E3H dynamo

[raindodger]

Mornin' Gents.
I have a very low output from my dynamo.  The brushes are good, the com is clean, the field coil shows 2.5ohms with no shorts to frame and the armature has been 'growled.  I have bridged D & F in the usual way and connected the meter from the bridge to the frame.  I've also flashed the field.  But when I spin it at 1200rpm (in the right direction) it will only generate 4volts.
What am I doing wrong?
I seek wisdom from your goodselves.
raindodger.

[Triton Thrasher]

I think I'd spin it faster, just to see.

[raindodger]

Hello, Tritonthrasher.
Thanks for the suggestion.  I tried it this afternoon, spinning the shaft at various speeds up to 3000 rpm.
More speed does indeed give me more volts, I measured 13 volts at 3000 and a current of 7amps. However, unless I ride permanently in second gear I'll never charge the battery.  Lucas recon that max output should be available at 12-1500rpm, and the cutout should pull in at a little over 1000.
I think the unit is shot!!!
raindodger.

[alanp]

I don't quite understand the 'max output at 1200/1500rpm'. Are they talking engine revs or dynamo revs? Has anyone checked the number of teeth on the timing case gears and drive ratio to the dynamo to compare the revs you see on the rev counter with the actual dynamo revs? If it's engine revs, that's like saying you get full output at tickover which no one I know has ever seen and must be a wicked rumour to confuse us simple folk. I must be missing something here. I'm running the dynamo drive with a 20% overspeed than standard and a DVR voltage regulator to ensure I'm charging at town speeds with the lights on. I have a suspicion that there's 'nowt much wrong' with raindodger's dynamo.
Experts please jump in.
Alan

[Triton Thrasher]

So at what rpm does it do 7 volts?

That's what you need in a 6 volt system.  Try wiring the six volt regulator and battery in and see how it performs.

[BSA_54A10]

7 Amps * 13 Volts = 91 Watts and that is exactly what it is suppose to put out.
Sounds like it is a perfectly good 6 Volt unit to me.
You can get 12 Volts from a 6 Volt unit but you need to spin it faster  to get double the Volts out of it.
Are you running 6 V or 12 V ?

[raindodger]

Hello, Gents.  I've just carried out a more comprehensive test and here are the results.

Load resistance    1.8ohms
Dynomo speed      3000rpm
Volts out             4.1
Amps out             6.8

Load resistance     3.2ohms
Dynamo speed       3000rpm
Volts out              7.0
Amps out              4.0

I'm getting about 28watts from this thing, should be 40watts.  There is also evidence of burning on the com and the voltmeter needle vibrates so the DC is not smooth.  In spite of the growler test being OK? I think the armature is US.

raindodger

[Triton Thrasher]

Has the commutator been skimmed, undercut  and cleaned?

[trevinoz]

Raindodger,
                               Is the armature an original wind or a rewind?
If a rewind has the comm connection 1 segment out or the number of windings on each coil not the same, you will get reduced output.
I have one of these on the bench at the moment so I will do a load test later in the morning.
The E3H has a 13 tooth sprocket and the E3L has 11 thus it will be driven slower.
 Trev.

[fido]

So at what rpm does it do 7 volts?

That's what you need in a 6 volt system.  Try wiring the six volt regulator and battery in and see how it performs.

It has not been stated if the voltage readings were taken under load or not. If they were no load readings between the frame and shorted F & D wires then a reading of 7 volts would certainly not be enough.

[Triton Thrasher]

7V would be normal at something under 2,000 rpm, I guess.

Sometimes I have more faith in trying the whole system out on the bike, than fiddling with cheap multimeters and interpreting the results.

[raindodger]

Evenin' Gents.  Repeated the load tests with the same results.  As it's the wrong dynamo for the bike I don't feel inclined to spend money on it.  I'll search for an E3L which would be correct and also have larger 'cojones'.  Thank you all for your comments and advice.
raindodger

[trevinoz]

Just for interest's sake, I ran the E3H at 2500 revs with a battery and headlight connected for load.
4.8 Amps at 7 Volts but that was all that the load was requiring.
At around 2000 revs the light reached maximum intensity and the regulator took charge of the output.
The E3H was only used until 1948.
 Trev.

[raindodger]

Afternoon Gents.  Picked up a E3L at a jumble last weekend, Not pretty, come corrosion but all there.  Blew out the spider's webs and dust and it motored well on 6volts.  I know that doesn't prove anything so I set up the same test rig as before.
Load resistance                  1.3ohms
Dynamo speed                   3000rpm
Voltage out                        7.2
Amps out                            8.4
Looks like I found a good unit for very little money.  All it needs now is a good clean, new brushes and bearings and I'll be motoring!!
Thanks for all the advice and comments.
raindodger