Pin and Bushing help needed

[EddieWalker]

My grapple works pretty good, but not great. I've come up with a few ideas that might cut down on my problems, but haven't had any luck finding what I think I need.

My problem is that I have two seperat arms that close on my FEL to create a grapple. Each one works independent of the other. What is happening is they are twisting and bending on me. I've reiforced them to the point they are too heavy to install and they are still bending.

I'm now going to try 2x4 steel tubing.

The other problem is the pivot point. I just drilled holes through half inch steel and put a grade 8 bolt through there to pivot on. I'm using a one inch bolt, and that seems to be plenty strong enough, but my grapple wobbles on it. This movement allows the grapple to twist and in turn, bend.

My solution is to make the end of the 2x4 tubing like the end of a hydralic cylinder. A solid piece of steel that is either welded to the end of the 2x4 tubing, or through it. Then a matching bushing that goes through the 1/2 inch steel plate that attaches it to the FEL.

I'm doing something wrong, because I'm sure the parts must exist online someplace, but so far, I haven't found them. Does anybody know a source that has somethng like this?

I'm also open to any and all suggestions on another way to create a rock solid pivot point for my grapple that doesn't involve me having to machine it myself. Cutting and welding is about the limits of my fabrication skills.

Thank you,
Eddie

 

[EddieWalker]

Techincal data.

The space between the half inch plates is three inches.

The 2x4 steel tubing is the actuall ouside measurements.

I have one inch bolts, which are working fin, but would prefer to have pins that I don't have to use massive wrenches to take on and off.

I'd like to be able to grease it, but can drill and tap for zirk fittings pretty easily myself.

Thank you,
Eddie

 

[MarcusCarr]

I purchased some 1.5"OD 1/4" wall steel tubing to use as bushings. Cut a length of tubing 2-3 inches long. Drill a 1.5" hold in your steel. Slide the tubing into the hole, so the hole is centered on the tubing. Weld it in place. Now use a 1" pin to pivot on.

This will give you a greater surface area around the pin and the welds will limit lateral movement. For even better performance, drill a hole in the pin or bushing and install a zerk fitting so you can grease it.

Keep in mind that the power of your cylinder is probably much greater than the strength of the design with 1/2" material. If you pinch down hard enough, you will bend 1/2" steel, assuming it is mild steel. Use the bushings and a light hand on the hydraulic valve and you should have a winning combination.

Marcus

 

[AlanB]

Eddie, if you want to buy off the shelf stuff, McMaster Carr is the place.

McMaster-Carr

Type in Bushing, or sleeve bearing and start from there. Not sure how to link the webpage after I drilled down, but sure you will find it from there.

Most machine shops keep "bushing stock" on hand.

As much as you do, I am sure there is a machine shop you work with, give them the dimensions and they can knock you out some quick (and my experience is) and reasonable to exact dimensions. The thing I do with the shop that does stuff for me, is to specify how quick I need it, and that greatly effects my prices. It also helps that my wife helped the owner resolve several pond problems he had

When I drop a backhoe bucket off to have the bushings bored, and needed it the next day, it was one price, when I had some peices made I was getting for some future work, and he put his guys on it when they were caught up, it was a bit cheaper. But we have a great relationship developed over a couple of years.

Anyway, I think what you are wanting are sometimes called weld in button bushings, They are pretty common and if you look at your buckets etc. you will see them welded in.

Good luck

 

[KYErik]

Yep- what Marcus said. Around here metal/welding shops sell it as "dimensional tubing" and its sold by the foot.

Its not cheap- around $15 a foot depending on the diameter. They sell it by ID as well.

 

[dfkrug]

Eddie:

What Marcus describes is DOM (drawn over mandrell) tubing. You
can get this from some steel dealers or mail order from Metco Supply.
There are other TBN threads that deal with this issue. Some TBNers
say you can get this bushing stock from some tractor dealers, but
that has not been the case here.

If you are going to use this bushing stock to fully pass thru your
rectangular tubing, it will make a great pivot. What you then need to
find and buy is some 25mm or 63/64" rod for pins. I had much less
prob finding that vs. the DOM tubing. No lathe work will be reqd.

BTW, I have used lots of this stuff for pivots, esp in my CADDigger
project.

 

[MarcusCarr]

dfkrug makes an excellent point on the 63/64 rod as pins. The tubing is exactly a 1" inner diameter, and the pins that I use are 1" pins. This combination requires that I slightly hone out the tubing.

Marcsu

 

[EddieWalker]

Thank you everyone. You've given me some new words to use in my searches. I have a pretty good steel shop here in Tyler, and a machine shop that's very reliable, very good and very pricey. hahaha

Eddie

 

[john_bud]

Yeah, that is too true. The DOM and 1" pins I made were negative clearance. Not having any machine tools, having v large parts that weighed 500 to 1000# and being a cheap sob - I used the old bolt and sand paper method.

Get a 5/8" bolt that is longer than the bushing by about 2-3". Do the Marie Antoinette (cut off the head), and use a sawzall to cut a verticle slit down the length of the bolt about 2 1/4" deep. Put long board sand paper into the slot and wrap it tight. Power it with a drill and you have a hone.

