Tiny Tim Tank Battery Charging Unit

Hi Peter,

I had a look at mine last night. It's difficult to be 100% sure what's going on with so many dirty wires crammed in!

I think mine is broadly the same as the diagram you posted above. However I also have the 'extra' wire...





Starting from the +ve terminal I have a wire to the ammeter. From the same terminal in the ammeter there is a connection to one side if the starting switch. The other side of the starting switch goes into the casing to the starting coil 'S' on the diagram. This is a cable with a brown tag. There is a second almost identical brown cable which comes back out of the casing and connects to a terminal on the mounting screw if the starting switch. I can see this goes into the coils in the casing. I think this is the wire labelled 'F' on the diagram that goes to earth. I think the mounting screw on the switch is just a convenient place to connect this to the chassis.

The third cable from the housing is yellow with a yellow tag. It goes into the casing but doesn't connect to anything here, it's just routed through the casing to the voltage cutout/regulator. This is the cable labelled 'B' and the yellow tag says 'Batt' on mine.

Where we deviate from the diagram is the ignition cable, it looks like the military variant has a different voltage regulator/cutout with just two connections 'gen' and 'batt'. The ignition is connected to the +ve connection on the fuel pump.

Hope this helps!

Also mine has 3 capacitors, the condenser cap which I think is the one you want the value for has no text/value written on it. I don't have anything to measure it. I suspect it's not that important though and certainly won't be the cause of your voltage output issue.

Hi, Will I must apologise. I have only just found out how to view your reply in page 2. All the info and the photos will be of great help, when I’ve
Compared your wiring to mine. Yours is in very good condition compared with mine. Their condition allows no letter to be seen!
I can now have a chance of understanding Where the wires should go.
Many thanks for your great help
Peter76.

Hi, Will, yesterday saw me rewiring the connections under the amp meter housing to the same layout as your information and photos.
I connected starter leads to a vehicle and the amp meter showed positive charge going back to the vehicle battery. Success !.
A test meter showed 17 volts at 7 amps with moderate revs at the vehicle battery.
When removing the starter leads, the gen still ran on with its own generated spark plug supply. Interesting, it had to be stopped by removing the spark plug cap.
It must show that your wiring is correct. With gratefull thanks for your invaluable assistance in solving and proving the correct circuitry.
Still not sure when the voltage cutout will control the 17 volt charge. Perhaps, this will show when I increase the engine revs to produce more amperage? One or two things to find out yet.
Regards,
Peter76.

Your next issue is not to increase the revs, 17 volts is way to high, 14 volts is max if you don,t want the battery to boil.

Maryalice

Many thanks, Maryalice for your knowledge. I now have a route to the complete answer.
I will build a switch in, to kill the coil supply to stop the engine. Also one or two refinements.
Best Regards,
Peter 76.

Hey Peter,

Glad you got it working! I agree with Maryalice you are definitely getting to many volts out so maybe dropping the RPMs should get you to where you need to be.

I'm still working on mine, I have replaced the wiring where the insulation had gone and fitted some new brushes but when I press the starting button it only spins very slowly. I am wondering if one or more coils is bad. I hope not!

I think my next step will be to try to get the engine running and see if I can start it with a pull cord....

Hi, Wii and MaryAlice, great to have all your guidance. I have just ran the unit connected to my car battery. You were spot on with excessive revs, have now reduced by the carb wheel and now have a reading of 13.8 to 14.02. Seems quite happy at those revs when under load!
I can perhaps now turn my attention to building on a loading ( lights or something) for display, also, it is normal to restore to factory appearance or leave as found with MOD markings and rust?
Will, I hope you have success in using the rope starter. I have tried this and had instant starting. I was surprised how quickly the carb is primed for starting after turning on the fuel supply. My compression is 43psi, do you think yours is a lot higher?
I recently completed restoring A complete 2CV engine and gearbox complete with pedals for display. Would this be acceptable to show this
on this website, if so, under which heading should it be seen.
Best Regards,
Peter 76.

