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Re: Third brush/ Summer & winter? mileometer

Nick,

"I believe the offending link connects the field windings with the 3rd brush, removing the resistance in the half and full charge positions..? presumably this has a similar effect to whacking the 3rd brush over to get maximum charge out of the dynamo, but only when needed (when cleverly fitted with a switch).
My question is simple... It seems like a good idea and is clearly widespread practice*, but in the long term, is it harming the dynamo?"

The Austin Seven electric system is fairly basic- the Dynamo charge rate is set by positioning the third brush and checking the output.
The output is sent via the Cutout which is a simple switch to connect the dynamo to the Battery when the charge rate is sufficient to feed the Battery.
The Summer half charge (in the early Dynamo at least) is a resistance coil of wire inside the Dynamo which is inserted into the Dynamo feed to the Battery to soak up some of the Dynamo charge and not over supply (you hope) the Battery, the same result is given by switching on the Lamps.
It has no effect on the Dynamo charge rate which as noted above is set by moving the third brush, it is just a rather crude attempt to not overcharge the Battery.

Connecting the two terminals together on the early coil motor Dynamo will not harm the Dynamo but the Battery may be overcharged, which is another problem.

Cheers, Tony.

Location: Melbourne. Victoria, Australia.

Re: Third brush/ Summer & winter? mileometer

Thanks to you all for those pointers

Re: Third brush/ Summer & winter? mileometer

As Nick has said 6 amps max or even less.
Any more it will fail in the longer term for sure.

Nick Turley

Location: The Centre of the Universe

Re: Third brush/ Summer & winter? mileometer

This may or may not be relevant but Ian McGowan kindly explained to me how to fit a resistor to make the summer/winter charging rates work in this thread:

http://pub25.bravenet.com/forum/static/show.php?usernum=2099944454&frmid=5&msgid=1006443&cmd=show

Complete success and easy even for the electrically challenged!

Michael

Re: Third brush/ Summer & winter? mileometer

Hi Nick L

The added switch is simply doing what the summer/winter switch does normally; shorts out the field resistor in the Winter position and with lamps on. Often used when a
simplified substitute main switch without the S/W function is fitted.
The dynamo output (as distinct from battery charge indicated by ammeter) is vaguely the same lights on or off. The vital thing is that not excessive. The lights off ammeter charge current is the guide.

Location: Auckland, NZ

Re: Third brush/ Summer & winter? mileometer

Just to clarify, the summer resistor does not reduce output by absorbing it but by reducing the field current, the strength of the magnet field, and hence the output. Later voltage regulators do the same but a larger resistor is switched in and out at high speed and at varied interval to maintain desired output volts and hence avoid overcharging.
Using the summer facility to reduce charge reduces wear of the timing gears, brushes, bulbs, and saves a few mousepower.

Despite all, Ford 8s made do without.

Location: Auckland, NZ

Re: Third brush/ Summer & winter? mileometer

I knew I would get it wrong- that will teach me to meddle in electrics

Location: Melbourne. Victoria, Australia.

Re: Third brush/ Summer & winter? mileometer

Hi David,

Reading through your initial comment again - I suggest you move the third brush the full amount each way, then test. (You suggestted that you planned to move the third brush 'a little').

When I switch to summer charge, it isn't an immediate change. I've never timed it, but I would guess it is around 20 seconds to settle at a lower charge rate. I may be wrong, but it seems like a long time - can't imagine what the reason for this would be.

Good luck,
Colin

Location: Towcester

Re: Third brush/ Summer & winter? mileometer

I have moved the third brush & the output is now on the scale at 6-8amps on winter charge. I will make up & put a resistor wire between the output terminals on the dynamo & see if the summer charge setting then works as well!
Even more to the point I think that my A/R lever is operating on the wrong side of the distributor....so when I "advance" I am in fact retarding! This could explain why advancing the ignition has no positive effect on progress! The car starts really easily & runs smoothly so I don't think the "natural" setting is far out. I will disconnect the lever & move the distributor by hand & see how it affects the revs! Then move the clamp to the correct (outside) of the distributor & try not to disturb too much!
Watch this space.
I want to get the RK running properly before I start to resurrect the 1932 AG tourer which arrives shortly from USA & hasn't run "for a hell of a long time" according to the previous keeper!

Re: Third brush/ Summer & winter? mileometer

My RK has the adv/ret rod on the inside. The lever on the end of the steering column of on the other side too so it works correctly. I think you'll need to turn the clamp plate the other way up to get it to the outside.

Re: Third brush/ Summer & winter? mileometer

If the engine becomes delightfully smooth as "advanced", then it is likely being retarded! A retarded engine accelerates sluggishly as revs rise, and sounds flat.
There is vast reading available under Search for advance.
In Jan 2016 an interesting (and confusing) discussion about lever placement and results under Gas Column Control Crank and Rod Dimensions.
Judge advance by actual performance and not noise. Use no more advance than necessary.
With the levers at right angles the total range of the hand lever is 25 crank degrees or so, therefore little movement of required, esp once underway.

Location: Auckland, NZ

Re: Third brush/ Summer & winter? mileometer

Well. Remind me not to ask questions about my engine. On Tuesday I will be mostly buying a new battery. Dead as a dodo... Still, it is somewhere between 10 and 15 years old...

Location: Colchester

Re: Third brush/ Summer & winter? mileometer

Clamp plate reversed & all works as it should....no dramatic increase in urge nor decrease in noise(I am pretty deaf though!) however things do seem a bit smoother. More miles under the belt I think is the real answer.
What a helpful lot you are! Pity I cannot locate a group relatively close to Stratford upon Avon (apart from a 750MC group who meet this side of Birmingham)
Regards
David

Re: Third brush/ Summer & winter? mileometer

It is only in recent times that I have seen Seven owner handbooks. Mention of advance on the Forum prompted me to check the instructions. Drivers are advised to almost fully advance to start (including hand crank!) and to drive with full advance and only retard when it rumbles! All pretty vague to me and certainly to anyone completely unfamiliar. It is curious that such a huge control range is provided when use of so little is implied.
The low comp auto distributors retarded 6 crank deg, corres about ¼ range of manual control. (Later h.c distributor retarded 16 deg but that head not fitted to ordinary manual advance cars).
Hand advance or override is an intriguing toy. Can often shift advance drastically and only the noise and crank stress changes.

The gear changing advice also curious. A quite spirited 8 in 1st and 18 in 2nd, but allowed to drop to 18 mph in top (by which speed on any serious hill 3rd best omitted!)

Location: Auckland, NZ

Re: Third brush/ Summer & winter? mileometer

David.

I have recent experiance of Speedograph. Be warned they can not fully overhaul your speedo. They will not rechrome.

With respect to the high charge. I ran my RL at that level of charge for 15 years. The cut out did eventually stick and I needed a new one. This was not neccassarily high charge related.

But do not be quite so concerned about the scare stories, my dynamo is still fighting fit.

Location: not north wales any more

Re: Third brush/ Summer & winter? mileometer

Bob.
That might explain why the handwritten instructions on "how to start the car" said "move lever to full retard" - which would have been full advance....
Whatever - it starts & runs pretty nicely now. I think it was easier to reverse the plate than to try & alter the lever at the base of the column. Mind you the plate was dished, but no suggestion as to whether the concave dish went under the distributor or on to the dynamo housing.... I fitted it so the lever was engine cover side as per Mills photo.
I will graphite grease the speedo cable & if I feel strong enough have a look at the (no doubt solid) grease in the casing. My old TR3A actually snapped the rev counter cable as the instrument went solid (after about 2000 rpm!)
David