# Adapter/Coupler Question



## DIYguy (Sep 18, 2008)

It's hard for me to envision exactly what you mean... but I think you need to make some spacers and a longer coupler. How about a sketch?


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## Woodsmith (Jun 5, 2008)

I would be concerned about any flexibility in the pto plate where you bolt it to the flywheel and where you bolt it to the motor shaft. If it flexes and there is any imbalance in the flywheel clutch assembly then it will whip as it spins.
Also you will need to reinstate a pilot bearing for the gearbox primary shaft.

The better option would be to use the pto disc centre to make up a coupler that is a tight and locked fit to the motor shaft. The outer end of it can be machined to imitate the crankshaft end for the flywheel and pilot bearing. The length can then be made to suit whatever adaptor plate you can get.

Ultimately the whole assembly needs to be rigid, and balanced, on the motor shaft.


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## green caveman (Oct 2, 2009)

Thanks for the comments and making me think more about the design.

I have a readily available supply of 2" or 4" polyethylene. It's easy to machine and cheap so I'm thinking of using a 2" sheet for the adapter plate. The Young's Modulus (stiffness) of PE is not that good, but I think that 2" will work. A 2" PE plate would be about the same weight as a 1/4" steel plate.

So, if I just mill this so that it's flat on both sides and then drill holes for the motor and the bell housing bolts, then I have a simple, flat, shape as in the diagram. (Dumb question - is the transmission shaft perpendicular to the face of the bell housing?)

If I then add a polyethylene spacer between the PTO disk and the flywheel, I can calculate the exact thickness of the spacer (somewhere about 1 - 1 1/2") so that the distance from the front face of the motor (attached to the adapter plate) is correct so that the flywheel/clutch/transmission/etc. distances are all correct.

Does this make sense, anyone see any problems?

I was further thinking that it might be easy enough to hollow out the flywheel to, say about 1/4", or even less, and then back-fill the space with a PE donut. I think that this would reduce the rotating mass considerably with any loss of performance. Essentially, you'd have PE flywheel with some steel cladding - the shell of the old flywheel. I'd keep the hub of the flywheel for the pilot bearing, and probably enough to attach the PTO disc. Thoughts? Thanks!

PS I'm not doing the machining, so I'm assuming that the people doing this can keep the alignments and make the pieces symmetrical/balanced.


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## azdeltawye (Dec 30, 2008)

green caveman said:


> .... The Young's Modulus (stiffness) of PE is not that good, but I think that 2" will work....


 
I would recommend against making an adaptor plate out of polyethylene. Over time it may cold flow when exposed to high pressure/stress/loading. This would allow the adaptor plate to distort and compromise your motor alignment.


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## green caveman (Oct 2, 2009)

Darren,



azdeltawye said:


> I would recommend against making an adaptor plate out of polyethylene. Over time it may cold flow when exposed to high pressure/stress/loading. This would allow the adaptor plate to distort and compromise your motor alignment.


An interesting thought. If you figure the motor has a torque of 400 ft-lbs applied at right angles 6" from the center you have a force of 200lbs. 6 bolts you have a force of 33lbs per bolt. (Is it really that low? or where did I mis-estimate?)

I don't think that you're going to get much room temperature creep at those kinds of forces - even 10x. Wear is a more interesting possibility. If anything is loose it's going to cause more problems that if you had a harder material.

I woke up this morning concerned about making a PE coupler spacer. I think that so long as it's a spacer it'll be OK, if it becomes load bearing then I'm not so sure. But if the calculation above is even close, then I don't think that there will be a problem even at load.

It's strange, you meet PE in bags and flexible storage containers. When it gets to 2" it's a pretty stiff material . If you have a plastic chopping board, try bending that - an that's probably less than 1/2". Isn't there a 3rd power relationship between thickness and stiffness?

A 2" thick sheet of PE is an interesting piece of material and so a fun thing to use in an EV conversion - but only if it would actually work!

If it weren't so heavy it would be a good material for a battery box being totally inert to acid (and just about anything else).


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## DavidDymaxion (Dec 1, 2008)

Don't forget the tranny multiplies the force! My transaxle in my car has about a 10:1 first gear -- I might be getting as much as 5000 lbs of force on my adapter. Another way to look at it: On my car, the motor and adapter hold up the transaxle near the axles. The motor holds up one end, and the far end of the transaxle is held -- there is no mount in the middle near the adapter. During a hard launch, there is about 3000 lbs of weight on the rear wheels -- yet the car can still spin the rear wheels. This means the axles are turning with 3000+ ft*lbs of torque. The adapter also has to be able to handle that.

Here's another hint: Do you seen anything in any car's driveline made of plastic? Believe you me, if the car makers thought it would work they would be using plastic for driveshafts and bellhousings and more.


green caveman said:


> Darren,
> An interesting thought. If you figure the motor has a torque of 400 ft-lbs applied at right angles 6" from the center you have a force of 200lbs. 6 bolts you have a force of 33lbs per bolt. (Is it really that low? or where did I mis-estimate?)
> 
> I don't think that you're going to get much room temperature creep at those kinds of forces - even 10x. Wear is a more interesting possibility. If anything is loose it's going to cause more problems that if you had a harder material.
> ...


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## green caveman (Oct 2, 2009)

DavidDymaxion said:


> Don't forget the tranny multiplies the force! My transaxle in my car has about a 10:1 first gear -- I might be getting as much as 5000 lbs of force on my adapter. Another way to look at it: On my car, the motor and adapter hold up the transaxle near the axles. The motor holds up one end, and the far end of the transaxle is held -- there is no mount in the middle near the adapter. During a hard launch, there is about 3000 lbs of weight on the rear wheels -- yet the car can still spin the rear wheels. This means the axles are turning with 3000+ ft*lbs of torque. The adapter also has to be able to handle that.


Is that force really being transmitted back to the motor mount/adapter? Seems to me that the motor can't put out any more than the torque required to stall the motor - 200-400ft-lbs. - and so that's the only force it can exert on the adapter plate. Kinda out of my realm of expertise, I'm new to this.

Even if you figure 3600ft-lbs you're still only at about 300lbs per bolt. The limit would be stiffness and 2" of PE and 1/4" of steel should be about the same.



DavidDymaxion said:


> Here's another hint: Do you seen anything in any car's driveline made of plastic? Believe you me, if the car makers thought it would work they would be using plastic for driveshafts and bellhousings and more.


If it were just an engineering decision then car bodies would be plastic. In that application it would be lighter and rust resistant. They don't make car bodies out of plastic because of the cost. LDPE is about $8/lb so it's not a particularly low cost material. Well, the Corvette, Tesla and probably others do, but that's because they're less cost sensitive.

If cost were no object you'd have plastic driveshafts. (OK so carbon fiber, but that's a plastic composite). Might remove weight where it counts (rotating parts) and probably significantly decrease W/m. Could make a nice bellhousing too.


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## DavidDymaxion (Dec 1, 2008)

Obviously the tranny multiplies the torque (don't worry, energy/power is still conserved, the tranny transforms low torque at high rpm to high torque at low rpm).

So what resists all the twisting force in the car? It's a case of it depends. In a front engined, rear wheel drive car the motor/tranny unit twists with about 900 ft*lbs of torque, the body of the car resists that (that's why the transmission tunnel has thick, strong metal).

What about a VW? Here the motor just hangs. It and its adapter just has to resist motor torque (and bouncing forces from bumps in the road). If you want the motor to resist a 10g jolt, though, that is a momentary force of about 2000 lbs on the adapter.

What about my Porsche 911? The motor/tranny puts out 3000+ ft pounds of torque. This is resisted by the back of the motor and the front of the tranny -- so yes the adapter has to be really strong to resist this much force -- it is in the load path.

So it is a case of it depends -- if the torque is resisted by strong motor mounts (that's the case for my V8 ICE car), the motor/tranny interface has to handle about 1000 ft*lbs of torque. Many front wheel drive cars run the load path through the motor, so you'd have the 10x force multiplication do deal with there.

There's a reason you don't see sheet metal adapters! They need to be as strong or stronger (due to more torque) than a bell housing, plus in some cases resist significant bounce forces.


green caveman said:


> Is that force really being transmitted back to the motor mount/adapter? Seems to me that the motor can't put out any more than the torque required to stall the motor - 200-400ft-lbs. - and so that's the only force it can exert on the adapter plate. Kinda out of my realm of expertise, I'm new to this.
> 
> Even if you figure 3600ft-lbs you're still only at about 300lbs per bolt. The limit would be stiffness and 2" of PE and 1/4" of steel should be about the same.
> 
> ...


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## green caveman (Oct 2, 2009)

DavidDymaxion said:


> There's a reason you don't see sheet metal adapters! They need to be as strong or stronger (due to more torque) than a bell housing, plus in some cases resist significant bounce forces.


The bellhousing design is different - the force on the material is perpendicular to the force on the adapter plate. It's a bell so you're resisting a bending torque on the lip of a surface not across the plane of a solid material. 

For the adapter I think that the overriding design criteria is stiffness. The forces are (relatively) low. An 1/8" steel sheet would resist the 2000lbs of force in plane, but would flex on every bump.

I'm not a structural engineer, but my recollection is that stiffness is a third power, which means that 3/4" aluminum is stiffer by almost a factor of 10 than 1/4" steel and stiffer by a factor of 4.5 than 2" of PE. BUT 2" PE is stiffer by a factor of two than 1/4" steel. (I'm pulling the Young's Modulus - the parameter that gives you a measure of the material's stiffness - for the various materials from EngineeringToolbox).

The coupler might be a totally different question.

It really is just that 2" PE is just a very odd, unusual, and therefore cool material.


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## azdeltawye (Dec 30, 2008)

green caveman said:


> Darren,
> 
> 
> 
> ...


I suppose at a bare minimum you could insert steel sleeves in all the bolt holes to prevent the fastener heads from imbedding themselves in the material.


