PRO RIDE MOTOR MOUNTS FOR TURBO APPS

[mountainhorse]

Here are my thoughts on Pro Ride motor mounts in turbo applications... some of the turbo builders have broken mounts during testing...

Here is what I posted in another thread.
http://www.snowestonline.com/forum/showthread.php?p=2521691

Any thoughts?? I could be way off.

"Stronger" is a relative term that can apply to many different aspects of a fastener design.
Hardeness or toughness may be better terms here.

Grade 8 bolts would be more similar to a Class 10.9 fastener.

From what I can tell... The Socket Head Cap screws that Polaris is using are a very high grade Metric, Class 12.9 Alloy Steel (self locking)... they have a tensile strength in excess of 170,000 psi with a Rockwell hardness of 35 - 45.... It is a pretty high quality bolt.

The titanium high strength Race fasteners that I have seen used are made from Ti6Al-4VA... it's most attractive property however is its lightwight... it IS strong... but has similar yield and tensile strength to the Class 12.9 Alloy steel. IMO, a Ti replacement fastener of the same dimensions will fail as well.

In my opinion…. to make the stock mounting system stronger... it would be better to use a cap screw with a longer unthreaded section that would insert further into the motor mount strap… or all the way through and Install a Stainless “TIME-SERT” into the far end.

The clamping aspects of this fastener, IMO, are much less important than the locating aspects of this fastener. The bolts do NOT seem to be failing in tension, but in shear.

From what I can tell from others photos (I don’t have a motor mount/strap/cap-screw in my hands) the bolts are failing from impact shear … in the treaded section of the bolt, which is exposed to the shear loads the engine as it tries to rotate, as a unit around the axis of the crank, in the mounts. The treaded section of the bolt starts inside the mount rather than inside the strap. The failures seem to be happening along the grain boundary of the threads at the shear plane… ie the bolt is shearing in the weaker threaded section rather than a stronger unthreaded shoulder section of the bolt.

ARP makes some very high grade Cap Screws with reduced wrenching 12 point heads... their "ARP 300" stainless bolts are very tough, very high quality fasteners with rolled threads and consistent metallurgy. They are rated at 170,000 psi and have a Rockwell hardness of around 45.

Rather than finding a custom fastener, a longer ARP bolt with a longer unthreaded section could be used and the threads could be trimmed at the end. I've used these same type of bolts from ARP to fix the problematic front PTO mount bolt on the turbo 2008-2010 800cfi Dragons. The strap would have have the threaded section bored (partial depth) to accommodate, snugly, the larger diameter of the unthreaded section.

Here is a crude cross-section of what I'm talking about.

Again, this is just my Opinion.

Under the extreme loads of turbos… stronger bolts will not keep the motor from twisting in the sled… that is where the additional mounts in the FTX arrangement will come in handy with the huge twisting loads that a turbo engine can put on the mounting system. Twisting moves the clutches out of alignment… Clutches that are not aligned make more heat, shift poorly and waste power.

Also, under the extreme forces produced by a turbo engine, the plate will help to isolate & stabilize the crankcase from the twisting forces that are not isolated by the two, separate, mounting straps.

I don't think this will be a problem on the non-turbo sleds... but time will tell.

I have a feeling that these motor mount/plate combos from FTX/Power-Addiction will be popular among the boosted crowd!!

 

[mountainhorse]

Norway brings up an excellent point...but I've not been able to find a M10 50mm x 1.5mm pitch socket head cap screw in a Class 10.9 specification.

This is the closest to grade 8 as possible... class 8.8 is equivalent to a grade 5 fastener.

Norway:

Shain, I've not seen a grade 8 in metric. Metric usually comes in classes like 8.8, 10.9, 12.9 etc.

Can you tell our readers where to get their hands on the bolt that you replaced?

Thanks in advance.

On metric bolts, we had one of our tracked Hagglund vehicles (big thing with 5.9 Cummins and midsection steering) literally come apart. The front part started to "walk away" from the rear. 24 bolts had finally given up since we abuse them a lot.

My point; they use metric 10.9 bolts that was hard to find so we thought of going to "the next level", 12.9

Manufacturer of vehicle says no good, will break sooner. MH nailed it, what is stronger?? The 12.9 is harder and might have even higher tensile strength, but would not be "flexible" enough in this aplication!!

So from this my thought would be 10.9 bolts over 8.8, but not 12.9.


RS

 

[FTXMOTORSPORTS]

Just my thought process here fellas...why not eliminate some of the twisting/shearing force to begin with?
Also, there is not enough meat in a stock mag motor strap to counterbore the shoulder of the bolt and retain proper thread engagement IMO. Next thought...run the bolt through the strap and retain with a nut-oops, the strap is angle cut so a nut won't seat properly...hmmmm, maybe mill an angled block so the nut can have a flat seat? how do you keep that angled piece from shifting around and fretting/coming loose from getting worked hard?

Back to point A--eliminate some of the excessive twisting (both vertical and horizontal) to begin with and the shear load on that bolt goes WAY down-

Curt