SKS Rennkompressor mods

[Rouxkeloos]

The SKS Rennkompressor is a very nice pump. The SKS German website says:

"Der RENNKOMPRESSOR ist seit mehr als 50 Jahren die beliebteste Pumpe des internationalen Radsports und der einzig legitime Vater aller Standpumpen." The English site says: "The RENNKOMPRESSOR has been the most popular pump in international cycling for more than 50 years and the sole legitimate ancestor of all bike stand pumps." This translation does not do the German justice. Here is my attempt: "For more than 50 years the RENNKOMPRESSOR has been the most beloved pump in international sport cycling and is the only legitimate father of all stand pumps". So, I'm going to try to turn mine into more of a father figure with some mods. Let us start with the handle:

Let us see if we can do anything with the steel hardware that attaches the handle. I suspect that some are stainless and others galvanised. Vinegar is an environmentally responsible way to strip the zinc.

It is only the dome nut on the top that is (galvanised) mild steel, the rest is stainless. The stainless need to be mirror polished. The dome nut I would like blued—that blue-black oxide that is often used on firearms. But before we do that, let us file a star into the dome nut. 

Next, I started on the new handle. The original handle is wood, but I wanted something nicer. I like the handle shape of the Topeak JoeBlow so I used that as an inspiration for my design. I measured my delicate digits for the finger cutaways. 

Those two cylinders at the bottom is to help me to locate the part when I turn it around on the CNC. Unfortunately the piece of oak—a gift from my brother–was too short to include workholding on the ends and forced this inelegant solution. 

The bottom was machined first and then flipped around. The oak machined well and the surface finish was very nice. After some sanding it was coated in linseed oil. 

 

It is currently drying. More episodes to follow. In addition to the cosmetic changes, some technical mods will follow.

[Rouxkeloos]

After the oil dried, the pump was reassembled. I'm happy with how the grain shows—the funny thing with getting old is that stuff like grain patterns make you inexplicably delighted... 

Now I would like two add two chucks. The solution I'm implementing is to use pneumatic line couplers to swap chucks quickly. No matter how hard you try, it is impossible to standardise valves in your household. Even if you are a god amongst men who manage to do it, you might still be blessed by being appointed by the universe as your residential complex's official children's bike inflator. I'm happy to do it, but I had to do some client education after a few unfortunate incidents where a Sunday afternoon nap was violently disrupted.

Nitto is a Japanese company that manufactures miniature pneumatic couplers. Things of beauty with tolerances that would make Germans weep. In the above photo, the Silca thread on Schrader chuck is also visible. The Presta side will be represented by a Hirame head—another example of Japanese manufacturing prowess.

Two-ear clamps and a nail puller take care of the crimping duties. 

 

So we end up with two 150 mm sections that can be swapped out.

The coupling looks like this in context:

Lastly, we need to ensure that the hose stays in place, which calls for a bit of thread lock where the hose screws into the pump base. I saw other people on the internet that threaded a pneumatic coupler into the base, but I did not want to buy an imperial tapered thread tap for single use. As a metric follower, I also don't want to risk burning in hell for such a small but significant transgression. 

I'm happy with the outcome. But the Silca chuck is not on par. I like the idea of a thread-on chuck, but Silca's one isn't a joy to use. So the idea is to get a Milton one next time I order stuff from Amazon (whenever my wife is not looking):

Does it work better than the standard Rennkompressor? No, but it makes me happy.

 

Edited September 7, 2022 by Rouxkeloos
Removed pic that was duplicated

[Mongoose!]

wow you did an excellent job. well done!

[Rouxkeloos]

The Milton pump head arrived, and I also decided to up the size of the compressor fittings. The benefit is that I can attach it to the tubing without a clamp. This is done by heating the tubing with a heat gun and applying some grease inside the tubing to encourage it. Once it sets, it will not come off on its own. 

The upsized compressor fittings do not feel like it impedes the airflow (the previous ones did). I need max flow to get tubeless seated without a compressor.

I like the Milton pump head. It seats fast, stays on and breaks off cleanly with a satisfying short psshh of air. 

 

The last and final step would be to 3D print a clip that stores the extension that is not in use. I don't have any experience calculating printed plastic's elasticity, so that research will take a while. It has appeared to me that there are faster ways to inflate a bicycle tire.

 

[Rouxkeloos]

And finally, the 3D-printed ring to keep the extra valve head is done:

[ichnusa]

Well done!

I love your attention to detail and appreciation of the finer things in life!

Your patience in ordering from Amazon and waiting for parts to arrive is also admirable!