# Crawler Crane Undercarriage Project



## RVJimD (May 14, 2015)

I am trying to make the track pads for a model crane undercarriage.  What I have so far is pictured above.  My question is how to proceed in a way to produce parts that are the same dimensions and will be sort of generic so that each pad will fit to any other pad.  I started out with flat 1/8" thick bar stock and cut the sections to the rough length (or width actually).  The pads are 1.5 x .5 and I am planning to use either piano wire or maybe brass rod to hinge them together.  I have a few that are hinged as a prototype.  What I found is I needed the cogs sticking up in the second from the left in order to drive the assembly.  So, I decided to try using 1/4" thick stock and mill about the top half away leaving the slot down the center and eventually beveling the slot flanges so they will fold together as they round the wheels at each end.  (Boy, this must be hard to follow...)

I also made a fixture block to hold a double stack of six each in the vice for milling.  This seemed okay, but it seems like I still didn't get very repetitive results.  I know this is all due to my inexperience.

But, when I decided to try the "three dimension" versions it seemed to complicate everything.

To simplify my question, would it be better/easier to mill the slot along 4 or 5 inches of the bar stock first, or, mill the overlapping fingers first, which would mean cutting the pads into individual pads first in order to make the finger notches on the leading and trailing edges of each pad?

I'm looking for any tips on what order or other ideas of how to produce the parts.  I will need about 40 or so of these.

Thanks for looking, and if nothing else enjoy the pictures...




Jim


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## astjp2 (May 14, 2015)

Make in batches, do all of the same cut for say...30-100 parts, then make the next cut and the next...it keeps your setups minimum.  The only  drawback is if you mess up one, you mess up the entire batch. Tim


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## RVJimD (May 14, 2015)

Tim,  that helps.  I think I have been thinking that way but not actually doing it that way.  Now that I have settled on a design I should be able to do as you suggest.

Jim


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## stupoty (May 14, 2015)

That looks really good, 

The advice previous is good, some sort of set of jigs to hold each stage.

Good luck, make sure you post pics of the progress 

Stuart


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## RVJimD (May 15, 2015)

Progress!  I made a bunch more of my newer style pads and DID batch them.  This is working much better now.  I also made a simple vise stop block which really helps.  I think I made about 25 or so and then decided to "finish" 6 of them to make sure the design is going to work.  So, the picture of the vise shows the drill guide that I was using for the version 1 pads, I need to widen the slot  a bit.  I will drill the six pads and bevel the drive dogs and then work on the drive roller.  Once I prove all that, I can come back and make another 40 or so pads!


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## rock_breaker (May 16, 2015)

Nice work. I hope to follow in your footsteps some day.
Are you following the design of a particular crane? Also do you have a scale ratio? 
The track pads on a P & H 1900 AL shovel are very similar to your design.  If memory serves right the triangular portions are wider on each side of the pad and like your design fit into recesses on the propel tumbler.    
I hope my work looks as good as yours when I  get to that point.
Have a good day
Ray


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## RVJimD (May 16, 2015)

Ray,

Thanks for the comment.  I am making the undercarriage to fit under my NyLint truck crane.  So, the scale is approximately 1:16.  I am using some photos of plans/drawings of a Bucyrus 22-B that I found on the web.  I could use more drawing so if you know where I could find some on the web that would help.  In the first picture I have the crane sitting on an undercarriage from a diecast Oliver Dozer which looks a bit too small so I enlarge the photo plans until it looked about right.


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## Terrywerm (May 16, 2015)

Track sections are typically made of twelve pieces per section:  One pad, two rails (one left, one right), one pin, four bolts and four nuts. Photos should give you a better idea than any description I could give.













Track Rails and track chain



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						The chain is made of rails and pins
					



Rails and a chain, which is an assembly of rails and pins.













D4 Rails And Shoes



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Track assembly, rolled up, but gives a better idea of the assembly













Minidozer Track



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Welded track sections that someone came up with for a mini-dozer.

Track pins are normally a press fit in one end of the rails, but fit loosely in the other end.  The exception is the master link, which has a loose fit on both ends. The pin that fits there is held in place by a cross bolt rather than being pressed in.