I just don’t think that a soft plastic such as polyethylene is an appropriate material choice for an adapter plate is all. If you must use plastic then perhaps a phenolic resin based material such as bakelite would be more suitable…


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## green caveman (Oct 2, 2009)

azdeltawye said:


> I suppose at a bare minimum you could insert steel sleeves in all the bolt holes to prevent the fastener heads from imbedding themselves in the material.
> 
> 
> I just don’t think that a soft plastic such as polyethylene is an appropriate material choice for an adapter plate is all. If you must use plastic then perhaps a phenolic resin based material such as bakelite would be more suitable…


Many of the harder plastics are more brittle and might fatigue and fail pretty quickly. 

PE's pretty tough - good resistance to cracking but, the bolt holes are pretty good stress concentrators and a sleeve of some kind would decrease that.

I'll go back and visit my local source of all things odd - the Black Hole in Los Alamos - and see what I can find.


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## ga2500ev (Apr 20, 2008)

I'm working on my adapter plate and came across this thread. I need a plate for a 1992 Geo Metro. It looking like aluminum is going to be both lighter and cheaper than steel. What I'm unsure of is the grade and thickness required for the application. Other threads that I've seen on the subject talks about 5/8" thickness. But it's not clear as to why that hickness was chosen.

Can anyone outline the different grades of aluminum alloy? It seems in general that the higher the number on the grade, the stiffer the aluminum is. How can you determine if 3003 is acceptable as opposed to 6061 for example?

Any help in this area would be appreciated. I finally have my coupler straight. I'm working on a particle board adapter plate template. Transferring to metal will be the task after that.

TIA

ga2500ev


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## dtbaker (Jan 5, 2008)

the plate I have (made by CanEV.com) is 6160 I think.... the critical thing is the depth the clutch plate sticks in is critical for proper clutch action. Alignment of course being important.


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## green caveman (Oct 2, 2009)

ga2500ev said:


> Can anyone outline the different grades of aluminum alloy? It seems in general that the higher the number on the grade, the stiffer the aluminum is. How can you determine if 3003 is acceptable as opposed to 6061 for example?


I think that the most important differences for this application are the Young's modulus, and the tensile strength. The Young's modulus describes the stiffness of the material. You can look these up for the various grades of the aluminum. (I think that 6061 is actually stronger, but 3003 is stiffer).

I'm a materials scientist, not a structural engineer, so, one thing I've been trying to determine from this thread is the loads associated with the adapter plate. It might be good to start a thread to see if anyone has actually calculated these, but it seems to me that the torque exerted by the motor on the adapter are actually pretty low. This tends to be reinforced for me by the fact the that the entire force of the motor/ICE is transferred through the clutch plate which is pretty thin.

I *suspect* but have little evidence to support it, that the bending forces on the plate are significant (as mentioned above). That is, when you drop into a pothole, the force the motor exerts on the plate is considerable. Since, when there was an ICE engine, the transmission and engine were joined in a way that made that connection pretty stiff, I would assume that with an EV you'd want the same quality of connection. In this case, a stiffer material (higher modulus) will work better. BUT, the stiffness increases non-linearly with the thickness of the material. For a simple beam this is a third power relationship, so a thicker plate will yield a much stiffer connection. So, for a given weight, I think that aluminum, probably any aluminum, will be stiffer, because the plate will be thicker.

I have no idea what constitutes "stiff enough". I know people have used 1/4" steel, and that seems to work. It's not very stiff because it's not very thick. I suspect that any 5/8 or 3/4 aluminum will be stiffer than 1/4 steel, so if the stiffness of 1/4 steel is sufficient, 5/8 aluminum probably is also.

Finally, the issue that Dan raised, which is spacing. If you're keeping the clutch in place, then the distance from the flywheel to the transmission should be the same as it was when the ICE was in place. If you've removed the clutch, I don't think that this is particularly important.

In my case, I need something like 1.5" between the front of the motor and the front of the bellhousing to leave space for the flywheel, clutch, coupler, etc. etc. That's either a thick chunk of aluminum, or some extra machining, eg a donut spacing the motor from the plate. Probably both.

The spacing is why I wanted to use a plastic material. It's lightweight, seems to have enough strength and stiffness, but since it seems that the motors may run at temperatures that are close to the melting point of this material (~100C), I think I'll go for the more traditional metal solution. Creep becomes a problem as the temperature approaches the melting point of the material and/or as the force reach the plastic deformation stress.


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## ga2500ev (Apr 20, 2008)

dtbaker said:


> the plate I have (made by CanEV.com) is 6160 I think.... the critical thing is the depth the clutch plate sticks in is critical for proper clutch action. Alignment of course being important.


I'm going with a clutchless setup. It's tough enough trying to balance the coupler in addition to the flywheel, pressure plate, and clutch disk.

ga2500ev


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## Woodsmith (Jun 5, 2008)

green caveman said:


> An interesting thought. If you figure the motor has a torque of 400 ft-lbs applied at right angles 6" from the center you have a force of 200lbs. 6 bolts you have a force of 33lbs per bolt. (Is it really that low? or where did I mis-estimate?)


