3dprint | L21 Degrees of Awesomeness

Story time

This is a simple one but solved elegantly and quickly because of CAD and 3D printing, I have an old bike repair stand that was falling apart, still working but overall wobbly and unreliable. I’ve been thinking about restoring it, but I got my hands on a much nicer and reliable one.

The old one was mounted by getting its main tube through the top and hose clamps to the leg. The new one had a huge bracket that could either be screwed to the wall or to a countertop. I already had a big tube firmly attached to the bench so I wanted to reuse that. Well, the new stand’s tube is bigger than the old one’s so I needed to add a spacer to it and there’s a million ways to do that. I have CAD and a 3D printer so I took that route.

I was going to write something simple and short; this is just a solution to fit one tube over a smaller one but here I am, starting SolidWorks and a design walkthrough. I can’t stop now, sorry.

Design

The fixed tubing protruded about 5 inches from the benchtop, but the spacer didn’t have to go the whole way through, I didn’t want both to bind and also it was an unneeded waste of material and time, so I thought of making it in two parts, a base and a cap.

I usually start by sketching and sometimes modeling the reference material, in this case it would be the fixed tube and the new stand tubing but it was supposed to be something quick so I sketched the outer diameter + clearance of the fixed tube and the inner diameter plus clearance of the new stand tubing to use as reference for the cross-section.

Started with the base, added a bottom flange to protect the benchtop from the stand tube as it rotates and then flanged again up to hide its edge. Revolve feature, straight-forward.

Then the cap, designed inverted for ease of 3D printing, added a flange as a stop over the fixed tube and a chamfer to facilitate the stand insertion. Again, revolved sketch.

And this is it, I reduced outside material on the cap to reduce friction from the stand. For testing, I printed small sections of each (about 6mm) to quickly test fit and kept tweaking the first sketch until I got a good press-fit for the fixed tube and a slip-fit for the new stand.

Product listing if interested:

https://cyclingdealusa.com/products/cyclingdeal-wall-bench-mount-bike-repair-stand-premium-bicycle-mechanics-maintenance-workstand-with-adjustable-360-degree-rotatable-clamp-head-for-mtb-mountain-road-bikes-up-to-25kg-55-lbs

Why I didn’t restore the old stand?

I didn’t because it hadn’t crossed my mind, and I got the new one almost for free which is a very nice upgrade overall in usability and materials. Now that I think of it, it could be a cool future project, but then I don’t think that the 3D printed PLA/PETG parts would stand better than the original injection molded ABS.

What would I have used if I didn’t have a 3D printer? Masking tape? I don’t know, what would be your approach with your skills and equipment? Machining? Turning? Getting rid of the tube and screw the stand to the wall or bench? My bike “shop” is a 7ft x 5ft portable shed so no walls and didn’t want to reduce the bench top area with the big bracket.

I decided to print my keyboard shelf parts on the P1S on PETG and gray color. But before that, I wanted to implement some changes to improve the mounting and sliding action.

Things I wanted to address in order of importance:

Improve sliding action and allow for grease
Use more standard screw length eliminating my custom spacers
Use PETG instead of PLA since the latter started shaving against the aluminum
Replace the ugly print quality of the older ones
Another color (gray, also neutral but different from desktop)

The image below shows the changes but in summary, I increased the side clearances to reduce/eliminate wall friction, strengthened the slider ribs and added a flange to help retain grease if added, and increased corner fillets (rounding) to reduce/eliminate stress concentrations:

For the screw mounting, the shortest screw length I found at the hardware store was 1″ so I adjusted the mount spacing to take 1/2″ so they would thread 1/2″ into my 3/4″ desktop. Also, I didn’t pre-drill holes for them so some material would kick-back/lift out around the screw which separated the flat surface on the mounting brackets so I added chamfering around the mounting holes to help take it: