QUOTE (lapuwali @ Oct 7 2005, 03:20 PM)

Hm. If the adapter plate is 1/2" thick Al plate (like the KEP plates), that's going to end up being as strong or stronger than the magnesium ears at the end of the transaxle. Mg is 1/3 the strength of Al, and castings are always weaker than billet. I think you're severely underestimating the strength of that Al plate.

You may be right there, but you have to admit this is one piece that you definitely do NOT want to fail! The transaxle mounting ears were engineered by folks with advanced knowledge and experience in this sort of thing, whereas this is my very first stab at it. I think (don't recall, but I'm pretty sure) that the tranny mounting ears are nicely curved and transition to the casing w/o any stress risers (sharp transitions where tensile forces concentrate and a crack can start). And since it is so far back, compared to the TIV mount, this mount will be carrying way more than 50% of the engine/tranny load. Fortunately, most of the vibration will be in the up/down and left/right directions, with front/back (of which there is less in the first place) being contained more by the tranny mounts.

My main reason to shy away from Al is that if you take a piece of it and bend it, it doesn't take long before you get a crack or tear. Mild steel seems to fare much, much better. Also (again, I still haven't done my homework) I was picturing a much thinner (than 1/2") plate. Given the axial distance from suby crank flange to the rear edge of the ring gear, it seems that the adapter plate should be as thin as possible. And if using steel allows doing away with a full under-the-engine type mounting bar, it could be even be a net weight savings or at least a break-even.

QUOTE (Mueller @ Oct 7 2005, 04:01 PM)

how about something like this for the motor mount? the bar is bolted to the adapter plate..the little "wings" attach to the engine mounts under the suby motor, and the other end of the bar attaches to a bulk head mount.... the factory 6 uses a single bolt on bulkhead mounts and has been used for bigger/heavier six motors

Hey, that's a pretty interesting idea; there's a lot that I like about it. Much of the engine weight is supported farther forward (at the stock Suby mount points), and no risk of bent bolts like was feared with the sideways bar strategies (connecting to stock 914 mount points on the chassis.) The force on the engine adapter plate will be much smaller in magnitude, will point straight downwards, and have less vibration to contend with. This would swing my vote back towards an aluminum adapter plate (see previous entry in this thread). I think that the suby engine casing doesn't surround the flywheel 360 degrees, but is open at the bottom; so it would be possible to have a thin adapter plate and still have a meaty section at the bottom for bolting the bar into. Also, the bar doesn't interfere with the shift linkage, another plus. I think (we'll have to see) your idea could be used with a mid-engine radiator setup, which I really want to do.


The main thing I'm concerned about is just how well the bar will prevent up/down motion of the engine. The P6 engines you mentioned mount to the bulkhead over a very short span, whereas this is a pretty long reach. I'm not saying that there is a problem, only that my first hunch is that it looks kinda spongy. OTOH, the stock 914 mounting scheme struck me as very "airy" at first. (I also thought those guys at CERN were blowing a little too much hot air when they called their cute little idea the "world wide web". )

BTW, I think it is so cool that you can just jot down your ideas in a 3-d CAD system. I just use words or wave my hands around.

I like the idea Mike, but I see two flaws with it and one spot where it could be improved. First flaw I see is that all of the rotational torque of the engine and transmission are now going to be placed on the transmission mounting ears. The distance between those is substantially less than the distance between the original engine mounting points on the car. Maybe the rotational torque isn't too significant, but it seems like suspending the whole mass from three points might be scary. Even the 911 engine mounts have _some_ spacing...

The second flaw was pointed out already, but could be improved by using both the stock engine mounts (repalced with solid blocks of metal) and the adapter plate as well. That would provide two points of attachment along the axis of the support bar which would stiffen up the structure a lot.

You could then fix the first problem by coming out into a Y shape and maybe even use the stock mounting locations??????

Oh, another thing... All of this would have to sit pretty low, because of the oil pan on the subaru engine... This would bring the center of mass of the engine up higher which kinda sucks.

