TVT - Gang Motor
Posted: Sun Jun 16, 2019 5:17 pm
Over the summer, on days when it was too hot to work outside on the track, I started building a little battery powered Gang Motor and a matching trolley for one of the TVT track gangs.
Nothing complex, but it used up some spare IP engineering wheels and axle box castings left over from older projects. I also wanted to try a drive system that was a bit more sophisticated than the one used in Ivan's Ezee range of kits.
Building finished back in February, but it has taken until now to finish painting and decalling the model. The original plan was to build two of them, but that didn't happen.
The first photo shows the first drive train and associated electronics assembled for testing, showing the underneath of the chassis. The motor is a small 6V MFA-Como geared motor, with plastic mitre gears and my simple transistor speed control.
The gearbox is machined out of a lump of brass and the gears are 0.5Mod mitre gears, which were the smallest I could find locally. The speed control, reversing switch and on/off switch are to the right and the charging socket is between the gearbox and the battery well.
The next photo shows the chassis from above. From left to right are the speed control board, motor, charging socket, battery pack, speed control and switches. The battery is four AAA size NiMH cells. The yellow disc is the PTC resistor that acts as a 1amp resettable fuse, limiting current from the battery if a short occurs.
Well, that didn't work when tested..........
On investigation, it turned out the motor starting voltage was about 4.5V. So with a 4.8V battery and the voltage drop through the drive transistor, the motor never saw enough volts to start. Back to the drawing board.
The next photo shows the solution, using just an on/off switch and a reversing switch instead of speed control. With this arrangement, the chassis trundled around at about 10 scale mph, although the acceleration would give a dragster a run for it's money. With the drive on the front axle, it can't do a wheel stand though.
Before anyone asks, lithium batteries are not the answer, as they won't fit in the space available, which is 25mm x 25mm x 100mm and also contains the motor, charging socket and switch panel.
With everything running, the next job was fitting some bodywork. The drive is small enough to fit into something resembling a VR NKS narrow gauge gang motor, but I decided to fit some weather protection for the TVT track gang and the body work was made to resemble the works motor that runs the weed killing train.
The next photo shows the chassis fitted with it's wooden bodywork, made from thin ply and clear pine sawn to size on the little bench saw.
A gang motor needs a trolley for carrying replacement sleepers, tools and anything else needed for routine track maintenance, so the remaining parts went into a simple flat truck to match the gang motor. This took all of a couple of hours to assemble, much of which was spent scribing a piece of ply for the deck.
That was where things stopped for several months, but while waiting for the arrival of the electronics to convert the new Walker railcar to battery power, I decided to finish the model off over the weekend and since it wasn't raining it ran trials today.
The first photo shows the portrait shot of the finished gang motor and it's trolley.
The last photo shows it trundling around the track at about 10 scale mph. The driver figure is 1:20.3 scale and shows how small this thing is. The sun also put in a short appearance during the run.
An interesting exercise, but one that didn't work out entirely successful. In retrospect, it would have been better to use a 3V motor and MFA-Como do have a 3V geared motor of the same size as the 6V ones, but the local distributor doesn't sell the gear ratio needed. I've since worked out how to swap the motors between gearboxes, so if I build anything similar in the future, I'll try the lower voltage motor, as there is already a spare speed control.......
The current drive runs OK and being simple to use keeps the kids amused, but while spur gears are more efficient than worm gears, it sounds like a mobile chaff cutter when running. The motor looks small even by HO standards, but the gearbox ratio means it is more powerful than it looks. If it meets an obstruction the driving axle will slip and not stall the motor. The gang motor can pull the weedex train without any strain on reasonable gradients, so it doesn't notice the little 4 wheel trolly as a load.
Regards,
Graeme
Nothing complex, but it used up some spare IP engineering wheels and axle box castings left over from older projects. I also wanted to try a drive system that was a bit more sophisticated than the one used in Ivan's Ezee range of kits.
Building finished back in February, but it has taken until now to finish painting and decalling the model. The original plan was to build two of them, but that didn't happen.
The first photo shows the first drive train and associated electronics assembled for testing, showing the underneath of the chassis. The motor is a small 6V MFA-Como geared motor, with plastic mitre gears and my simple transistor speed control.
The gearbox is machined out of a lump of brass and the gears are 0.5Mod mitre gears, which were the smallest I could find locally. The speed control, reversing switch and on/off switch are to the right and the charging socket is between the gearbox and the battery well.
The next photo shows the chassis from above. From left to right are the speed control board, motor, charging socket, battery pack, speed control and switches. The battery is four AAA size NiMH cells. The yellow disc is the PTC resistor that acts as a 1amp resettable fuse, limiting current from the battery if a short occurs.
Well, that didn't work when tested..........
On investigation, it turned out the motor starting voltage was about 4.5V. So with a 4.8V battery and the voltage drop through the drive transistor, the motor never saw enough volts to start. Back to the drawing board.
The next photo shows the solution, using just an on/off switch and a reversing switch instead of speed control. With this arrangement, the chassis trundled around at about 10 scale mph, although the acceleration would give a dragster a run for it's money. With the drive on the front axle, it can't do a wheel stand though.
Before anyone asks, lithium batteries are not the answer, as they won't fit in the space available, which is 25mm x 25mm x 100mm and also contains the motor, charging socket and switch panel.
With everything running, the next job was fitting some bodywork. The drive is small enough to fit into something resembling a VR NKS narrow gauge gang motor, but I decided to fit some weather protection for the TVT track gang and the body work was made to resemble the works motor that runs the weed killing train.
The next photo shows the chassis fitted with it's wooden bodywork, made from thin ply and clear pine sawn to size on the little bench saw.
A gang motor needs a trolley for carrying replacement sleepers, tools and anything else needed for routine track maintenance, so the remaining parts went into a simple flat truck to match the gang motor. This took all of a couple of hours to assemble, much of which was spent scribing a piece of ply for the deck.
That was where things stopped for several months, but while waiting for the arrival of the electronics to convert the new Walker railcar to battery power, I decided to finish the model off over the weekend and since it wasn't raining it ran trials today.
The first photo shows the portrait shot of the finished gang motor and it's trolley.
The last photo shows it trundling around the track at about 10 scale mph. The driver figure is 1:20.3 scale and shows how small this thing is. The sun also put in a short appearance during the run.
An interesting exercise, but one that didn't work out entirely successful. In retrospect, it would have been better to use a 3V motor and MFA-Como do have a 3V geared motor of the same size as the 6V ones, but the local distributor doesn't sell the gear ratio needed. I've since worked out how to swap the motors between gearboxes, so if I build anything similar in the future, I'll try the lower voltage motor, as there is already a spare speed control.......
The current drive runs OK and being simple to use keeps the kids amused, but while spur gears are more efficient than worm gears, it sounds like a mobile chaff cutter when running. The motor looks small even by HO standards, but the gearbox ratio means it is more powerful than it looks. If it meets an obstruction the driving axle will slip and not stall the motor. The gang motor can pull the weedex train without any strain on reasonable gradients, so it doesn't notice the little 4 wheel trolly as a load.
Regards,
Graeme