Last modified: 2025-06-18 21:23:20
< 2025-06-17 2025-06-20 >I'm going to try to make some rod arms out of flat bar.
Here's a first attempt:
That was cut 150mm long and then bent in half, with the idea that it would be long enough for the long arms, which are 60mm between hole centres. It was not long enough so I made a short arm instead, 25mm between hole centres.
It was relatively easy.
I bent it cold. Drilled it after bending so that the holes definitely line up.
I didn't have a piece of 12mm steel handy so I used the unthreaded portion of an M12 bolt, it measures 11.8mm diameter.
The split in the clamp was just the thickness of the bandsaw blade, and the split closes up before the clamp is fully tight, so the split wants to be wider.
Other than that, I think a good success. It lacks any facility for keying, but I can do that later if it proves to be necessary. So I guess widen the split in this one, then make another like this, then make 2 larger ones.
OK, slight change of plan. I don't have a 16 mm drill suitable for steel, so I tried drilling the 16 mm hole with a masonry bit, but it took ages and didn't work very well. So the new plan is to turn the ends of the kingpins down to 12 mm instead.
The longer arms need a 10° bend in them to account for the steering axis inclination, I made the bend by clamping an M12 bolt in the big hole, bolting an M8 one in the small hole, hammering on the M12 bolt to bend it, and then sliding the kingpin (with 10° cross-drilled hole) over the M12 bolt to see that it becomes perpendicular with the M8 bolt. It seemed to work OK.
So just one more arm to make this afternoon, and then I'm done with arms.
Update:
Looks good, just waiting on the steel delivery now.
These parts have printed:
In yellow ABS-GF because I can't imagine wanting to use the entire spool of it otherwise. And this is just "0.20mm standard" settings. The plan is still to reprint in PC-Max once satisfied.
The bearings are a very tight fit, but they do go in.
And I can't see if the gears mesh properly because I don't have shafts yet. I think steel is arriving today.
And the gears fitted to their shafts with Loctite 603 or 628 or whatever.
They are not a very good fit on the shafts, if they ever come off I will obviously need to add a key. And maybe remake the shafts out of actual 12 mm rod, instead of 12 mm hot-rolled steel turned down to fit within a 12 mm diameter.
I tried to be economical with material and these ended up about 3 mm too short for me to be able to secure the wheels with split pins and washers.
The tentative plan is to drill and tap the ends M8 or whatever so that I can use a bolt to hold a retaining washer or something. Need to decide before welding because it will be much more annoying to drill and tap once welded.
< 2025-06-17 2025-06-20 >