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RSR Through Bolts

Does anyone have any details of the RSR thru bolts?

I have seen an account where they are described as acting as 'shuffle pins' and also having a mass in the cntre to break up resonances.

Any images or sketches would be great.
Old 12-29-2011, 06:59 AM
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Bruce Anderson's 911 Performance Handbook discusses this. In his first (1987) edition, there are pictures on page 58 with discussion. In his current Hanbook you get abit more thorough discussion at pages 94-5, but no pictures I could quickly spot.

Developed for the 917, and used on the 935 turbos, they used two part spherical self-aligning washers with a special nut for each end to avoid bending stresses. When I mentioned this (one can buy this kind of snazzy washer fairly easily) in a discussion, some pooh poohed the notion, suggesting that surely the case hole location could be designed so no such stresses would arise. Me, I think Porsche knew something the commentators did not, though just what I don't know. Since the cylinders are offset, maybe it is not possible to have the through bolts exactly normal to the case/crank centerline.

"The threaded portion of the stud and the nut were designed to eliminate the notch effect of the threads." The bolt head also looks to be something other than the usual hex, though I don't know just what it is or why it was used.

Because of these special features, Porsche found that it could usually reduce the diameter of these bolts one size to save some weight.

The center portion of these bolts was of a larger diameter (you can see this in the photo) to stop or limit the travel of sympathetic harmonic vibrations, per BA. I suspect this is simply of the pre-reduced diameter.

There is no mention of these serving as shuffle pins, and that is not possible for various reasons. Many of these passages serve also as oil passages, so you couldn't block them. For those which don't carry oil, you would have to do some careful machining to make them precisely coaxial on each case half. This is no mean feat.

To me, if you want to strengthen the main bearing web joints, the best mousetrap is to bush them, similar to what Porsche does with the #1 bearing. I was able to reverse engineer the system a machinist (now out of business) had come up with to make these bores coaxial, and Craig Garrett did this for me on a case, so he could do it for any and all I suspect.
Old 12-30-2011, 12:05 PM
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Bolts

I have a set of the 917 type bolts for a 911 engine, and can take close up pictures if it is desired. I have read that they were used as shuffel pins. You cannot see it in Andersons pictures but the center fat part of the bolt has a flat machined on it so oil can get buy it.

Mike
Old 01-11-2012, 02:32 PM
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Mike,

Yes please and maybe even a measurement or two. Major diameter at parting line would be good to know and then of flat spot as well.
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Old 01-11-2012, 02:57 PM
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Your going to want to check the thru bolt bores in the case, I don't remember them being machined that accurate to use for alignment and the outside case hole is smaller than the inside bore on a stock case.
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Old 01-11-2012, 04:57 PM
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I am thinking the through holes get reamed to match the special bolt.
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Old 01-11-2012, 06:40 PM
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Craig, who knows how all this works (or doesn't work) on stock production motors has the same thoughts I had. The trick for using anything to pin the main bearing bores together is getting a super accurate "register."

I think that standard shuffle pinning is done by drilling the pin holes in one case half, and then using short rods with a pointed end as a transfer punch in those holes to punch hole centers into the other case half, which is then itself drilled using the punch marks to center the drill. One machinist of my acquaintance believed that wasn't really accurate enough to get the full benefit of zero possible motion of the two halves of the webs. Maybe some laser magic stuff is accurate enough? (I had a standard shuffle pinned case once, and it went together and came apart well enough, though I didn't use a bore gauge on the webs as assembled and torqued).

It may be that the 917's through bolt holes were initially drilled to the same size, and then maybe reamed to be exactly the same size, all with the case bolted together. These bolts have a thick diameter at each end, and are turned down in between except for the center with that anti-harmonic bit. That would fit the bill, assuming the flat spot left enough area for the oil needed on the other side to flow through.

I don't think that stock cases are through drilled as part of machining the castings. And the bores of the holes in the middle are distinctly larger than those out on the surfaces. Exact register of these holes in the middle is not needed in a stock motor.

Hard to imagine any of us thinking we should have our own special through bolts made up, though, just to gain the advantage of better locking the case halves together. If you want to do that, contact Craig and see what he charges to install bushings. Or any of the other experienced machine shops to see what their shuffle pinning runs.
Old 01-11-2012, 07:29 PM
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Bolts

Pictures and measurements tomorrow. As a side question, does anyone have any 98mm RSR cylinders with 83mm head stud spacing and no groove in the sealing surface, need 2. Also 98mm RSR piston with no machining, need one

Mike

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Old 01-11-2012, 09:06 PM
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pictures and measurements








