Simple cart axle size question

[Bill D]

I am designing a simple mobile base for a heavy,1,300 Lb., wood planer. Hand pushed only. Not using swivel casters. My question is for say 500 pound wheel loading what straight axle diameter is adequate? Simple design just a horizontal axle with the load bearing straight down along it's length. Wheel at each end. No real projection of unsupported axle except what is inside the wheel hub. Picture the wheels on a handtruck.
I have no idea about the math involved so just asking for what you have seen for similar loads. I was thinking maybe 5/8 inch axle. Depending on wheel I may have to turn down the ends to fit. Prefer no bigger then 1.25" so it fits in my lathe headstock.
Bill D

 

[fciron]

Get a wheel rated for at least your desired load. Make the axle to fit.

 

[Bill D]

Get a wheel rated for at least your desired load. Make the axle to fit.

I see them rated for over 1,000 pounds with a 1/2" axle. I think that is for a caster application with support on both sides. I know from experience a bicycle axle must be supported on both end or it will break or bend.

 

[Gordon Heaton]

Yes, Bill. Wheel rating is only valid for the type mount. Supported on both ends you only have to worry about shear. From personal experience with absolutely no engineering involved, I would use 3/4" as minimum, 1" as murphy-proof for a cantilever mount.

 

[fciron]

Good point about support. Increase your safety factor, one point of contact needs roughly twice the strength of two points of contact.

 

[Bill D]

Good point about support. Increase your safety factor, one point of contact needs roughly twice the strength of two points of contact.

I agree it needs double the strength for a single support but there is also leverage coming into play so it probably needs even more increased strength. Wheels I am looking at are about 2" wide at the axle.
Bill D

 

[fciron]

yes there is some bending to consider, but it’s not much and there’s no reason for you to be working at the hairy edge of failure. A wheel that is rated for four or five times your 500lbs. should be able to handle that 2” lever arm. (That’s already a safety factor in the ratings and you’re only increasing it.)

 

[crossthread]

My wood planer vs axle diameter spreadsheet says 5/8".

 

[henrya]

1” pipe with bored and inserted stub axles to suit your wheels. Cheap and easy to make.

 

[Bill D]

1” pipe with bored and inserted stub axles to suit your wheels. Cheap and easy to make.

I like the cheap and easy idea. I bet pipe is cheaper then solid rod. One inch NPT does seem strong enough to me.
Bill D

 

[Rob F.]

But 1" pipe will have an OD of aprox 1 3/8". Do you need to bore the ends? 3/4 pipe would be plenty strong 1 1/16" od & if you get sch 80 it is really close to 3/4" ID