If it is 400 lb-ft then at 6" (1/2 a foot) that would be 800 lb of force.
At 2' it would be 200 lb of force.


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## Carroll_1 (Dec 18, 2007)

ga2500ev said:


> I'm working on my adapter plate and came across this thread. I need a plate for a 1992 Geo Metro. It looking like aluminum is going to be both lighter and cheaper than steel. What I'm unsure of is the grade and thickness required for the application. Other threads that I've seen on the subject talks about 5/8" thickness. But it's not clear as to why that hickness was chosen.
> 
> Can anyone outline the different grades of aluminum alloy? It seems in general that the higher the number on the grade, the stiffer the aluminum is. How can you determine if 3003 is acceptable as opposed to 6061 for example?
> 
> ...



We use/recommend 6061-T651 aluminum alloy for adapter plates. Typically, the base adapter plate is machined from .750" thick plate, with an accompanying 6061-T651 spacer ring(s) whose thickness is determined by the motor and trans/clutch specs for a particular application.

We caution against using MIC-6 aluminum, which is a cast and ground aluminum with much lower tensile strength. It's a great looking product, but not appropriate for adapter plates, motor mounts, etc.

Here's a link that details the various aluminum alloys and heat treat levels. 

http://www.aircraftspruce.com/catalog/mepages/aluminfo.php

Hope this helps.

Craig


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## green caveman (Oct 2, 2009)

Woodsmith said:


> If it is 400 lb-ft then at 6" (1/2 a foot) that would be 800 lb of force.
> At 2' it would be 200 lb of force.


Thanks for the correction. 800lbs is still pretty small compared to the tensile strengths of any of these materials. I don't really know how that stress is transferred. I assume that a bunch of it is frictional forces at the face of the motor so that area is pretty large, the stress will be pretty low.

ICE's are generally mounted on rubber mounts, so have a little travel, but not much. Presumably, when they drop, they are supposed to take the transmission with them (or vice versa) so that the bending in the drive chain is in the U joints. I assume that if the motor or transmission drop independently and there is an upward (downward, left, right) force on the front shaft of the transmission because the plate flexes it would eventually cause transmission problems.

The vibration of the ICE probably causes more force than the flexing of the adapter plate. (That's just a wild guess based on no hard data, and very little knowledge).

Is there any field failure data? Anyone had a plate/transmission/coupler fail? Fatigue cracks a bolt holes? Bolt failures? Anyone using an unusual material that does/didn't work?


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## green caveman (Oct 2, 2009)

Carroll_1 said:


> We use/recommend 6061-T651 aluminum alloy for adapter plates. Typically, the base adapter plate is machined from .750" thick plate, with an accompanying 6061-T651 spacer ring(s) whose thickness is determined by the motor and trans/clutch specs for a particular application.


Thanks for that, it was one of the designs I was considering, it's good to have confirmation that it should work.




Carroll_1 said:


> We caution against using MIC-6 aluminum, which is a cast and ground aluminum with much lower tensile strength. It's a great looking product, but not appropriate for adapter plates, motor mounts, etc.


Is that based on field experience, or just that "6061 works and is about the same price so why risk a lower strength annealed product"? Do you have some evidence that the higher tensile strength is needed? I ask this in the spirit of increasing my knowledge, not as a criticism of your choice (I can't really see any advantages in the MIC-6 unless the cost is dramatically lower which seems unlikely).


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## Woodsmith (Jun 5, 2008)

There really shouldn't be any relative movement between the motor and the transmission. The two should be rigidly bolted together and fully aligned to ensure that the shafts all turn on one axis.
Ther should be very little chance for the adaptor plate to flex as the motor mounting diameter would be not much smaller then the transmission bell housing diameter.
I am using 22mm thick aluminium plate and will probably add a second plate to make up the thickness needed when I have a motor to bolt on.

If there is still concern that the adaptor plate will flex then some bracing can be added between the motor frame and the bell housing bolts. A simple pair of rigid struts from the tail end of the motor to the bell housing at the top and side would provide a lot of support.

The rigid motor/transmission assembly will then sit on rubber mountings, preferably in the same orientation and fitting as the original set up wit the ICE. The assembly can then move as one unit and the joints in the drive shafts will take up the movement.

Although the ICE vibrates more then the motor the motor will exhibit torque reactions in the same way as the ICE that will need to be transmitted to the chassis. Also the rubber mounts will absorb the bouncing of the assembly as the vehicle travels over bumps in the road.
The other purpose of the rubber mounts is to allow the chassis or frame of the vehicle to twist and move without putting stresses through the motor and transmission components.


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## Carroll_1 (Dec 18, 2007)

> Is that based on field experience, or just that "6061 works and is about the same price so why risk a lower strength annealed product"? Do you have some evidence that the higher tensile strength is needed? I ask this in the spirit of increasing my knowledge, not as a criticism of your choice (I can't really see any advantages in the MIC-6 unless the cost is dramatically lower which seems unlikely).


