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RSR Type Engine mount cross bar
Hi,
I'm actually thinking about drilling my standard Engine mount cross bar to give it that outstanding RSR-Look. Has anyone out there experience in doing that . Need information reg. How many holes; which diameter each, some reinforcement neccassary, etc. Are there any risks connected with this (less rigidity and/or dynamic stiffness) Thank you in advance and I am looking forward to receiving some helpful comments and pictures HJT911 |
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10-17-2011, 09:02 AM
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Max Sluiter
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It will be less rigid. The holes, even if smooth, create stress concentrations. If drilled and not deburred sufficiently, they will cause fatigue cracking.
I think the RSR mounts were originally stamped, which is a cleaner cut than drilling. I would also want to reinforce the ends where the bolt tubes are mounted, and add a sort of I beam flange on parts of the crossbar to regain the rigidity lost with the drillings.
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1971 911S, 2.7RS spec MFI engine, suspension mods, lightened Suspension by Rebel Racing, Serviced by TLG Auto, Brakes by PMB Performance |
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10-17-2011, 09:20 AM
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Registered
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I have done it by hole saw and then radiusing the entire thickness by grinding and sanding. This extra work was not for beauty, rather to eliminate stress risers.
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10-17-2011, 10:11 AM
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Registered
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2022 GT3 Manual, 73 Carrera RS 2.9 Twin-Plug MFI Carbon Fiber Replica Former: 18 GT3 Manual,16 Cayman GT4, 73 911S, Two 951S's, 996 C2, 993 C2, BMW 635CSi Euro, Ferrari 550 Maranello, 06 Evo IX w/ many mods |
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10-17-2011, 10:25 AM
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Registered User
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Thank's for the reference.
Had just a look at Clints homepage. Looks like the bar has also one flange only as it is standard and not two as it was for the original RSR Bar. |
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10-17-2011, 12:31 PM
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10-17-2011, 01:14 PM
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AutoBahned
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nice!
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10-17-2011, 03:13 PM
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Platinum Member
Join Date: Jul 2001
Location: Leave the gun. Take the cannoli.
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Very nice, and considering you can easily sell your un-drilled one if it is ok, it's a rather inexpensive upgrade.
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10-17-2011, 03:26 PM
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Registered
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Talk to Alan at Canford Classics in England. He makes very good quality reproductions at a very reasonable price.
The originals were curved on both the top and the bottom for rigidity and then the holes were punched to eliminate weight. |
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10-17-2011, 05:53 PM
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Registered
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I have an OEM that I can take some pix of if you need one to reference, but as others have already pointed out, you will weaken your bar and RSR bars have curved edges top & bottom which also helps rigidity.
That being said, I may order this one for my SC... Rennline Stainless Steel Engine Mount Cross Bar - Porsche-Rennline, Inc.
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Byron  20+ year PCA member  Many Cool Porsches, Projects& Parts, Vintage BMX bikes too |
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10-17-2011, 07:10 PM
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Registered
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I used two different sizes for the holes.
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78’ SC 911 Targa - 3.2SS, PMO 46, M&K 2/2 1 5/8” HEADERS, 123 DIST, PORTERFIELD R4-S PADS, KR75 CAMS, REBEL RACING BUSHINGS, KONI CLASSICS |
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10-17-2011, 11:02 PM
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Quote:
JR |
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10-18-2011, 03:47 AM
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Platinum Member
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Quote:
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10-18-2011, 04:16 AM
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How much of an issue are the stress issues you guys talk about if the bracket is used on a basically stock motor?
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10-18-2011, 04:26 AM
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Almost Banned Once
Join Date: Feb 2009
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This is an original one from an SCRS. ----- You gotta love ugly welds.
    
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10-18-2011, 04:35 AM
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Peter,
Do you happen to know which is the top side, as Porsche installed that in the car? Thanks, Jeff |
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10-18-2011, 04:49 AM
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Registered
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This is the Rennline version that came with my car.
Rennline Stainless Steel Engine Mount Cross Bar     Cheers Al
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People are mushy - Paul Hawkins on the merits of where to crash on the Targa Florio Last edited by quozl; 10-18-2011 at 04:59 AM.. |
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10-18-2011, 04:56 AM
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Almost Banned Once
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Location: Adelaide South Australia
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Quote:
The top is as you see it in the first photo. The side shown in that photo is also the side that faces the rear of the car. I absolutely love how this thing is made. It's all about function.
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- Peter |
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10-18-2011, 05:07 AM
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Peter,
Thanks for the additional information. It's interesting to see how Porsche made these, and how the aftermarket "copies" are made in a completely different way. Cheers, Jeff |
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10-18-2011, 05:39 AM
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Max Sluiter
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Quote:
The main issue is fatigue cracking. Drilling the holes will shorten the lifetime of the part but it is difficult to know by how much since it depends on how the hole is drilled and finished. If it is deburred and beveled nicely then it may not really be an issue, but stamping the hole out is better.
__________________
1971 911S, 2.7RS spec MFI engine, suspension mods, lightened Suspension by Rebel Racing, Serviced by TLG Auto, Brakes by PMB Performance |
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10-18-2011, 08:42 AM
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Porsche
1971 Porsche 911S
1973 Porsche Carrera RS 2.7 Replica 2.7RS
1974 Porsche 914-6 3.0
1988 Porsche 911
1970 Porsche 914-6
1976 Porsche 914 2.0
1987 Porsche 924S
Black Beauty
One of One
Cabby (Last)
"Toad Hall"
1985 Porsche 944
BFG
1955 CMC Speedster
1981 Porsche 911SC
B&B#2
Black Pepper
Stella
Blau Frau
