6V Dynamator - first hand experiences...

[Ian Williams]

So as at last we at last seem to be getting some honest answers I will nail my colours to the cross, you could accuse me of having an axe to grind well maybe I have. I had dealings with Accuspark about four years ago, their customer service then was appalling to the point of being quite rude, sadly not uncommon there days! I have experience of their electronic distributers and found no real advantage over a perfectly sound original, in my experience the claimed improvements here are true but only over a worn unit, the build quality is not as good as Lucas and I wonder how well they will work after 20 or 30,000 miles. I have no experience of the Dynamator as I have stated I see no real point to the unit, I stick with 6v and run late model dynamos, they are plentiful and easy to rebuild, most problems I encounter when doing so appear to be bearings, brushes and insulators, unless that is I encounter one where someone has tried to seriously push the charge rate up. I guess the Alternators will help with Battery life, however in most cases excessively short battery life is more to do with the owner rather than the dynamo, you must keep your charge rate low and use the summer winter switch appropriately, you must also keep your battery full charged when not using the car. I agree that back in the 60's and 70's many owners would have loved an alternator and bright 36w headlights bulbs, but today that is irrelevant, almost nobody drives long distances at night and those that do have access to LED lamps which cure the load deficiency of the std 6v system. Accuse me of being a purest maybe, I prefer to see it as a voice of reason...if it ain't broke don't fix it, and if you want modern conveniences don't buy a vintage car.

[squeak]

 I guess the Alternators will help with Battery life, however in most cases excessively short battery life is more to do with the owner rather than the dynamo, you must keep your charge rate low and use the summer winter switch appropriately, you must also keep your battery full charged when not using the car.

I run 8 batteries here and am plagued with short battery life. Not afraid of long trips (recent 6000 miles in UK) but most are shorter hops, and long periods of idleness like the mower. It would be nice to keep the charge near the top without shuffling the charger around the various sheds. I have never liked the look of a conventional belt drive alternator added on, so the Dynamator 6 volt gets a tick from me, if only my wallet were not glued to my trousers.  cheers  Russell

[Ian Williams]

Not sure in your case that an alternator will solve the problem Russell, probably a better investment is few maintenance chargers, they will soon pay for themselves in reducing the number of batteries you buy, and they are a dam sight cheaper than a dynamator for each car!....... either that or use your cars a bit more often

[squeak]

I hear your advice Ian, still tugging at the wallet

[Ian Williams]

Careful you will tear your trousers!

[Stuart Giles]

Some weeks ago, Ruairidh sent me a pair of the supplied dynamator gears and asked me to have a look at them and comment. So this is what I found with the main drive gear:

I Started by checking the Outer and root Diameters of an Austin and Dynamator gear  -this is called the addendum and dedendum in gearspeak –which I will try to minimise in the rest of this screed. The dimensions are within a couple of thou’ on both, so no issue there. The Helix angle is the same on both gears too.

IMG_3197 
However, when the dynamator gear was meshed with a good factory camshaft gear it could be seen that the camshaft gear was being ‘wiped’ by the top portion of the dynamator gear teeth as opposed to the Austin dynamo gear where the main contact was on the flank of the teeth as would be expected.

After seeing this I ‘printed’ each gear by rolling them along a fresh piece of Plasticine. This produces a ‘rack form’ i.e. straight sided tooth form in the modelling clay as the rolls across. It’s a good ‘quick and dirty’ way of seeing something called the pressure angle of a gear without needing to use sophisticated measuring equipment. The pressure angle of any gears in mesh with each other must match exactly for smooth running and reliability. It’s not easy to see in the photo here, but the angles formed (the pressure angle) are not the same between the Austin and dynamator gears.

IMG_3202 

I didn't have a really good distributor gear to check the mesh of the dynamator distributor drive against. But from the wear pattern on the gear Ruairidh supplied it would appear to also have an issue with the pressure angle.

[Ruairidh Dunford]

Thank you for taking time to do this Stuart.

[Colin Reed]

Hi Ruairidh & stuart,
                
Now that is the way to help the manufacturer correct a problem,
just plain facts no need to lose the plot .

Colin NZ

[Bob Culver]

Hi Stuart

I take it the pressure angle is less so the teeth are more vertical and the top edge digs in?  I dunno if ordinary practice applies to skew gears but perhaps they assumed Sevens belonged to the 14 deg era? Tinkering with blue would presumably reveal. But how do you judge angle from such a shallow clay impression? or is it an illusion? Curious they got the angle so wrong yet backlash presumably OK.
It would ruin the gears but presumably one of each faced flush would enable the teeth to be compared shoulder to shoulder..
Has it been established what made of?
You would have expected the maker to have tried  meshing with blue!

[Stuart Giles]

Hi Bob,
          Yes, the teeth on the dynamator gear are at a steeper angle.

regarding my measurements, of course the quick and dirty method I described isn't a substitute for a full set of DP gear tooth gauges or the complicated multiple  vernier measuring device I saw being used when I was an apprentice.  Looking at a gear I can't immediately tell if it has a  20° or a 14.5° pressure angle, but if printing a known pressure angle gear, and then the unknown gear, There will be a different impression if the pressure angles differ, this can be seen even with the shallow print left by small DP number gears. This was what happened with the factory and Dynamator gears; unfortunately, it doesn't look so obvious  in the photo I put up as it did in "real life" in my workshop.