Water Pump CVT?

Just thinking out aloud here.

Way back there was a system used called CVT (I believe also known as DAF Variomatic) which used pullies that had a v cross section and the pulley side spacing was variable meaning the belts ran on an increasing or decreasing diameter meaning change of speed at the other pulley

I know on the old VW aircooled engines you set the belt tension in a similar way by clamping the fan pulley tighter forcing the belt further out. But this was a manual setting and not variable once the engine was running.

Has a system like this ever been developed for water pump and alternator pullies whereby the alternator and waterpump can be run at fairly constant RPM irrespective of engine RPM?

This, I imagine would be a big selling item on cars like ours where they are likely to see some high revs (possible WP cavitation) and yet will also see low speed work so permanent pulley diameter change is not that good an idea

Cheers
Ian

An electric water pump would solve the cavitation problems, plus save a little from less parasitic drag.

But, directly to your point: Iinstead of variable pulleys to drive the alternator and water pump, I would think that a "two-speed" setup using epicyclic gears might do the same thing, using only a simple clutch not unlike the old setups that drove the thermostatically controlled fans.

IanAnderson said:

Has a system like this ever been developed for water pump and alternator pullies whereby the alternator and waterpump can be run at fairly constant RPM irrespective of engine RPM?

This, I imagine would be a big selling item on cars like ours where they are likely to see some high revs (possible WP cavitation) and yet will also see low speed work so permanent pulley diameter change is not that good an idea

Cheers
Ian

Click to expand...

I am still puzzled by all the posts I see on water pumps, overheating, and the use of electric water pumps.

The T70 I have has a standard 302 water pump and fairly "standard" mid engine cooling layout - front radiator as large as will fit, e fans, a large pulley to slow the pump down, and a big header tank along with appropriate radiator and manifold bleeds. It doesn't go above a t-stat temp of 190F in 100F (seriously, no BS) air temp street driving, and it doesn't go above 190F on the race track again, in 100F air temps (100F and serious abuse on track).

I truly believe a lot of the issues people experience with mid-engine cooling has to do with the system layout and use, not the type of pump. Until I got my system correct I had a lot of the symptoms that folks consistently report.

Ron, I'd like to hear more about "I truly believe a lot of the issues people experience with mid-engine cooling has to do with the system layout and use, not the type of pump." I'm one of those reporting water pump (WP) failures (2) in less than 1000 miles. Mine were caused by the impeller separating from the shaft (1st) and the metal backing plate separating from the impeller (2nd). Both causing heating issues. I'm now ordering a Stewart "stage 3" WP and praying this fixes the issue. Tell me more about your thoughts on "system layout and use" please. Thanks. (sorry about the thread stealing Ian) Hopefully Ron might give some insight to issues you might be having.

Don't apologise for thread drift - I've been the cause of that before!!!

To me a constant (ish) sped on Alternator and WP would seem to make sense - accelerating all that stuff in each gear draws power too

Just I've never see such a system and wondered if it existed - resumably made by a Kiwi as they seem to have great lateral engineering thinking

Cheers
Ian

ps I have only had one cooling problem- the seal on my WP failed - slow drip but better fixed than a dry engine

tractorboy said:

I'm one of those reporting water pump (WP) failures (2) in less than 1000 miles. Mine were caused by the impeller separating from the shaft (1st) and the metal backing plate separating from the impeller (2nd). Both causing heating issues. I'm now ordering a Stewart "stage 3" WP and praying this fixes the issue. Tell me more about your thoughts on "system layout and use" please. Thanks. (sorry about the thread stealing Ian) Hopefully Ron might give some insight to issues you might be having.

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Hi Jimmy,

My comments were not directed at someone like yourself who has experienced impeller failures. I'm been on the forum since 2001 and the general underlying current of mid-engine cooling setups with a mechanical pump has been negative but I'm not sure we're separating pump issues from overall system problems.

Over the years I've observed a lot of comments around overheating, air in the system, insufficient cooling, and so on. And one gets the impression that folks feel the mechanical pump is at fault and I am not sure that is the crux of the matter. In your case it appears the mechanical pump suffered impeller failures (and who knows, maybe I will have one next) and is to blame, but in the other cases reporting about overheating I am not so sure.

On my own build thread I experienced cooling problems, exactly the type that I've seen folks fret about and blame on the pump which then causes some folks to go electric. But in the end the pump I had nor radiator size had anything to do with the cooling problems, instead of was related to the plumbing of the system and air bleeds. Once those were issues were ironed out the system purges easily and runs like a top.

And you can bet the next time the water pump comes off I'll be adding some welds to the impeller shaft attachment points.

Sorry Ian, back to your variable speed water pump pulley.

Ron