Suggested Axles

[pballdan]

I'm looking for a steel to use as axles on a human powered vehicle (a 2 person bike with 4 wheels) It has to be easy to weld (tig) and must be able to be heat treated after welding. It will have a threaded end, and the other will be keyed. Anyone have suggestions?

[chipmaker4130]

I don' know, but the guys who do will probably need answers to the following:

Are the axles cantilever, or suported both ends? What would be the diameter and max load? Are you heat treating for a bearing surface (integral ball bearing race) or just for overal strength and rigidity?

Another factor to consider is the effect welding has on your heat-treat (tends to embrittle the base metal at the weld junction).

[pballdan]

I don' know, but the guys who do will probably need answers to the following:

Are the axles cantilever, or suported both ends? What would be the diameter and max load? Are you heat treating for a bearing surface (integral ball bearing race) or just for overal strength and rigidity?

Another factor to consider is the effect welding has on your heat-treat (tends to embrittle the base metal at the weld junction).

The axles are cantilever (rolling on two timken bearings), max diameter 1", approximately 6" long, max torque approximately 75 foot pounds, heat treat for extra strength and wear resistance, it must be a weldment because the shaft diameter is about 1" but a 3" diameter flange needs to be welded on to hold a disc brake. I figured that would be easier and cheaper than machining from a large solid piece.

If it is possible can I heat treat the shaft and brake flange seperate then weld and temper?

[chipmaker4130]

Hello again, a 1" shaft is pretty big for a bike-type vehicle, and using bearings as you describe should alleviate wear except for the brake disc. The max load I was refering to in the case of a cantilever shaft is the radial load or bending moment. If I were going to the trouble of heat treating the shaft, I would use a much smaller diameter of something like drill rod and save the weight too. Being a biker myself, every ounce counts!

[Lew Hartswick]

I think if it has 4 wheels it isn't a "bicycle" . :-)
How about a quadracycle? :-)
...lew...

[Carld]

There seems to be a lot of detail missing.

Cantilever means the axle is stationary (welded or anchored to the frame). The flange is to hold the caliper I assume since the rotor would be secured to the wheel hub. The flange could serve as the stop for the bearing if there is a small dia. extending out for a seal wear area and as a stop for the inner bearing race.

I don't have a clue as to where the 75 ft lbs of torque enters the picture, unless that is what you intend to torque the bearings to which would be about 74 ft lbs to much.

I would suggest 1045 cold roll as it can be welded and heat treated. It does get brittle when welded as I understand it and has to be annealed after welding. Tool steel would not be a good choice.

As Lew said, it's a quadracycle, not a bicycle.

If independent wheels, how do you propose to drive each wheel?

[chipmaker4130]

Well now, he never said it was a bicycle. I understood it to mean a lightweight frame and spoked wheels, designed for light loads. Cantilever means supported on one end, with a free overhang or projection. Drill rod is readily available, fairly cheap and can be tempered to work nicely in such an application, although there are surely alloys better suited.

I am curious as to the purpose of the project, and whether it will have some sort of enclosure for the riders? It sounds like fun.

[pballdan]

There seems to be a lot of detail missing.

Cantilever means the axle is stationary (welded or anchored to the frame). The flange is to hold the caliper I assume since the rotor would be secured to the wheel hub. The flange could serve as the stop for the bearing if there is a small dia. extending out for a seal wear area and as a stop for the inner bearing race.

I don't have a clue as to where the 75 ft lbs of torque enters the picture, unless that is what you intend to torque the bearings to which would be about 74 ft lbs to much.

I would suggest 1045 cold roll as it can be welded and heat treated. It does get brittle when welded as I understand it and has to be annealed after welding. Tool steel would not be a good choice.

As Lew said, it's a quadracycle, not a bicycle.

If independent wheels, how do you propose to drive each wheel?

Yes it is a quadracycle...

The axles are not cantilever in the sense that they are welded and stationary with respect to the frame, but the are only held at one end by two timken roller bearings mounted in the steering knuckles. The wheel is then keyed on one end of the shaft and is removable, the other end (on the opposite side of the steering knuckle) is keyed to a U-Joint and driven by a half-shaft. (Kinda like the front wheels on a front wheel drive car.) This is were I mean that 75 lb ft of torque comes in. I came up with the number based on that an average rider should be able to apply at most 200 pounds of force on the pedal at the peak, with the lowest ratio, it came down to be around 150 lb ft at the output of the differential. I then divided that in half because each rider powers two wheels.

The brake discs will be attached to the flange on the axle, not the wheel hub. We decided this because we wanted to be able to remove the wheels quickly and replace them if they should be damaged.

I was thinking about 4130, but have never used it myself.

This is the front end of the vehicle I am talking about.


The entire drivetrain is being redesigned and rebuilt. When I get back to school I can get some more pics.

If you want to see the type of vehicle I am talking about google Nasa's Great Moonbuggy race.

[Carld]

Bike implies bicycle to me, maybe not to others. However, he did say 4 wheeled bike soooooo----, he wins.

Hmm, nice looking vehicle. You are going to run into a serious problem if the caliper is rotating with the wheel. How do you propose to have the cable operated caliper have a cable connected to it if it is spinning with the wheel. All the caliper brakes I have seen have the caliper stationary and the rotor spinning with the wheel.

4000 series steels are very brittle after welding. I suppose it can be treated but I would still go with a cold roll. 4--1" axles would carry a polar bear as a rider if the rest of the vehicle held up.

Maybe you better go back and look that quadra bike over real close.

[chipmaker4130]

Wow! What a machine. Having seen that, you could use 4130 or 4140 and forget about heat treating except to relieve stress at the weld. Anything that would damage 1" 4140 would cause death or dismemberment to the rider.