keyways

[ubersoldat]

Hi, could anyone tell me why do wee need keyways on the rear axle? Are they necessary?

 

[ryf]

on simple mechanics side.. they unify the axle and its drive and braking parts to make them non-slip attachments to the axle.


if you are asking on a design level...the keyways are an engineered "weak spot", a cheap, easier to replace binder for the axle. it would be stronger to weld the parts to the axle, but then you would have no way to change gearings later or depending on cart design, get the axle off with out a new axle and bearings.
if you are custom building a cart, and considering all welded/no keyway.. you better make darn sure its the way you want it before you weld it... at $40+ dollars an axle for simple 1" stepped ends, you don't want to keep replacing those. not to mention the $6+ a piece bearings and whatever parts you've welded on!

 

[ubersoldat]

on simple mechanics side.. they unify the axle and its drive and braking parts to make them non-slip attachments to the axle.

But the hubs do this trick. For example they(hubs) hold the sprocket and they are attached to the axle by bolts witch tighten their grab. Well as I imagine it - bolts are used to grab the hubs(sprocket or brakes no matter) to the axle.

 

[kibble]

Yeah, but without the keys even as tight as they may be they could still slip. Plus you could only tighten them so much before the threads strip. With the key, it only needs to be tight enough for the hub to hold itself on. The key takes care of making sure both parts turn together.

 

[ryf]

kibble is exactly right

 

[Russ2251]

My question is why would you not want a keyed axle?
In addition the the above statements I would think a keyed rear axle would serve as a kind of protection to other drive parts in case of some failure elsewhere in driveline. I would rather lose a key (cheap to replace) as opposed to a new axle (not cheap to replace).

 

[ubersoldat]

Well the point is I'm asking if the keyways are necessary is because I don't know how to make them. If I'll buy a plane iron tube with nothing no keyways and stuff I just don't know how to make them. Are they made by hand or are they made with an axle?

 

[kibble]

Oooh.... that's where you'll have a problem. If you have a hub with the keyway in it, making a keyway in the axle isn't too extremely difficult. You can actually make one with a rotary tool like a dremel and lots of patience. You'd only have to make it long enough for the hub in the area where you want it. If you don't have any keyway on either, however, making one inside the hub would be a pain in the @$$ unless you have the tools to actually make one. Here's a picture of the keyway I made on my engines crank shaft because it didn't have one. I slowly ground away with a metal cutting blade so that it wouldn't be all deformed or too deep.

 

[ryf]

nice job, you took your time on that one!

 

[ubersoldat]

And how does a keyway, similar to yours on the engine shaft, helps the hubs to be tightened up to the axle? I mean all I see is a notch.
By the way thanks for the answers they really help

 

[kibble]

It doesn't. The hub itself should have some way to tighten it onto the axle. The key keeps both parts from slipping. I'll take some pics of one of my hubs and axle with and without key so you can see what I mean.

 

[ryf]

the keyway on a motor is the same as having a keyway on a axle, they serve the same purpose, there are set screws to keep the parts from shifting side to side on the axle/shaft-as well as remove "jiggling" which causes vibration , the key keeps the clutch/brake/sprocket from freespinning when under load.

if you really don't get it at this point you might be better off ordering an axle with precut keyways. you've had several good explanations and a great picture. I'm not saying that to offend you, but only to help you in success, or you can waste a lot of money learning.

 

[Russ2251]

Oooh.... that's where you'll have a problem. If you have a hub with the keyway in it, making a keyway in the axle isn't too extremely difficult. You can actually make one with a rotary tool like a dremel and lots of patience. You'd only have to make it long enough for the hub in the area where you want it. If you don't have any keyway on either, however, making one inside the hub would be a pain in the @$$ unless you have the tools to actually make one. Here's a picture of the keyway I made on my engines crank shaft because it didn't have one. I slowly ground away with a metal cutting blade so that it wouldn't be all deformed or too deep.

Mr.Kibble:
I'm impressed with workmanship on this shaft. Please give details. What did you use to cut this keyway and how long did it take?

 

[kibble]

Ok, ubersoldat, here's the difference between having a keyway with keys and not having them. The hub pictured has a bolt that when tightened, holds the hub to the axle.

See pic 1

With a square key in the keyway, both will spin in unison because neither can turn without making the other do the same.

See pic 2

Take the key out, however, and the axle is prone to turning freely within the hub. This is an extreme example as I didn't have the hub tightened to the axle. but you can clearly see what the difference would be.

See pic 3

@Russ:

I'm glad you like my shaft!

The only things I used to make the keyway on the shaft was a sharpie to mark where the keyway would be and how wide, a dremel with a metal cut-off wheel and lots of patience. It took about 30 minutes to make sure that the key fit in without being too tight or too shallow.

I began by making two lines where the keyway would be and then I cut two grooves into the shaft. I made sure to stay within the boundaries of the marker lines.

I slowly ground away at the walls to make the way wide enough to accept the key.

Carefully I ground away at the bottom of the keyway to keep it square and to make it deep enough for the keyway to go in without having either side raised too much. You just have to slowly and carefully grind parts of it away. It's very tedious but worth it. The pulley in the background of shaft is the pulley that would be put on it.

I'm thinking of cutting off the end of the shaft where it becomes tapered.

Update: 8/14/08, I uploaded the pics that are missing from this post as attachments. The server I originally had the pics on is no longer up. Please refer to the attachments by number. The first is pic 1, second is pic 2 etc.

 

[ubersoldat]

Hey thanks I got it, I didn't pay attention to the KEY, so I didn't got the point at first. Thanks for answers.

 

[kibble]

Hey, no problem! Glad to help.

 

[Kenny_McCormic]

Here's a picture of the keyway I made on my engines crank shaft because it didn't have one. I slowly ground away with a metal cutting blade so that it wouldn't be all deformed or too deep.

That looks like CNC work!

 

[kibble]

It was "hand-CNC'ed".:arf: