Diablo & Lightning

-Very Very Enlightening-

The Ideal Drive System for Trams, Trolleys & Interurbans

This movie introduces the Diablo and is best viewed in Full High Definition.

The second movie shows a step-by-step assembly of the Diablo Kit. It is a longer running movie at 24 minutes and is also shot in Full HD.

Diablo & Lightning - Update of the Spring Belt Drive for HO.

The Diablo Power Truck and Lightning Trailing Truck are a new take on the old spring belt drive truck, substituting the metal spring belt for a modern synthetic rubber drive belt. The design is very similar to the old spring belt drive, but the Diablo employs four tiny ball bearings and brass axle bearings to improve reliability and provide quieter, smoother operation.

The name Diablo was given because of the shape of the drive pulley, of which there are two in the design, which is reminiscent of the child's toy of the same name. The trailing truck is called Lightning because of its habit of rolling off the bench at lightning speed if not tied down.

Although the trucks can be used as a replacement for the older spring belt drives, it is primarily intended for new construction. The Diablo and Lightning will only be available for HO or 16.5mm gauge operation, as the design is not adaptable to other gauges.


  • Choice of Wheelbase and wheel size. No 'One Size Fits All' as with other mechanisms.
  • Wheelbases starting at 4' 9" and going up in 3" increments. New wheelbases being added all the time.
  • Range of 7 wheel sizes, 24", 26", 28", 30", 33", 36" & 40".
  • Choice of insulated wheels for two-rail operation or non-insulated wheels for overhead power collection.
  • Tight turning radius - down to 5 and a half inches!
  • Adjustable Ride Height for both Diablo and Lightning.
  • Easy to assemble kit with comprehensive, detailed instruction sheet. Now available already assembled!
  • No soldering required. Simple assembly tools.
  • All necessary hardware supplied in kit, with spares for items that get lost.
  • Flexible floor mounting, no complicated cut-outs as required by other mechanisms.
  • All-wheel power collection option for Diablo.
  • Fixed, stationary drive shaft, no need for complicated universal drive connections.
  • Large selection of genuine Mashima drive motors.
  • Specially priced kit containing Diablo, Lightning and Mashima Motor Drive combination.
  • Smooth, quiet operation with beautiful low speed performance.


The Diablo and Lightning can be used in any situation where you require a 2 axle or four-wheel truck drive. Trolleys, trams, interurbans, multiple-unit suburban cars, small electric locomotives are all possible to power using the Diablo. It is intended for situations where the motor is contained in the interior or cab of the model, allowing a larger, more powerful motor to be used for improved performance and reliability.

Design Improvements - Belt Drive.

The Diablo uses a single synthetic rubber drive belt instead of the original single or double metal spring belt. This provides quieter and smoother operation. The belt is made from a synthetic material called Chloroprene Rubber, and is specially designed as a drive belt, similar to those found in VCRs and disk drives. It is not a cheap rubber band or O ring, and will last almost forever. The belt has a precise square section and runs in a V groove in the pulley for maximum grip. The belt is replaceable, and we supply a spare with each drive just to ease concerns.

Brass Wheel Bearings

The wheels feature brass bearings and the axles come pre-assembled with the wheels, worm gear and bearings already fitted together into a finished axle. You have a choice of wheels insulated for two-rail operation, or non-insulated wheels where the model will be run on a system equipped for overhead power collection.

Ball Races

Four tiny ball races support the main drive shaft and the lay shaft that drives the wheels. These ball races are high quality products and will ensure the drive will provide years of trouble-free operation. In addition, the ball races are of the sealed variety to prevent dirt or grit from getting inside and causing wear. In the photograph at the top left of this page, you can see one of the races on the left end of the main drive shaft.

Metal Worm & Worm Gear

The worm is our standard steel worm, combined with a brass worm gear. We do not use plastic gears, so there is no chance of gears splitting and failing. The worm and gear provide a fixed 15:1 drive ratio.

