Dragline Crawler Build
 

For a few weeks now I have been learning how to run my new bench sized mill and lathe and loving it! I have always wanted to scratch build a dozer and my first big project is building a crawler undercarriage for my NyLint dragline conversion. My conversion was completed last fall but I never got the truck powered. Thanks go out to Jared and Steve for all the good info in Jared's thread of his BE 22 build.

Here are a few pictures of my crane and the track pads so far. I have gone through at least four variations of pad designs to get one I hope will work well and still look "sort of" scale. Paramount in my project is to have it look good enough but also not make production of parts to complicated.

http://i1291.photobucket.com/albums/...psyfjlu3j2.jpg

I believe the scale is 1:16 on the crane and I tried to eyeball the pads against crane and adjust the drawing Steve posted to get some reference for other parts. The second pad from the left is most similar to my final design choice. I will be using 1/8" x 3/4 x 1.5" aluminum bar stock. I messed with some thicker material but it was a pain to machine the detail of the drive dog ears on the top of the pads and I found a way to use 1/8" and still have the drive dogs.

http://i1291.photobucket.com/albums/...psv8c4dz1x.jpg

This is a stack of the pads that I am NOT going to make. The "third dimension" of the drive dog ears on top of the pads really added a lot of extra steps and problems to the machining operation, like issues of holding the part and just extra machining steps.
http://i1291.photobucket.com/albums/...psuziplg6f.jpg

This is the drill guide I made to locate and drill the holes in the pads.
http://i1291.photobucket.com/albums/...pspzp225vz.jpg

I need to adjust the drill guide to perfectly center the holes on the pads and then I'm ready to start making a bunch of these things!

Jim

Re: Dragline Crawler Build
 

Here are a few more pics. These are my final choice on the design and you can see I am looking at the pitch of the tumbler and pad links. I will make an actual drive tumbler and mill the drive dogs into the side of it on the outer radius. With the pads wrapped around the idler it looks like it should work.

http://i1291.photobucket.com/albums/...pswyilrtth.jpg

http://i1291.photobucket.com/albums/...psjrimpsh1.jpg

http://i1291.photobucket.com/albums/...psppvqzejj.jpg

Jim

Re: Dragline Crawler Build
 

Nice work jim-I know what you are dealing with. Making those drive dog ears on the pad adds a lot of machine work. I spent a week+ making one pad perfect and that is why I made a mold and cast all of them. I'm sure you noticed the pitch changes as you transition from flat to the circle and that was the tricky part for me making the drive sprocket. Never got it exactly right. Looks like you have it figured out. Keep the pictures coming.

Re: Dragline Crawler Build
 

Tom,

Thanks, I thought I read a comment you made on another thread about the pitch, so I was aware of that going in. That would be a real issue if you didn't realize that and made a bunch of parts and THEN figure that one out! :(

Jim

Re: Dragline Crawler Build
 

Got a batch of pads mostly finished. Still putting the slot in middle that receives the drive dog part. And, I still need to drill the hinge holes. Going to be fun and should start to go faster once I get all the pads finished.

http://i1291.photobucket.com/albums/...psg4k7dyqn.jpg

http://i1291.photobucket.com/albums/...psj5uj5hyo.jpg

http://i1291.photobucket.com/albums/...psbp2kes5q.jpg

http://i1291.photobucket.com/albums/...psjlqazpgg.jpg

http://i1291.photobucket.com/albums/...ps6cpdshyb.jpg

http://i1291.photobucket.com/albums/...ps945tuezr.jpg

Jim

Re: Dragline Crawler Build
 

Looking good jim, but I am puzzled by one thing :confused:. The pads look to be about 1/8" thick so why didn't you just use 1/8" flat stock and avoid all that milling. Am I missing something?

Re: Dragline Crawler Build
 

Tom, the stock is 1/8". I WAS experimenting with 1/4" stock where I machined the dogs on the one side but that was a lot of extra work. With the current pads pictured I am milling the leading and trailing edge hinged slots as well as the short slot on the one side to accept the little channel part that becomes the drive dog. I hope that clears it u a bit?

Jim

Re: Dragline Crawler Build
 

Looks like you've got it figured out, Jim. I'm planning on using brass for the pads and soldering the lugs on. I like your drilling fixture.

Re: Dragline Crawler Build
 

Ah, ya the brass would work good I bet, nice and heavy too where you want it.

