machines which I have made, am making, or intend to make, and some other stuff. If you find this site interesting, please leave a comment. I read every comment and respond to most. n.b. There is a list of my first 800 posts in my post of 17 June 2021, titled "800 Posts"

Tag: JCB 3CX

Making a JCB 3CX Slew Lock Plate

I have a 35 year old JCB back hoe, a left over from when I grew olive trees and made olive oil. These days it is used only as a yard crane, and other small jobs on a 5 acre property. But since I am between model engine and cannon projects I decided to expend some TLC on the rather neglected JCB.

One feature which always made me grimace was the broken slew lock plate.

The slew lock plate supports the excavator boom and jib when the backhoe is driven between jobs. It takes the weight of the rear end, taking weight off the hydraulics. Unfortunately the old plate has been broken and re-welded so many times that it is IMO beyond repair.

A new plate is $AUD 1300 + GST I could not find a machine for wrecking, and was told that wrecked JCB 3CX’s are almost unknown, most owners, mostly farmers, keep them going for ever.

So I measured up the plate, drew it up on CAD, and had it laser cut from 20mm plate.

The laser cut bits. 20mm plate and 25mm plate hinges. Cost? $AUD 180 including steel supply.

Deep V fillets were ground, and MIG welded with the 25mm hinge pin in position during the welding to keep the hinge pins aligned after the central portion of the pin is cut out.

Fitted to the excavator boom. I decided to not use the thin metal sloped flanges present on the original part, which I presume are to facilitate engaging the plate to the king post pin seen in the photo. I will engage the plate manually, by removing the securing pin (left) through the back hoe rear window.

Feb 2023 postscript. The slew lock plate has been in use since installation, and it is showing no signs of distortion despite me activating the hydraulics on several occasions, having forgotten to release the plate. I do need to exit the cabin to release the plate, which is a bit of a nuisance. I am thinking about adding a spring release mechanism so the plate pops up when the boom weight is taken off the plate.

I have had requests for copies of my plans for the plate. I am prepared to send them but with the understanding that I am not a qualified engineer, and I make NO representations about the suitability or safety of the design.

JCB CX3 Backhoe Cylinder Seals

My JCB is a 1986 model, 35 years old. I have owned it for 10-12 years, using it for manure handling, as a yard crane, tree transplanting, and twice to lift a 50,000 litre water tank onto a tray truck. (in combination with a front end loader). Despite its age and hours of work (about 7200), it has been very reliable.

When I first bought it I engaged Enzed P/L to inspect and change any suspect hydraulic hoses, because many of them showed signs of cracking and delayering of the exteriors. And one had burst. I think that the onsite Enzed engineer remade and installed about 8-10 hoses.

Then recently, the hose to the rear bucket and boom controller burst. Well, actually it was the metal fitting which was crimped to the hose which split and allowed the hose to separate from the fitting, spilling quite a bit of hydraulic oil onto the ground. Enzed were on the job within a day, and an hour later the new large diameter hose and fittings were installed.

The hydraulic oil level was well down, and topped up with 20 litres.

I had been aware that one of the hydraulic cylinders had been leaking for many months, so not all of that 20 litre deficit was due to the burst hose. It had been leaking at the rate of one drop every 6 seconds for a long time, and increased to one drop per second recently.

I had recently purchased a kit of new seals for the leaking cylinder. After watching some YouTube videos, I decided to have a go at replacing the seals myself. No big deal really, except that I had not worked on a cylinder this large before.

This is the ram. The hydraulic hoses have been disconnected and covered with a clean rag to minimise any dirt entry. And the large heavy pins at each end have been removed.

The large gland nut was loosened before I removed the end pins. I had been warned that the nut would be extremely tight, and that it would be easier to loosen the nut while still attached to the JCB. The only spanner/wrench large enough was a Stillson wrench. I did not enjoy using it because it bit into the nut and marred the smooth surface. I had priced a new open ender spanner, but the cost was high so I used the Stillson. The Stillson was about a meter long, and the nut would not budge, despite using all of my strength and weight. Using a 1.5 meter pipe extension, the nut finally moved, and I loosened it until it stopped fighting. I caught much of the hydraulic oil which spilled out in a bucket, not to be reused of course.

I carried the ram into my workshop. At that moment I decided that any future resealing jobs on larger rams would be done professionally. It was quite heavy.

In the workshop I completed the removal of the large gland nut, discovered that the gland O ring and the main seal were in pieces.

Then removed the piston and its rod from the cylinder by pulling carefully.

The piston seals looked OK to my inexpert eye. But I had purchased a whole new kit of seals, including the piston seals and guides, so I replaced them all.

The new piston seals above, and the new gland seals inside and out, bottom. The gland and piston, and my hands were cleaned thoroughly, multiple times before and during the procedure. Most of them went on without much difficulty. The big rubber seal on the outside of the piston was the hardest. For that I used a heavy cable tie looped through the seal, to pull it into position. All good so far.

By the way, I had obtained a JCB service manual for my machine online, from Best Manuals, (USA) for $US19.99 and downloaded electronically. It had some very useful information. Including that replacement seals might be different from the originals. And they were. They looked different.

The seals went onto the piston fairly easily, with the assistance of a large cable tie, which was used to pull the large central rubber seal into its groove. The remainder of the piston seals were split, and positioned easily. The gland seals fitted easily, except for the large internal rubber seal which required considerable pushing and effort.

The gland was then pushed onto the piston rod, then the piston was screwed on, after cleaning the threads, treating them with Loctite 7471, and thread retainer 720. Then tightened with wrench and 1.5m extension.

