Scott Generating Set Restoration (Continues)

Connection box wiring, completed.

As autumn has replaced summer with a vengeance and rain being the order of the day, when I have had spare time, I have had to postpone the testing of the alternator/exciter, until I can be assured of dry weather. Electricity and wet weather do not mix well.

I have therefore spent what little time I have had available, to continue with the re-wiring of the connection box and the Allen West circuit breaker. With the circuit breaker mounted onto the connection box using the resilient mounts, I was able to finish the wiring and test some of the functionality.




Connection made to the input and output terminals of the Allen West unit.


There are two lights fitted to the set, a warning light and a dial light. The warning lights indicates the power is being fed to the output, once the "On" button has been operated and is permanently lit all the time the output is energised. The dial light is used to illuminate the meters under the cover on the canopy and is controlled by the switch on the canopy top. The dial light is available whenever the engine is running and is not dependant on the operation of the circuit breaker. This feature is to allow for the correct voltage and frequency to be set, in poor lighting conditions, prior to the output being switched onto the load.

Each bulb is fed from its own 130/10 step down transformer. Both of these transformers are mounted on the connection box, one on the inside with the other, on the outside. During earlier tests one transformer was found to be open circuit. Until I can source a replacement, I have decided to use the one good unit to illuminate the warning light. It is unlikely I will need to view the meters in the dark and I can always confirm voltage is being generated by observing the voltmeter, which is across the input to the set, so not reliant on the output being switch in. The illumination of the warning light is a good indication that all is well with the circuit breaker and also provides a safety reminder.

As I didn't have the correct size of terminals available, I used the original wires, which I treated to a layer of heat shrink, to protect against cracked insulation.




Warning light transformer fitted to the inside of the connection box and re-terminated using the original wires, following an application of heat shrink sleeving. The switch is for the currently unused dial light.


Once the warning light transformer had been fitted, I was able to test its wiring and functionality. Not having 130 vac source available, I tested the transformer in reverse, by applying a 12 vac supply to the connections which feed the bulb and measured the corresponding voltage on the connections on the input side of the transformer. The nominal 12vac supply connection on the output connections generated a open circuit reading of 145.8vac on the input terminals, which is a reasonable result.




Checking the wiring and functionality of the warning light transformer. The two thin black wires are feeding 12vac into the warning light connections while the meter is connected to the circuit breaker output terminals.


Having finished testing, that just left the 8 way plug to be terminated.




Connection box awaiting the connection of the flexible umbilical and 8 way plug.






The finished article, ready to be fitted to the canopy.

To be continued.......

Neil.

Initial Electrical Generation Testing.

With the weather looking reasonable, I took the opportunity to attempt some initial electrical generation tests. As I have mentioned before, this set has never been seen to generate any output whilst in my possession. However I do know that it had, at sometime in the past, been modified so as to be able to produce 240v AC. During my restoration of the set, I believed I had identified the modification, so as to revert it back to standard but had not been able to test if I had been successful.

The exciter generator was to be tested first. I had already performed some basic static tests to prove that there was continuity through the brushes, commutator and the various windings but now it needed to undergo some dynamic testing. This was to ascertain if the generator still retained sufficient residual magnetism to produce the excitation voltage. If there wasn't, the generator would have to be motored to restore the magnetism.

Although the exciter is rated at 200v DC, as it is series wound, it will only produce this level of output when it is presented with a load. Under no load conditions a reading of anywhere around 20 volts may be expected. With the exciter generator output connected to a multi-meter and the engine started, a voltage reading was taken. Fortunately there was an output of approximately 12v, sufficient to proceed to the next phase of testing.



Exciter open circuit output measured at 12 volts, sufficient to prove basic functionality, ready for the next stage.


The next phase was to configure the wiring for the set to operate without the umbilical connector being in place and therefore without the voltage regulator in circuit. As the regulator is a set of tapped resistances with values from 0 ohms to 170 ohms, in series with the field coil, it was a simple job to link out the wiring at the socket, to simulate the lowest resistance setting on the regulator. With the voltmeter connected to the appropriate socket connections for one phase of the alternator output, the set was started up once more. It was with great relief that an output of 145v AC was recorded, which is almost exactly correct for an open circuit measurement.




Link wire loop to bypass regulator and voltmeter connections across output B & C




No load voltage reading of 145v AC across output B & C. An almost perfect reading.


The next test was to check the voltage between output A & C, confusingly a reading in excess of 250v was recorded. Further investigation will be required to understand why this was being produced, as it was believed the 240v modification had been reverted to normal.



The unexpected (unwanted!) over 250v reading across output A & C, further investigation will be required.

Overall a successful day's testing, both the exciter and alternator have been proven to be basically functional. Further investigation will be required to understand the 240 voltage output issue, before a loaded test can be undertaken.

More progress to follow.....

Neil.

Nice work Neil. When you are finished please summarise this thread for Stationary Engine Magazine, I'd love to see it in print.

Good news Neil, sounds like your making progress!

Alan

StuartTurnerSteve wrote:Nice work Neil. When you are finished please summarise this thread for Stationary Engine Magazine, I'd love to see it in print.

wot 'e sed

Thanks all. As Alan said, I'm making progress, albeit rather sporadically and with a number of false starts. The latest issue being the output voltage conundrum. Following on from yesterday's investigations, a repeat of the tests was undertaken, to make certain of the facts and to confirm what each phase was actually producing, in terms of the voltage and frequency.



Phase A - B, confirmed output of 140v AC and 50Hz.




Phase B - C, 140v AC at 50Hz.




Phase C - A, Confirmed an output well in excess of 250v at 50Hz. Presumably it would read 280v. Unfortunately the carburettor ran out fuel before I could change the meter range!


Having confirmed the output on each phase, I was very pleased to see the frequency was almost exactly 50Hz but it also confirmed that the C - A phase was definitely double the other two. Unfortunately I think I will need to remove the alternator from the set and get it onto the bench, to undertake the investigation and hopefully the rectification.

I agree an article for S.E.M. would be a good idea but it would need to wait until I have at least completed the rebuild. Even then it would take some careful reviewing, editing and selective summarising, to produce something usable by the magazine.

Need to finish it first!.......

Neil.

I think it would need to be spread over several issues to do it justice.

Alternator Back on the Bench!

Following on from the initial electrical generation test, I was faced with the issue of the erroneous voltage output on one of the phases. To investigate further I felt it was best to remove the alternator, so any work could be undertaken inside, as wet weather could now be a problem. I had hoped that this level of disassembly would not be necessary for some considerable time, especially as the alternator, less exciter, weighs in at 140 lbs.






A sight I was hoping not to see for a long time, the alternator back on the allotment trolley. Yes, I still owe the wife a replacement, having bent it moving the alternator the first time!




Alternator lifted back onto the bench, all 140 lbs of it.

Having just about avoided a hernia, an inspection of the wiring and its connectivity was undertaken. The field coils are fixed, being bolted to the casing, with the two exciter wires being directly connected to them. It would not seem possible to modify the excitation to vary the output on a single phase. That only leaves the rotating armature and its wiring as a possibility but having examined the armature there is nothing obvious that could be considered as a later modification. Each set of brushes are directly wired back to the output terminations, being wrapped inside the field coil bindings. For the output to have been doubled, two of the phases would have to have been wired together in series but there is no indication of any disturbance of the armature wiring. Testing each armature winding produced very similar results of approximately 1 ohm across each phase. So nothing obvious to indicate any difference in the wiring of the phases.








The brush wiring, all looking very standard. The only possible place where the wiring may have been altered is under the string lacing at the end of the armature but it looks very tidy as compared to the output socket wiring modification.


I don't know if the alternator armature is delta or star configured but the output is not referenced to ground. However when I originally took the alternator wiring apart one output wire had been cut and the output socket pin was connected to the frame and the other leg would have effectively been the output of two of the windings, providing the voltage doubling effect. Having returned this wiring back to standard I believed I had reverted the output back to a standard 130v 3 phase system. Unfortunately the initial tests do not seem to support that theory.





The original wiring, showing the cut output wire and the grounded output socket connection. Now all reverted back to standard, although the output still seems to be incorrect.

I am now left with no option other than put everything back together again and try the alternator on load and see what is produced. I'm not willing to take the wiring apart any further than I already have. If there is a complex modification deep inside the armature windings, it will have to remain as part of the unit's history. As long as the set is able to produce power for demonstration purposes that is all that is needed. I doubt I will ever get the opportunity to test it on a real, Kerrison Predictor fitted, Bofors gun!

Now to put it all back together again.....

Neil.

I am probably barking up the wrong tree, but is it possible there is a short somewhere producing the same effect as the wiring being modified?

Thanks for your suggestion but I don't think so, as I have tested the resistance of each of the phase windings and they all appear to be similar and there is no short to the body of the alternator. However nothing is off limits in terms of possibilities until it is proved otherwise!

Neil.