One other note on tracks: Cranes, excavators, and other tracked machines that only use the tracks for moving the machine from work place to work place usually use what is commonly known as a "street pad" which typically has three or four shallow grouser "teeth". This allows the machine to move across a paved surface without damaging the pavement. Many times cranes have no grousers on the pads at all, and use a smooth pad or shoe. Dozers and crawler tractors  have only one large grouser per pad, so that they engage the ground better for pushing or pulling large loads that require brute force for movement.

I don't know if any of this helps or not, but thought I would offer what I could.


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## RVJimD (May 16, 2015)

Terry,

That does help, I like the pictures.  One thing I didn't realize until I started working on this was how different the drive sprocket is from a dozer compared to a crane.  One using a sprocket like a gear and the crane using a drive cog like was shown the other day on the tracked snow thrower thread.

Jim


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## RVJimD (May 17, 2015)

I was pulling my hair out trying to get a drill guide that positioned the hole in just the right spot.  My lack of experience was really getting me I think?  But, I think I finally came up with a good solution.  I need to insert the track pads into a milled slot that holds the vertical and then I put the guide block with pad into my drill press vise and drill the hole.  Well, I made about three of these and kept screwing up the hole location in the last step of making the guide.  Here is my solution.  I decided to bore out the top of the guide where I was trying to accurately locate the guide hole, and made a round bushing that drops into the hole and I hold it in place with a set screw.  This let me make as many top bushings as needed until I got one I liked.  I can also make one in steel if the aluminum proves too soft for the job.








Jim


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## RVJimD (May 22, 2015)

I have settled on a 1/8" thick stock material design and have the pads almost finished.  I also checked the diameter of the tumblers and pitch of the track pads.  I still have some work to do to finish the pads but it seems like it is all coming together.  Hopefully I will get to start or the side frames this weekend.










Jim


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## RVJimD (May 24, 2015)

New Question...

In the last picture in my above post is the prototype tumbler.  The final drive tumbler are yet to be designed but what are my options for turning this tumbler, and I don't mean on the lathe but from the axel shaft on the undercarriage.  The center hole is 1/4".  Thing I have thought about so far but not decided on are:

Tap the hole and use a thread on the end of the drive axel with a locking nut on one or both sides.  I don't really care for this idea.

Broach a key way and do it with a slot and key.  I don't have any broaching tools.

Make a hex on the end of the shaft and make hex on the inside hole on the tumbler.  I like this idea but how do I broach the hex hole in the tumbler?

Other ways to do this are greatly appreciated!

Thanks for watching my project!

Jim


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## Terrywerm (May 24, 2015)

You could make the tumbler with a raised boss around the axle hole, then cross drill through the boss and the axle and use a small spring pin to secure the tumbler to the shaft. Another method would be to drill and tap the boss for a small setscrew, running the setscrew up against a flat on the axle shaft.


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## RVJimD (May 24, 2015)

Terry,

Great idea!  I was thinking about drilling from the outside diameter of the tumbler and doing a set screw but I didn't like the idea of not having easy access to the set screw once the pads were in place covering up the hole.  That may be the winning design idea!

Jim


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## Terrywerm (May 24, 2015)

If you really feel ambitious you could make your own miniature split taper bushings, but they would be a lot of work!


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## RVJimD (Jun 4, 2015)

Quick little progress report.  I have all the pads milled out, I am still drilling the hinge holes and the drive dogs need to be cut and riveted in place.  Wow, what a LOT of pieces and small parts and steps!  Anyway, I drilled three different bolt circles on a test tumbler and got one that looks like it will work.  I didn't want to start right off milling the profiled version that I plan to make until I get things "dry fit" using a simpler method.  The bolt circle and brass tubing looks good and the final milled version will actually drive at the outermost edge of the tumbler wheel instead of like the tubing looks.

Sorry about the portrait shot...




Jim


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## RVJimD (Jun 5, 2015)

A lot of the reason I like to post project builds like this one is because it keeps me motivated.  Here is the setup I am using to drill the link holes in the pads.  They are pinned together with 1/16 brass tube.  I had been drilling these holes on the drill press but the chuck is a bit off and I decided to try making a bit holder for a 3/8" collet to put into the mill.  I have a R8 drill chuck for the mill but it won't close down small enough for a 1/16" drill.  I just turned a piece if aluminum in the lathe and center drilled it 1/16".  It us turned down to fit a 3/8" collet which is a common size for me for end mills so I can switch between them without changing the collet.  The 1/16 bit is a good slide fit and I glued it in place with CA.  Thanks to whoever suggested this idea!

