All Things CAD, Design, Prototyping and Fabrication

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I design dropouts. Here’s a couple examples… This first set went on my personal track bike.

Frame 3 Dropout

I build my bikes exclusively welding… no brazing skillz here so I like hoods!

Photo Oct 19, 1 32 09 PM

These cross/road dropouts have a polished stainless cover too.

Photo Oct 25, 4 30 32 PM

Here’s a set that I reverse engineered. A very common dropout supplier was on back order. I re-designed, mocked up with the 3D printer, then had 20 sets CNC’ed.

Drive Side 5

Here’s what the cross/road dropouts looked like part way through the process…

Photo Oct 07, 2 19 55 PM

Do you want your own custom set? Email me and let me know!


Jeep Crossmember

Over the last year I decided that it was time to get my Jeep back up and running again. A couple years ago I decided to pull the 283 Chevy motor out of the ’67 CJ 5 and drop in a 4.3 Vortec V6 from a ’98 Blazer. The project sat for a longtime but I’ve slowly been putting it back together.  More about the individual Jeep projects to come.

Since the Jeep had sat for so long the rear gas tank was dry and rusty so I pulled it out to eventually get the tank cleaned. As any project like this goes, a simple afternoon project turned into a bunch of extra work.  It turns out that when the shocks had been installed a thick plate was welded to the front of the rear crossmember to gain some extra travel for the rear axle. Over time the crossmember cracked at the edges of the plate and it resulted in a crossmember that I could rotate significantly by hand.  The crossmember was almost completely torn in half and also cracked out in the corners.

Photo Aug 24, 2 30 11 PM

Corner torn clean off!

Cracked Jeep CJ5 Crossmember

Torn thru at corners of left shock mount plate

Jeep CJ 5 Crossmember

Torn thru on the right side too

Cracked Jeep CJ5 Crossmember

Cracks all the way thru back side

It was time for this old one to come out and a new one to be built and installed.

Photo Oct 20, 2 11 55 PM

Raw stock and the old crossmember

The old crossmember was riveted in place. Those rivets all came out with some gentle persuasion from the angle grinder, sawzall and 3 lb sledge. One more pass with the sawzall down the center and the old one was out.

I decided to go with 2″ x 4″ x 1/4″ wall tubing for the new one and also used a short piece of 1/4″ plate to get the extra height inside the frame rails. If I did it again, I probably wouldn’t have gone with the full 1/4″ wall thickness. I think it was a bit overkill. Both in terms of strength and that my air cooled TIG torch gets hot pretty quick at 200 amps.

I started by drawing everything out in Solidworks in 3D then transferring the lengths and angles to 2D.

Crossmember 3D Model

Crossmember 2D Drawing 1Crossmember 2D Drawing 2

Down at the shop I rotated the stop on the horizontal bandsaw to the correct angle, cut a test piece, checked it to the drawing and cut all the pieces. While I was down at the shop I also turned, drilled and tapped the bosses that would become the mounts for the upper shock mounts.

Photo Oct 20, 4 53 48 PM

Bandsaw making angled cuts.

Photo Oct 20, 5 19 30 PM

All the pieces cut.

Photo Oct 20, 4 54 27 PM

New shock mount bosses with shock stud partially installed.

Back home I beveled all of the edges on the grinder before getting everything welded up. I had to purchase some updates for my torch before welding the crossmember. I have mostly been welding very thin tubing for bike frames so I bought a new 1/8″ collet setup. Once all that was in place I welded everything up.

Photo Nov 04, 7 37 03 PM

Beads are laid

Photo Nov 04, 7 48 35 PM

Welding complete

Because the previous crossmember was riveted in place I welded nuts inside the crossmember on the tops and bottoms then welded nuts to the end caps and welded the end caps in place.

Crossmember-Shock Mount 1

Paint applied

A couple coats of gloss black and it’s ready to go back in.

I ended up having to cut out a stiffener on the frame to get the crossmember in that I weld back in place soon. I don’t have a MIG so it’s nearly impossible to get inside the frame rail with the TIG torch. I also had to cut out the mounts for the gas tank skid plate. Those pieces will all get welded back in when I get a chance to borrow a MIG.


Fully installed

With the crossmember back in place I drilled and tapped a hole for the gas tank mount and also fabbed a new bracket for the brake lines and drilled and tapped a hole to mount that also. Mounted the shock studs and shocks and we’re back in business.