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Old 03-16-2010, 05:24 PM   #1
joeswamp
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Default Floor jacks and hydraulic seal types

This post is really directed at HiBall, but other jack experts please chime in.

OK so like everyone else on here I've learned a whole lot about floor jacks from all the recent discussions. However one thing I'm still confused about is floor jack seal design. It sounds like the "universal cheap import" jacks use O-ring seals (which fail quickly), whereas the good jacks use cup seals or something more substantial.

So for example, the AFF 200T:



is an example of a cheap import jack. We see on its part breakdown:

http://www.affjaxx.com/parts_docs/200T.pdf

That the ram is sealed by parts H3 and H4 (an o-ring and "o-ring returner"). I believe the o-ring returner is the part HiBall says not to mess up when you attempt to rebuild the jack, as they're hard to find.

Another Chinese jack, the $200 Norco 71232:



seems to use different seals on the ram. According to the part breakdown:

http://www.norcoind.com/norco/downlo...2_Exploded.pdf

parts 80 and 81 (a u-cup seal and back-up ring) seal the ram. This would be a good seal design right? Norco's are Chinese but not made by Shinn-Fu I believe.

Finally, we look at a high quality floor jack, the Made in USA Milwaukee Model 40:



Here's the crazy part, if we look at the parts breakdown:

http://www.milwaukeehydraulic.com/model40.pdf

The ram is sealed by parts 68 and 69 (an o-ring(!) and 2 backup washers).

So what's the deal here? If o-rings are really that bad, why does Milwaukee use them? Or is it the Shinn-fu hydraulic unit design and/or quality that's the real issue here? What about Chinese jacks that use u-cup seals?
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Old 03-16-2010, 10:24 PM   #2
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Default Re: Floor jacks and hydraulic seal types

Ok. I finally got some puter time. In reference to the 3 models you listed here, First off the Low Profile jack. It does use the Junk Ucup retainer with the Oring similar to the one in my tutorial and this Pic.

DSC00982.jpg

These are very poor design and the oring isnt used as a sealing surface, It is in fact used as a loaded ucup and the pressure from the fluid uses the oring to keep the pressure uniform around the very thin Ucup retainer.

The Norco jack in the picture is your typical Import design that has been used for many years. That jack actually uses Poly Ucup so i will vouch for that part of the jack. I still dont think its worth the money when compared to the HW models but is hands down better than the Previously discussed Oring/Ucup retainer. You can find actual Ucups in the older Imports including the legendary Green/White Sears Jap jacks.

Now for the million dollar question. The Milwaukee jack does utilize oring on both Pumps and the Ram, But the main difference is how they are used. Instead of being inside a U cup retainer (see pic above) its used as a compete sealing surface where it gets a 360 degree seal inside the Ram. This is a very good design and im sure a few of you have torn hydraulic cylinders down where the same design is used. When you consider the tight tolerances that are used it works very well, Not to mention there is a backup on each side of the Oring, which is like injecting a Oring with steroids. I cant really vouch for Milwaukee jacks, Ive probably only worked on 2-3 in the 20 years ive been rebuilding jacks. There not near as common as a Walker/Lincoln design despite there History.
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Last edited by Hiball; 03-17-2010 at 05:42 AM.
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Old 03-17-2010, 09:17 AM   #3
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Default Re: Floor jacks and hydraulic seal types

OK now I get it, thanks so much for the explanation.

So the modern cheap imports use this super thin ucup seal and the o-ring is used to preload it against the cylinder wall -- I believe this type of seal is called a "loaded lip seal" and is a more modern design than the traditional u-cup. In your rebuild tutorial you say that the thin o-ring retainers (the actual sealing part) usually don't go bad -- I would have expected those to fail first, rather than the o-ring. How do these modern import jacks typically fail?

Interesting that Milwaukee uses o-rings the way it does, this must be a really old design. I'm surprised it works as well as it does -- it probably requires tighter tolerances and finishes on the piston and cylinder, and I'd bet that's one of the reasons this jack is pricey.

Thanks again.
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Old 03-17-2010, 12:04 PM   #4
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Default Re: Floor jacks and hydraulic seal types

Quote:
Originally Posted by joeswamp View Post
OK now I get it, thanks so much for the explanation.

So the modern cheap imports use this super thin ucup seal and the o-ring is used to preload it against the cylinder wall -- I believe this type of seal is called a "loaded lip seal" and is a more modern design than the traditional u-cup. In your rebuild tutorial you say that the thin o-ring retainers (the actual sealing part) usually don't go bad -- I would have expected those to fail first, rather than the o-ring. How do these modern import jacks typically fail?.
Yes, you are correct a actual Ucup with a solid U-portion is called a Loaded Ucup. I wouldnt classify these Ucup sleeves with a Oring insert as a "Loaded U cup" but without a doubt thats how there being used. The reason they fail is because this design relies on the Oring being flexible enough to keep the very thin sealing surface uniform inside the cylinder upon Pressure entry, When they harden they lose that trait. When that happens you get Oil bypass, the jack seaps and oil bypass on the tank nut account its not designed to keep that amount of oil back.
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Old 03-17-2010, 08:37 PM   #5
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Default Re: Floor jacks and hydraulic seal types

OK I researched this a bit more and the type of seal on the modern Chinese jacks seems to be called a "piston cup" seal. However it's being used in an unusual fashion; after looking at lots of catalogs I can't find an example of one being loaded or energized with an o-ring. Usually the bottom part of the seal has more relative area and it's clamped between two pieces, like this:



According to one manufacturer, the very thin wall version of these seals have an advantage because they're so flexible -- they seal over a wide range of pressures and don't initially leak before pressure is built up. I suspect these seals allow Shinn Fu to build their cylinders with sloppier tolerances, which work until the o-rings harden up.

