大型尺寸蜥蜴履带（宽度75毫米）

Large scale (75mm wide) caterpillar track

2023-08-27 01:10:01

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Summary

This is a large scale track, 75mm wide x 1" pitch, intended for medium to large robots or tracked models.

It is designed to run on ISO16a or ANSI 80 standard sprockets - metal or plastic, as preferred.

(I'm using printed sprockets based on a design from Cults3D, with the hubs adapted to fit my motors & bearings, so I cannot publish those designs - you can find them here:
https://cults3d.com/en/3d-model/tool/ansi-80-roller-chain-sprockets-with-hub )

UPDATE - I've added versions of the inner and outer link that have matched, flat, upper surfaces so rollers can be used for idlers rather than only sprockets. These also make the appearance closer to conventional bulldozer tracks.

For maximum life, the chain pin bearings and rollers use bearing bushes, with steel clevis pins joining the links.

The bushes I used for the pins are 6mm bore, 8mm o/d by 5mm long for the outer links and two 10mm long for each end of the inner links.

I also considered nylon or PTFE bushes - 5mm and 20mm sections of 8mm o/d x 6mm bore nylon pneumatic tube could work for the pin bushings, and 16mm o/d x 14mm i/d tubing is available in some kind of plastic - eg. PTFE. 15mm sections of that could work for the roller bushes?

Edit - I've just printed a tread plate in TPU (previously untested / WIP) and it was a perfect push-in fit to the sole of the outer link. Photos added. That was printed with 50% infill and is still very stiff, so I think it could have been OK at 20% - I will try another at that.

The outer pins on the tread plate protrude through slightly. I did that so they could be melted over to prevent being pulled out, though I don't know if that is needed.
If you want to try it, a "clean" way it to put a piece of aluminium foil over the area to be heated, then gently wipe over the area with a soldering iron until the part has flowed enough. It creates less fumes than direct heat from an iron, and does not mess up the iron tip!

Print Settings

Printer:
Kossel XL
Rafts:
No
Supports:
Yes
Resolution:
0.2mm layer height
Infill:
80%
Filament brand:
Various
Filament color:
black
Filament material:
PETG
Notes:
I used high infill for maximum strength, you can adjust this as needed.

The inner link halves should be printed with the outer face flat down; no support is needed.

The outer links should have the flat sole down, and support everywhere to retain the shape of the bearing pin holes.

Post-Printing

Assembly:

After printing, clean up the top surfaces of the outer link "foot" if needed, and carefully file the inner surfaces of the link sides if there are any stray bits or unevenness - only a minimal amount of clean-up should be needed, no real material removal.

For the inner link halves, ensure the inner surface around the hole the opposite pins will fit is flat, and that the roller area the bush will fit to has no stray material or joint lines.

Fit the two 15mm roller bushes and the two halves of the inner link should press together by hand, though the initial alignment can be tricky. If it gives problems, use eg. the end of a file corner ways on to scrape the inner side of the sidewall hole, to put a minuscule chamfer on it. That should allow the two parts to interconnect and a good squeeze by hand or a tap with a soft hammer (or screwdriver handle) should get the sides flush with the pin ends.

Both the inner and outer links need the pin bores cleaning up to ensure they are the correct size and burr free. Use an 8mm drill bit gripped in a vice or pliers and twist the link sections on to that by hand. Rotate the link a few times then pull it from the drill bit while still rotating it.

After cleaning the pin bushes can be fitted. Use a long 6mm screw, bolt or clevis pin as an alignment and press tool.

Put one bush on the screw, pass it through the link & put another bush on the far end.
Press both bushes by hand.

For the outer link, the bushes are 5mm long and generally I've found they with start by hand and push in around flush by pressing on the screw head. Swap sides to do the opposing bush.

The 10mm long bushes for the inner links can be started by the same method & again pressed by had from each side, but not often to fully seat them - use a small vice to squeeze the bushed in, once they have been started and are aligned.

Or, add washers and a nut to the alignment screw, and tighten until until the bushes are flush with the link sides.

Additional parts used:

For the outer link bearing pins: 6mm bore x 8mm o/d composite lined metal bushes 5mm long. (Or 5mm long sections of 8mmx6mm nylon air line?)

For the inner link bearing pins, 6mm bore x 8mm o/d composite lined metal bushes, 10mm long. Fit one bush from each side of each bore.

The inner link "roller" bushes are similar again, but 14mm bore x 16mm o/d, 15mm long. Again, similar size plastic tubing could be used, cut in to 15mm sections. PTFE tube is available in that size.

I got all the metal bushes from this supplier on Aliexpress:
https://teclachiara.aliexpress.com/store/230702

Scroll down & you should see Composite bearings as a product category.

The other parts are 6mm x 40mm clevis pins, 6mm washers, and split pins to suit the clevis pins.

These should be available from various suppliers on ebay etc., or engineers supply shops.
I suggest using all stainless steel parts if the track will be used outdoors.

The clevis pins are 40mm to the end - some suppliers give the working length, between the head and the split pin hole.

It would also be possible to omit the 6mm x 8mm bushes and use 8mm clevis pins or plastic pins, or rod sections with split pin holes drilled? I've not tried that and do not know how well it would work, but could reduce the cost.

How I Designed This

I could not find a suitable large track for one of my robot projects, so I ended up creating this!

I first though of industrial "attachment chain" as a basis to a track; that would only need suitable sole plates adding to the attachment brackets. ISO 16a, 1" pitch, seemed to be an appropriate size

However, that is very! heavy and seemed like overkill for my application - though possibly suitable for really heavy duty machines?

Next idea: Use the readily available dimensional drawings or some CAD models I'd found and print a chain the same as the metal one. I quickly dropped that as the relatively thin link walls and angle plates would not be very practical or strong enough if printed to the same dimensions.

So, then this - keeping the links with the same pitch, inner width and roller dimensions so it's compatible with the same standardised sprockets, but built from scratch in every other way to take common size bushings and pins for strength and durability.

The separate tread plates are still a work in progress, I was planning those to be in TPU but they could be any material as preferred.

The untested prototype tread has just a few round pads.
That is added as a step file as well as a .stl, so it can be used as a basis for whatever treat pattern best fits your requirements - eg. flexible road treads or bulldozer style rigid "finned" plates.