1/12 Scale Cat D11 Bulldozer project

[SVS]

Couple ways to look at that.

Even tooth sprocket would have worn twice as fast maybe taking bushings with it.

Odd tooth sprocket would have lasted till bushings needed turned, then got replaced when pins were turned.

I’ve got a 48’ model D7-3T. It’s worked itself out of a job but I’m too sentimental to move it on.

[A.K. Boomer]

Couple ways to look at that.

Even tooth sprocket would have worn twice as fast maybe taking bushings with it.

Odd tooth sprocket would have lasted till bushings needed turned, then got replaced when pins were turned.

I’ve got a 48’ model D7-3T. It’s worked itself out of a job but I’m too sentimental to move it on.

You guys clear some things up for me - does odd tooth mean every other tooth is missing or just odd number compared to even numbers ? if the latter why would that make a difference in wear,,,

also - do you mean to tell me the bushings are not roller? they are fixed? if so that's crazy for accelerating wear in itself, heck even our witch ditch trencher which (no pun intended) basically runs submersed in sand and dirt has real rollers and yeah they wear too but can't imagine if they were fixed it would be horrible wear on the sprockets and chain...

only thing i can think of for the dozers is it would weaken the track, and as we all know they do need their torque to do what they do...

[SVS]

Chain is double pitch….sprockets are odd or even tooth count. RB figured it out in op.

Bushings don’t rotate and there is no need for them to. Look at a roller chain. Do those bushings rotate?

[Willy]

Bushings in these types of service stand up way better than a roller since they can withstand and carry much higher loads due to the large surface area compared to a roller.
Impact and shock loads are the death of a roller. Ditch Witch runs fine on sand and dirt, rocks not so much.

[RB211]

Ok, the track pads took more trial and error than I thought they would, there's a lot more going on with them then one would think.

[A.K. Boomer]

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Bushings don’t rotate and there is no need for them to. Look at a roller chain. Do those bushings rotate?

Do roller chain bushing rotate? why yes that's what gives them the name "roller chain" --- used on my bicycle and in car engines and without them the engine would disintegrate in short order as well as my bike drivetrain...

[A.K. Boomer]

Bushings in these types of service stand up way better than a roller since they can withstand and carry much higher loads due to the large surface area compared to a roller.
Impact and shock loads are the death of a roller. Ditch Witch runs fine on sand and dirt, rocks not so much.

This is more along the lines of my thinking as to why this type of equipment uses fixed bushings,,, but not so much the shock as the load,,, much more robust for slow high torque type setting,,, and look what those machines can push,,, but as far as the ditch witch not being able to take spike load shock --- Iv ran one many years in the state of colorado and I can tell you that the only thing that gets them is the constant grinding of the sand and dirt but without the roller? oh man they would be toast in short order but what really would suffer is the little 6 tooth drive sprocket...

as far as shock iv spent hours riding basically what looks like a mechanical bull - stinger intermittently contacting and chunking out massive granite rocks with it's carbide teeth and the only real concern for me was worrying about my kidneys as the entire machine is bouncing up and down on nothing but it's roller chain connected to carbide spikes....

[Willy]

I think what SVS was getting at was that while the roller rotates the pin and bushing do not.

[RB211]

I’m going to use 5/16 1” dowel pins. Aren’t they hardened? The sprocket can be a wear item. Maximum RPM of the sprocket will be around 150 RPM all out. These things aren’t speed demons. I do enjoy the conversation.

[A.K. Boomer]

I think what SVS was getting at was that while the roller rotates the pin and bushing do not.

Oh ok - well that's what I was wondering is if they were calling the outer bushing the actual "pin" itself too,,, as if they were one unit --- did not make any sense as you have to have a rotating component when engaging the sprocket right??? unless I guess really slow and high torque maybe just robust as rotating bushings and rollers take up allot of space and then look what your left with a small pin....

[SVS]

I should correct myself-Tracks aren’t exactly like roller chain. The bushing is press fit into the inner rails. The pin is press fit in the outer rails.

So-the bushing is not free to rotate relative to the link it’s part of. Pin, of coarse, rotates within the bushing.

Basically a chain made of “half links”.

[RB211]

Small update for today. Designed the Load Roller. Had to redesign the big idler so the width between the two matched. Based it off pictures from the internet. Taking a small break from CAD, I have to do a flight tonight.

[RB211]

Been busy with a lot of stuff since being home, from computers to drones. Some more goodies came in from AliExpress like cylinders, radio control valves, and a really cool miniature hydraulic filter. I also got my FDM printer going again so I’ll print a few track test pieces. Tomorrow I’ll post pics.

[boslab]

A thought crossed the void in my head, last year I refitted my 3 ton excavator with things called “ city tracks” steel plate on the chain with dense rubber pads, all kinds of clanking and jumping when crawling or skidding or finally gave in and replaced the sprockets, tooth count wasn’t the problem it was radial pitch out for the chain, worked fine after ( the council didn’t like me on the public highway with wedge tracks)
mark
ps looks to be a great model, I do like CAT. And jcb for that matter

[Frugalguido]

I question for RB, how long did it take you to learn the CAD program to be able to do these drawing? And where did you learn it? Nice job!