My very untidy workshop, undoing the piston nut. The same setup for tightening. The manual specified 300 ft-lb, but my torque wrench does not measure such a large tension, so I just used all of my strength to tighten the nut, using the extension. The aluminium jaws are just supporting the rod. Most of the pressure is held by the foreground vice.

Then I attempted to insert the piston into the cylinder. But it would not go. So I pushed harder. Still no go. Tried wiggling. twisting, pushing harder. No Go. Bummer. 4pm on a Friday afternoon. Long holiday weekend imminent. Threw the parts into the boot and drove to Enzed. About 15″ away. Maybe there is a special tool or press to push the parts together?

They helped me immediately. I guess that my previous business a few days earlier and quick payment of their bill helped. They mounted the cylinder in a chain- pipe vice, and pushed and strained, but no better result than I had. The piston with its new seals just would not fit into the cylinder.

So, he compared the old and the new seals. The new ones were 0.3mm thicker than the old ones. And the diameters seemed larger. I had bought the seals from a JCB dealer, who had said that they were “after market”. Originals no longer made for such an old machine.

Discussion. Decision. Use the old piston seals. The new gland seals seemed fine, so keep them. The old piston seals appeared to be in good condition, and they were installed. And guess what? The piston slid into the cylinder with some pushing. The gland nut was tightened. (with a Stillson I noted).

The charge for 30 minutes of heavy, dirty, specialist time??? $AUD 23.00. I said, “that seems too cheap”. “That’s OK” he said. They will continue to get my business.

Today I re-installed the ram on the JCB.

Fired up the diesel. No leaks!

Operated the bucket control……no leaks, but no movement! Bummer! What now.

Hmm. Could I have put the hoses on back to front? No. They looked correct.

But hang on, the cylinder is facing the wrong way! The paint scuff marks which were on the outside are now facing inside!


So, left the ram as was, switched the hoses, and tried again.

WOO HOO! No Leaks! (including when I tried different ram positions off camera).

JCB 3CX 4×4. Next project?

I am still waiting to pour bronze to make a 1:10 scale Ottoman bombard. I have all the equipment and materials ready to go. But, held up by 1. needing some dry, wind free days, 2. ability to have a friend on hand to assist with the pour. I need 2 successive days for making each mould and doing the pour. Waiting, waiting. Meanwhile, SWMBO has had me breaking up a concrete drive, manually loading the broken up concrete, and transporting it to the recycler. It took 3 x 2 ton loads, so far, and still more to go.

Then in lockdown, we decided to fix a leaking balcony at home, and replace some rotting, ceiling boards under the leaks. At 71, I dislike working on ladders, above my head. Almost finished, thank goodness. And no more broken bones.

The leaks have been fixed. And the 8×2 beams are intact.
Fortunately I was able to buy some boards to match the old ones. Doesn’t look much, but those patches took 4 sessions of about 4 hours each. Even more fortunately, SWMBO does not trust my painting skills, so she will do the painting after I have fitted the corner mouldings.

The lockdown restrictions eased a bit last weekend, permitting me to visit my workshop. I have been waiting for some suitable weather to burn some rubbish, and it was not too windy a couple of days ago, so this was the first task…

First weeks of spring, and with a fire permit obtained from the local authority, I had some fun with this. But even so, I had to put out some spot fires in the surrounding grass, which has already started to dry off. I am glad that I did not wait another week or two.

I have been considering my next modelling project. Nothing really is grabbing my attention. But I had to use the JCB backhoe to load the concrete onto the tipping trailer and I was aware that the JCB is looking really tired. Not surprising, considering that it is 36 years old, and has 7200 hours on the clock. I bought it third hand, more than a decade ago, and used it for general farm jobs, including manure handling, transplanting mature olive trees, as a yard crane, moving machinery, digging trenches. As a general farm machine it was incredibly useful. When the farm was sold, it was just about the only big machine which I retained, because even on 5 acres it is still used occasionally.

Transplanting a 10 year old olive tree. Even with many cut roots, they transplant very successfully.
Handy for heavy lifting. My tractor at back was not getting any use so it is on permanent loan to a neighbour.
4 way bucket at the front, can lift 1.5 tons. One of the rams has developed a leak, and will need resealing. The Perkins diesel starts easily and runs well.
The back end is slightly loose, but not bad for its age. The tyres are down to about 15-20%. As you can see the paint work is ready for renewal, but there is no serious rust. The white roof is worst, so that is the first item for repainting. The rams are all good.
I made this grab attachment for picking up vegetation trash, heavy beams etc.
…like this heavy RSJ…
I do not know what this plate is called. It secures the boom during travelling. It has been welded/repaired more than once, but as you can see the left hand yoke is broken and non functional. It is a casting. I have been searching for another one from a wrecked JCB, but no luck so far. So I am drawing up plans for fabricating one from 20mm steel plate. Some more laser cutting and mig welding required. (ps. it is called a “slew lock”).
The interior of the cabin is not too bad. All of the controls function. The rapid steering knob was missing, so today I fitted this gear stick knob from my “might be useful one day” collection. It has a large spider embedded in the clear plastic.

So, until some new model engineering project takes control of my life, I will spend some time and TLC on the JCB.

Backhoe grabber

OK. so this is a photo of a gadget which I made few years ago. It is a mechanical grabber which bolts onto a backhoe arm and bucket. Seen here picking up a 5 meter I beam which must weigh 200-300 kgs.
The grabber is very useful for picking up heavy, big, prickly, dirty, rubbish and other farm stuff. Good for grabbing fence posts and pulling them out of the ground.
I wish I could say that I invented the idea, but alas….