Backhoe Pin/Bushing replacement in Woods 750 Backhoe

[Dataway]

I've got my woods 750 disassembled, the holes in the boom and dipper are shot (sure wish they didn't use hardened pins).

Plan is to get them in the milling machine and take the holes out to 1 1/4" and bush them. They use 1" pins.

Any tips, hints, ideas, advice on bushing material, machining, clearances etc??

Also need to replace the lower bearing in the pivot housing ... anyone done that before?

Thank you for your expertise.

JohnnyB

 

[Dataway]

PS. Can I get away with high load bronze bushings ... or should I use hardened steel like a "drill bushing" Only issue with the hardened steel is the hole in the booms would have to be spot on because I couldn't adjust the OD of the hardened steel bushing on the lathe.

 

[Snobdds]

You should be able to order a pin kit that has the bushing, and pin with zerk fitting in one nice package.

 

[Dataway]

The Woods 750-3 does not use bushings like were used on the earlier models. I have found the bushings are available for the earlier models, same diameter pin, bushing is ID 1.00 x OD 1.24 x Length 1.5" .... so... that should work in the later boom and dipper if I bore out the booms. What I am wondering is if these earlier model bushings are hardened steel ... not sure about using hardened steel bushings with a hardened steel pin ?? Might be ok, I'm not sure.

Looks like if want to rebuild it using OEM parts I can use the various bushings that were used in the early 750's, and OEM pins from the later model 750's. But again ... would have to bore out the booms ... but would have to do that anyway. Assuming the early model bushings are hardened steel ... I'm going to have to hold the boring to probably .001" accuracy to get the press fit right.

Sure wish they kept building them like the early models that had bushings in all the necessary locations.

Might have to fabricate a couple of the pins that for some reason are priced crazy .... like $150. Most of the pins run around $40 which is fine.


Or are you saying someone sells a retro-fit / repair pin and bushing kit?

 

[Snobdds]

Take a look here. Should be able to order the bushing.

Parts for Woods BH750 Backhoe

 

[Dataway]

There is no bushing on that model of the BH750 .... they stopped using bushings at some point earlier.

I know where to find the early model bushings. That's the easy part. The hard part is modifying a 750-3 to take the bushings.
And I'm not sure if the early model bushings are compatible with the late model pins .... as far as hardening goes ... and I can't use the early pins because they are different length.

Basically I'm looking for advice on the machining, bushing fit, pin hardness etc. from someone who has done this before.

 

[arkydog]

go find a company that services logging equipment. they might,should be able to help you.

 

[ddbackhoe]

I've got my woods 750 disassembled, the holes in the boom and dipper are shot (sure wish they didn't use hardened pins).

Plan is to get them in the milling machine and take the holes out to 1 1/4" and bush them. They use 1" pins.

Any tips, hints, ideas, advice on bushing material, machining, clearances etc??

Also need to replace the lower bearing in the pivot housing ... anyone done that before?

Thank you for your expertise.

JohnnyB

IMO, something, somewhere has to have some give to it. Picking what and where is the hard part. When possible, I've been using these NU series Self-Lubricating Bearings and Bushings - National Precision Bearing. That way if someone forgets to lube, ok and if they do lube, ok.

I would not use hardened bushings with hardened pins.

 

[LD1]

I wouldnt use bronze on the bushings. It pounds out and deforms quickly.

The only hoes I have worked on have been industrial machines so I dont know what is typical in smaller ones. But industrial stuff use both hard bushings AND pins. With the tins being only slightly softer. Reason is the pin is usually the easiest to make, and replace. The pin is hard....not so much for wear resistance, rather toughness. You dont want a soft carbon/mild steel pin in there. They bend and break too easy.

When I did mine, I used either 4140 or 4340 pre-hardened. It was about 50Rc. I dont see what the big deal is about adjusting a bushing in the lathe even if hard. At least up to about Rc60. Do you not have carbide tooling? If not, get some.

As to the wear, what caused it? Lack of grease? No grease getting to the pivot? How is your pins set up? I have seen some that can free spin through everything and has necessary grease points, and retained with snaprings. Others are captured pins with a tab and retaining bolt or similar, that are only allowed to spin in one of the connections points. Those types of pins only need to worry about bushing and grease holes on the part that spins.

