Backhoe Building a thumb for a model 48 Backhoe

DanMc77 · Jun 14, 2017

Here's a cylinder I'm looking at.

Maxim 3 PSI Welded Hydraulic Cylinders | Bore 2'' Bore - 3 PSI 2 X 14 WLD CYL 1.25 ROD 288-312

Seems to me that it would be a lot easier to cut off the pivot pipe on the end, and weld it back on rotated 90 degrees. I'm not talking about cutting off the end of the cylinder, just the pivot pipe.

Edit: Here's one that's set up just like I need:
Hydraulic Cylinder Tang - Magister Hydraulics

texasranger556 · Jun 14, 2017

DanMc77 · Jun 14, 2017

I ordered the one at Magister Hydraulics. It has a tang end with zerks, 2.0x14x1.25, side ports. If I don't weld on it then it will have a two year warranty.

DanMc77 · Jun 15, 2017

Is the model 48 bucket cylinder a 2" bore? I measured 2.6" on the OD of the cylinder, so maybe it's a 2.25" bore?

Anybody know?

DanMc77 · Jun 18, 2017

I dropped by the local JD dealer. They were able to look up the bucket cylinder specs. It's a 2 1/4" bore. My thumb cylinder is a 2" bore.

Here are some pics showing the final wood prototype using the cylinder from Magister.

You can see the internal ribs that close on the dipper and protect the thumb cylinder. The ribs will need to be made a little shorter to avoid interference with the forward hydraulic port.

We made great progress yesterday with getting it fab'ed up in steel. The sides are 1/2" steel, with 3/8" reinforcement near the end. The center plate is 3/8" steel bent on a huge press.

DanMc77 · Jun 18, 2017

Here's a video showing the cutting of one of the tines. One of the wood tines is screwed to his jig and used as a template. The cut steel part is 1/8" larger on each side due to the size of the little knurled rotating stylus that follows the outline.

kennyd · Jun 18, 2017

Wow that is looking great! :thumbsup::thumbsup:

DanMc77 · Jun 20, 2017

I spoke with a guy at Bailey International, the people that carry the Chief G series control valves. The relief valve in a hydraulic control valve is there to protect the pump, not anything on the output side, so the A and B ports are blocked in neutral. A relief valve is needed to protect the thumb cylinder and lines against excess pressure from the bucket.

Yesterday the following parts were ordered from mobilehydraulics.com for a total cost of $154 + shipping. Their prices are very reasonable.
* CHIEF G Series: 10 GPM, SAE 10 Inlet/Outlet, SAE 8 Work Ports, 3 Spool, 3625 PSI, 1500-3625 PSI Relief Setting
* CHIEF Directional Control Valves (G Series): Power Beyond Plug SAE
* Prince RV Series Differential Poppet Line Relief Valve: No. RV-2H, 1500-3000 PSI Adj. Range

Also ordered some SAE 8 plugs to close up the unused work ports until some future time when they might be needed.

DanMc77 · Jun 20, 2017

The next thing is to start working on hydraulic lines.

Is steel piping cheaper than hoses? I've had replacement hoses made up locally for the front loader and the fittings get quite pricey.

Is there a good online source for low cost but good quality hoses, fittings, etc?
Edit: Anybody use discounthydraulichose.com? They look pretty good.

texasranger556 · Jun 20, 2017

If you really want a relief valve, look into a cushioning valve, then there's no return to tank.

I went with Discount Hydraulic Hose who I believe are a site sponsor as well. It's all import stuff but everything I've bought so far has had no defects that I can see. They ship from Philadelphia so where I live it gets here next day if I order in the morning with normal ground shipping. The site makes it pretty easy to find what to need.