Jim

Re: Dragline Crawler Build
 

Okay jim-now I got it. You were showing pictures of the pads that you were milling the drive dogs in. I thought you were milling all those chunks down to 1/8". Do you have a plan for making the drive dogs? That looks like really small pcs. to make individually.

Re: Dragline Crawler Build
 

I have been out of the shop for awhile but before I left I DID get the pads all finished and started assembly. I wanted to check my pitch and it is close but I am going to have to turn a few more tumblers to get one perfect. I used the rotary table to hold and drill a bolt circle and simply used brass tube to check the diameter and pitch match between the pads and the tumbler. Here is a picture to show my first test tumbler. If anyone has tips or info on this type of thing I am all ears, I am not a machinist, engineer or designer. I'm just trying things until it looks okay and works reasonably well...:p (Tom, I hope you are reading this... ;) )

http://i1291.photobucket.com/albums/...pspuxb9dv2.jpg

Jim

Re: Dragline Crawler Build
 

Great progress cant wait to see the end result im sure it will be killer

Re: Dragline Crawler Build
 

Jim, check out this link, it should help clear up some. If I can help anymore let me know some of your deminsions that you are bound by.

http://www.engineersedge.com/gear_formula.htm

Re: Dragline Crawler Build
 

Ehow instructions for circular pitch...

Instructions
1
Measure the gear's diameter. For this example, imagine a diameter of 6 inches.

2
Multiply this answer by the constant pi, which is approximately 3.142: 6 × 3.142 = 18.852.

3
Divide this answer by the number of teeth around the gear. For example, if the gear has 28 teeth: 18.852 ÷ 28 = 0.673. This is the gear's circular pitch, measured in inches.



Read more : http://www.ehow.com/how_8660734_calc...lar-pitch.html
You might start by wrapping the hub with the track and counting how many cogs you need.

Re: Dragline Crawler Build
 

Ah, I knew there must be a formula for this. I am just now reading your post, so I will apply the formula to my current parts and see how it compares and then adjust and make a new part.

I don't really want to make the tumbler any larger, so this information should help a great deal!

Thanks,

Jim

Re: Dragline Crawler Build
 

YW, it looks like another cog or two might do it on the same diameter.

Re: Dragline Crawler Build
 

Jim-welcome to the world of old shovel style tracks. This was a nightmare for me, but after many ruined parts I made it work. I don't think this formula will work for you because you have already determined your pitch by making the track pads first. All I can tell you is what I did. I think you need to wrap your pads around the sprocket and measure the pitch in the circle. Of course it will be different than with the pads lying flat but You will need to set the pitch that will work on the circle and in the transition from the flat to the circle. This is the tricky part. If the pitch is perfect for the circle the drive dogs may catch on the edge of the sprocket cut out. If you cannot make the math work on degrees you may have to change the dia. of the sprocket and this is where the never-ending circle begins. You may have to angle the sides of the drive dogs and put a greater angle on the sides of the sprocket grove to keep the drive dogs from catching on the edge. You may also have to round the top corners of the drive dog.Here is a diagram-
http://i305.photobucket.com/albums/n...psh5a9vx61.jpg
You may also have to have divider plates for your rotary table depending on how the math works. Good luck-hope this makes sense.

Re: Dragline Crawler Build
 

This could be totally wrong but it worked on my Bruder dozer conversions. I took the chain pitch in my case- 0.375 and times it by the number of teeth I wanted. This number gives you circumference. Divide that by pi (3.14) which gives you diameter. Then divide this number in half which gives you(radius) the distance from center in which you need to cut the teeth. Divide 360 by the number of teeth and that's how many degrees apart they need to be. Use an end mill or drill bit to pop in the appropriate amount of teeth. For me making regular sprockets I then go back over them with a slightly larger cutter moved outward on the teeth. This gives the tips more angle to clear as the chain moves on and off of them. Clean them up a bit with a file and I'm good to go. It should be noted that your disc of metal needs to be slightly larger than your intended pitch circle for this to work. Hope this works if nothing else makes sense.

Re: Dragline Crawler Build
 

Tom,

Thanks. I thought I would probably need to angle the drive dogs on the pads. I have dividing plates so I can try that if it comes to that. I think I might start by just making a few more samples and make them a bit smaller each to see if it get better.

Also, I figured it would be simple to just drill the holes like I did and use brass tube to see if it looked close. Then, if I get where it looks like it should work I will make an actual tumbler and mill it to look like it should.

Jim

Re: Dragline Crawler Build
 

Reg, yea, that does make sense, thanks

Jim