Zenith-Stromberg Throttle Shaft Interconnect Replacement

[puff4]

Alpines supplied with twin Zenith-Stromberg CD150 carburettors have four plastic pieces on the throttle shaft linkage (Rootes PN 5044280) that provide a type of 'universal joint' functionality that prevents that shaft from binding when the carburettors are slightly misaligned (which they usually are). These parts become brittle over time and fracture where the locating pins are inserted, often making them sloppy or even non-functional. The items in discussion are circled here on a factory parts manual page:




Mike Hartman and I have been discussing the way forward in terms of replacement, given these are no longer available. He asked if I might be able to reverse-engineer some replacements, and I promised to do my best. What is shown below is my 'first cut'.

I will be 3D printing some this coming weekend when I've returned home. This print will allow me to confirm that the measurements are spot-on as-re the originals, but I suspect I'm pretty close with what I have so far.

Once I've confirmed the design, I'll be happy to supply either DWG or STL files to those who wish to make some for themselves. Mike has suggested he may try to get a pair made via CNC in metal to see how they look, but of course they may also be 3D printed in Nylon to be very nearly identical to the originals.

Here is the preliminary result of my reverse-engineered design:

If this video doesn't play, click the "YouTube" text in the window and it will open in a new page in YouTube.

 

[DanR]

Thanks kevin for you and Mike's efforts to make these "little" buggers. They are surely needed for our Alpines....

 

[puff4]

Thanks kevin for you and Mike's efforts to make these "little" buggers. They are surely needed for our Alpines....

Happy to help, Dan.

 

[alpiner]

This is great news and will be much help in supporting efforts to keep the CD150 carbs working properly.
Any thoughts in making the links available for sale? Also, the pins that attach the plastic connectors to the shafts are a challenge. I've used small nuts and bolts as replacements, but have had to drill out the holes in the shaft.
Alpiner

 

[JBS]

I have 5 pairs (10 pieces) pm me if interested. Jerome (alpineinnovations.co.uk)

 

[puff4]

I have 5 pairs (10 pieces) pm me if interested. Jerome (alpineinnovations.co.uk)

Where did you get them? And are they NOS or reclaimed?

 

[puff4]

This is great news and will be much help in supporting efforts to keep the CD150 carbs working properly.
Any thoughts in making the links available for sale? Also, the pins that attach the plastic connectors to the shafts are a challenge. I've used small nuts and bolts as replacements, but have had to drill out the holes in the shaft.
Alpiner

My printer won’t do Nylon without significant modifications, so I’ll leave that to someone else. It takes a very hot printer and a ventilation system to do it properly.

As to the pins, they are simply tiny roll pins and should be available commercially. I’ll have a look at some point, but I’m currently visiting with my relatives in Kalamazoo, so my time is limited.

 

[JBS]

Where did you get them? And are they NOS or reclaimed?

New and un-used, possibly re-pros.

 

[puff4]

Just to complete the subject, I've printed a test piece, and the measurements were spot-on - the metal shafts fit nicely in the slots, they have full movement, and the holes are tight enough to secure the roll pins.

Note: I used garbage PLA filament, so the print's finish is pretty rough... good filament and a higher resolution print will give much better results. I also recommend that they be either printed in Nylon, or that they be CNC machined in aluminum or brass.

If someone needs the STL file to create these, please let me know via PM. My only request is that it is not used for profit.

 

[puff4]

A better print.

Many thanks to Mike Hartman who loaned me one of the originals for dimensions and fit checking.

(Mike, I’m sending one of these to you, too.)

 

[alpiner]

Very nicely done. That's a win for all of us keeping our classics running. I love having twin Strombergs under the bonnet which require old school techniques for tuning.