The rotor end of the distributor drive shaft isn't splined, it has a tang
like a screwdriver. Unfortunately it's made by cutting slices out with right
angle intersection of the cuts.
I'm not sure that the shaft is the real problem. Looking at the pieces of my
broken pump it's clear that the ear on the pump shaft (the female side of
the joint) broke first and then the distributor drive shaft broke. If the
drive shaft broke first there wouldn't have been any way for the ear to also
break. I think we need to relieve the stress riser on the rotor shaft by
radiusing the bottom of the slot, and then make a drive shaft or modify the
existing shafts to radius their stress point. That alone should make the
parts many times stronger. If we did this by modifying existing parts we'd
need to do something to relive the stresses that have already been imparted
after the radiusing is done.
-----Original Message-----
From: owner-fot@autox.team.net [mailto:owner-fot@autox.team.net] On Behalf
Of MARK J WEATHERS
Sent: Thursday, July 08, 2004 5:06 AM
To: Timothy F. Murphy; 'FOT'
Subject: Re: Pump Shafts
We make a lot of parts out of maraging, but it is probably about $20 per
foot for that size range. Heat treat costs are high too so we would need a
big run. 440 stainless is another choice. Both can get to Rc 50 or more
without size changes but I would have to check how brittle it gets. Size
change during heat treat shouldn't be too big a deal anyway, the parts can
be centerless ground to the right diameter after HT fairly cheaply. Case
hardening other steels is an option as well. If Iremember though, the rotor
end is splined, that may be a complication.
Mark
----- Original Message -----
From: "Timothy F. Murphy" <timmurph@execpc.com>
To: "'FOT'" <fot@autox.team.net>
Sent: Tuesday, July 06, 2004 4:29 PM
Subject: Re: Pump Shafts
> Any thought to making the shafts out of maraging steel? This is a
> "space age" material or "super alloy" that has the very desirable
> property of being able to be heat treated at something like 400
> degrees fahrenheit which virtually eliminates distortion or size
> changes. We used it at G&L to machine the "fingers" used for the tool
> holders, which had rather complex and precise geometry. After
> machining the heat treating left the parts as they were with the
> tolerances intact. The finished product was very tough with excellent
> mechanical properties. One problem - it's expensive stuff or it used
> to be. I did have some "prototype tools" made up by the R&D
> machinists which just happened to work really well on one or another
> of my cars. Great stuff.
>
> Just a thought,
> Tim
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