Although I've never had an adapter plate failure (never built one from MIC-6 so I have no direct experience), I have broken a motor mount and a few other stressed components that we accidentally manufactured from MIC-6 material. In my opinion, the 6061-T651 is a far better adapter material. The costs for the two materials vary according to market but are generally very similar. I only offer the MIC-6 caution because the materials can easily be mistaken. We CNC machine over a hundred thousand pounds of both 6061-T651, MIC-6, and other aluminum alloys per year, and I still grabbed and used the wrong material for some prototype parts. I know, embarrassing  but it can happen.

Craig


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## green caveman (Oct 2, 2009)

Carroll_1 said:


> Although I've never had an adapter plate failure (never built one from MIC-6 so I have no direct experience), I have broken a motor mount and a few other stressed components that we accidentally manufactured from MIC-6 material.


Interesting. Any more details, how much material and how long did it take (assuming it was a fatigue failure).

The mount is supporting the motor and transmission. A couple of hundred pounds, but the pothole stress is probably pretty high.



Carroll_1 said:


> In my opinion, the 6061-T651 is a far better adapter material. The costs for the two materials vary according to market but are generally very similar.


I hadn't really thought about the motor mount yet. Steel might work better here.



Carroll_1 said:


> I only offer the MIC-6 caution because the materials can easily be mistaken. We CNC machine over a hundred thousand pounds of both 6061-T651, MIC-6, and other aluminum alloys per year, and I still grabbed and used the wrong material for some prototype parts. I know, embarrassing  but it can happen.
> 
> Craig


Well heck, next time pick the wrong material for the adapter plate instead of the mount. Inquiring minds long to know.


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## dtbaker (Jan 5, 2008)

I would add a vote in favor if using the original rubber motor mounts if possible, and pretty stout steel with good gussets/fillets, etc.... My first end mount had a flat section in cantilever which didn't last long.... but is still fine after added a L section and doubling the thickness to 1/4" in high stress area.


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## green caveman (Oct 2, 2009)

dtbaker said:


> I would add a vote in favor if using the original rubber motor mounts if possible, and pretty stout steel with good gussets/fillets, etc.... My first end mount had a flat section in cantilever which didn't last long.... but is still fine after added a L section and doubling the thickness to 1/4" in high stress area.


Well, if you figure 10G's per pothole (wild guess) then you have about 2500lbs riding on the mount. In general, steel has better fatigue properties than aluminum. Strength/weight probably favors steel.

In construction, the anisotropic engineered lumber products, such as LVL's, tend to beat out steel - I think in strength to weight, but I may mis-remember. I don't know what would happen to those under dynamic loads. I suspect that the fatigue properties would be pretty bad.


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## DavidDymaxion (Dec 1, 2008)

Don't forget the tranny multiplies torque, and if you have a transaxle or FWD that includes the diff that multiplies torque even more. The axles can put out about 10 or 12 times the torque of the motor (or ~40x for a 4WD with low range!). You need around 2000 to 3000 ft*lbs of torque to spin (burnout) the wheels on many cars. Depending on the design of the car, this torque might get reacted through the tranny case (like the old VW bug with the motor dangling), but it might also get reacted through the adapter (FWD and my Porsche's transaxle). It depends on your car's design, but your adapter can see 1000's of pounds of force.

A hint these forces are pretty high: Despite a larger radius, and greater mating length for friction, the bolts holding the tranny to the motor are about as big as the car's wheel studs and nuts.

Despite the beefiness of transaxles and diffs, high performance cars can flex these parts enough to sometimes cause problems. Some cars have high performance parts available to strengthen the diff pumpkin or transaxle side plates.

Note so far this doesn't even consider vibration or road bumps! That adds even more force.


green caveman said:


> Thanks for the correction. 800lbs is still pretty small compared to the tensile strengths of any of these materials. I don't really know how that stress is transferred. I assume that a bunch of it is frictional forces at the face of the motor so that area is pretty large, the stress will be pretty low.
> 
> ICE's are generally mounted on rubber mounts, so have a little travel, but not much. Presumably, when they drop, they are supposed to take the transmission with them (or vice versa) so that the bending in the drive chain is in the U joints. I assume that if the motor or transmission drop independently and there is an upward (downward, left, right) force on the front shaft of the transmission because the plate flexes it would eventually cause transmission problems.
> 
> ...


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## green caveman (Oct 2, 2009)

DavidDymaxion said:


> Don't forget the tranny multiplies torque, and if you have a transaxle or FWD that includes the diff that multiplies torque even more. The axles can put out about 10 or 12 times the torque of the motor (or ~40x for a 4WD with low range!). You need around 2000 to 3000 ft*lbs of torque to spin (burnout) the wheels on many cars. Depending on the design of the car, this torque might get reacted through the tranny case (like the old VW bug with the motor dangling), but it might also get reacted through the adapter (FWD and my Porsche's transaxle). It depends on your car's design, but your adapter can see 1000's of pounds of force.
> 
> A hint these forces are pretty high: Despite a larger radius, and greater mating length for friction, the bolts holding the tranny to the motor are about as big as the car's wheel studs and nuts.
> 
> ...