Weird that I can't find an example of an "o-ring inside a piston cup seal" from a mainstream manufacturer though, and it definitely looks like getting one of these from a normal hydraulics supplier might be difficult.
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Old 03-17-2010, 11:21 PM   #6
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Default Re: Floor jacks and hydraulic seal types

Quote:
Originally Posted by joeswamp View Post
OK I researched this a bit more and the type of seal on the modern Chinese jacks seems to be called a "piston cup" seal. However it's being used in an unusual fashion; after looking at lots of catalogs I can't find an example of one being loaded or energized with an o-ring. Usually the bottom part of the seal has more relative area and it's clamped between two pieces, like this:



According to one manufacturer, the very thin wall version of these seals have an advantage because they're so flexible -- they seal over a wide range of pressures and don't initially leak before pressure is built up. I suspect these seals allow Shinn Fu to build their cylinders with sloppier tolerances, which work until the o-rings harden up.

Weird that I can't find an example of an "o-ring inside a piston cup seal" from a mainstream manufacturer though, and it definitely looks like getting one of these from a normal hydraulics supplier might be difficult.
The reason you cant find a "Oring inside a piston cup seal" is because they are hard to find and have a short life span. Here is some examples of some more piston cup seals along with a standard Ucup and a loaded Ucup. The most common type of Piston cup used in hydraulic jacks are leather cups, Here is a variety of them and they sit over a stem and get fastened with a washer and nut.



Next you have your standard Ucup.


Now the loaded Ucup.



And now you have the Import special.




Which one do you want in your Jack?

Those are all versions that are used in a Piston sealing sitsuation, The opposite of Piston seals are gonna be your rod seal. You will find these on most of your Import jacks where the seal is inside the hydraulic unit and the rod floats inside of the seal like this.



Hope this explains things for you.

Steven
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Old 03-17-2010, 11:32 PM   #7
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Default Re: Floor jacks and hydraulic seal types

Such great info (and not the easiest info to find either). I'll bet those leather piston cups pre-date the invention of the o-ring.

Thanks so much for taking the time to explain all this stuff.
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Old 03-17-2010, 11:42 PM   #8
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Default Re: Floor jacks and hydraulic seal types

Quote:
Originally Posted by joeswamp View Post
Such great info (and not the easiest info to find either). I'll bet those leather piston cups pre-date the invention of the o-ring.

Thanks so much for taking the time to explain all this stuff.
The Leather Piston cups are still used in alot of todays hydraulic equipment but they are quickly being replaced by Ucups and definitely pre-date orings.

Steven
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Old 10-10-2011, 05:24 AM   #9
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Default Re: Floor jacks and hydraulic seal types

Can someone please help? I have a 45-year old trolley jack originating in Sweden and would like to replace the worn and hardened leather cup seal with a new, efficient seal. The cylinder is 32mm dia, the old seal is 10mm wide and has a 6mm mounting hole.
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Old 10-10-2011, 09:21 AM   #10
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Default Re: Floor jacks and hydraulic seal types

Cool thread guys! I have a majorly old AUSCO long frame jack that I remember my father getting from a friend about 45 years ago. He made some new parts for it and I recall the leather cup seal soaking in neatsfoot oil or jack oil for along time before it was supple enough to reuse. I finally stopped using that jack about 10 years ago because it would weep around the ram when left sitting. I bought a kit for it back then but have yet to overhaul it. Hopefully HiBall won't mind if I ask some questions when I tear it down. I was told the jack was from the 1930's.
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Old 10-16-2011, 04:30 PM   #11
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Default Re: Floor jacks and hydraulic seal types

Some more explanation on seals. Look at the U seal, this is a drawing of "Loaded U cup seal" without the Oring it is a U cup seal. Loaded U cups come with Orings and Quad rings.
http://www.hcrcnow.com/how-to-measure-seals.php
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Old 10-16-2011, 04:45 PM   #12
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Default Re: Floor jacks and hydraulic seal types

Quote:
Originally Posted by Jan Greeff View Post
Can someone please help? I have a 45-year old trolley jack originating in Sweden and would like to replace the worn and hardened leather cup seal with a new, efficient seal. The cylinder is 32mm dia, the old seal is 10mm wide and has a 6mm mounting hole.

