Making a spline

[Matty F]

As usual I've not done this before. The spline will be in a drive shaft that expands and contracts by about 3 inches. It needs to be reasonably frictionless. Not a lot of power is being transmitted through the spline, like about what twisting by hand would do. I want to be able to make the spline with simple tools. I thought maybe a rod that slides in and out of a tube that has a couple of slots in it. And a pin through the rod. I have two days to design this!

[Nthkentman]

As usual I've not done this before. The spline will be in a drive shaft that expands and contracts by about 3 inches. It needs to be reasonably frictionless. Not a lot of power is being transmitted through the spline, like about what twisting by hand would do. I want to be able to make the spline with simple tools. I thought maybe a rod that slides in and out of a tube that has a couple of slots in it. And a pin through the rod. I have two days to design this!

Square tube within a square tube if revs are slow and torque minimal and space allows

[Nightjar]

A good idea, but I would use square rod for the drive shaft, which could then be turned round where you need bearings. The square tube would then only need to be a short length coupling two pieces of rod.

Colin Bignell

[Matty F]

Revs are about 3 rpm. How do I make a square tube?

[Nightjar]

It is commonly used in metal furniture construction, so you might be able to scrounge some offcuts.

To make it, start with a round steel tube and a square* bar that fits inside that. Heat the tube to red heat and hammer to shape using the square bar as a former. If you reduce the tube to fit the square bar you are using as a former, you only need to shape a short length at the end of the tube, as the square bar will slide up inside the round part of the tube. If you can't do that, you will need to use a larger square bar as the drive shaft, which won't then slide inside the round part, and square off quite a bit more length of tube.

*Going this route, it would probably be easier to use hexagonal bar.

Alternatively, cut a square hole in a disc of metal, to suit the size of a piece of square bar, and weld the disc to the end of a bit of round tube.

Colin Bignell

[harryagain]

Making splines (low volume) can be done using a dividing head on an end mill machine. Or lathe. Very slow process and highly skilled.

Mass production is done with a broach, ie progressively sized dies the componemts are forced through. Makes a spline in seconds. Expensive tools to make. Needs expert knowledge to set up.

Splines have to be accurate or they soon fail. So it depends on the usage to some extent.

Buy one in is best. The commonest/cheapest ones are from dive shafts on cars. Some motor bike gearboxes have them on the clutch plates Some clocks have them for smaller ones again so you could see/contact a horologist.

If you want a one off, it will cost a fortune.

[Muddymike]

x2 but I would call it box section, and would weld a short length of small box onto the end of the input round bar and let that slide into a longer length of larger box section for the output shaft.

Mike

[The Natural Philosopher]

what size, what power?

don't make one, buy one.

model makers use em. car makers use em, ship builders use em. Bound to be a suitable one around.

e.g.

[Tim Lamb]

In message , harryagain writes

Investigate the nearest farm nettle patch. All tractor powered farm machinery will have drive shafts with sliding components: square section and multi-tooth spline.

[Dave Liquorice]

minimal

So would I, bar isn't going to collapse/slowly deform under load. If it's a very snug fit in the tube it will help that retain its shape as well. Not sure is soft mild steel "furniture tube" would be good enough long term even at the low torques involved. The square bar would need the corners rounding so that the faces of the bar bear on the inner faces of the tube. May be advantageous for the faces of the tube to be slightly concave so the bearing point is down the center of the bar face rather than on the corners. Much less chance of the corners rounding off.

Matty doesn't give a size for this other than it needing 3" of movement. It could be something small, less than an 1" across or steam engine tram size, > 6" across...

[Phil]

Google 'roll pin'

[Nightjar]

On 26/09/2013 08:39, The Natural Philosopher wrote: ...

...

I'm not sure that is a concept that Matty understands.:-)

Colin Bignell

[Matty F]

I was going to have an axle made of about 5mm rod. It's to make a one wheel drive track welder into a two wheel drive. When the rail is greasy the one wheel drive slips. Since the track varies in width (especially on corners) the second wheel has to slide sideways using quite a strong spring.

[dennis]

Drive both the wheels on the same track? Just need a couple of gears and a chain then.

[Bob Minchin]

Square tube is quite standard to buy in. It is usually resistance welded and so there is a ridge down the inside of one face which you will need to file off to get the square bar to slide nicely inside.

[Tahiri]

That is why his posts and their responses are always so interesting!

[news]

You could visit the local Stihl dealer and see if they have the tube from a scrap pole pruner, I expect our fitter has a few as I've replace 3 stihl HT131 so far this year. I could ask him, I'm in Surrey.

AJH

[Dave Liquorice]

Will that be resistant enough to not turning into a coil? I'm thinking that the guage of the tram track is 4' or so... I guess if you can get three or four support bearings along the length it'll be OK.

Ah the one wheel drive thread I've not been following that one recently.

Some one else has already mentioned drive two wheels on the same side as it's simpler. Have you got a differential for this drive shaft? Mind you railway stock has wheels joined by a solid axle, presumably one or other wheels slip when going round a corner?

[Matty F]

I'll just make the axle big enough. It depends what I find on the steel rac k!

Railway wheels have a bigger diameter by the flange. When they go round a c orner the train moves to the outside of the curve and moves up on the bigge r diameter. The wheel on the inside of the curve is then running on the sma ller diameter. There is no slippage if all curves are the same diameter. Ot herwise there is a noise called "flange ring" that causes wear on the wheel s and rails unless they are lubricated (and sometimes they are).

I've found some right-angle gearboxes that I could use, so I could have fou r wheel drive if I want! I can't have a belt or a chain as that will get in the way of the welding that needs to be done.

[F Murtz]

What is this track welder? does it run on real rail tracks?if so what is it with 5 mm axles?