How do I do this?

[badabec]

Hello, this is for the pram top for a Citroen DS Decap, the mega expensive one.
The pram top is dead simple. The 'bearings' consist of holes in arms rotating on pins, about 13mm diameter.
The holes have elongated. Plan is to drill out and ream all the holes to a standard size. Then make bronze bushes which will be shrink fit.
The problem is the pins, they have various degrees of ovality.
Because this car has hydraulics opening and closing the rag top, the pins are welded both sides (forces involved).
How can I overcome the ovality?

I can't spin them in a lathe, it would need a massive swing.
Are there tools with for example three grinding wheels that could slip over the pins? They are only 3/4" long.
Any ideas?

They don't want remove the pins for some reason.
I'd rather make new pins, but, hey ho.

With the manually opened rag top, you can feel if it snagging and adjust the pull.
With hydraulic one it just carries on regardless, no safety stop and needs manually turning off at the end of its travel.

 

[Brad93]

Build up with belzona 1111 and a clamshell form.

 

[Agroshield]

Build up with belzona 1111 and a clamshell form.

Does it have a minimum thickness? What does that imply for the mating part? It would not work well simply building the pin back up to round and original diameter as the belzona would feather out to nothing at the unworn sections.

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Post a picture of the parts. If they will fit on a milling machine, you can use a boring head with the cutter facing inwards. Then shrink fit a thin sleeve to them to bring back to diameter. You could bolt them to (a milling slide mounted on) the carriage of a lathe and hold the cutting tool in the lathe spindle. With some care and considerable faffing, the job could be done on a decent drill press

No boring head? Pins are short? Find a rotabroach cutter with suitable ID (you would have to go into a shop and measure this) and use to shave down the pins.

 

[Martin-Sy]

milling machine, you can use a boring head

Beat me to it!

 

[Brad93]

Does it have a minimum thickness? What does that imply for the mating part? It would not work well simply building the pin back up to round and original diameter as the belzona would feather out to nothing at the unworn sections.

---

Post a picture of the parts. If they will fit on a milling machine, you can use a boring head with the cutter facing inwards. Then shrink fit a thin sleeve to them to bring back to diameter. You could bolt them to (a milling slide mounted on) the carriage of a lathe and hold the cutting tool in the lathe spindle. With some care and considerable faffing, the job could be done on a decent drill press

No boring head? Pins are short? Find a rotabroach cutter with suitable ID (you would have to go into a shop and measure this) and use to shave down the pins.

It works exactly like that, feathering out is no problem.

Don't shoot down a product you have no experience of

 

[wyn]

I've used belzona and a machined clamp to rescue the bearing surface of a roots type blower.
It lasted for years till the place shut.

 

[Brad93]

I've used belzona and a machined clamp to rescue the bearing surface of a roots type blower.
It lasted for years till the place shut.

Someone told me they done this regularly on blower units using belzona.

We metal spray but the belzona would be better in some circumstances

 

[ajlelectronics]

belzona would be better

What is it, some form of loaded epoxy?

 

[Gragson]

What is it, some form of loaded epoxy?

Pretty much, I have a 1kg pack, I've used it, it is very good.

Belzona 1111 (Super Metal)

Belzona 1111 (Super Metal) is a 2-part epoxy-based repair composite designed for metal repair and protection.

www.belzona.com

Cheaper sometimes on ebay

Pardon our interruption...

 

[addjunkie]

Pretty much, I have a 1kg pack, I've used it, it is very good.

Belzona 1111 (Super Metal)

Belzona 1111 (Super Metal) is a 2-part epoxy-based repair composite designed for metal repair and protection.

www.belzona.com

Cheaper sometimes on ebay

Pardon our interruption...

I have fixed many things over the years with Belzona 1111, it is very good and machines well. Corroded flange faces, eroded pump casings, scored pins, slurry pumps, idiot marks on a mill table, holed two stroke crank cases. Only down side it is blooming expensive.

 

[Kram]

Pictures required. It certainally sounds French!

Can you crudely grind the pins down with a belt finger sander or grinder. Using plain poundland type epoxy, fit a hardened sleeve. I'd suggest a shrink fit but it sounds like the sleeve needs to be split in two peices to go on?
As your also doing the bores you could make them oversize to allow the sleeve with less removal from the pins.

Belzona does sound like good stuff apart from the expense and rarity of it. Metal would be cheaper.