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.
Nicely done John.
Nice work John. Looks very professional and more substantial than the oem version.
Looks like a cracking job 👍🏼
Been trying to find a replacement for my trashed slew plate for ages now, came across this through a Google search. Mines a 34yr old 3cx and your old plate looks the same as mine. Any chance I could get the details of your design??? I could then find someone local to machine it for me.
Steve for the UK.
Steve, I have sent a private reply to your email. John
John, nice write up on your repair. I have an old 3c and snapped my slew plate in haste today, but not before distorting the distorting the pattern pretty drastically. Because of that, I would also like to have a copy of your 2d cad files if that would be possible. I’m going to go the water jet route so may modify to accommodate jet draft. How does one get ahold of you?
Thanks in advance.
I will need your email Peter. Use “at” instead of @ and “dot” for .
Nice work! I bought a JCB 4CX last year, now i’m changing the gland seals on the main boom cylinder. My slew plate is missing. Could I get a copy of your design for the slew plate. it looks exactly like on the 4CX.
Sure. You will need to send me an email address. John
The slew lock plate is missing from my 1986 3cx. Can I purchase the drawing/file for this design so I can get one made..?
dxf file sent to your email Stan.
Hi John would really appreciate the file as well have a local engineer that will make one for me but size and measurements would be great, just bought a 1985 3cx and mine is missing Regards Andy
Andy, what is the measurement centre to centre of the pivot tabs? Another reader found that my dimensions did not suit his 3CX. John
Hi John first chance I’ve had to get a measure at it 29cm outside edge to outside edge, one of my mounting eyes is broken off so going to weld on new mounting points anyway.
I am pretty sure that my dxf drawing would suit your 4CX, but I will need an email address.
Great job john, i am also in desperate need of one for my machine, called local dealer and he said $1480 +tax!!!!! Any chance you could send me your sketch at firstname.lastname@example.org??
pdf and df files sent.