Tech: a REAR wheel speedo drive

[whizzerick]

Local code requires a working speedometer, as per OEM in 1974.

Since I'm running an early Sporty drum instead of the original single disk (1), I can't use the '74's speedo drive/spacer up front.

Besides, I don’t want to clutter the front end with a cable and a speedo. I fabricated a bracket and installed the speedo to the left of my seat (2).

Instead, I thought I could use the rear wheel to drive the speedometer. There is ample room on the left side (3).




With a BFH in a vise, I cracked open the original speedo drive, revealing the precious inner elements that will be used in the project (4).

I carefully measured everything (5), and essentially reverse-engineered a new speedo drive/spacer from the parameters of the original (6).




Using basic woodworking tools (7), I built a casting pattern that will provide a 'blank' for machining the drive/spacer (8).

Menu board letters are added forming the AMF anagram, to stump the HD experts as to the origin of the part ... (9).

The pattern is painted, 'gating' is added (10).





Because of the shape of the work, a follower has to be prepared out of plaster and plywood. We are ready to cast (11).

[whizzerick]

I cast a blank in beautiful yellow brass, a strong alloy with a very high machinability index (12).

And machined away (13). This is all very new to me, and I'm learning as I go.





Everything went according to plan (14). I will probably have to bend the tang of the drive's 'arm' upon assembly to seat it in the hub's recess.

(To account for the reduction in wheel circumference (94,72%), the speedo face will be re-calibrated with additional spacing between numerals) (15).

[CB550 Matt]

nice fab work, you get out to ride test it yet?

[littlebike]

Hot Dam, You got some major Skills, but you know that .Awesome!!

[NaK]

Holy shit. I can't get enough of this type of stuff.

[whizzerick]

Originally Posted by CB550 Matt

nice fab work, you get out to ride test it yet?

I wish... This is a pic of my backyard at 5 am this morning.
That glow is from my inground pool fence lighting...

[chip]

Holy shit, southern boy here. I have never been in snow that deep. Don't think I would like it much. I'm already jonesin for spring and summer. I cant stand the short gray days of winter.
The speedo drive is nice work.

[zboy403]

I'm very very impressed! Nice fabbing!

[Bumpstick]

Beautiful!!!!

[ElkCreek]

Awsome post! Thanks a ton. I suck at Math, so Im out...But The casting principal is something I will try with less "precision" required parts. Good to see how little it really requires to produce a one-off part. NO CNC's!! Basic tools. Cool Shit!! 20 feet of snow outside helps too!!