Need help with alt pulley - LotusTalk - The Lotus Cars Community
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post #1 of 5 (permalink) Old 12-06-2015, 03:26 PM Thread Starter
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Need help with alt pulley

Hello fellow Lotus folk. I need help.
I am building a 71 Elan +2 for a customer, and I got a rebuilt engine for it. It has these "cogged" pulleys, and I need one for the alternator.
I have dug through a pile of parts and can't find one.
Can anyone help?
Also, he wants me to do the electric headlight raising "upgrade", and got me Miata set-up. Could use input on that too.
Thank you in advance,
Heavy Metal Alfa/Lotus
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post #2 of 5 (permalink) Old 12-06-2015, 03:57 PM
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Those XL drive pulleys are NOT rated to drive an alternator. They are designed to only drive the water pump. The cog drive setups to drive an alternator use a larger pitch belt. If you want to try to make it work with those pulleys, McMaster-Carr or Graingers sells cogged drive pulleys you can machine to fit.
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post #3 of 5 (permalink) Old 12-06-2015, 05:32 PM Thread Starter
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It seems to me these would make the alt run too slow imho.
I'm bummed, it looks like I'll have to change the water pump and crank pulley
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post #4 of 5 (permalink) Old 12-08-2015, 12:14 PM
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Glenn, I am assuming your '71 Plus 2 is LHD and has Federal Failsafe lights with the bar between the two pods as shown right side of the attached drawing?

Have successfully done the electric pod lift project on my '69 Federal Plus 2, LHD. I used Toyota sourced motors, but the Japanese ones (and I think Porsche) are all essentially the same except for variations in the electrical connector and wire colours. I understand my Esprit pod motors are completely different; just mentioning to relieve confusion for folks used to the different type.

The motors themselves have a rotary switch and diodes built in to them. They rotate in one direction only, and stop after 180 degrees of rotation at a set position. If wired correctly they will stop in both the up and down positions; incorrectly wired and they may continue rotating, particularly when not under load.

When I looked at Miata wiring diagrams I noticed some sort of light pod controller; I did not use anything like that component in my setup. That said, my set-up does not have a flash to pass feature or the ability to raise the pods without turning on the headlamps. My set-up does require one or two Bosch-type changeover relays to control stopping the motor at the raised and lowered positions. Adding flash to pass requires changing the turn signal stalk and some sort of timer relay, so considerably more difficult; much easier to add to the driving lights!

The wire colours on your particular motor are not all that important as you can determine what each of the four wires is for pretty easily at the bench. One caution when playing with the motor though; they are damned strong so watch the fingers!

Again, I am assuming you have the Federal light switch as shown (items 38, 39, & 40)? This is important for the wiring of the motors. Please check you have this set-up so I don't get confusing when adding more details. To identify the switch type I mean, it should have two Burgess microswitches attached to the side of the vacuum switch body with a metal plate and small screws. Several headlight and sidelight wiring schemes were used over the Plus 2 production run, so we need to check exactly what you have.

I only needed to use one motor. Linkage gets attached to the lever left side of the bar by items 47, 48, & 49.

The most important mechanical sizing issue is to get the motor arm length correct so the pods are not over-driven and crack the fibreglass. I chose to re-drill and bend my pod bar lever in a slight 'Z' shape to shorten it's effective length, therefore matching the pod lever displacement to my existing motor arm length. I did this as the motor arm had the linkage all attached. Other options depending on the motor arm length are shortening the effective arm length by drilling a new linkage hole in the existing arm, or removing the existing arm and replacing it with something longer. Kind of hard to explain, but basically measure the pod lever displacement you need for full travel, and make sure your motor arm effective length is 1/2 the required displacement. Close works OK as the linkage will bend a bit anyway in the up position and the down position can be fussed when mounting the motor. The vacuum actuator travel is quite a bit longer than required, so don't use it a a guide.

I found a steel fence post bracket or similar at Home Depot that I was able to easily modify to act as the motor mount. I have seen others use a mount directly from a Miata or fab something up. Anyway, I recommend having the mount be strong and large enough to mount at least one of the stock springs shown in the Failsafe setup (items 45 & 46); this will reduce pod vibration.

The other item is to have an easy means to clock the mounted motor to match the pod bar lever movement. If the motor isn't clocked exactly the pod action will seem to over travel slightly. Simple as having the motor mounting holes slotted to allow a bit of adjustment.

I was able to use the threaded turnbuckle type linkage from the Toyota to connect the motor lever to the pod bar lever. They generally have plastic ends attached to threaded rod; one end is left hand thread so the length can be easily adjusted. I had to extend the length with some metric ready rod and a coupling nut. If you don't have something like this from the donor vehicle, I would suggest getting something similar from the RC model car world...

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HTH and gets you started. Let me know details on the switch and I can provide the wiring diagram details and a few links to pictures of what I and others have done.


PS I had an Alfa Berlina back in the day; cool car! Can't believe GTV prices now!
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Calgary AB
'69 Elan Plus 2
'00 Esprit V8
'87 BMW M6 & '84 BMW R100RT

Last edited by stugilmour; 12-08-2015 at 01:38 PM.
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post #5 of 5 (permalink) Old 12-08-2015, 12:28 PM
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I'm not helping but... Stu I'm pretty sure I don't have the fail safe set up. I'm going to check tonight. Pretty funny considering our cars are two serial numbers apart

1969 Elan Plus 2
1990 Esprit Turbo SE
1986 Porsche 911
1982 Esprit Turbo SOLD
1970 Europa SOLD
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