Pat,
I think you have an advantage over the rest of us in that you have all the
pieces away from the car and presumably won't have to take too much apart to
run an experiment with your new impellor(s). I have one of Bill T's new ones
but haven't got around to installing it in my 'L' yet!
To determine which of the impellors is going to do the best job for you, you
need to decide which of the cases you are going to use and then build a
simple test rig. There are many variables that can enter into the final
equation but at the moment the only thing you're really interested in is
'flow'.
You will need to count the teeth on the the crankshaft drive gear for the
pump and the teeth on the pump shaft gear. From those two numbers you can
calculate the ratio between the crankshaft and water pump speeds. You'll
probably want to run your test at several different speeds so that you can
draw some pump curves so you'll need different size pulleys for your pump
and/or drive motor. (Do you have any Meccano?) You'll need a small electric
motor, hose, clips, a couple of big buckets and a stop-watch.
Build your test rig so that you have at least a foot of positive pressure on
the inlet side and about six feet on the discharge to simulate some
resistance. Its not important to be exact so long as its the same for each
test. Assemble the pump, fill the inlet bucket with water and prime the
system.
When you're sure you have no leaks, empty the discharge bucket and run the
pump for a set period of time. Its a lot easier to flip a switch on and off
than than to try to stop the pump when the water level reaches a mark.
Measure the volume in the bucket and repeat two or three times. Average the
volume, convert to GPM (or litres per second if you must), change the pump
speed and do it all again. If you do everything the same way each time, the
results you get will be comparable and you won't need to worry about the
fact that the inlet side pressure is going down as you lower the level in
the bucket. If that is a major concern then you can always use a cistern
with a ball float to control the level. When you've run your three sets of
tests and plotted the flow graphs we can discuss your findings!
Cheers, "Bob".
----------
>From: Patrick Mullen <pmullen@direct.ca>
>To: Bill707@aol.com, "Kahler, Jack" <MGJack@aol.com>
>Cc: NA-MMM <mg-mmm@autox.team.net>
>Subject: Re: Water Pump Impeller & Cooling generally
>Date: Thu, Feb 10, 2000, 6:56 PM
>
> Jack, Bill:
>
> Many thanx indeed for the beautiful impeller which has just been
> delivered by Canada Post to our house - I didn't even need to collect it
> from our friendly "Letter Carrier" just over the border. I appreciate
> the gift very much.
>
> I hope to test it in the NB when I have it running, possibly versus an
> original worn one AND against the one in a Barry Walker jobber pump I
> bought 20 years ago. The challenge will be to design an experiment which
> shows up the differences.
> I have done a lot of thinking about cooling MMM engines but have had no
> practical experience (at least not since I blew a cylinder head gasket
> in my water pump-less M-type in a traffic jam for the 1951 Farnborough
> Air Show).
>
> How do I test it under real life conditions when the ambient temperature
> will probably change with the time of day while I change the impeller?
> What if the three impellers are of slightly different blade widths? (I
> wd prefer to keep the same pump body for all 3 impellers for the
> experiment).
>
> What variables wd be meaningful to measure?
>
> - Obviously temperature in the header tank is one. This wd probably only
> be meaningful under racing conditions or under arduous conditions such
> as driving foot-on-floor on a midsummer afternoon up several miles of a
> good gradient Interstate Hwy such as the Siskiyou Pass on I5 between
> Oregon and California.
> - I like Pip Bucknell's suggestion of putting a restraint in the hose
> from the cyl head to the header tank (see 1998 Y'book p30). Pip
> suggested this to pressurise slightly the water between the pump and
> the h.tank hose; this in order to reduce the bubbles on the metal
> surfaces in the block & head and hence presumably to increase the heat
> transfer. By measuring this pressure we wd have some idea of the
> efficiencies of the various impellers.
> Any other ideas?
>
> While on the subject of cooling water:
> (a) What about the late Geoff Coles's article in the 1971 Y'book p28
> where he points out that many of the prewar racers blocked off the water
> flow thru the block mainly or fully, and diverted it to flow into the
> core/frost plug in the rear of the cyl head? This is of interest to
> everyone now that we no longer have leaded fuel. I imagine that the
> potassium based fuel additive available in Anzacland and even a cyl head
> with hard inserts for the exhaust valve seat wd perform better with the
> coolest possible water available to the exhaust valve seats - it also
> keeps the bores warmer and hence less likely to wear due to overcooling
> I imagine. Has anyone tried this?
> (b) How about using a (failsafe?) thermostat as Pip's restricter? This
> wd avoid overcooling. Didn't the KN version of the N engine have this?
> Where was it placed?
>
> Comments and advice please, Pip?, Bob Rich?, all gurus? in OZ-UK-NZ-NA
> et al.
>
> Cheers.....Pat
>
>
> Bill707@aol.com wrote:
>>
>> In a message dated 2/2/00 16:10:21, MG Jack writes:
>>
>> << Bill...Will send Pat an impeller tomorrow at no charge. Good test case!
>> Jack >>
>>
>> Pat... we're granting you a "comp" impeller due to your tireless work on the
>> tech articles etc... I havn't seen the ones that Jack has made... they were
>> done on his auto-router, whereas mine were done much more laboriously on a
>> CNC mill. I specified that the hole be 15/16", or some such, but slightly
>> under .5" to allow you to ream to your exact shaft diameter. Also you'll have
>> to provide for your own fixing screw.. I believe I used a 10/32 set screw.
>> Good luck!
>> Bill
>>
>> -----------------
>> Forwarded Message:
>>
>> Subj: Re: P/N gears and water impellers
>> Date: Wednesday, February 2, 2000 16:10:21
>> From: MG Jack
>> To: Bill 707
>>
>> Bill...Will send Pat an impeller tomorrow at no charge. Good test case!
>>
>> Jack
>
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