Rack and Pinion help

[LyNx]

I'm looking for an "off the shelf" Rack and Pinion set but finding nowt.

I'm looking for a rack around 500mm long, with two pinions of different diameters (say 20 & 50 teeth). I have found the single components on RS but i can't see how you connect the pinions a bar.

Can anyone with experiences with this stuff give me any advise. I'm trying to move a rail left and right via two handles from the top (lets say, like the W-rat). The rack is going to be fitted to the rail. I can't work out, using 8mm rod to form the handles, how do you connect the pinions to the rod? If both pinions are fitted to the rack, will there be too much resistance from one that the other won't rotate?

Items i've been looking at.

Rack = Module 1.0 steel gear rack, 500mm long (item :521-7770)

Pinion = Module 1 steel spur gear,20 teeth (item : 745-444)
Pinion = Module 1 steel spur gear,50 teeth (item : 745-501)

am i making any sense? is there any easier way to move this rail accurately

 

[SketchUp Guru]

Andy,

I think the pinions would have to have a center hole to fit on the rod. They'd likely be fixed in place with a set screw or two. As far as resistance from having two handles and pinions fitted, there shouldn't be much unless you have something applying friction to the shaft of the crank. If the crank passes through a snug fitting bushing for example you might have problems. If you could run the shaft through a lubricated bronze bushing or a bearing of some sort, I think you could keep friction to a minimum.

Or do you want some friction to keep the assembly from moving when you don't want it to?

 

[LyNx]

Or do you want some friction to keep the assembly from moving when you don't want it to?

Thats going to be a trial, until i mock this up i won't know how freely the bar moves.

 

[Hitch]

Have a look a www.davall.co.uk for the parts. Also it may be worth giving Marchant dice a ring, i know they stock similar stuff, and were pretty helpfull last time i used them, 01805 623486.

The pinions may be piloted and need drilling and taping, so 2 grubscrews can be tightened onto flats machined onto the shaft.

 

[LyNx]

thanks for the links. I'll give them a ring in the morning.