I don't think that this is correct. The increase in Torque is through the gearing in the box. The force coming back will see the opposite effect.

The only item generating torque is the motor, so I don't think that the force on the motor can exceed the torque that it can generate.


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## dtbaker (Jan 5, 2008)

green caveman said:


> The only item generating torque is the motor, so I don't think that the force on the motor can exceed the torque that it can generate.


But the FORCE on individual bolts and plates and motor mounts can be higher with longer moment arms, and subject to sudden increases as wheels hit bumps or slip on sand and then catch on pavement, etc. even for those od us not doing 'burnouts'.


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## DavidDymaxion (Dec 1, 2008)

Just what I said, the tranny multiplies the torque. It's not intuitive, but yes, the torque can exceed the motor torque. Here's a thought experiment:

Put yourself into a large barrel, firmly attached at one end. At the other, open end is a steering wheel, firmly attached to a concrete wall. You turn with all your might, and make maybe 100 ft*lbs of force on the wheel, and there is an opposite torque on your barrel. Now you get clever, and use a long lever, or a block and tackle, or planetary gears, or whatever. You now can twist the wheel with 1000 ft*lbs of force, and the barrel reacts with 1000 ft*lbs in the opposite direction.

There is no violation of conservation of energy, since you can only apply this force 1/10 as far, or at 1/10 the rate. You the human are still only able to apply 100 ft*lbs of torque, but the force is multiplied by 10 by your simple machines. Follow the load path, and you see the torque has to be reacted by the barrel you are inside.

Now, make that barrel the motor case+adapter, you are the armature, your simple machines the gears in the tranny, and the wheel the tranny output shaft. The adapter in this case has to resist the multiplied torque.

Fine points: This assumes the motor is attached at one end, and the transaxle at the other end. Some cars, like the old VW bug, just let the motor dangle, so the torque multiplied load path is just through the tranny case and not through the adapter, the adapter in that case would see only motor torques (plus bouncing forces from bumps in the road). An in-between case would be a typical RWD car -- The motor and tranny resist about 3x the torque (so the adapter could see 3x the motor torque), and the rear axle mounts resist the other factor or 3 or 4 of the wheel torque.


anonymous said:


> I don't think that this is correct. The increase in Torque is through the gearing in the box. The force coming back will see the opposite effect.
> 
> The only item generating torque is the motor, so I don't think that the force on the motor can exceed the torque that it can generate.


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## green caveman (Oct 2, 2009)

DavidDymaxion said:


> Put yourself into a large barrel, firmly attached at one end. At the other, open end is a steering wheel, firmly attached to a concrete wall. You turn with all your might, and make maybe 100 ft*lbs of force on the wheel, and there is an opposite torque on your barrel. Now you get clever, and use a long lever, or a block and tackle, or planetary gears, or whatever. You now can twist the wheel with 1000 ft*lbs of force, and the barrel reacts with 1000 ft*lbs in the opposite direction.


I think that there's still 100lbs on the barrel.

Let's make it static rather than a barrel. I'm going to push up on a bar attached to the steering wheel. I'll do this while standing on a bathroom scale - to make it easy, I'll zero the scale while standing on it, so my weight is removed, only the additional force I apply will be measured.

If I push up with all my 100lbs of strength a foot from the wheel, I'll apply a torque of 100ft-lbs to the wheel and a downward force of 100lbs. The scale will read 100lbs.

If I move along the bar so that I'm 10ft from the steering wheel, and apply my maximum strength of 100lbs, I'll apply 1000ft-lbs of torque on the wheel. The bathroom scale will still read 100lbs. 

So yes, I can apply more torque, that's what happens when the motor powers through gearbox, but the forces are the same.


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## Woodsmith (Jun 5, 2008)

Relative to the forces within the motor and the transmission primary shaft you are right that the torque, and forces are the same.

However, the gearbox does multiply the torque to the wheels. Now, that torque has to react against something. That something is the transmission casing, and then the mounts, and through to the vehicle frame.

When you see a drag race car pull a wheelie it is because the massively multiplied torque going to the wheels is reacting, through the axle, against the frame of the car sufficient to make the front of the car lift into the air.

Watch this video http://www.youtube.com/watch?v=Jxv2hOlFav4&feature=fvw and see how the torque reaction of the left side truck's transmission causes the frame of the truck to twist as it tries to resist the reaction. That isn't a thousand lb-ft of engine torque that does that, that is the multiplied torque through the gearbox casing.


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## green caveman (Oct 2, 2009)

Woodsmith said:


> However, the gearbox does multiply the torque to the wheels. Now, that torque has to react against something. That something is the transmission casing, and then the mounts, and through to the vehicle frame.


