Motor Mounts: Caterham or Birkin Style?

[SkinnyG]

I'm building a 7 clone based on Lotus 7 Series 2 plans.

 

Soon I will be working on motor mounts. Is there a distinct advantage to the Caterham style mount (fastener in tension, using the equivalent of a Jag XK motor mount) or to the birkin mount (fastener in shear, poly bushing)?

 

Caterham:

 

http://www.biggles.net/images/duratec/e0018.jpg

 

Birkin (sorry for the large hot-linked pic):

 

http://4.bp.blogspot.com/-i7WJcwuFDTQ/TZr913i4LvI/AAAAAAAAAEg/VmsjGaCrViM/s1600/IMG_0073.JPG

 

Thanks in advance.

[maurice1]

Hi

I have had my Birkin on the road here in Brisbane for the last 2 years with a 2.0 litre Duratec fitted and have not had a problem with the engine mounts if you go with that design.

That includes an off at something over 100mph at our local track where I ended up nose first in a tyre barrier.

Cheers

Maurice

[pi7ot]

11 years and 28k miles on the zetec Birkin. Probably less torque than the duratec.

Choice would depend on availability, I would think.

 

 

m

[cs3tcr]

Greg,

I would opt for the Cat/Jag mount. I would think it would give a bit more "wiggle room", ie if the motor is too low in the chassis you can always add a spacer between the mount and the bracket. I had to do this to my old Seven, and the Eleven. Or if the motor is too high, you could remove some material from the vertical tube of the engine bracket.

[slomove]

Keep in mind the Birkin Motor mount changed about 2000. Older models like mine had the cylindrical rubber dampers with vulcanized end plates mounted vertically in a metal cup (is that what you mean with "shear"?). Yhey are really cheap from MSC.

http://www1.mscdirect.com/ProductImages/6218731-11.jpg

 

Newer Birkins have (I believe) rubber bushings on the engine mounts that are oriented horizontally.

 

Not sure what is better or why they changed. But I had to replace them because the end plates came off after a couple of years.

Edited February 26, 2012 by slomove