-Tony

QUOTE (TonyAKAVW @ Oct 7 2005, 04:52 PM)

I like the idea Mike, but I see two flaws with it and one spot where it could be improved. First flaw I see is that all of the rotational torque of the engine and transmission are now going to be placed on the transmission mounting ears. The distance between those is substantially less than the distance between the original engine mounting points on the car. Maybe the rotational torque isn't too significant, but it seems like suspending the whole mass from three points might be scary. Even the 911 engine mounts have _some_ spacing... The second flaw was pointed out already, but could be improved by using both the stock engine mounts (repalced with solid blocks of metal) and the adapter plate as well. That would provide two points of attachment along the axis of the support bar which would stiffen up the structure a lot. You could then fix the first problem by coming out into a Y shape and maybe even use the stock mounting locations?????? Oh, another thing... All of this would have to sit pretty low, because of the oil pan on the subaru engine... This would bring the center of mass of the engine up higher which kinda sucks. -Tony

I agree Mike's drawing won't work, but only because of the oil pan issues. Again, like Mike said the ORIGINAL 914/6 mounting system used ONE BOLT at the bulkhead to hang the engine, so 100% of the torque loads were fed through the transmission ears.

The KEP adapter plate is approx. 1/2" thick, and it's Al. They don't seem to have any problems with adding that additional spacing between the transaxle and the engine.

You are not going to bend 1/2" of Al without applying VERY serious loads to it. Just as magnesium is 1/3 the strength of Al, so Al is 1/3 the strength of steel. A 1/2" plate of Al is just as stiff and strong as a 1/8" plate steel, and weighs about the same.

There's no reason the "ears" on the adapter plate couldn't use smooth, wide-radius bends. Indeed, it would be a very good idea to do so. The only stress riser there would be the hole you'd need for the bolt to mate it do the tube you'd hang the whole thing from, and you could radius/chamfer the hole.

If the ears had 1/2" of material to either side of the hole, that would give you one full sq. in of material in each ear. Al has a tensile strength of 20,000psi, so both ears together would be able to hold 40,000lbs, or roughly 150 Type IV engines. I'd say that's a pretty good safety factor, considering the worst loads it would see short of a major crash would be about 2000lbs (engine flopping around from several G of flopping around over bad bumps).

i was thinking of something like this, the ears are welded to some blocks that bolt to so kind of plate on the longs behind the suspension ears like my mount does

triangulation is the key. you will have to have a mounting system, but if you triangulate it, you will make it stronger.

QUOTE (scott thacher @ Oct 7 2005, 07:23 PM)

i was thinking of something like this, the ears are welded to some blocks that bolt to so kind of plate on the longs behind the suspension ears like my mount does

Yeah, I'm thinking along these lines too. Just one small change I might make :

I have converted my Vanagon Syncro over 4 years ago to a Subaru engine, in
particular an er27 engine, out of a XT6. This is a 2.7 l 6cylinder. After looking at
Kennedy components cost, the decision was made to do it myselfe. Measured engine,
trans, machined adapter. Had no access to large enough lathe. Had a machine shop
turn down the Subaru flywheel to fit Porsche 911 starter ring gear, used on 2.7 up
motors. actually starting with 1970 motor thru sc, the rest was machined to same
dimensions as Vanagon flywheel. Balanced and still running flawless after at least
70k miles. Dimitri

Yeah - the back of the car kind of oscillates from side to side as it scrabbles for traction. Once the tires warm up a bit tho it goes away and you have to concentrate on shifting and not hitting anything now that you're doing 100mph.




On a more serious note - I haven't noticed any vibration back there that's caused me worry. I'm a little concerned about the other end where the EDIS wheel is bolted on the front of the harmonic balancer - but that smoothes out above idle anyways.

link to suby conversion thread

http://www.914world.com/bbs2/index.php?showtopic=40733

jim