Futaba servo spline pitch, size, count etc.

[BrendanP]

Do any of the forum RC enthusiasts know standard Futaba servo output shaft spline pitch, size, count, angle etc. specs?

I'm having a some parts cut and rather than attaching them via a horn I'm thinking it would be simpler to go straight onto the splined output shaft.

All I can find so far is that Futaba have 25 splines on the shaft. No info on size or angle etc. I emailed Futaba OEM tech support but haven't heard anything back as yet so I thought someone here might know.

 

[Wrenow]

No clue on the engineering specs for the Futaba splines. However, before you go machining your own, you might want to look at the selection of hubs, adapters, gears, etc. made for Futaba splines already available from Servo City. Oddly (to me), they are under the "control Arms: section. http://servocity.com/html/servo_arms___horns.html

Particularly, you might find the shaft and hub adapters and shaft couplers interesting - http://servocity.com/html/servo_shafts___couplers.html

Cheers,

Wreno

 

[BrendanP]

Hi Wrenow, I was actually thinking of you when I posted. I was already aware of the SC stuff.

I'm trying to bypass the whole hub/adapter/horn concept and be able to attach the part directly onto the servo shaft. Its not a one off project otherwise I would just use an off the solution. Speed and simplicity of assembly is important.

I might take a servo to a tool maker (watch maker?) around here and get them to measure the splines.

 

[Wrenow]

Actually, if you are going to do that, why not just replace the final output gear (to which the spline is attached) with what you want?

Alternatively, instead of machining, have you considered doing a silicone mold of the spline and then casting it into your part in an engineering grade urethane like those from http://www.smooth-on.com/ ? Pretty easy to do. And, once you have the mold, you can make the parts in just minutes.

One of our model warship combat gun designers locally is looking to cast some of the more complicated bits of his design, and he is a machinist by trade (actually services the CNC machines for little companies like Lockheed).

Cheers,

Wreno

 

[BrendanP]

I was going to have the female part to go onto the spline laser cut.

Can you ask your buddy if he can shed any light on the output spline specs Wrenow?

If you need plastic parts laser cut Wrenow BC Laser Works in Oregon is good to deal with and cheap. He'll do CAD drawings cheap as well you just need to give him a rough sketch or description. He can cut gears too.

 

[Wrenow]

Thanks for the tip on BC Laser Works. I have gotten good results on laser cutting from http://www.pololu.com/, which also has lots of other stuff a picaxer might find useful.

You do realise that doing a laser-cut will add a slight kerf, which may be good or bad for your application. Molding the parts would be pretty inexpensive, and fast.

I will ask my buddy if he knows or can determine the specs (I am not sure he uses Futaba. Personally, most of mine are Hitec or JR).

Cheers,

Wreno

 

[Wrenow]

Brendan, since ServoCity makes them, have you tried contacting them on the specs they are using for their Futaba arms, hubs, etc?

Cheers,

Wreno

 

[Wrenow]

Still another possibility. Put the splined gear (and a precise ruler or, better, square) on your scanner and scan it in at high resolution. Enlarge it several times its real size (you will have the scales to make sure everything scales correctly in both directions and there is no directional distortion). You can then analyze all the parameters you want. Might want to input the scan into Inkscape (free drawing program available for both Linux and Windows) to do some of the measuring/drawing, etc. You have the number of splines, of course. What the OD is, ind the inner OD is, tooth width, tooth angle, curves/chamfers etc. could all be determined. At least pretty close.

You could include one spline and one arm (so you have both a positive image and a negative image) to compare. I think that is what I would do. Easier to get the Max OD from the spline, the min OD from the arm.

I have sent out a query to my guy, and will let you know if I hear anything back from him.

Buy the way,http://www.emachineshop.com/
has a gear design utility (their software is free) that might make your visualization and generation of the specifications a tad easier.

Of course, if you were to use the Servo City hubs or shafts, or, for that matter, the molding technique, you would not be stuck with Futaba or futaba clones as your only source of servos.

http://www.strikemodels.com/ for instance, carries some very interesting servos, including a standard size servo that is a sail-winch servo, getting 6 turns, as I recall. About twice the number of rotations as the similarly priced, but almost twice as large, Hitec. I am not sure what spline they are using.

Again, I will let you know if I find out anything.

Cheers,

Wreno