Gears for Portescap gearbox

[Tickplan]

Does anyone know if it possible to buy the individual gears for a Portescap gearbox? I bought a gearbox (only) off a certain well-known auction site quite cheaply thinking it would do as a spare for my other in-service 'boxes. Now I have it I am wondering if I could buy a final drive gear (the brass one with the grub screw) and the small bevel nylon one that fits to the motor drive shaft to make the gearbox complete. I would probably have to make a new spacer bar to fit say a Mahima motor (or buy a new Portescap, the motors for which are still available and not unreasonably priced). This all may be too much trouble but having seen what "complete" Escap RG4's are going for it seems a pity not to make the effort and further investment. Thanks in anticipation of your responses.

 

Bryan

[DLT]

Does anyone know if it possible to buy the individual gears for a Portescap gearbox? I bought a gearbox (only) off a certain well-known auction site quite cheaply thinking it would do as a spare for my other in-service 'boxes. Now I have it I am wondering if I could buy a final drive gear (the brass one with the grub screw) and the small bevel nylon one that fits to the motor drive shaft to make the gearbox complete. I would probably have to make a new spacer bar to fit say a Mahima motor (or buy a new Portescap, the motors for which are still available and not unreasonably priced). This all may be too much trouble but having seen what "complete" Escap RG4's are going for it seems a pity not to make the effort and further investment. Thanks in anticipation of your responses.

 

Bryan

Hi Brian,

 

I have bought replacement final-drive gears for RG4s from Ultrascale http://www.ultrascale.co.uk/

I dont now about the little bevel-gears though, but I'm sure it would be worth an enquiry.

 

Hope this helps,

Dave.

[Horsetan]

Does anyone know if it possible to buy the individual gears for a Portescap gearbox? I bought a gearbox (only) off a certain well-known auction site quite cheaply thinking it would do as a spare for my other in-service 'boxes. Now I have it I am wondering if I could buy a final drive gear (the brass one with the grub screw) and the small bevel nylon one that fits to the motor drive shaft to make the gearbox complete.....

 

Yes, I saw that one on eBay!

 

It is not possible to buy individual gears out of that 'box - certainly not the first stage plastic bevels, or the next two steel idler spurs. Many years ago, it was possible to get only the brass final drive gear as a spare from the now-defunct H.A. Blunt & Sons of Mill Hill for about a quid each, but that was all. I bought five, of which one later found its way to someone in Australia. The rest I have kept for my own purposes.

 

Ultrascale only produce contrate-and-pinion gear sets (there are two types that they sell) moulded in Nylatron, and having bought a set myself, I think they are slightly too big to act as direct replacements for the original RG4 bevels. The other thing you have to think about is how to continue the drive to the steel idler gears, since the Ultrascale contrate does not have a matching "cog" that would mate with them.

 

Nothing stopping you making your own gearbox to incorporate them, though.....

[bertiedog]

The final gear is available from Ultrascale, or at least a substitute to the same DP, but the bevels are not made, they were a one off design, although a gear machinist could copy them. They really were the only specialist part of the design, the spur gears are standard pitches and diameters, first grade components though.

It would be possible to duplicate the design in parts from Ultrascale parts, but using a lager contrate for the first gear.

 

The reason behind the use of the bevel gear was the fact that most coreless motors cannot take end thrust, no pressure from the gears along the shaft, but this can be overcome in other ways, with a drive shaft and sliding joints, allowing coreless motors to power a more conventional worm and gear design.

 

If a flywheel is used, then a drive shaft is a must and the drive from the flywheel requires no special gears or consideration of end thrust, as the motor is isolated.

 

Today a lot of coreless motors are different in design to the 1970's and can take end thrust, but make sure of the type.

 

There is nothing inherently unique or better designed about the Portescap. it was just more expensive to allow 1st grade components to be used more efficiently, other designs can work just as well, and Ultrascale gears can work as quietly and efficiently in simpler design gearboxes.

 

It does date from the days of Romford motors and wonky gears, and was light years away from these, but modern Mashima motors with Ultrascale worm gears, (plus spur gears if needed) compare most favourably in both quietness and performance. it is all down to the standards of assembly and setting up the gears.

 

Stephen