Re: Anti-Scalp Roller Mod\'s?
One more thing....
Just e-mailed the folks at Castercity.com asking for their advice. Here is what I said:
I am looking for some replacements for the anti-scalp wheels on the mowing deck of my tractor. The OEM (Kubota) wheels are a hard, black plastic (like the ones on you riding lawnmowers at home). These wheels are plain-bore. No spanner bushing, grease zirk, bearings, etc. The mowing deck itself weighs over 250 lb. and the tractor/deck combo weighs over 2300 lb. The purpose of the wheels is to glide just at the top of the grass and 'catch' the deck when going over rough ground to prevent scalping. They are NOT intended to carry weight at all times. That being said, they DO take extreme shock loads when the deck dips down or when an immovable object is encountered (like a tree root protruding above the ground). The bottom line is that the OEM wheels wear out every each mowing season. The unprotected hub wears ('wallows') out and the 3/8" axles wears and becomes egg shaped (due probably to lots of grit/dirt getting inside the axle/wheel contact surfaces).
I frequently participate in a compact tractor web discussion group (Tractorbynet.com) where many of us are having the same problem. I was 'elected' to be the test subject in the search for an improvement. So, if I can find a replacement wheel that will last, several other folks are likely to follow behind me with additional purchases. Are you game to help me out?
Here's some specs I am looking for:
Size: OEM is approx 5" Dia by 2" W. Need to stay close to the 5" diameter due to space limitations. Can go a little wider, but would rather not go any narrower….do not want wheels to leave an marks in soft ground.
Tread: Very pronounced crown, smooth tread surface (wheels will encounter sideways 'sliding' when making sharp turns)Very much in appearance to your crowned gray rubber caster wheel here:
http://www.castercity.com/GIMRW.HTM
Axle size: The OEM axle is ~5/8", but I could easily go to 3/4". I'm afraid that 1/2" may be too small….but I do not have calculations or any data to verify that. Maybe with the correct grade of steel axle I could reliably go with the 1/2" axle size?
Bearings: Some type of roller bearings (you advise) would be preferred. Probably need some sort of bearing seals to keep dirt out. Need grease zerks….tractor fanatics love to grease stuff.
Elastomer: Need a polymer that can handle substantial shock loads without shattering or severely chipping. Looks are not an issue - small dings and scratches are not a problem (but would prefer black in color if given a choice).
Hub Width: OEM is somewhere in the 2.25 - 2.5" ballpark. This is not critical except to the extent of need to spread shock loads (?).
Also, OEM is a offset hub design, not a centered hub. But, I can make a centered hub work…just may have to use some sort of spacers to keep the wheel out away from the mower deck body. I only need to keep the wheel out from the body by ~1/2".
Price: A set of 4 OEM wheels cost me ~$35 or $8-9 each. So, must balance price of this new wheel against price of a set of 4 OEM wheels each year. Basically, the new wheels should be economically attractive in the long-term.
One other note: these are fixed position wheels, no castering.
Check out this page for pics of the EOM mower deck wheels:
http://www.carverequipment.com/images/BX2230_with_60_in_mmm.jpg