Piston cups are available, I have only seen them in Standard not metric. Also they come in rubber(Buna) or fabric. Leather are available, but I can not find them 1 at a time. The closest to the size you need is, 1-1/4"OD with a 1/2" Lip and the center hole you have to make. If this will work, let me know.
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Old 10-16-2011, 05:33 PM   #13
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Default Re: Floor jacks and hydraulic seal types

Quote:
Originally Posted by Jan Greeff View Post
Can someone please help? I have a 45-year old trolley jack originating in Sweden and would like to replace the worn and hardened leather cup seal with a new, efficient seal. The cylinder is 32mm dia, the old seal is 10mm wide and has a 6mm mounting hole.
A Properly installed Leather Seal will give you Many Years worth of Service. Do you have a Model Number? I have lots of useless data for Jacks from that Era, Including OEM sizes.
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Old 05-10-2012, 08:26 PM   #14
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Default Re: Floor jacks and hydraulic seal types

I have a Astroline AM200F 2 ton floor jack that I believe needs new seals. All of a sudden stopped working. Anyone know where I can find these? Thanks
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Old 10-13-2012, 07:09 AM   #15
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Default Re: Floor jacks and hydraulic seal types

R.I.P. Norco!
While looking for a jack I checked out Norco Hiball mentioned here. Our local auto shop sells them and always swore by them. I was looking for the 2.25 ton 71232 thats been around for yrs. For 200.00 jacks they were tuffer than most & lifetime warranty. Well' those are gone for good now!
Its been replaced with 71233 and its junk. Hard plastic wheels,no cylinder kit {whole cylinder only},its so low a nickle would barely go under it. Too low for rough driveways it will drag.

I moved to the 2 ton 71202A. Same jack that US jack sold for along time model D-51226 now discontinued through U.S. Jack. Has a rebuild kit from norco. Nice jack, except it has nylon wheels. No steel wheels? Theres replacement nylon wheels so when you wear them out for 87.00...WTH? Not for me, jack cost over 325.00 + sh. too. Over 450.00 under U.S. Jacks name. Its an Import people! Damn.

Moved on to the 3.5 ton 71335 suv jack. Guess what? Too low for rough driveways. Plastic wheels? YUUP!
Rebuild kit? Notta! Replacement cylinder only! Half as much as jack cost new.
Whats happening? Norco's supplier said no more jacks under 4 ton made by them. No warning to Norco. Guess they grabbed the first thing they could get to sell? Better keep grabbin though because these are crappy jacks.
This said, it gets even worse for some past buyers. If you bought the 71232 and it develops any warranty issues that deem it unrepairable and Norco replaces it. You are a proud owner of the 71233 plastic wheeled P.O.S. that drags the ground and not the 71202A. Norco even changed the wording on thier site from Heavy Duty to "economical" for the 71232 to match the quality of the 71233. Guess we were'nt supposed to see thier old flyers on it.

Norco would of had to give you the better one if they kept thier lifetime warranty the same. So they changed thier warranty to include the 71233 P.O.S...It didnt have a lifetime originally. It came out with a 1 yr warranty. See P.O.S.!

Well with all this happening it stopped me from buying norco and the recession going on, my timing was just right for a change! Sales being slow on jacks for 2012 It appears to be alot of jacks on sale. I cought a HW w93642 on sale for 296.33 delivered from THETOOLWAREHOUSE and I'm very happy with it. Free 2 day sh too guys. Signed up for thier emails first and got 10% off first purchase.

I'm not sure what Norco's going to do with all thier stock, but I can see alot of thier jacks going on ebay for sale in the near future. Alot of the 71233 models from warranty replacement sales. Thats what Id do with that P.O.S as soon as they replaced my 71232 with it....Oh''Did I mention the 71233's a P.O.S.? I believe I warned everyone,its a P.O.S.!
Norco' these jacks are not your regular quality. Please find your customers some good jacks.

I felt the need to tell you folks you may want to look at them before buying one online? I'm sure the 71202A is a good one since its certified through all the dealerships inluding Toyota, {thier hardest to please I know from experience by supplying them parts} but for the money the 71202A you may find a HW like I did.
It needs steel wheels ,maybe they'll get some for it soon. They're a good company and offer good service. Been around a while but I cant see these low end jacks selling much longer unless they do something soon. Maybe they're designing some good jacks for the future? Time will tell. Hope they bring jobs back home again after this. {we can wish}.
Look at Norcos close before buying is all I'm saying. Its even hard to tell there black plastic wheels & not steel close up on the sales floor but they are plastic!

D-51226 US Jack version: Click & Scroll.
http://www.usjack.com/products/Compl...2012-index.pdf

Norco 71202A wearing nylons & Others P.O.S.'s....
http://www.norcoindustries.com/produ...oor_Jacks.html

Last edited by 123Go; 10-27-2012 at 01:21 PM.
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Old 06-28-2014, 07:43 AM   #16
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Default Re: Floor jacks and hydraulic seal types

Wonderful thread. It has helped me to understand my jack. I need the "U cup" for the ram on my jack. Where is the best place to find a replacement. There is no name on my jack so I will have to go by measurements. I cannot find one locally.
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