Re finish - your choice oily rag or full on bling ! It's your project.
Re 2CV - if you must      A few of us have posted stationary steam engines. The Shed would be my preference.

Hey Peter,

I always think engines look best as close to original as possible, I would be inclined to keep the Military markings and just give it a good clean for display.

I would certainly be interested to see the work you've done on the 2CV engine and gearbox. Probably stick it in the shed as Woodsman suggested.

Some progress today:

I can start it and using a chord and once it's running it keeps going. It's generating electricity fine.  I think I have two issues to solve.

1.  It still won't turn over on the starter button. I can see it's trying but it just won't spin.  I suspect the replacement brushes I have fitted may not be suitable or that the starting winding may be faulty.

2. The revs and consequently the voltage are too high.  If I reduce them using the adjustment wheel they go down to a point and then the engine stalls.  I suspect the timing is out.  I can't find any timing markers - Peter did you find any timing markers on yours?

Here's a brief video!  https://www.youtube.com/shorts/ieU_HNCbbjk?si=UvIXnuzP4DF5vNvz

Hi, many thanks for all your posts, it’s great to have all your feedbacks.
I have decided to just clean the Tiny Tim and leave the stencils and enjoy the patina of a WW11 item. I have enjoyed this project and would
consider acquiring another unit, even possibly a 24 volt model.
Will, you mentioned not being able to reduce the output voltage down to assume a useable voltage. Is there any possibility that you may have
A 24volt model. I think they were made with 6, 12, and24 volt outputs.
Will, regards, timing marks. I only found a fixed timing system by operating the cam which was positioned on the driven shaft by a single
Woodruff Key ( very small) The only adjustment I found was points gap.
An acquaintance of mine has told me that the top tray over the gen was to project the unit from damage when the crew entered.
Thankyou for the video.
Regards,
Peter76.

AHH yes now I look again it seems the adjustment is limited to the points gap.

I made some good progress at the weekend, I swapped out the brushes expecting it to make no difference at all. Previously the generator didn't have the power to turn the engine over on the start button, now it spins perfectly. Also the spark is much stronger.
I have not yet run it on the engine as I plan to now re-assemble everything and fit a proper fuel tank.  I'm pretty confident changing the brushes will solve the issue where the engine would only run at high rpm.

I never expected brushes would be so crucial, the only difference I can see in the ones that are no good is they are manufactured in China. I suspect the material used is sub standard.

Hi, very interesting regarding the brushes, waiting to hear the result after the rebuild !
Regards,
Peter76.

Had another look at the Tiny Tim yesterday,

Looking at the points; on mine there is some adjustment. So the fixed contact can be moved in and out to set the gap and the points are fixed to a plate that can be rotated to adjust the timing. I haven't measured it but it looks like it gives about 15 - 25 degrees of adjustment. I took a bit of wire to feel where the piston is whilst rotating the engine. It seems TDC is where the rope pull slot is at the top most position in its rotation.

I set the points to TDC and it runs well but some occasional pops and bangs so I think it needs a little more advance. I had a good search online but wasn't able to find any instructions/ specifications so I think I'll experiment with it once I have a proper fuel tank rigged up.

I'm not sure I'm happy with the method of adjusting RPM by either leaning out or enriching the mix. When I lean it out the engine is not running smoothly at 14.5v which is what I am aiming for. The other way it has to be very rich to get the voltage down. I wonder whether in a tank this was not a problem as they may have fed the output power into the tanks voltage regulator. I'm considering rewiring it with a 12v regulator from something else. But we will see.

Just waiting for some bits to arrive to build a fuel system. At the moment I'm fuelling it from an old water bottle!