There are a ton of good material choices for pins and bushings. o1 drill rod (hardened), 1144 stressproof, 4140/4340 steels, hydraulic cylinder rods, etc. On a machine that size with 1" pins....dont know how long they are....but I would't be at all opposed to using a 1" shoulder bolt. Already pretty hard and tough, and nicely machined. Just avoid mild steels and brasses/bronzes

 

[Dataway]

Thank you guys for the advice.
I did find some OEM bushing for a earlier model that I'm going to assume are the right material (but again designed for a machine was made to accept them)
For the areas that were not ever bushed on any model (the ram pivots) was thinking high load bronze, 40,000 lb when using a pair of them.
Shoulder bolts ... great idea. I had planned on making a couple of ram pins with "high strength" 1045 medium carbon rod, but I see McMaster has shoulder bolts that would probably work with modification.

I do have carbide tooling ... but last time I tried to turn something hardened (case hardened) it didn't go very smoothly.

I guess I could also just order the earlier model bushings and modify their length to use in the ram pivots also.

Most of the pins are clevis type ... just slide through, pin to a flange on the outside of the boom. ... so yes, pinned on one side, free on the other side of the connection. All the ram pins are pinned in the boom pivot hole, free with grease fittings on the end of the cylinders.

I've had this machine for 10 years, but it was a rental before I got it .... damage was done due to lack of lube before I got it.
Being a small Woods BH, it's not the highest quality piece of equipment out there, just trying to tighten it up enough that I it doesn't look like it has palsy when it operated

 

[Snobdds]

What ran piviot points are you talking about...?

 

[Dataway]

The points that need the most work are Boom to main housing (the boom holes are egged), Boom to dipper (the boom holes are egged), both bucket pivots in the dipper. And the Boom Ram to main housing is sloppy ... problem is the slop seems to be in the Ram sleeve ... which was taking abuse because the boom to main housing pivot was so sloppy.

Any idea how to get the main swivel bearing off the kingpin? They appear to be pressed on. Can't remove the main housing from the frame because I can't get the bearings off the king pin. Not a huge deal, I would have like to replace the lower swivel bearing, and do a bit of welding on the housing ... but not absolutely necessary. Can do the welding in place if need be.

Pivots that need work circled in red, kingpin bearing in green.

 

[r8nger]

I do a lot of line boring, usually larger holes on loaders , excavaters, etc
Go with the hard bushings,.003-.005 interference fit , pressed in frozen, then you might have to use a small grinding wheel and flap wheel for the finish fit, The smaller holes are actually harder to do, then say, a 4" hole.

 

[Dataway]

Thank you, I was wondering what the fit should be.

The line boring will be tough, the boring bar in my BP won't reach both sides at the same time, so I'm going to have to flip the boom over to bore the other side. I'll have to turn up a 1 1/4" rod to fit the finished hole on the far side, turn it down to 1" to fit a collet and use that to align the second hole. I'd use a big drill bit, but my guess is it would make the hole a couple thou to large.

 

[LD1]

I hope you don't misunderstand that post. .003-.004 is for the OD of the bushing.

Pin to bushing needs to be clearance, not interference. 0.000-0.001 is what I would aim for.

 

[Dataway]

Was just thinking I could make up an 8" or so boring bar out of some 3/4 or 7/8" cold rolled, cut down a 1/4" carbide lathe tool and mount that with a set screw .... put the whole shebang in a collet and reach both holes at the same time. Although I wouldn't have the easy adjust ability of my regular boring head. Just thinking out loud, really don't want to have to flip the boom and realign it ... only weighs maybe 100 lbs ... but still would be a pain.

 

[LD1]

What does your boring head look like?

Instead of chucking direct In the collet, make a longer bar for the boring head. Just make sure the part is true in the mill.

 

[Dataway]

LD1 ... yep you beat me to it ... I was just thinking ... why not a longer boring bar in the head Although it only takes like a 1/2" OD bar ... so I'd have to go real slow ... but that's ok.

And yes ... I interchanged "interference" and "clearance" like a novice

 

[TMGT]

I made a line boring setup a couple years ago, pretty simple and works well.

I used spring bushings when I made my backhoe, pins were made out of 1144 stressproof.

Mcmastercarr has a decent selection of spring bushings.


My drive system, fixed at between .005-6in per rev.

 

[Dataway]

TMGT ... very interesting ... on close examination of the part diagram it really looks like the OEM bushings for the earlier model BH750 are indeed straight slot spring bushings.

Just looked at the 1144 and ordered 3 feet .... yep, it's harder and 25% stronger than the 1045 I planned on using. Also ordered a pair of the spring bushings to take a look at them.

Thanks,