Guys
I talked with a fellow racer this summer who is a machinist and owns a
reputable shop about “carving out” an uprite. He thought that might be cost
prohibitive due to scanning costs and CNC time. This is something I'm very
unfamiliar with so I don’t have any reference about real world cost.
He suggested I fab one using 6061 T6 material in jig and having it cryo treated
post welding to bring it back to T6.
I actually considered this and had designed the jig. When I put out the
question for a spare and found the raw casting it just seemed like the right
thing to do would be to cast a new part. Now cost wise for one or two pieces
cast verses machining it’s probably a wash. But to be able to offer as close as
possible Period correct replacement bits to the community I figured I would put
it out there.
I now have enough commitments to be able to go ahead and cast 10 maybe 12 at a
reasonable price. Clearly cheaper and at least close to the original parts. The
shrinking issues have addressed with the pattern maker.
Thanks
Tom
Sent from my iPhone
On Nov 29, 2018, at 12:37 PM, Don Anderson <donandersonracing@xxxxxxxxx>
wrote:
It seems to me that if you are going to 3D scan the part, cast the plug, then
CNC machine the hollow inside out, as well as the bearing race seats and seal
seats, why not just CNC the entire upright and shot peen it to look cast ??
It's "one step shopping" with a perfectly reproducible part.
Don
On Thu, Nov 29, 2018 at 11:30 AM Lee Johnson <leejohnson1313@xxxxxxxxx>
wrote:
Scott --
Interesting input, especially the "now vs. then" comparison of casting
design rationale.
Do you have a suggested source for 3D scans (if not for this, perhaps
for other projects)? What method(s) can be used at semi-amateur price
points?
Lee
On 11/29/18, scott correa <spektr98273@xxxxxxxxx> wrote:
Gentlemen,Thanks for being a subscriber to Bobsy Talk email. Be sure to also check
As a Manufacturing Engineer, I am of the opinion that it is foolhardy to
make cores for the major bores on the casting. These parts will be post
processed on a CNC mill. The original reason to cast the bores near net was
to minimise expensive machine time and setup on manual machines where labor
costs were high. Today it would be more cost effective to dispence with
the bore cores and just machine tbe bore as an interpolated plunge cut.
Easy Peasy in the current cnc world. Additionally, you would not be
subject to core shift with the resultant problems with non-predictable
remaining wall thicknesses. The quick and dirty way to get these made as
castings would be to plug all the holes in tbe casting with Play Dough, 3d
scan them, add a material offset and supply this shape to tbe casting
house... Also round up to tbe next higher 1/4 inch to keep dimensioning
simple and have the casting be +.125/ -000.
On Nov 29, 2018 9:31 AM, "Tom Quaranto" <tquan277@xxxxxxxxx> wrote:
Lee
Yes that area is hollow to the bore area for the lower thru shaft to A arm
attachment.
I was thinking of having extra material added the hollow area at the bottom
of the pattern to prevent the hollow area being open to the shaft area. If
you have ever had to remove the shaft it’s difficult due crap/moisture
getting into the shaft as it is open after drilling. (At least on mine
currently in use on my cars)
Part of the cost is due to having to have molds made for the bearing bore
area and the hollow space you are speaking about. I thought due to the
material strength difference the slight loss in thickness would not be a
concern.
Your thoughts are appreciated as we are at the right point to make any
changes/improvements.
Tom
Sent from my iPhone
On Nov 29, 2018, at 10:10 AM, Lee Johnson <leejohnson1313@xxxxxxxxx>wrote:
file. If
Tom --
I am also likely to want a pair of raw castings. Will PM you for some
off-line discussion.
Following are comments to keep "Bobsy-talkers" apprised of other
upright technical matters:
1) I just finished a phone call with Ron Mong who said the original
casting patterns are long gone, so no glory there!
2) Your original thought that the extra material is to allow for
machining tolerances is most likely correct. The patterns used to make
the molds casting would be even a bit bigger than the finished raw
casting you have in hand. Shrinkage allowance for the TBD magnesium
alloy used back-in-the-day might have been different than what is used
for Al castings.
3) My recollection is that the lower part of the casting (where the
oval thru holes are) is hollow (beyond the outline of the oval holes).
It shouldn't be to hard to create an approximate core to recreate that
hollow space. Do you know if the foundry would plan to do so?
My thanks also for doing this legwork!
Lee
On 11/29/18, Tom Quaranto <tquan277@xxxxxxxxx> wrote:
Gents
I thought a pic of the original Unmachined Bobsy uprite to be used as a
master for the proposed casting might be helpful. The #10 makes
identification easy.
I have more pics but the freelist site limits the size of the email
also check the regular Bobsy website from time-to-time atyou want more pics email me directly with your need at:=========Thanks for being a subscriber to Bobsy Talk email. Be sure to
Tquan277@xxxxxxxxx
Tom
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