# Lexan (Polycarbonate) spacer



## piotrsko (Dec 9, 2007)

the stuff gets wierd properties when you heat it up, outgasses and all that.

I wouldn't use it


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## EVfun (Mar 14, 2010)

Lexan Polycarbonate would be an interesting material to use. It would have to be beefy because it does have more flex than aluminum. Polycarbonate will be invisibly destroyed if it come into contact with brake fluid. It does something to the structure that is far larger than any slight visible damage and most of its strength is lost.

I think it could be an excellent material for a showy exposed motor conversion like a street rod. The whole idea of big, thick, beefy, *clear* motor mounts is excellent!


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## TomA (Mar 26, 2009)

got8 said:


> Hi Everybody,
> To take my head alway from the EVC disaster I was thinking of an alternative material for the spacer between motor and tranny.
> Well I used to play with Lexan a lot back in the days. I have a few pieces of 1/2" Lexan laying around. this stuff is extremely easy to work with and can handle over 250F degree heat.
> I would need to stack 3 layers and use nuts and bolts.
> ...


I don't think 1/2' polycarbonate is going to be stiff enough to hold the motor and transmission with enough dimensional stability. You're most likely going to have excessive movement for the coupler/bearings/clutch etc. which would lead to vibration, premature wear and failure of something. Lexan is tough, yes, but it is neither hard nor stiff, and I think its a poor choice where holding the precise position of the components that are fastened to it is critical.

Just my $.02

TomA


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## Woodsmith (Jun 5, 2008)

TomA said:


> I don't think 1/2' polycarbonate is going to be stiff enough to hold the motor and transmission with enough dimensional stability. You're most likely going to have excessive movement for the coupler/bearings/clutch etc. which would lead to vibration, premature wear and failure of something. Lexan is tough, yes, but it is neither hard nor stiff, and I think its a poor choice where holding the precise position of the components that are fastened to it is critical.
> 
> Just my $.02
> 
> TomA


This was something that would be concerning me too, quite aside from the material suitability for the environment.

You say you would use three layers. a solid piece of 11/2" lexan would be a lot stiffer then three 1/2" layers bolted together. If they were bonded together then that may be different.


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## TomA (Mar 26, 2009)

Woodsmith said:


> ... a solid piece of 1 1/2" lexan would be a lot stiffer then three 1/2" layers bolted together.


That's probably not commercially available. I've seen 1"- in bank glazing.

Polycarbonate that thick is also going to be as or probably more expensive than aluminum, and it will be harder to work with. I dulls machine tools astonishingly fast.

Still, it would be kind of cool...


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## RKM (Jun 9, 2008)

I agree with the previous posts. I work with polycarbonate, using it for shielding. It is a wonderful material, cuts like butter. I wouldn't use it for a structural application such as a motor mount. As Woody says, it would be far better if the laminates were bonded or a single piece. I haven't looked it up, but I suspect the poly will be much heavier than Al.

My catalogue shows 1.5 inch sheet is available, but I'd hate to pay for it.

Polycarb is too soft and lacks rigidity (IMO). I admit it would look great.

Rob


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## TomA (Mar 26, 2009)

One last thing: Polycarbonate is heavier than aluminum, yes, and you're going to need a pretty big chunk to compensate for its lack of rigidity, of it so it will be significant...


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## got8 (Feb 3, 2010)

just got back from Foxwood casino had a great time.
thank all for the insight on the Lexan.
I am only considering it because I have a 4'x8'x1/2" sheet laying round doing nothing. the thickness of my coupler require me to use a 2" spacer. I am thinking 3 ply 1/2" lexan sandwitched between 1/4" aluminum plates. I am guessing there will be acceptble minimal flex once bolted together. I f I am not wrong we only need to worry about the twisting of the spacer cross section wise. Will the flex disk in the drive shaft absorb most of the initial torque transfer? 
just a side note, Lexan should be a better vidration absorbing material than any metal.
then there is the lexan not so friendly with chamical that might come into contact with. I am going to soak lexan in samples of gasoline, antifreeze, brake fluid and ps fluid. it would be interesting to see what would happen if I bake it in the kitchen oven. with all these test except for the oven test it might take some time to see any change.


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## TomA (Mar 26, 2009)

got8 said:


> just got back from Foxwood casino had a great time.
> thank all for the insight on the Lexan.
> I am only considering it because I have a 4'x8'x1/2" sheet laying round doing nothing. the thickness of my coupler require me to use a 2" spacer. I am thinking 3 ply 1/2" lexan sandwitched between 1/4" aluminum plates.


Don't do this. You're going to have variance stack-up between plates, and there really won't be enough precision to properly couple the motor with the transmission, even if you oh-so-carefully pinned it all together. Save the lexan or sell it on Craig's List. It would make a fine electrical or (dry) battery box, too.

2" of anything is also going to be really heavy, even just aluminum.

I suggest you do this in one piece of aluminum, then see how much of it you can remove (mill away) to save weight.

TomA


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## Woodsmith (Jun 5, 2008)

got8 said:


> I am thinking 3 ply 1/2" lexan sandwitched between 1/4" aluminum plates.


That will be 5 layers bolted together.

With the weight of a motor hung on the front and some vibration the layers will slip downwards using any slack in the bolt holes to pull the bolts at an angle.
If you were to dowel it then the dowels would have to be very, very large diameter to reduce slip to something negligable.

You could trap the whole assembly in a frame to control lateral slippage but it would all be adding weight and bulk to get the performance of something much simpler and lighter.

You would be best off either having one accurately machined component as Tom suggests or two sheets of aluminium. One bolted to the bell housing and one to the motor. Align the two and then bolt through and dowel together.


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## got8 (Feb 3, 2010)

thank you all for caring.
I am going to stick with aluminum and save the Lexan for battery tray or partitions.


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