Lotus Elan

Miata/MX5 headlight motor question

PostPost by: disquek » Mon Mar 11, 2019 5:54 pm

Hi,

I've read thorough all of the threads on this I could find.

My car is a US Federal S4 with a single failsafe vacuum actuator.

I've got the MX5 motors and understand the wiring and the basics of the linkage. I plan to replace the vacuum actuator with the motor in the same location. I will modify the motor arm length to provide the stroke needed.

My question is about how to keep the pods stable at the end points without stressing the fiberglass and if the motors move to fast.

The original system was all about the stops on the pods to limit travel. It used "springy" linkage to push the pods to those stops without over stressing them. It used the spring to provide some force against the stops in the open position and it used a bend in the actuator rod to provide some spring in the down position.

I've ordered new "buffers/bumpers" for the stops, so I will have fresh rubber there.

The new system (I think) wont have much give in the linkage. So I'm thinking that it will need to be pretty precise. Trying to achieve precision in home built linkages in fiberglass cars doesn't seem like the best idea. Especially when the penalty for overstroking the linkage is a hole in the nose of the car. Federal car's linkage is VERY close to the skin when the pods are up!

I'm wondering if the spring is needed, since with the very rigid linkage of the motor arm, it's not able to provide force to the pods to keep them against their stops. Is a single motor strong enough? I've also heard the argument that the spring helps slow the motor when closing the pods to prevent slamming.

Wouldn't they then slam open?

I was also wondering if, given the two way nature of this style of spring, they could be installed so their "neutral" position is mid stroke and so they would dampen in both directions (albeit with half the total force).

Thank you, this forum is a wealth of information!

-Kyle Disque
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PostPost by: mbell » Mon Mar 11, 2019 6:36 pm

This is an area I want the revisit at some point.

I have a single mx5 motor and ridged arm with slightly bigger stops on my +2. No spring.

What's I've noticed is some flex in the under body where the motor is mounted (vacuum pod mount). I haven't really driven the car at night so not sure if that translates to noticable headlight bounce or not. I'd like to remount the motor to something more rigid.

They are also quite quick, possibly to quick. I think the Spyder kit has some intelligence (pwm) to allow the motor operation down that is probably a good thing.

I think some kind of spring or damper on them would probably be a good thing.
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PostPost by: disquek » Mon Mar 11, 2019 7:22 pm

I'm wondering if a PWM speed controller like this one couldn't be used to slow down the MX5 motors.

https://www.amazon.com/Controller-10-50 ... 46&sr=8-11

-Kyle
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PostPost by: prezoom » Mon Mar 11, 2019 10:29 pm

A speed controller probably would be a good idea, as the rotation of the lever arm is pretty rapid. I have the Miata motor on my Plus2, and the movement is almost violent. I used heim joints on each end of the control rod, and originally set it up with a "short" rod adjustment to keep the pods from jamming against the stops. Adjusting the overall length to align the pods with the body, both down and up. Also used new stop pads. On the Plus2, it was easier to modify the lever arm for the lights rather than the arm on the motor to get the correct throw, and it took a couple of tries to get the pivot location exactly where I wanted it. The position of the arm on the motor can be where ever you want it. But, basically it has to be almost straight up and down as the arm on the motor operates in 180 degree sweeps, or 360 degrees from down to up to down. You could do away with the stops once you get the throw ratio adjusted since the motor controls the stop locations. Or, as I did, have the stops adjusted as a soft stop, not completely tight against the pods. Just enough to support the pods in each position.
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PostPost by: Spyder fan » Tue Mar 12, 2019 8:35 am

disquek wrote:I'm wondering if a PWM speed controller like this one couldn't be used to slow down the MX5 motors.

https://www.amazon.com/Controller-10-50 ... 46&sr=8-11

-Kyle


That's a bit over specified for the Miata motor unit, It draws less than 3 amps. This is what I used for mine https://www.amazon.com/uniquegoods-Cont ... ay&sr=8-18

What I found when setting up mine was that the motor was too fast and that the downward movement was quite jerky and a bit violent. By using the original spring the downward movement is controlled and damped. New bump stops that you have already bought and careful adjustment of the control rod will give a firm positioning of the headlamps in the up position without damage.

