian.

[Adrian Harris]

I removed the wheel axles by holding one end in a vice and turning the other with a spanner until either the nut came free, the thread stripped or the end of the axle broke off

The axle could then be tapped.

Adrian.

[Adrian Harris]

The method of opening up the bogie frame was to hold the centre nut in place and tighten up the outside bolt:

StretcherCloseUp.jpg (36.84 KiB) Viewed 1407 times

Adrian

[Adrian Harris]

This gave me just enough clearance to insert the razor saw:

RadiusArmDuringSurgery.jpg (46.21 KiB) Viewed 1406 times

You can see another bogie frame in the background, with the M6 bolts in place.

Adrian

[Adrian Harris]

The end result:

RadiusArmAfterSurgery.jpg (41.41 KiB) Viewed 1405 times

Once I had got them to this stage, I used the vice and various drifts, which I had turned from the old wheel axles, to push the pivot out through the arm. This in turn needed twenty to thirty seconds of heat from the torch, hence the burnt brown paint where they started out Olive Drab.

Adrian

[Adrian Harris]

I finally managed to free the last two pivots today. I made the mistake of drilling through them completely, in the vain hope that if I increased the drill size incrementally, eventually the pivot would free up and come out.

In the end, I had to use a needle file a produce a channel in each side of the pivot though to the aluminium, and then split the pivot apart with a filed down screwdriver. This reduced the stiction enough for me to be able to pull the remains of the pivot out with a pair of pliers.

The next tasks will be to turn 12 new pivots and then turn and thread 12 new axles.

The one thing I can't do is remove the remains of the one bolt which broke off in the bogie frame, so I will shortly be taking that to see if I can have it removed by EDM (Electro Discharge Machining)

Adrian.

[simon_manning]

well done adrian,what a difficult task,i hate jobs like that,

regards simon manning

[Robert E Morey]

Adrian,
Oye didn't know you were having to do surgery to remove the pins! Great job on finally removing them all. I'd recommend 303 stainless for the replacement pins. I replaced my wheel bearings with oil impregnated bronze instead of brass. This would reduce the initial rusting although nothing would last in the rain and weather.

Its good to see these tanks will stand up to a beating!

I'm enjoying following your salvage effort.
Bob

[Adrian Harris]

Glad you're enjoying my reverse build

> I'd recommend 303 stainless for the replacement pins.

I'm still niggled by the various discussions which say that stainless against aluminium is actually worse than mild steel against aluminium. eg:

http://www.bssa.org.uk/topics.php?article=89

> I replaced my wheel bearings with oil impregnated bronze instead of
> brass.

I have found a supplier of Oilite bearings in the UK but I'm not sure I will be able to remove the current bushes as they appear to be glued in place.

Adrian.

[Allan Richards]

Adrian,

Its good to see that you have the guide plates on these suspension units. I am surprised that the tank has seized up so solidly as its not been outside for many years, I would have thought that the assembly grease would have protected it more than it has. I would recommend heating and cooling to see if you can break the corrosion bond, boiling in oil could work. Certainly replacing the axles with stainless is the way to go.

[Robert E Morey]

Adrian,
The article says stainless pins or fasteners in Alum plate should pose little risk. I think if you add a little lube oil or grease you'd be fine. I use SS SHCS as much as possible and they don't seem to corrode like the black oxide ones. The article does say things should be kept dry to prevent the galvanic reaction.

As for the wheel bearings, I bought solid bronze rod and machined it to size. I couldn't find a premade bearings the right size. There are plenty of plastics that would make good bearings too. Plastic bearings may be better in a harsh wet invironment than metal.

Good work throughout.
Bob