First of all the bolt will not go into a 2.7 Mag case. Second the hole in an aluminum 3.0 RSR case is 12mm, and the diameter of the bolt at the fat center point is 10.88mm so it cannot be acting as a shuffle pin, there is just to much clearance. The bolt is 252mm total length, and 243mm under head to the end, the 12 point head is 15.29mm in dia., the threads are 10.76mm( nominal 11mm?) fine threads. center fat section is 10.88 dia,, and from the flat to the other side is 10.23mm. the body of the bolt is 9.43mm. The nut is 15.00mm across the flats, and 18mm long

mike
Old 01-12-2012, 11:05 AM
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Thanks, Mike

I wonder what that 12 point (sort of) bolt head is called, and why it is used in this application. Save a few grams without sacrificing strength?\

Good luck on finding Ps and Cs for that rare 83mm head stud spacing factory race motor you have. What a challenge. But you never know what broken sets someone may have lying around.
Old 01-12-2012, 11:19 AM
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Walt,

Not sure if this will apply to you as it does me. Years ago I had Competition Engineering setup a type 4 2 ltr case for me. They did not shuffle pin that case but reamed the through bolts to use a 1/2 inch grade 8 bolt (no oil passage I know). The bolts had to be tapped through the case to get them in place. Less material was removed from the main webs than any other approach. A lot of track miles later I took the motor down and noticed rub marks on the center main bolts, this was new, the center webs had cracked and were held in place by this bolt. Yes I had to replace the case.

I would love to see how these bolts fit into the case they were built for.

Also on the shuffle pin most shops I know of do not transfer the holes with a punch, a fixture is used built for the task to make alignment perfect for the pins.
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Old 01-12-2012, 07:43 PM
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917 bolts

I will look into this further. The holes in the 3 liter RSR case are to big, the holes in the 2.7 case are to big, once you get past the fir 1/4 inch or so. If you insert them from inside the case they go right in, the hole is to big, but there is a step in the hole close to the outside of the case and they will not go through. I got them from Bob Beasley a 1000 years ago, maybe he can shead some light on the application. Also Dave Brown, a Machinest from North Carolina said these type bolts are a shuffle pin subsitute, which was desireable so the case could move a little, to prevent cracking? I will keep checking and report back.

Mike
Old 01-12-2012, 09:43 PM
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Anyone got a 917 case lying around for inspection?

Well, why not? I have a junk 2.7 case for that purpose. And a sand cast case with a big slot from one spigot up to the parting line, too - it might be worth having repaired.

Plus it appears these were also used on the 935s. More of those motors around than spare 917s??
Old 01-13-2012, 06:18 PM
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More info

I talked to John Truman today ( long time Porsche guy ) and he says they were designed as a shuffle pin substitute and mine must be for a 917 , or at least a case with smaller cross bolt holes. Anyone know the diameter of the cross bolt holes in a 917, or 935 case?
Old 01-13-2012, 06:36 PM
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I asked this question because some bolts are available on the UK and described as follows:


911 / 930 / 964 / 993 RSR C-Case Through Bolt This bolt can be used to "Shuffle Pin" the crank case and allow easy disassemble of the engine for routine maintenance and Repair, this method of case pinning was used on all the factory 935 engines to prevent the crankshaft being nipped as the cases distorted through the increase in power, these bolts are specially made to be used in the later cases, some case machining is necessary to accommodate the bolts and the new oil sealing arrangement.



The photo isn't great but they appear to have hex heads and have the increased diameter in the centre.

I can't see how they stop the cases 'shuffling' in the same way as dowels as a long bolt will always be relatively 'soft' in bending so if the clamping force isn't sufficient to stop movement I don't understand how they work.

It was my understanding that this design was used to eliminate an 'Eigen mode resonance' that allowed the bolt to lose clamping force at a given rpm and eliminated shuffling in this manner.

If this is correct I could be tempted but at aound $2200 per set + case machining I would like to understand more. Also there doesn't appear to be any spherical washers so they seem different to the bolts in the above photos.

I have always worried about conventional shuffle pins and how that can be fitted without line boring the cases after machining. I don't think that using pointed pins to mark centres would be adequate to allow the cases to line back accurately enough without some clearance around one of the pins and I if there is clearance is there any point ?

I also don't know about availabilty of bearings for oversize cases but I am sure someone here will know.

I could be tempted but at aound $2200 per set + case machining I would like to understand more. Also there doesn't appear to be any spherical washers.
Old 01-14-2012, 03:29 AM
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Joe901

Thanks for that information. John Truman did mention that after shuffel pinning the case should be line bored, so your concern seems correct. I will contact Carl Thompson about my bolts, he may have the demensions for 917 bolts. I am interested in finding out what I have. The current price is interesting in that several people have said that a set of the Porsche bolts nuts washers cost around $1700.00 back in the seventies Could you tell us who the Mfg. is of your studs, I may sell mine and buy the correct ones for the RSR case.

Mike
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