If you look again at the other threads you will see the use of the original spring
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PostPost by: ericbushby » Tue Mar 12, 2019 10:23 am

Alan,
Thankyou, I have saved that one for if I ever need it.
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PostPost by: disquek » Tue Mar 12, 2019 1:18 pm

Alan,

Thank you for your insight!

With the speed controller, do you still think the spring is needed? Or is it a "both" or a "one or the other" thing?

-Kyle
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PostPost by: Spyder fan » Tue Mar 12, 2019 2:49 pm

Yes the spring is required due to the cranking of the motor linkage arm causing a slack disconnected motion for the downward travel of the pods. It will work okay without the spring but the closing motion will be jerky. Hope that bit of gobbledegook explains it?

Here is an old movie file from when I was testing the system prior to fitting a motor speed controller or the spring. notice the downward movement is very jerky and probably prone to cause damage with all the bouncing around.

https://www.dropbox.com/s/yukg7asg7l8vz ... 1.MOV?dl=0
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PostPost by: disquek » Tue Mar 12, 2019 4:57 pm

Despite being at a point where all I have left to do is make the rod and play with the PWM speed controller, I think I'm going to abandon this project.

I just dont see, given the play/wiggle/imprecision in the factory pivots/linkage/bar how you can make the pods steady (not vibrate).

The RD bumper/buffer pieces are too big (they are for 5/16 bolts - they came today).

With steel bolt on fiberglass pod there is zero tolerance for misalignment of the stops.

Modern cars used precision pivots and linkages to hold the light pods steady.

Lotus used flexible links in the spring and vacuum actuator to hold the pods against the stops to keep them steady.

It seems that the hassle of dealing with the vacuum system might be less than dealing with marrying the two philosophies of keeping the pods steady at their end points.

I question if anyone that's done this has a result that doesn't vibrate and if they do, I'd like to know how they did it.

-Kyle
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PostPost by: mikealdren » Tue Mar 12, 2019 6:17 pm

I haven't done mine yet but as I see it....

For the later (failsafe) system, you use the Lotus spring to hold the lights open against the rubber travel stop. This provides a clamp to hold them reasonable stable. You close the lights using the vacuum pod.

For an electrical system, do you not you "simply" replace the vacuum pod with the motor?
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PostPost by: disquek » Tue Mar 12, 2019 7:47 pm

There is no rubber stop. The stop is a steel bolt against the fiberglass pod shell. This is as it was from the factory.

RD Ent sells a rubber bumper, but it's for a 5/16" bolt head. The stops are 1/4" bolts. So they are VERY loose (they will fall off).

Read the rest of my prior post for the difference between the Lotus and the MX5 linkages/stops.

-Kyle
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PostPost by: Bud English » Wed Mar 13, 2019 1:53 am

The "buffers" are called out in the parts manual, at least for the +2. It's not just a bare bolt head.

I bought a dozen pool cue end bumpers for the price of two of the stock "buffers". They give a bigger area for the contact with the fiberglass. After inserting the bolt through the hole in the bumper I filled the void with silicone sealant. The fixed bolt/bumper can be adjusted by hand and the lock nut tightened down when it's in the correct position. OEM it's not, but it works well.
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PostPost by: mbell » Wed Mar 13, 2019 3:09 am

I bought some bigger bumpers from McMaster rather than the slip over the bolt head things that are original.
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PostPost by: disquek » Wed Mar 13, 2019 5:40 pm

Do the 2+2s have 5/16" bolts for the stops?

The baby Elans have 1/4" bolts. Hence the RD Ent bumpers not fitting.

I looked on McMaster (my happy place) for 1/4" bumpers, but the only ones I found were over 1" tall, which wont fit.

Can you share what you used?

-Kyle
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PostPost by: mbell » Wed Mar 13, 2019 5:44 pm

My memory is they are also 1/4".

They may have been listed as "dampers" rather than bumpers. A metal washer with big ring of rubber. Will try get my spares out and look identification when I get home this evening.
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