Let me look at this a different way. It may not be correct, but I haven't yet seem the flaw in the logic, feel free to let me know where I'm in error.

OK, so I have a circular bellhousing, 24" in diameter. I'm going to attach a 1ft rod to the front drive shaft of the transmission and apply 100lbs to it. 100ft-lbs of torque. I think we're clear that this will cause a reaction of 100lbs against the bellhousing casing (1' radius bell housing remember). If I measured the force on the housing, with, say, a spring scale, it would read 100lbs.

Now, on the back end of the transmission, let's imagine that this 100ft-lbs of torque translates to 1000ft-lbs. So the planetary gears in the transmission give a 10-fold increase. 

So, I find the right incline, crank the rod in the front of the transmission with 100lbs, transmission goes round and round, and in exactly this configuration my spring scale reads 100lbs, there's 1000ft-lbs out the back of the transmission, ultimately through the diff and to the back wheels and along we go (very slowly).

Now, same conditions. I'm going to take a 10ft rod and now, instead of turning the front of the transmission, I'm going to apply 100lbs to the back of the transmission. 100lbs at 10ft is 1000ft-lbs. So now I can crank this rod round and round (lift kit required) and under the same conditions as above the car is going to go along, at the same speed and, out of the front end of the transmission, I'm going to see 100ft-lbs of torque (something has to be resisting this). I'll still have a reaction force of 100lbs on the transmission bolts and my scale measuring the reaction will read 100lbs.

The torque is amplified (as the speed is decreased) backwards through the transmission, but the torque conversion is reversed, as the speed increases so at the front of the transmission you see the reduced torque. If you consider the force, rather than the torque, amplifying/reducing the torque backwards and forwards through the transmission doesn't change the force on the motor/front of the transmission.

To get the effect you see on the video, where the front end twists while the vehicle is not moving, you need a motor with enough stall torque to twist the vehicle, and corresponding brackets on the motor to resist this. Since the vehicle isn't moving, the torque amplification through the transmission is irrelevant, it's just the stall torque of the motor that counts.


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## dtbaker (Jan 5, 2008)

yeah.... and the stall of an electric motor is at almost zero rpm. 

point being that the motor mounts for an electric motor had better be AT LEAST as stout as the ICE, and probably more so....


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## DavidDymaxion (Dec 1, 2008)

Let's change the scenario just a bit. Let's say you are in free fall. You have a long lever, where the fulcrum is attached to the inside of a big box. You put a scale on the lever, and push so it reads 100 lbs. You are pushing on the box with 100 lbs of force. The other end of the lever is 1/10 as long as your end, and pushes on a 2nd scale attached to the inside of the big box. The scale reads 1000 lbs! The box has to handle this 1000 lbs of force or the scale will break right through it. The box you are inside has to handle the multiplied force.

Your example needs to include the floor you are standing on, and that the wheel is bolted to -- the floor finishes the load path and has to be strong enough to handle 1000 lbs.

For the EV, you have to consider the case (tranny, adapter, and motor) and how things are bolted to the car.


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## Woodsmith (Jun 5, 2008)

Imagine the transmission in a front engine, rear wheel drive car.

At the front end you apply 100 lb force on a lever 1 ft long.
What are you levering against? If you are the motor then you are levering against the bell housing bolts only.

At the back end of the (your 10:1 example) transmission there is, say, 1000 lb-ft of torque.
That is 1000 lb of force on a 1 ft lever (or 100 lb on a 10 ft lever).
What is that force levering against?
That force is the drive shaft levering against the transmission tail shaft casing.

Note that both the motor and the drive shaft are levering against the transmission casing both in the same direction. 100 lb-ft at the bell housing and 1000 lb-ft at the tail shaft casing.
Where does that leave the transmission casing? It is trying to oppose the combined force at both ends.
So does the transmission case spin around and round? No, it is prevented from doing so by the mounts that are opposing the 1100 lb-ft of reaction torque by transferring it to the vehicle frame.

What happens at the frame?
Well, the frame twists a bit, or a lot, depending on the amount of torque it can handle.

The weight of the vehicle, and the stiffness of the frame, transmits that torque into the road.
At the back axle it causes one side of the axle to press down harder into the road then the other side causing wheel spin on one side.

It is generally the right hand wheel that spins because all that torque is causing the pinion gear to try and climb up the ring gear and to try and rotate the whole ring gear and axle in the same direction.

So the front of the diff pinion lifts up causing the vehicle to try and pop a wheelie, the right hand rear wheel lifts and spins and the left hand front wheel lifts as teh right hand front wheel bears down hard into the road to oppose the torque from the transmission.



Have a look at this tool http://www.diytools.co.uk/diy/Main/sp-1-11886-94194-sealey-torque-multiplier.asp?iCategoryID1=11886.
It is a torque multiplier for your socket set.
It consists of a planetary gearbox attached to a long handle.
This shows you the 
insides of it. 

