Mast supports to chassis - dealing with odd attachment angles

One of our students is working on a tripod leg solution of sorts. The support connects a mast with the chassis in a forward and downward direction, without co-planar surfaces or typical angles enabling 90 degree brackets. I told the student my guess for how to do this is a) figure out how to cut the ends of the supports so the edges mate with the mast and chassis planes, and then we’ll have to create some custom cut and bent brackets to connect things together given the odd angles.

Curious how experienced folks would approach this. Thanks


If you’re specifically asking how to do it in CAD, then I’d recommend moving this to #technical:cad. If you’re asking more practically, that’s a different question.

For CAD, the answer will likely depend on which platform you’re working on (Solidworks, Inventor, Fusion360, Onshape, etc)

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It should be noted there is nothing crazy with angles here, key is the mast is 90* to the lower surface (frame). So the top angle is just what it looks like from top down and bottom angle is just what it looks like from the side.

In case you wanna get fancy


I wouldn’t call myself an ‘experienced folk’ but things I’ve done in the past:

  • Use Dyneema + bowlines and a turnbuckle to create ‘stays’. Would be less useful given your CAD above though.

  • a tubing bracket maybe?


1/8" wall angle. Cut off one side of the angle at each end. Bend and twist remaining side as needed, rivet/bolt.

I’ll try to get a couple pictures of an application like this in a couple hours.


I recommend using eye bolts connected with either tube and tube connecting nuts or tapped hex shaft for creating diagonal supports.

If you wish to use tube, you can buy tube connecting nuts, tube, and eye bolts from rev or mcmaster carr:

We did something similar on our robot last year using shaft; this year we switched to tube, which we’ve found to be a bit nicer.
Here’s some links to our onshape CAD:
Tube assembly:

Top level robot:

They’re also used on the rev ION concept robot this year:

I hope this helps!


As promised, doing it with angle aluminum. Cut, drill, bend in some order.


Thanks all for the suggestions! Several of these seem workable.

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Tie rods.

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Depends on what your fabrication abilities are. Back in 2014 we had to do something very similar and we basically bolted plates to the upright and drive base, tack welded a tube between them and then took it off for full welding. These days our build space doesn’t allow welding, and even if it did we wouldn’t dream of tack welding something in place like that, so we would either find a different design that uses flat gussets, or do 3d printed ends in a high strength filament.

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Thank you. found this technique in NASA’s robot design guide, but have been searching for compatible parts for hours now. Question: does this work with PVC pipes?

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Tube nuts should in theory work with PVC, but note that the inside diameter (ID) of PVC is often non-standard. It’s also hard to say whether the PVC will be strong enough to keep the tube nuts from pulling out.

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it is possible to do it with 1x angle and some brackets made of 1x or 1.5"x angle, w/o any precise angles, bends or twists.

On the mast attach your 1~2" long angle bracket. To start one bolt and leave it a little loose so you can just twist it. Looking at it from the side adjust it so that it points to the point on the chassis where you want it.

On the chassis again attach your angle bracket with one bolt and then looking at it directly from above twist it so it points to the bracket on the mast.

You now have two planes that are perpendicular to each other with their intersection being a line between the mast and chassis attachment points.

I know I’m replying far too late to assist the OP at this point, but since the thread got bumped…

One option is to use thin wall round tubing, then flatten the ends in a machine vice, and bend the resulting “tabs” you created to the proper angles. After that, drill a hole and bolt it to the existing structures.

Think this, but with another tab at a different angle on the other side to allow for the compound angle.

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I really like this one & appreciate all the suggestions. Thanks, everybody.

What we ended up doing was run two 1/8th wall 2x1’s from front to back outside the bottoms of our 2x1 uprights that bear our arm shafts, bolted the uprights to them, and then added some .25" bar from the uprights diagonally down to the chassis level front-to-back tubes. Our design is fairly lightweight, and it seems like enough additional support so far.