Integral Drive Shaft

The main drive shaft is an integral part of the drive itself, making it very simple to connect a motor. The older spring belt drives did not have a upper drive shaft, and relied upon the motor being in position above the drive, or use of a long motor shaft. The Diablo shaft itself is 20mm long and can easily be coupled to a motor using silicone tubing, also supplied in the kit. We try to supply everything you need.

Due to the integral design, the input shaft to the Diablo is fixed in position and does not rotate with the truck, so you can use any type of motor or coupling you wish, providing it can connect to a 1.5 or 2.0mm diameter shaft. Hollywood Foundry can supply you with a range of Mashima motors and flywheels, or an assembled motor drive to complete the drive train. See the test unit below, showing such a drive arrangement.

Rugged Material

The Diablo and Lightning are constructed from 0.7mm thick etched brass for maximum strength and rigidity. That's just a little under 1/32" thick. We went to a lot of trouble to source this thicker material for this project and then had to convince our etching company to work in this thicker material. The resultant etches suffer a little more from cusping, but we are prepared to live with that for the increased strength.

Height Adjustable Mounting Plate

A square mounting plate, pre-drilled for 2mm mounting screws (supplied), attaches to the Diablo drive via the top mounting plate. The mount is a little under 1 inch square so it should fit most models. The top mount attaches to the mounting plate via small screws and a range of supplied washers allow the height of the truck to be adjusted with respect to the floor of the models.

Manufacturers can elect to incorporate the mounting plate in the design of their model's floor, we will happily supply a dimensioned drawing for how to design the mount. In fact, we can even manufacture the floor for your model from the same heavy duty brass material used in the Diablo. All you need to provide is drawings or sketches of your floor, we will do the rest.

Keeper plate & Side Frame Mounts

The bottom keeper plate protects the bottom of the drive and retains the axles in place. It is fastened with two small screws and is easily removable for cleaning and lubricating of the drive. The plate has two tabs on the side for mounting your own choice of side frames. The tabs have hatching on the outer surface to improve the keying of adhesives when side frames are attached. If you wish to solder cast brass frames, then it is simple to do because the keeper plate is removable.

All-Wheel Power Collection

Normally the Diablo and Lightning collect power from one side only. Therefore it is only necessary to rotate one truck with respect to the other to collect power from both rails in a two-rail power system.

If you choose the insulated wheel option, an etched phosphor-bronze power pick-up is supplied attached to a piece of insulating printed circuit board. The pick-up has a wire already attached and only needs to be glued in place when assembling the Diablo. The pickup bears on the back of the insulated wheels, adding two more wheels to the power collection system. The pick-up kit is not supplied when you choose the non-insulated option.

Minimum Radius Operation

The Diablo can rotate through 25 degrees with respect to its drive shaft. It is limited to this amount of rotation by the mounting plate to prevent chafing of the drive belt. However with the average truck spacing of around 100mm or 4 inches found on many trolley models, this allows the Diablo to negotiate curves down to 5 1/2" radius if necessary.

The test rig shown above has a 6' 0" wheelbase Diablo, 28" wheels and 29' 0" truck centres. It is equipped with matching Lightning trailing truck, and is powered by a Mashima 1620 motor and flywheel combination. The whole rig is mounted on a piece of FR4 fibre glass board. Power pickup is from each truck. Use of a larger motor of this type produces very good low speed performance, with the drive beginning to move off at 2.0 volts on the track. The 15:1 drive ratio still allows for good top speed as well.

This test rig was used on our test track running down to a 5 1/2" radius curve, which it handled without trouble. For even better performance, two Diablos could be used driven by the single central motor.

Sizes - Wheelbase & Wheels?

The Diablo and Lightning are constructed from etched brass components, so separate etch designs are required for each wheelbase produced, however we can make them down to 4' 6" wheelbase, and upwards of 10' 0" if required. Initially we will have three sizes available out of a proposed 20 sizes:

  • 5' 6" or 19.25mm
  • 5' 9" or 20.1mm
  • 6' 0" or 21mm

then add sizes in groups of 3 as demand dictates. If a manufacturer wishes a specific wheelbase for a product, it can be easily accommodated, and usually with a fast turnaround on etching.

