Lotus Elan

A/C add on/tech question

PostPost by: rdssdi » Tue Jan 25, 2005 2:52 am

I have copied an e-mail I sent to Vintage Air. A supplier of after market
A/C - heater - defroster units. The following correspondence outlines my
concerns involving such an undertaking. Are there any engineers on the list that
could help me better understand this problem. Suggest any texts? I have no
experience with this. I only know it can be a potentially serious problem. I
understand car companies do exotic tests to determine correct damping and
ancillaries effects on the crankshaft. It is certainly beyond my capabilities. I
knew that when I sold my business and took some time off I would get my self in
trouble!



I am thinking of updating my 1969 Lotus Elan +2 by installing your A/C-
heater -defrost 05000 series. The car is now the subject of a complete "body off"
restoration. An ideal time to undertake such a project.

I have yet to determine whether or not the unit will fit in the place of the
original Smiths Heater Unit.

My initial concern is with damping torsional vibrations in the crankshaft
and accessory drives. My concern is knowing before hand that these forces are
understood and designed for. The Lotus twin cam engine does not utilize a
damped crankshaft pulley. The addition of the compressor mass and required double
crankshaft pulley could cause vibrations and/or crankshaft seal or
crankshaft failure. The block used for the Lotus twin cam is the Ford "Kent" engine
with a Lotus twin cam head. The water pump and engine front cover is also
unique to the Lotus variant.

It may be possible to use a crankshaft pulley from a Ford Cortina or Pinto
or Capri that was supplied with factory A/C. I will ask several engine experts
about the similarities of the Lotus and Ford Kent engines and crankshaft
pulleys.


I am concerned that even though the system works and may be vibration free
uncertain harmonics could cause premature crankshaft or ancillary failure.
What are your thoughts on this?

Thank you.

Robert Seligman
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PostPost by: twincamracing » Tue Jan 25, 2005 4:21 am

understand car companies do exotic tests to determine correct damping
and ancillaries effects on the crankshaft. It is certainly beyond my
capabilities.

Most performance oriented machine shops doing in-house balancing are
likely to give you a closer tolerance to the factory balance factor
than the factory does in a production application.

I knew that when I sold my business and took some time
off I would get myself in trouble!

Wives really appreciate the guys not being underfoot during those in
between times ;)

I have yet to determine whether or not the unit will fit in the place
of the original Smiths Heater Unit.

Let us know.

My initial concern is with damping torsional vibrations in the
crankshaft and accessory drives.

A good balance job of the reciprocating assembly will reduce the
inherent vibration resulting in a smoother running engine with added
benefits including reduced engine wear improved efficiency and
increased performance.

My concern is knowing before hand that these forces are
understood and designed for. The Lotus twin cam engine does not
utilize a damped crankshaft pulley. The addition of the compressor
mass and required double crankshaft pulley could cause vibrations

and/or crankshaft seal or crankshaft failure.

Adding or reducing mass in the reciprocating assembly is cause for
rebalancing of the assembly. Otherwise no sweat with a double pulley.

Considering the small displacement of the Lotus powerplant an efficient
compressor will reduce load on the crankshaft and a wide open throttle
cut out switch to disengage the compressor clutch would be prudent.

Here's a quick way to additional reading material
(you may have to cut and paste to get the whole link):
http://www.google.com/search?hl=en&q=cr ... gle+Search

Check the bibliography at www.eurospares.com for additional text

R134 isn't as efficient as the old R12 refrigerant and tends to utilize
a larger condenser core which hangs out in front of the radiator. Give
some thought to engine cooling upgrades to compensate for the
additional heat load from both the air flow through the condensor and
the load of the engaged compressor.

I hope I've given some justice to your concern.

Cheers,
Scott



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PostPost by: steveww » Tue Jan 25, 2005 11:45 am

I have heard of A/C compressors which are driven electrically rather
than mechanically, might be worth a look and would help with the packaging.

scott potter wrote:
>understand car companies do exotic tests to determine correct damping
>and ancillaries effects on the crankshaft. It is certainly beyond my
>capabilities.


Most performance oriented machine shops doing in-house balancing are
likely to give you a closer tolerance to the factory balance factor
than the factory does in a production application.


>I knew that when I sold my business and took some time
>off I would get myself in trouble!


Wives really appreciate the guys not being underfoot during those in
between times ;)


>I have yet to determine whether or not the unit will fit in the place
>of the original Smiths Heater Unit.


Let us know.


>My initial concern is with damping torsional vibrations in the
>crankshaft and accessory drives.


A good balance job of the reciprocating assembly will reduce the
inherent vibration resulting in a smoother running engine with added
benefits including reduced engine wear improved efficiency and
increased performance.


>My concern is knowing before hand that these forces are
>understood and designed for. The Lotus twin cam engine does not
>utilize a damped crankshaft pulley. The addition of the compressor

mass and required double crankshaft pulley could cause vibrations
and/or crankshaft seal or crankshaft failure.

Adding or reducing mass in the reciprocating assembly is cause for
rebalancing of the assembly. Otherwise no sweat with a double pulley.

Considering the small displacement of the Lotus powerplant an efficient
compressor will reduce load on the crankshaft and a wide open throttle
cut out switch to disengage the compressor clutch would be prudent.

Here's a quick way to additional reading material
(you may have to cut and paste to get the whole link):
http://www.google.com/search?hl=en&q=cr ... gle+Search

Check the bibliography at www.eurospares.com for additional text

R134 isn't as efficient as the old R12 refrigerant and tends to utilize
a larger condenser core which hangs out in front of the radiator. Give
some thought to engine cooling upgrades to compensate for the
additional heat load from both the air flow through the condensor and
the load of the engaged compressor.

I hope I've given some justice to your concern.

Cheers,
Scott



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