Two dynamos?

Post by **Sidney'61** » Thu Mar 12, 2009 8:19 pm

Hi,
Just a though, not that I plan this myself.
As alternators seem to be apparently so unreliable would a possible upgrade be simply to add an extra dynamo?
Of course a different fanbelt would need to be devised but throretically two dynamos would give twice as much power and it should work, anyone tried it?

Post by **Lukey** » Thu Mar 12, 2009 8:40 pm

It sounds mad and overly complicated. Why are alternators unreliable? Can't you buy them brand new for £30 anyway?

Post by **alex_holden** » Thu Mar 12, 2009 8:41 pm

You'd still have the basic dynamo problem, which is that they don't put out any power at tickover (eg. sat in a traffic queue).

Post by **PSL184** » Thu Mar 12, 2009 8:42 pm

The only problem with the dynamo is that at low speed (idle) the charge rate can fall off sufficiently to give less than the battery may be consuming (with lights, heater on etc). But, the battery will only take a certain charge (hence the regulator) So, 2 dynamos will only provide the same charge as 1 dynamo which kinda defeats the point....

Post by **Sidney'61** » Thu Mar 12, 2009 9:33 pm

Yes I see your points, never mind then.

.
I'll stick to just letting you clever people come up with the ideas

Post by **bmcecosse** » Fri Mar 13, 2009 9:55 am

Just fit an alternator - they are NOT unreliable ! I buy them for £1 at autojumbles - and put them to work on the car. If they work - that's fine (and they all have so far) and the one that comes off the car (and is therefore know to be good) goes in the boot as the spare. So far in many years Minor, Mini and TR7 motoring I haven't had any alternator problems ! I did have a loose connection on a wire going to the alternator last year - but that was easily crimped up at the roadside and on the way again in 5 minutes. Unfortunately it was pouring with rain at the time !

Post by **leyther8008** » Fri Mar 13, 2009 2:47 pm

A good idea in principle but the output would be a nightmare to regulate, two control boxes possbly? I did hear once that the military vehicles had a heavy duty generator fitted as standard, and as they once took travellers it might be worth speaking to the relevant expert on the military vehicles bit.

Post by **tortron** » Sat Mar 14, 2009 10:47 am

two dynamos - two regulators?
second battery in the boot?

Post by **Alec** » Sun Mar 15, 2009 7:55 am

Hello Andy,

if you are happier with a dynamo, fine. If you want more capacity then fit a larger dynamo. I'm sure there must be a few floating around second hand, try looking for sixties Jaguar spares for instance.

Alec

Post by **alex_holden** » Sun Mar 15, 2009 8:39 am

Alec wrote:if you are happier with a dynamo, fine. If you want more capacity then fit a larger dynamo. I'm sure there must be a few floating around second hand, try looking for sixties Jaguar spares for instance.

I think you'll also need the regulator box that goes with it. The Minor regulator limits both the charging voltage and the current coming out of the dynamo, so it would limit a bigger dynamo to the same capacity.

Post by **bmcecosse** » Sun Mar 15, 2009 10:05 am

Unless you have the later 3 bobbin regulator - pretty sure it simply operates on volts. This in turn of course drives the amps - if there is much electricity being used around the car (and/or battery is low) then the dynamo cranks out more amps until the battery volts float up to the regulator setting.

Post by **paulhumphries** » Sun Mar 15, 2009 10:17 am

Alec wrote:Hello Andy,

if you are happier with a dynamo, fine. If you want more capacity then fit a larger dynamo. I'm sure there must be a few floating around second hand, try looking for sixties Jaguar spares for instance.

Alec

Look at a dynamo body and you will see some have a small "step" part way along whereas others don't.
The ones without the step are higher output and were fitted mainly to cars with twin headlights. I think they may have been standard fitment to later cars during the overlap period alternators started to be more common.
I've got one I kept off my old Singer Chamois.
NOT a dynamo (modern alternator styles like one) but illustrates the "step"-
http://www.demon-tweeks.co.uk/resources ... RNATOR.jpg

Paul H.

Post by **bmcecosse** » Sun Mar 15, 2009 10:23 am

If feeling wealthy - you can go for this !
http://www.holden.co.uk/displayproduct. ... de=081.200

Post by **Helenginger** » Sun Mar 15, 2009 12:27 pm

Ohhh err.... How to double the value of our moggy in one step!!!

Post by **rayofleamington** » Sun Mar 15, 2009 11:02 pm

back to the original question/s.
The question itself is fairly sound - there are a few (expensive) production cars out there with twin alternator (when >120 amp alternators cost a fortune and needed water cooling etc..). These days bigger alternators have got cheaper.

I completely agree that twin dynamos would not be worth the hassle. As well as the twin regulator issue, you would need to be able to package the 2nd dynamo somewhere it can be driven by the fanbelt. Then you also need to have a long contact length between the belt and the pulley.
An alternator will generally have more than 180 degrees of the pulley in contact with the belt due to the higher torque requirement. A dynamo should have much less load so less to worry about but you still want to aim for >100 degrees around the pulley, and not to reduce the contact angle on the other pulleys. Therefore I'd guess that the belt routing is either going to need a dummy pulley or you'll have a 2nd dynamo in a wierd place.

If you'd think of a 2nd dynamo, it's much less hassle to carry a spare alternator (in the boot next to spare wheel). I'm still kicking myself for not bringing a spare with me on the first LEO. I had been planning to convert the pick up back to dynamo but that's one of those long term jobs that probably won't ever happen..