You put your 1/2" drive ratchet in one side of the multiplier and the socket on the other end.
You can then put in 500 lb of force into the ratchet and it will give 2000 lb to the socket to loosen that stubbon nut.
Why does the multiplier have a long handle?
It is because that 2000 lb of force at the socket has to be resisted by a long handle transferring that force to something that isn't going to move.



> In use, standard drive sockets of appropriate size are placed on the male drive square. A suitable drive tool is inserted in the female input socket. This may be an ordinary ratchet drive, a torque measuring device or under controlled conditions, a power drive. *This assembly is now placed on the part to be turned with the reaction bar restrained against some substantial part of the equipment being serviced.* At this point, any force applied to the input drive is multiplied at the output end of the X-4. For higher ratios of multiplication, two or more X-4's may be directly intercoupled. Impact type driving tools should not be used.


If the forces were the same as the input forces then you could just hold the multiplier with your other hand.



Hence, your bell housing bolts will only need to handle the maximum motor torque but the transmission mountings (and also the vehicle frame and suspension members) will have to handle the maximum multiplied torque that the transmission can produce.


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## green caveman (Oct 2, 2009)

Woodsmith said:


> Hence, your bell housing bolts will only need to handle the maximum motor torque but the transmission mountings (and also the vehicle frame and suspension members) will have to handle the maximum multiplied torque that the transmission can produce.


Since the car, beyond the transmission already the torque on that is not of much concern to me, but I agree with you, that's clearly subjected to the higher torques.

It seems that we're in agreement on the torque on the transmission bolts. 

It's my contention that the torque on the motor mount is same (inverse) of the maximum motor torque. Others seem to have suggest that this can be more than the maximum motor torque and I don't understand how.

In short, I still think that all the maximum forces and torques in front of the transmission are related to the maximum torque of the motor 

(and all the torques backwards of the transmission, including factory-designed mounts, are related to the torque amplified by the transmission).


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## Woodsmith (Jun 5, 2008)

green caveman said:


> It seems that we're in agreement on the torque on the transmission bolts.
> 
> It's my contention that the torque on the motor mount is same (inverse) of the maximum motor torque. Others seem to have suggest that this can be more than the maximum motor torque and I don't understand how.
> 
> In short, I still think that all the maximum forces and torques in front of the transmission are related to the maximum torque of the motor


That is only true in respect of the armature in relation to the motor frame.

The motor frame in relation to the vehicle frame is essentially the same component as the transmission casing as they are bolted together.

If the transmission mounts perished, for example, then all the transmission torque is reacted by the motor frame as it is rigidly bolted to the transmission.

The original design of the mounts would have allowed for all the transmitted torque reactions to be shared by both the transmission mounts and the ICE mounts.

The only way your motor mounts could see only motor torque is if the motor were mounted independently of the transmission and connected by a flexible (conventional short propshaft with U joints both ends) coupling.
Or of there were no mounts at all on the motor frame and all the mounts were on the transmission case.

As that is not usually the case the motor frame will experience the same torque reactions that the transmission experiences, through the bell housing bolts.

In a conventional in line engine car the torque reaction of the whole tranmission and engine assembly is controlled by the engine mounts while the transmission is only mounted to take weight. All the torque in the transmission is tranferred to the ICE and through the ICE mounting points to the frame.
Using a motor produces the same thing. The transmission has a soft rubber mount under the tail shaft and two big mounts on either side of the motor and all the torque of the transmission is transferred through the belhousing to to motor frame and to the mounts.

Sometimes you will find a torque reaction rod mounted between the bell housing and the frame to help relieve the ICE/motor mounts of all the torque reactions.

In a front engine, front wheel drive car it is often the same deal, just sideways.
There are some that are different. My MR2 mid engine has the main mounts on the transmission, three of them, managing the torque while the ICE/motor mount is at one end mostly just handling the weight. In that case the motor frame does not need to react or transfer much of the transmission's torque, just a small part of it but still more then the motor torque alone.


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## DavidDymaxion (Dec 1, 2008)

We are almost there. The situation is just as you state in some cars, but not all cars. Imagine a car where the motor mounts take all the force, and the tranny mounts are nonexistent, or very soft, or lift only with no torque fighting ability, or broken. Then the tranny case can't transfer forces to the car body, it transfers that force to the adapter, which transfers it to the motor case, which then transfers it to the car body.

Here are three cases:

o VW bug: The motor dangles. The motor only sees motor torque. This is your example.

o Porsche 911: There are mounts at the end of the motor, and at the far end of the transaxle. In this case the motor case and the tranny case see about equal forces, and see the total multiplied force.

o Chevy V8: The motor mounts are very strong and take the multiplied torque, and the tranny mount just hold up the tranny, but don't really fight the torque. This puts the torque loads on the front suspension attach points, rather than through the floorpan of the car. If you attached an electric motor in the same manner, the electric motor case, and your adapter, would see the multiplied torque load.



green caveman said:


> Since the car, beyond the transmission already the torque on that is not of much concern to me, but I agree with you, that's clearly subjected to the higher torques.
> 
> It seems that we're in agreement on the torque on the transmission bolts.
> 
> ...


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