Remember, I am a "noob" machinist so don't be afraid to offer tips or observations on my techniques.




Jim


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## RVJimD (Jun 5, 2015)

I was getting crazy drilling holes and had to do something different for a while!  If all the side rails turn out okay I will try to make them in steel to add a bit of weight.  I'm thinking I may also add some lead ballast where I can as well.






Jim


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## RVJimD (Jun 9, 2015)

Here are a few shots of the progress thus far...







Jim


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## Terrywerm (Jun 9, 2015)

Looking good, Jim.  Things are coming right along!


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## RVJimD (Jun 13, 2015)

How would you make these idler rollers?








I need to make 12 of them.  I am starting with 3/4" round aluminum stock.  They have a taper to help clear the drive dog tabs on the pads.  This is one of those things that I look at and think " that shouldn't be too hard", and then when I start making them I end up with two or three and NONE of them are the same.  I had been trying to make the taper using the side angle on my right hand turning tool bit, but that is problematic when it comes to doing the second (or left hand side if the part stays chucked up for the entire process, which I think it should).  So, now it finally dawned on me, use the compound to make the taper. 

My problems are:
Keeping concentricity.  (I think I solved this by NOT over drilling the center hole, so that when I pull the stock out, I don't start off on the next part with an off center hole.)
Getting the same length on the shoulders on each side.
Getting the center rib in the center.

I am using my dial indicator on a mag base to move the carriage in as I turn the shoulder.
Should I be doing this with the part chucked once for the entire part?  If so, should I be using a left hand turning tool for the left hand shoulder and Turing away from the chuck?

 I think this all comes back to one of my very first questions when I got started with the lathe, "how do you know what steps and what order and how to decide what tool or procedure"?

Thanks for any tips or suggestions.

Jim


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## planeflyer21 (Jun 15, 2015)

Sounds like you're on the right path...drill just deep enough to clear the made part, turn the shoulders down on both sides (enough that the front shoulder on the next part is already cut), with enough extra that the material removed by your parting tool cuts the rear shoulder of the first part and front shoulder of the second part to tolerance/spec.

Chip on, Jim!


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## RVJimD (Jun 16, 2015)

I got some of my Enco order today and it had some of the 2-56 screws I was waiting on.  I think I can shape the ears on the pads and get smooth operation.






Jim


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## RVJimD (Jul 7, 2015)

Several changes and a bit of progress...










Still messing with the fit and width of the idler tumbler and angle of the drive tumbler to try and get smooth operation.

Jim


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## RVJimD (Jul 14, 2015)

It is ALIVE!  Got some good stuff done today on the crawler project.  I still don't have the upper or lower rollers on yet so alignment is still a problem and without the lower rollers the ride is a bit bumpy.  

Here are two videos, one showing the crane in action on my pond sea wall loading sand into a toy dump truck.  The shorter video is a closeup of the crawler on the bench.











Jim


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## JimDawson (Jul 14, 2015)

WOW! Great job!


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## Bill C. (Jul 14, 2015)

Sometimes I would use a little layout die on the bed where the magnetic base is mounted to see if I might have bumped it while machining.  A very nice project.


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## RVJimD (Jul 16, 2015)

I made pins and idler rollers for top and bottom.  They really helped smooth out the pads as they transition onto the tumblers at each end of the frame.  I have a diggin video uploading now but it will be a while to finish.  Here is the shop test video...






Jim


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## RVJimD (Jul 16, 2016)

Crawler update.  

I am in the process of changing the style of the drive tumblers on my dragline crawler undercarriage.  I machined a few new drive dogs for track pads and made a new main and center idler wheel.  I need at least four more small idlers then I can test the new design.




Jim


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## Terrywerm (Jul 16, 2016)

It is interesting to watch the progression on this project. Keep it up!


