Headlamp lifting mechanisum - Vacuum tank

[terryp]

Hello all
I know I havent been here for a while but now I have sold my Elan (So 12 years of Elan ownership comes to an end)
I now have 2 x Ginetta G4 , one is a later S4 type and I have found an original pop up headlight bonnet. These bonnets were replaced as they couldn't get the reliability using a motor.
My question is , if I rig up a failsafe type arrangement with a Vacuum pod similar to the later Elans, do you still need a vacuum reservoir? i.e was the reservoir used for when the headlights were being lifted rather than pulled down?
Thanks
Terry

[nmauduit]

I would think the vacuum reservoir has the purpose of granting immediate and fast action at all times. If you're happy with waiting that you have enough vacuum at the manifold (depending on your engine cam profile, and rpm) to raise you headlights you should be able to operate without vacuum tank. You can always stick an aluminium bottle later on the pod side of the vacuum one way valve if you change your mind.

[terryp]

Thanks but with the failsafe design , you pull the headlights down, does that mean they will slip up under load?
Thanks
Terry

[pharriso]

Thanks but with the failsafe design , you pull the headlights down, does that mean they will slip up under load?
Thanks
Terry

Not if you have a non-return valve in the line.

[terryp]

So Phil, what was the reason for the tank on the failsafe design?

BTW hope you are well

Terry

[steve lyle]

Yes, the later models with the fail-safe system still used the cross-member vacuum tank.

[john.p.clegg]

Larger throttle opening produces little vacuum, with the failsafe headlights,your headlights will start to rise ,with the earlier system they will start to droop ( without a larger vacuum resevoir )..

John

[vxah]

Plus of course you need a reasonable vacuum reserve to keep the lights down when parked. I guess even the rubber hoses etc will seep air through given time? I like them to stay down for at least a couple of days..

[terryp]

So I will need a little tank somewhere. Perhaps a modified alloy catch tank or something.
Thanks everyone, now to find the parts!
Terry

[RichardHawkins]

Terry,

Vacuum tank design is a little tricky. Cylindrical or spherical is best. If the vessel is under pressure, the medium within the vessel will hold the vessel in shape, like a beer can, but apply avacuum and the beer can will collapse. I am not able to give specific design advice, but he general principle applies.

Hop this helps,

Richard Hawkins

[nmauduit]

Thanks but with the failsafe design , you pull the headlights down, does that mean they will slip up under load?
Thanks
Terry

Not if you have a non-return valve in the line.

and no leak... but that's possible with a clean and well maintained vacuum circuit.

The vacuum tank is an other issue, if you feel like saving weight it should be possible to operate without, esp. a failsafe version... Then if you change your mind, you can always make one out of an alloy drinking bottle (like for going camping).

[terryp]

Nice idea about the flask

I will get the mechanium working and then try to obtain a cheap vacuum unit.
Thanks

Terry

[pharriso]

So Phil, what was the reason for the tank on the failsafe design?

BTW hope you are well

Terry

I guess it was already there! On my car one of the DPOs designed out the vacuum reservoir & dash mounted vacuum switch & fitted an electrical vacuum solenoid near the headlights (a la late Plus2). Works perfectly!

Life is good thx. Sorry to hear you've sold the elan!

[terryp]

Phil
Yes I think you are right, I don't think the tank is required for a failsafe design. The only issue would be having enough vacuum to pull the lights down (after having them on) and if you were on full throttle (!) it may take a little longer. I think I will risk it!
Thanks
Terry
Happy to be 100% Ginetta again and also Webmaster of the GOC!