Thread: Mini excavator centre pivot/swivel help

Anyone have any experience servicing hydraulic swivels? My > 25 year old Takeuchi is leaking out of from the top circuit which is the blade ram. I have a manual but the OEM parts are pretty much not available any more so I’m looking for info on how to measure up for replacement O-Rings. I can get an accurate inside diameter from the shaft but the outside diameter is tricky, I don’t think I can snap gauge the grooves in the hub for depth. Any ideas or is there a common formula?







Ta, Ray.

Hi Good luck in your search
i hope i never have to go where you are now i have the TB 25 zero swing man do these little gals swing cheers

Try this formula Outside Diameter (OD) = Inside Diameter + (2 x Cross Section). Inside Diameter (ID) = OD - (2 x Cross Section). Cross Section (CS) = (OD - ID) ÷ 2.

@AR7 Cheers. My bestie gave me this little unit for nix, as I’ve been doing various repairs (mostly structural) on it for him for the last 15 years and he has just upgraded. So I don’t mind spending a few clams on it. At worst, I’ll pull the hub out too and just start experimenting with a bunch of O-rings. They’re only a couple bucks a pop and it ain’t rocket science. Much.

Originally Posted by erniec

Try this formula Outside Diameter (OD) = Inside Diameter + (2 x Cross Section). Inside Diameter (ID) = OD - (2 x Cross Section). Cross Section (CS) = (OD - ID) ÷ 2.

Don’t think he knows the cross section, as the existing rings will no longer be true to original size.


Sent from my iPhone using Tapatalk

@erniec thanks, but I was trying to avoid using measurements (like the cross section) of the old o-rings because they have probably deformed. I’m thinking more of trying to get the groove width and/or depth in the hub to give me a cross section and O/D for the rings.

use a set of internal calipers to measure your groove diameter set to id then measure with Vernier's. remember to allow for draw as well

What @NO4 said.
https://www.supercheapauto.co.nz/p/s...B&gclsrc=aw.ds

These or a better set from Blackwoods

I deal with hydraulic rams, rotators, motors and pumps everyday. Orings are measured from there ID with sections of 1/16(1.78mm), 3/32(2.62mm), 1/8(3.53mm),3/16(5.33mm) and 1/4(6.99mm) you can get metric as well tho. generally allow for 0.5mm draw. Your orings will be deformed if you measure the height plus the width add together then divide by two it will give you fair idea of the section,Pm me if you get stuck

O-rings have around 15% "crush" when installed. a little more on some static sealing arrangements. the o-ring groove will be something like 15-20% wider than the o-ring. almost certainly it'll be a metric size. if you can use some verniers to measure the width and depth of the groove we'll be able to work out what size it takes. just as a sidenote imperial o-rings have the crush built into them - eg an 1/8th o-ring will measure about 20 thou more than an eighth.

You can also assume that it will be imperial O-rings.
They come in standard cross sections, 1.78mm 1/16" 3.5mm 1/8", 5.33 3/16", and 6.99mm 1/4", (Difference between metric and nominal Inch sizing is the crush)

Measure the ID based on the shaft and then pick a cross section that will make then snug in the outside of the grove.
You may need PTFE back up as well either side of the oring.

https://www.sealinnovations.co.nz/

Assuming imperial due to the age and most hydraulic stuff is imperial with the exceptions of cylinders on mobile plant Excavators etc from Asia/Japan.
Z

Thanks for all the responses guys, very helpful, such a wealth of knowledge in this forum from all sectors of industry!

Much appreciated, Ray.

Originally Posted by ZQLewis

You can also assume that it will be imperial O-rings.
They come in standard cross sections, 1.78mm 1/16" 3.5mm 1/8", 5.33 3/16", and 6.99mm 1/4", (Difference between metric and nominal Inch sizing is the crush)

Measure the ID based on the shaft and then pick a cross section that will make then snug in the outside of the grove.
You may need PTFE back up as well either side of the oring.

https://www.sealinnovations.co.nz/

Assuming imperial due to the age and most hydraulic stuff is imperial with the exceptions of cylinders on mobile plant Excavators etc from Asia/Japan.
Z

I wouldn't assume nada with it re. sizing. Not too hard to measure and confirm sizing though. Be aware those can be a bitch on reassembly for pushing a ring out of place and pinching it leading to oddball performance i.e. a second ram moving/creeping when it's not meant to through a leak into the adjacent gallery. Oring grease on the orings on assembly to help support them, copious amounts of oil to lube everything else and being careful to slowly and deliberately push things back into place to avoid unseating something...