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## 12bolts (Jul 16, 2016)

Excellent work and attention to detail Jim. I love it

Cheers Phil


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## RVJimD (Jul 18, 2016)

I am reworking the frame rails for my crawler, but, it has a twist in it.  Here is a short video that should explain what I mean.  






Part of the reason I wanted to rebuild these parts was the same twist in the old parts.  

I tried to carefully drill the two sides while clamped together in the mill vise.

I tried to carefully turn the spacers in the lathe.  The order was...

Chuck the stock in the 3 jaw, center drill, drill center clearance hole to size.
Turn outside diameter down just enough T to make it round and concentric to the center hole.
Part off.  I faced one of them to match the length of the first.

I DIDNT  machine the inside mating surfaces of the bar stock.

If I loosen the clamping screws a bit and tweak it as I tighten it is better but I want to try and figure 
out what I might be doing wrong.

Jim


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## 12bolts (Jul 19, 2016)

Jim,
It may be that the spacers are twisting the opposing ends up, What happens if you independently clamp the 2 bars lightly to a flat surface and then fit the spacers. Gently tighten the spacers and also gently tighten the clamps on the bars. Just so they can slide together as the spacers are tightened but not able to get cocked up

Cheers Phil


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## RVJimD (Jul 19, 2016)

Phil,

That helped.  I put the assembly in the drill press vise and lightly tightened the vise, then tightend up the screws on the frame rails.

I guess there could be two unrelated issues.  The spacers not faced parallel AND OR the two sides simply move up or down as I tighten the screws.

Am I thinking correctly about facing the spacers to get them parallel?

I face the first end, then turn the diameter, then part off, flip it around and face the second end.  Is that proper?  Do I need to indicate it befoer the second face step?

Thanks for the assistance!

Jim


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## 12bolts (Jul 19, 2016)

Jim, If you can work with the "stickout" and still achieve the finish you want, no chatter, problems etc, then I would turn, face and part off without removing the part from the chuck. Then everything would be parallel and perpendicular after parting. No need to turn and face the end you parted unless you are adjusting for length. Are you working with bought tube or are you drilling it? Perhaps your drill is coming out the other end off centre. If so you could drill it through and then turn between centres to ensure the OD and ID are parallel. Bit of fiddling because then you would need to indicate the part to get it true for facing.
How many of these spacers do you need to make?

Cheers Phil


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## RVJimD (Jul 19, 2016)

Phil,

I'm using solid round stock and drilling it.  I only need four, but I think my twist was coming from the rotation and clamping action as I tightened the screws.  Using the drill press vise has controlled the problem well enough.

Here is a video of the first test.  The first side in the video is the new drive tumbler and associated parts.  About halfway thru I rotate around to the original side.  I'm already working on that side now.






Jim


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## RVJimD (Jul 21, 2016)

Got my undercarriage upgrade finished and it works really well.  The new drive tumblers are much easier to make now that I have learned how to make an octagon using the vise and a v block  I even made my own v block so it would nest the stock and fit my vise perfect .  It got some dirt on it during testing, here are some photos... 

Oh, and it anyone has a thought on it, I would like a better way to finish the tensioner.  The way they are now, the brass rod rotates and the tension holds it against the tensioner bolt.  Not ideal.  I would like to put a collar around the end of the shaft but it can't be threaded, otherwise it would screw into the rod and seize it.  I need to see this, guess I'll start searching the inter web...










Jim


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## kvt (Jul 21, 2016)

Jim,  How about this,  Take the ends of the threads off the SHCS and make a yoke to go over the axle    the end of the screw would seat in the yoke and push it axle to tension without seizing 
Or at least that is what I am thinking.   For that mater if you put a bearing in the yoke for the axle then it would  even reduce friction on the axle yoke interface.


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## RVJimD (Jul 21, 2016)

I think I understand what you are saying, that sounds like it would work.  A round collar around the axel, drill a short blind hole in the radius of that, take the thread off the end of the bolt.  I'll try it and post my results. 

Thanks!

Jim


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## RVJimD (Sep 1, 2016)

Here is a short video I made on using my Grizzly G0759 mill w/DRO to put a bolt circle of five holes in a pulley for the crane boom on the NyLint dragline.






Jim


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