Bottle Jack Rebuild - Piston Cup

[dabrian99]

Does anyone have any experience rebuilding bottle jacks? I have an old (prob 1970s) US Jack / Drednaut 3-ton I’m currently rebuilding.

I got an OEM kit from Lazzars HCRC with all the seals, o-rings, etc. the instructions are well…not real great.

I’m stuck on ONE last piece which is the Piston Cup that fits on the end of the piston that moves up and down when pumping the jack handle.

It appears the end of the piston has a “retainer” with a flare on it and I do not think the new Piston Cup will press over the retainer/flare. The cup itself is hard plastic and I’m concerned about breaking it.

Anyone have any experience replacing these!?

Some pics for reference.

 

[gregs]

Looks like a typical urethane U-cup with an expander inside. You can put it in hot water to help.

 

[dabrian99]

Looks like a typical urethane U-cup with an expander inside. You can put it in hot water to help.

Thanks for the tip! Will give it a go.

 

[Hiball]

I doubt you will ever get that Ucup over that keeper. I would grind enough material off the flared portion to remove the keeper, install the cup, reinstall the keeper and find a hard surface and introduce a hammer to other end to swell it back to secure everything again.

 

[dabrian99]

I doubt you will ever get that Ucup over that keeper. I would grind enough material off the flared portion to remove the keeper, install the cup, reinstall the keeper and find a hard surface and introduce a hammer to other end to swell it back to secure everything again.

Yeah that’s a solid plan B. I can maybe file it down enough to remove the keeper, reinstall, and reflare it with a punch?

 

[Hiball]

Yeah that’s a solid plan B. I can maybe file it down enough to remove the keeper, reinstall, and reflare it with a punch?

That was how the factory designed it, a lot of older hydraulic jacks used similar methods to secure seals/washers etc. I’ve still got some old HW NOS pump pistons from that era.

 

[gregs]

I have to agree with Hiball after looking at it closer. I think you are going to have to remove the keeper. I have stretched and compressed ucups more than I thought they would go, but that seems like a lot more than it could do.

Looking in the second picture the retainer is loose and away from the flare? Maybe you could carefully unfold the flare. Might take some heat an some patience. My only concern with filing it off is if you would have enough there to reflare it.

 

[Hiball]

Also, Depending on how tight that loaded cup fits the bore, you might need to remove the energizer to reduce wall pressure.

 

[dabrian99]

Based on all of the feedback, I did want to have a contingency plan in place. Turns out they do still sell a Piston Assembly separately that *should* have the piston cup installed (no pictures of the part available online). It’s like $20 shipped so no biggie to just swap out the whole assembly while I’m at it.

I’ll order it and prob still have a go at replacing the cup on my original just out of curiosity.

 

[Hiball]

Based on all of the feedback, I did want to have a contingency plan in place. Turns out they do still sell a Piston Assembly separately that *should* have the piston cup installed (no pictures of the part available online). It’s like $20 shipped so no biggie to just swap out the whole assembly while I’m at it.

I’ll order it and prob still have a go at replacing the cup on my original just out of curiosity.

I’d say the replacement piston will be a Newer style with a button end, versus OEM keeper with a staked style tip. It’s better obviously in regards to serviceability, as long the working length are the same. I suspect that’s a 1/2” piston, which was common across a multitude of brands.

 

[paulsomlo]

Based on all of the feedback, I did want to have a contingency plan in place. Turns out they do still sell a Piston Assembly separately that *should* have the piston cup installed (no pictures of the part available online). It’s like $20 shipped so no biggie to just swap out the whole assembly while I’m at it.

I’ll order it and prob still have a go at replacing the cup on my original just out of curiosity.

$20? That didn't come from the same place you bought the seal kit, no way.

 

[Hiball]

$20? That didn't come from the same place you bought the seal kit, no way.

It’s likely a Chinese replacement, Might even be a 13mm swapped in for good measure.

 

[dabrian99]

It’s likely a Chinese replacement, Might even be a 13mm swapped in for good measure.

Not sure of the origin but fat chance finding anything like this made in America anymore.

I’m just trying to restore it because it’s a nice USA made jack and I refuse to buy a welded, non-serviceable Chinese one to replace it.