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Dynamo - water pump interface

Posted: Mon Nov 04, 2019 11:51 am
by CZimm
I have a 1932 15 saloon which I am restoring. Not surprisingly the water pump does not work any longer. I had a new pump made but then discovered that there is at the end of the axle of the dynamo next to the water pump there is an added part with little fan blades and on the (old) pump there is a slim ring fixed with two set screws to the back of the pump. These two items are apparently not a normal fixture.
I am attaching a picture showing the part with the fan blades. I would be most grateful for any guidanceor advice as to whether this is actually a standard part and if so what its purpose is.
IMG_1414 (003).JPG

Re: Dynamo - water pump interface

Posted: Mon Nov 04, 2019 4:24 pm
by Stan Thomas
I'm not too familiar with your specific engine - but I can tell you the "fan" on the end of your dynamo looks to be some sort of home-brewed concoction.

So first question - are you a Club Member, because there is a specific Model Registrar for your car. Has he not been able to help you?

Re: Dynamo - water pump interface

Posted: Mon Nov 04, 2019 6:35 pm
by CZimm
Hi Stan,
thanks for your reply.
Yes, I am a member (have probably been for more than 20 years or so !
I shall be looking out for any observations from the model registrar!

Re: Dynamo - water pump interface

Posted: Mon Nov 04, 2019 8:42 pm
by qantasqf1
I agree with Stan and although I may be missing something here this seems to be an axial flow type cooling fan for the dynamo. God knows why it was fitted because the dynamo pulley piggybacks its own centrifugal type cooling fan which operates by drawing air from the rear of the dynamo through the openings of the rear bearing housing and pumping it through the internals and discharging it immediately behind the pulley itself. Unless the front cooling fan is missing (unlikely, since it’s cast with the pulley itself as far as I know) then there seems to be no point in this arrangement. The angle of this mystery fan’s blades will certainly pump air forward through the dynamo, but why was it considered necessary? Answers on the back of a postcard and sent to the usual address.

Re: Dynamo - water pump interface

Posted: Tue Nov 05, 2019 10:08 am
by Stan Thomas
I follow your reasoning Steve as the spurious fan (*) is designed to promote axial flow - but which most would be lost as the fan is not ducted.

So let's return to Christopher's original problem. Firstly of course engines don't have water "pumps" as such - they are impellers which draw water in at the central axis and centrifuge it out to promote flow, which means to work efficiently, there must be as little gap between the impeller and the casing as possible.

Errosion of the castings over the years therefore reduces efficiency, for which one remedy is to find and modify a larger impeller and machine it to fit closer in the original casing.

Not quite sure what Christopher means when he says he's had a water pump made - is it correct for the car?

I know Marcel has castings made - but I don't know if his range includes a water pump as such for your specific engine. Could you post a picture of the pump you had made?


P.S. (*) The spurious fan supports my theory of old cars - It's not the car at fault, its the bl**dy "expert" who had it before you!

Re: Dynamo - water pump interface

Posted: Tue Nov 05, 2019 12:26 pm
by Marcel Renshaw
I can confirm that the replacement pump is one made by me and supplied by Derek Sleigh.
I was confused by the additional fan on the dynamo. Having seen a good number of 15 dynamos and water pumps over recent years it was the first one.
I have checked the fit of replacement pump on a dynamo and there isn’t a fit issue so was unsure why an additional piece was added to the old pump.
The addition of a fan to draw air through the pump body holes seems of little use and even detrimental should the carbon bush develop a leak as it would draw water through the electrics of the dynamo.

Re: Dynamo

Posted: Sat Nov 09, 2019 9:27 pm
by JT7196
Hi this Dynamo does look a bit strange, as there appears to be no provision for wiring connections , and the whole back end of this Dynamo looks very different to the LA11 one , I do have a Dynamo with an original Pump fitted, but it is for an LA 11,
but no doubt one of Marcel’s Water Pumps could easily be modified to fit .
This would only entail changing the position of the alignment Dowels.

Cheers Alm😊😊

Re: Dynamo - water pump interface

Posted: Sun Nov 10, 2019 7:52 am
by Marcel Renshaw
The wiring connection is the blackish coloured Bakelite piece behind the spring. It looks correct for a Daimler 15. I just can't think why someone would add a fan.