We intend to produce wheelbases that increment by 3" on the previous size, that means a small jump of 0.875mm or 0.034" between sizes. As a result, the maximum error between the exact scale wheelbase you want and any that we produce is only 0.437mm or 0.017", that's around 17 thousands of an inch!

Wheels come from our stock of solid nickel silver NMRA RP25 Code 110 wheels. Sizes offered will be 24", 26", 28", 30", 33", 36" & 40". In metric, that's 7, 7.5, 8.15, 8.7, 9.6, 10.5 & 11.6mm. That should take care of most requirements!

Lightning Trailing Truck

The Lightning trailing truck can be supplied with the same wheelbase choices and wheel sizes as the Diablo. Lightning uses brass axles with pointed ends, running in brass pin-point bearings for minimum rolling resistance. The solid brass frame has a skeleton outer frame to hold the bearings with holes to keep the structure open. Cosmetic side frames can be glued or soldered to the outer surface of the frame.

To allow for maximum flexibility in mounting height, there is a choice of a raised or flat bolster section, plus supplied packing washers. These features allow a broad range of ride heights to be accommodated. Delrin insulators can make the mounting fully insulated from a metal floor, with a solder tag provide for electrical connection. A nickel silver swivel plate, seen in the top photo with two pins facing upwards, can be fitted to plastic, fibre glass or metal floors to facilitate mounting of the truck.

Mounting Dimensions

Two sets of drawings are available for viewing or download, showing the drilling templates for mounting the Diablo and Lightning, both are PDF files:

Supplied As a Kit

In response to modelers who asked for it, the Diablo and Lightning trucks are supplied in kit form to keep the price down as low as possible.

We now offer the Diablo and Lightning as fully assembled for those who do not want to buy them as a kit.

If you would like to find out if the Diablo or Lightning kit is within your capabilities to assemble, we welcome you to take a look at the assembly instructions. Just click on the picture links below to view the full color assembly instructions in Acrobat PDF form. WARNING: These files can be quite large in size. To save them for viewing later, right click on the picture and choose 'Save Target As' from the menu.

The parts supplied in the Diablo kit are shown below:

Each kit comes packed with everything you need to assemble your Diablo or Lightning. All you need in the way of tools is a large box cutter for cutting the parts out of the frets, a small cross-slot or Philips head screwdriver, a couple of small metal files and a pair of long-nose pliers.

There is no need to solder any part of the kits, even the electrical connections to the nickel silver solder tags are pre-soldered. Every part screws together with supplied miniature screws. All holes are pre-threaded, and the major assemblies like the drive shaft, lay-shaft and axles come pre-assembled as shown in the above photo.

Each kit comes with comprehensive instructions, with photos and superb 3D diagrams to help you assemble the kit as easily as possible. The degree of difficulty in assembling the kit is medium to low.

Test Units

We have motorised a Cooee Models version of a Melbourne W Class tram in order to demonstrate the performance of the Diablo & Lightning. These models were produced as collectors items, then later the company produced a motorised version from the factory in China. We happened to have one of the non-motorised models lying around, so it looked ideal to use as a test bed.

This photograph shows the Diablo, Lighting and motor fitted to the W class diecast metal chassis:

It was possible to retain some of the interior detail of the model by only cutting away the minimum needed to fit the motor. The motor is a 1624 size and provides very smooth performance. The Diablo and motor are both just on the bottom of the window line, so are not as obvious as some installations where the motor blocks your view through the car.

This is the view of the installation from the bottom:

Then in order to test the finished mechanism, we constructed a test track in HO gauge with very tight reverse curves, in fact the curves are 5 1/2" radius, and form three back-to-back curves to really test the ability of the Diablo to handle them. We are happy to report that the W Class tram can run around those curves at full speed, or at a crawl without any sign of coming off the track.

You can see by the overhang in the centre of the car just how sharp those curves are.

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