Not pretty, but it does work

jb

 

[MarcusCarr]

I like your idea. Can you explain "long board" sandpaper? I am not familiar with the term.

thanks,
Marcus

 

[dfkrug]

What I did for the many pivots on my CADDigger was buy the
1" ID DOM tubing and cut bushings. I welded them into the holes
in the steel plates then used a 1.000" hand reamer to
get each bushing pair into alignment for the 63/64" pins. There
would always be some tiny mis-alignment due to heat distortion
of the steel. The hand reamer was about $30 and
had 6" flutes. Heat management in these kinds of welds is very
important!

For the pivots in the rectangular tubing, one chunk of DOM tubing
went all the way thru, so it was much easier. No reaming necessary
here as the clearance with a 63/64" rod was about perfect. If you
use 1" pins and 1" ID DOM, you would need a 1 1/64" reamer, or
sand it out as described. Or you could sand your pins down. If the
1" bolts are a little less than 1" OD, that would work, too.

 

[Danno1]

.

Two places to try for metal are

Metals Depotï½® - Buy Small Quantity Metal Online! Steel, Aluminum, Stainless, Brass

and

Steel, Aluminum, Stainless, and Brass - All Metals Incorporated


Of course depending on what you buy, shipping could be expensive.


A longboard is used to fair the hull of a boat. The sandpaper would be strips ~ 2-4 in wide by the length of the board, anywhere from 12-24 inches. IOW, buy a 50 ft roll and cut the strips to the length you need.

.

 

[EddieWalker]

Thanks again for all the help. I never heard of the DOM, so that's what I'm going to ask for when I buy the 2x4 tubing.

This is one of those rainy day projects that I'll buy the materials for and wait for a wet/muddy day to put together.

Eddie

 

[hankus]

Eddie I think when they refer to DOM tubing they are referring to the round stuff, not the square stuff. Someone correct me if I'm wrong.

 

[GuglioLS]

Eddie,

DOM = Drawn Over Mandrel (Seamless Tubing) I hope you don't mind that I posted some pictures for you to take a look at. It's not cheap, of course nowadays what is? DOM is what I used on my grapple jaw bushings. 1" ID x 1/4" wall I used 1" hitch pins (0.997") OD the pins fit no problem, If you can't get the pins to slip into the DOM you can use a 99 cent H/F break cylinder hone on the ID of the DOM to get a nice slip fit.

DOM:.......................... 1" Pin FITS.................Welded in Place........... Jaw Brackets:



Larry

 

[MrJimi]

Eddie, do you have pictures of your twisting grapple, I was going to make mine like yours but after reading this, I am at a stand still, I do like 3RRL's and GuglioLS way much better but they have some very neat tools and skills that I don't have

 

[firefighter9208]

Eddie,

DOM = Drawn Over Mandrel (Seamless Tubing) I hope you don't mind that I posted some pictures for you to take a look at. It's not cheap, of course nowadays what is? DOM is what I used on my grapple jaw bushings. 1" ID x 1/4" wall I used 1" hitch pins (0.997") OD the pins fit no problem, If you can't get the pins to slip into the DOM you can use a 99 cent H/F break cylinder hone on the ID of the DOM to get a nice slip fit.

DOM:.......................... 1" Pin FITS.................Welded in Place........... Jaw Brackets:



Larry

Eddie,

DOM tubing is what is used to build roll cages in race cars. It is stronger, because it doesn't have a seam. Check with a local hot rod shop that builds roll cages. They might have some DOM scrap pieces they would give you. If not they can tell you where to get it or might can even order it for you at a discounted price.

Chris

 

[dfkrug]

Eddie,

DOM = Drawn Over Mandrel (Seamless Tubing) I hope you don't mind that I posted some pictures for you to take a look at. It's not cheap, of course nowadays what is? DOM is what I used on my grapple jaw bushings. 1" ID x 1/4" wall I used 1" hitch pins (0.997") OD the pins fit no problem, If you can't get the pins to slip into the DOM you can use a 99 cent H/F break cylinder hone on the ID of the DOM to get a nice slip fit.
Larry

Great pix and clarification of DOM tubing, Larry. I have not used 1" hitch
pins before, and the fact that they are undersized makes them an
excellent choice here.

I see in your last photo that you have some 1/2" plate with a pivot. You
may have already thought of this, but even 1/2" plate will bend easily
if not braced every 4-5 inches or so in grapple or thumb applications. You
don't want your grapple to twist.

 

[dfkrug]

Eddie,

DOM tubing is what is used to build roll cages in race cars. It is stronger, because it doesn't have a seam. Check with a local hot rod shop that builds roll cages.

That's a surprise. It seems (seams?) wastefull to use this expensive
tubing for roll bars. There are thickness requirements in the racing
rule books, but no requirements to use DOM. I recall reading in my old
SCCA book that you had to provide a test hole in the roll bar to verify
thickness. I would be shocked to hear that someone has fabricated
a roll bar with the 1/4" wall DOM tubing we are talking about here. Even
the thinner wall stuff would be wasteful.

DOM steel tubing is hot or cold roll-formed and welded, then drawn over
an internal mandrel one or more times to remove the steel flash from inside the tubing. The welds used in making tubing is specced (ASTM) to be as
strong or stronger than the base metal, so DOM tubing is not stronger
than other welded tubing of the same thickness and metalurgy. One
might even argue that removing the flash at the weld seam weakens the
tubing a tiny bit.

Is an entirely different subject to talk about BENDING tubing using
EXTERNAL mandrels to get the best possible bends in roll bar
fabrication.