Hi, Will, very interesting to hear your progress with timing and results. It seems to run a little rich on the plug but still smooth.
I don’t have much idea what my two connection voltage regulator is supposed to regulate. What ever output voltage I set with the carb adjustment, it does not energise the points to cut of the charge.
If of any help, I have a spare mower fuel tank you can have.
Peter76.

Hi Peter,

Thanks for the offer of the fuel tank! I have a fuel tank that I picked up from eBay last week. I'm just waiting for some connections to arrive to do the plumbing....

On the subject of voltage regulation I had a good look into what the little box with the relay is actually doing. So it turns out it's not a regulator but actually just a device to prevent reverse current... So the way that it works is when the generator is running current flows through the relay coil to earth which causes the contacts to close connecting the output of the generator to the external load (the battery you are charging). When the generator is not running the contacts open disconnecting the generator from the battery. So there is no voltage regulation provided, it seems to adjust the output voltage the only solution without modification of the generator is to adjust the rpms. I guess originally the unit would be 'factory tuned' to run at the correct (ish) speed!

Without this reverse current relay arrangement when the generator is stopped current would flow back from the battery through the coils of the generator and to ground which would quickly discharge the battery. Interestingly I found that there were two versions of this unit used on the 'Tiny Tim' generators. In the tank charging variants the reverse current relay works as I describe above. Once the generator is started it runs until someone stops it, I suppose because you want to charge the tank's batteries but also keep communication equipment, lights etc running.

Some versions of the 'Tiny Tim' were designed only for charging batteries and these have a unit with a third connection. Inside is an additional second relay which would cut the ignition to the engine once the battery was fully charged to prevent over-charging of batteries. I think this operated on the a coil between the battery output and ground. As the battery got above a certain voltage the relay would close and ground the ignition coil causing the engine to stop.

Another interesting fact, if you have a tank battery generating set without a fuel tank the chances are that it never had one because most allied tanks had petrol engines and the generator would share the tanks main fuel tank.

Maryalice

Yes! Mine came with the (I assume) original 12v SU fuel pump to supply fuel from the tank petrol tank to the generator. I'm replacing this with gravity feed but I'll keep the pump in the cupboard somewhere. At the moment it's full of rust and wont go but maybe one day I'll have a go at fixing it.

Hi Will and Maryalice, grateful thanks for your enlightening explanation re the use of the so called two contact regulator on my generator.
It is very interesting to note that there is a three contact unit for auto shut down. This info will be of great help should I came across another unit to restore.
My SU pump pulls well out of a plastic fuel container to run the generator. I have not replied until now as your notification email went straight to junk account this time? I only found it when delating all the Casino rubbish.
I am in the process of making an 8 bulb lighting board to use the output generated. I will soon see if the output will power 8 no 21watt 12 volt bulbs. I know of a Sherman Tank owner who has four Tiny Tim units, one sill in a crate, but as yet have not had chance to visit him.
Many thanks,
Peter76.

Hi Will and Maryalice, grateful thanks for your enlightening explanation re the use of the so called two contact regulator on my generator.
It is very interesting to note that there is a three contact unit for auto shut down. This info will be of great help should I came across another unit to restore.
My SU pump pulls well out of a plastic fuel container to run the generator. I have not replied until now as your notification email went straight to junk account this time? I only found it when delating all the Casino rubbish.
I am in the process of making an 8 bulb lighting board to use the output generated. I will soon see if the output will power 8 no 21watt 12 volt bulbs. I know of a Sherman Tank owner who has four Tiny Tim units, one sill in a crate, but as yet have not had chance to visit him.
Many thanks,
Peter76.

Have a look at Green Spark Plug Co. They have them in stock and alternatives.

Hi, Will and Maryalice,  thank you for your posts. I have finished making the test lighting load board, photo enclosed hopefully!.
Very satisfying to see an output being seen. I will now be able to construct a better appearance, perhaps for showing. I hope to run it again
Today and adjust the speed and check the output. Have to wait until the neighbours are up.

Regards to all.
Peter76.