A group buy on rebuild seals for 44.5mm slaves?

[raygreenwood]

Just asking again. I need to get projects done as I am able...and this one is one I could start and finish quickly.

I am having a replacement seal quoted for the 44.5mm slave. I had some made back in 1991-92 and they worked very well...though the material was incorrect.

The company that made them for me (Seal Jet)....now has much better capabilities....including the correct materials for our brake fluid and better machining capabilities.
The problem with making our seals by CNC machining method 15 years ago was that the material had to be right at 75-80 durometer minimum in order for it to be properly machined from a block of the material. Also....the profile of the seal we use is a variant of a "shaft seal". Its very difficult to machine the inside area and the bottom collar without special (and expensive) tooling being made.

Speaking with seal jet and looking at the design, we have come to the conclusion that the bottom inside lip could be removed and we would have (a) simpler machining (b) able to use softer material which is good and makes the seal easier to install (c) could insure even better sealing than stock by using a fine stainless wire wrap around the inner wall where it surrounds the piston...or using a silicone or EPR elastic band which is used as an internal hose spring on some hydraulic seals for this same purpose....which is simply to keep fluid from pypassing the cup on teh inside between the piston and cup.

Also...this seal would be just slightly oversize by about .005" to take up for any honing on our cylinders.
I have also developed a very cheap (about $6) and effective ( 1/4" diamter centering points every 120* made of teflon button with urethane spring washers behind them) mod for the piston that can be done on any drill press....to install piston center points on end of the piston forward of the seal.....which was one of the defects of this piston is that it cocks in the bore and wears the seal crooked because there is a lot of piston forward of the seal.

I have nearly finished the outer boot vacuum mold to make them out of pourable 350F silicone.
The CAD work at sealjet will probably cost in the neighborhood of $350. For the first batch that would equal out to about $10-15 per seal. To help me afford this....if others wanted seals and would chip in....I will mold boots for free for every seal.

Let me know who is interested. For the price of two six-packs you can have a new seal and boot. Ray

[danomight]

You can count me in! I have a NOS rebuild kit now, but like you have pointed out on other posts, the rubber is 30+ years old. I like your idea on the Teflon guides forward of the seal. I was planning on doing something similar.

Dan

[wshawn]

If there was enough interest in the UK could a few sets be posted to us over here? If so I'll post this on to the Type 3 & 4 Owners Club Forum.

[ubercrap]

OK, count me in then.

[raygreenwood]

OK. I have finished the engineering drawing of both the piston and seal. I am sectioning an old seal and photographing it tonight. I will get all of that off to my contact at Sealjet by tommorrow to generate a formal quote.
The nifty thing is that Sealjets claim to fame is their proprietary CAD/CAM CNC cutters. Once the programming, tool and material selection is done, their machine turns out a seal about every 2 minutes or less.
In the mean time, I will also upload some drawings so everyone can see the differences the new seal will have from the old seal.
Once the seals have been made once and the CAD program is complete, having new seals made...or changes to the old design...can be done quickly and cheaply.

These guys have saved my bacon numerous times in manufacturing by being able to make pneumatic cylinder seals in less than a 12 hour turn time...when the OEM manufacturer is looking at days or weeks for a seal kit.
They could also make the boot...and I will have that quoted just for the heck of it.....but that will be quite a bit more expensive than vacuum casting of pourable silicone.... for each seal because of the size of the plug of raw material they would start with. Ray