More Alternator Testing and the Canopy Finally Moves out of the Garden

It has been a while since my last update, in fact much longer than I thought, or wanted it to be. In the last post I left it where I had bench tested the alternator windings but had not identified anything that could be considered unusual or easily identifiable as a modification associated with the voltage change.

As I stated I was left with the only option of putting it all back together again and just live with the results. This was undertaken with the weather providing an opportunity to work outside and complete the reassembly.




Alternator back on the overworked and overstressed allotment trolly. (Still owe the wife a new replacement!)




Gently easing the drive spigots into the flywheel flexible coupler sockets.


Once everything had been mechanically reassembled, the exciter was mounted on the alternator and with its wiring reconnected and the drive belt replaced and tensioned, it was ready for a test run. Unfortunately the weather was not to be kind and I was only able to undertake a quick test, before the rain interrupted. Due to this, I was limited to a single loaded run which I wasn't able to film. However I did manage to connect a lamp, as a load, onto one of the phases and this resulted in the the lamp illuminating. On the face of it this was a good result, this being the first time this set had produced power into a load. However I didn't have a meter on the loaded phase and the fact that the bulb lit might mean the phase I was connected across was still producing 240v, not the expected 130v. I think the only proper way to test this will be to connect loads and meters across all phases simultaneously and then run the set, when hopefully I will be able to understand what is actually being produced.




Alternator and exciter reunited, with the wiring reconnected and drive belt in place and tensioned.


With the weather and my free time limiting progress on the alternator front, the only other area of the restoration I could progress was the canopy. This was being assembled in the back garden whilst the main engine was now mounted on the trailer on the drive out the front. Due to the canopy's size and weight it wasn't feasible for it to be carried through the garage, as that would have required moving everything out of the garage to allow this to happen. I therefore needed to jury rig a way to enable the canopy to be moved through the house.




The temporary wheels being attached, ready for the move.




Rear legs added to reduce strain on the front legs.




The set up being tested and approved by the neighbour's cat.


With the canopy prepared, all I needed to do was to wheel the canopy through the house. Not only did this require the approval of the wife but I actually need her to assist. It's a good job she appreciates my hobbies. So with her lifting the lighter end, while I lifted the heavier front end over the steps, I managed to thread the canopy through the house, out into the front drive and position it beside the rest of the set.



Set successfully negotiated through the house, onto the drive. I didn't think it prudent to take pictures inside the house!




Now positioned and covered up next to the trailer.


Not certain how much more can be achieved with the winter months ahead but hopefully some more progress will be feasible....

Neil.

At last an update!

It has been a long winter and spring hasn't been too good weather wise either. This has delayed progress on the restoration work, due to the units having to stay undercover outdoors. I did check on the state of the set late in January, just to ensure nothing had decided to nest or take refuge under the covers. I was relieved to find that there weren't any signs of damage.





A quick reveal of the two sections of the set at the end of January, happily didn't identify any storage issues.


Carburettor Rebuilds

During the extended winter shut down, I was able to take the opportunity to examine the carburettors. I had noticed that there was wear on some of the components and also a number of discrepancies identified on the needle and jet sizes. In the end I contacted the Amal specialists at Burlen who still supply some parts for the TT range of carburettors. Although they do not manufacture all of the TT parts, they were able to supply most of what I required, in terms of jets, needles and floats.



Stripped down carburettors ready for assessment.




One item which had Burlen confused was the spray tube. The one supplied was of a shorter length than those fitted to these units.




Original item on the left, replacement on the right.




Original fitment in the choke block.




Replacement item fitted. Tube does not extend into the cavity. I don't know how this would impact on the operation of the carburettor.


I contacted Burlen to query the difference and received this response from the technical support team.

Dear Mr Edwards,

I have never seen your longer choke tube before but I have found the drawing and part number 3355. It isn’t listed in any of the available 15TT parts breakdowns we have for motorcycles so may have been specifically designed to be used on lever operated carburetters like yours running at fixed throttle openings.


Engine Hoist

Having decided that these sets are too heavy for me to safely lift and move around on my own, I have invested in an engine hoist to assist with the heavy lifting. To provide the lifting capacity at the reach necessary I purchased a 2 Ton hoist from S.G.S. It is very large but hopefully it will prove useful.




Hoist ready for action, looking rather large!




Lifting the canopy ready to fit it to the generator base.




Up and over the engine chassis.




And gently lowered into place.




End result, engine base and canopy safely reunited.


Hopefully I will be able to make more progress soon assuming the weather improves. Unfortunately if the weather forecast is anything to go by, I will be waiting for a little while yet......

Neil.