OutdoorKing Repair Forum Forums Repairs and Maintenance Questions On Ride On Mowers Questions on Greenfield Ride On Mower Frames Greenfield Drive Axle Repairs

Have a 21st anniversary greenfield 8hp/28cut that I wish to get back on the road/grass. The rear drive sprockets have worn out and I am looking at replacing them. I am looking at putting the shaft in the lathe to cut the sprocket off and purchase a new one from a bearing shop. My main issue lies with the tapered axle ends where the alloy wheels are keyed on to the shaft. The alloy in the rims has chewed out which has allowed the key to move and has significantly flogged the shaft.
I am interested in recommendations on how to repair or overcome the damage.
At this stage I am looking at welding a new key onto the shaft and carefully grinding it back. The alloy wheels being flogged out I was thinking of drilling,tapping and putting a grub screw on the opposite side to the key to try and hold it in place.
Your thoughts?

First post - so Hello everyone.

HI Tritium, I hope your ID doesn't indicate what you mess with for a hobby. You haven't said whether the keys are rectangular or Woodruff, and you haven't said whether you have access to a milling machine. If they are rectangular keys, the usual fix is to mill another keyway in the shaft, 90 degrees around from the original one, then fit a key identical to the original one. That gets you back to having a fully repairable machine that uses standard parts. If you can source replacement sprockets, there is no drama relating to the job except for cutting the keyway, which is easy (as milling jobs go - you do need careful setting up, and a saw or endmill of exactly the right width to match a standard key).
Normally I would not expect a combination of a grubscrew and a loose key to work any better than a loose key by itself: in other words, not at all. I also think your plan to precision-grind the width of a welded-in key, in place, is impractical. You could probably deal with the height that way, but not the width.
So far as the wheels are concerned, the best solution is to get another pair. Short of that, depending on their design you may be able to either bore and sleeve the ones you have, or cut the centers out of the wheels, make new steel hubs, and bolt the new hubs to the old wheels.

Thanks for your reply and input Grumpy.
The ID I've imported from the Newtriton website and reflects that I drive a Mitsubishi Triton. A single atom of Tritium is called a Triton.








No access to a mill unfortunately. Woodruff keys are used.
As can be seen from the photos mower is close to its useby date. I just want to keep it going that little bit longer. I don't actually need a ride on (live in town) but want to use it for shunting my caravan around plus the odd mow here and there. I was also thinking of roughing the shaft up and using some bearing loctite and adding a few washers between the nut and wheel to push it on real tight. Another thought was to drill wheel and shaft through and pin the assembly. Basicly a low cost repair is what I am looking for as she isn't worth much. I bought three Greenfields together two older 11's and this 8. One of the 11's goes OK but leaks oil, the other goes but needs "start ya bastard" to get it going. Plan on selling those and keeping the little one as storage space is at a premium.

The wheel keyways look OK in those photographs. If that is correct, you only need a solution for the Woodruff keyways in the axles.
Long ago I knew a guy who had the same problem with a more expensive component: a Woodruff key in a vertical shaft driving the overhead camshaft of his 1937 MG NA. He silver-soldered the key in place. As my father predicted at the time, it lasted less than a week of driving to work. The bearing pressure silver-solder can stand is very low. Bronze would have had some chance. A good gas welder using mild steel filler could fix it permanently, but it would be hard work hand-filing the shaft on the two sides of the key to make it fit the hub again: probably a couple of hours of careful work, involving many expletives. (This was not a feasible solution for the MG - the vertical shaft was also the armature of the generator, and the windings would not have stood the heat). I think that kind of welding is a feasible way to repair it "as good as new". What I think I would do myself, is make a "stepped key". You would have to get someone to mill out the damaged keyways in the shaft to a greater width, so they were perfect again. You would buy or make Woodruff keys of the new width but the original diameter, then mill or file way part of them on each side to fit the hubs, so that each key would be thicker where it fitted into the shaft than it was where it fitted into the hub. My father taught me that trick long ago, when I had the same problem as you have, with one rear axle of a fairly rare model of 1937 Austin. He made the replacement key (a rectangular one, not Woodruff, IIRC) from high speed steel, so it wouldn't break again. (It didn't - thus losing me an argument. I had bet that the lower impact resistance of the very hard HSS would result in brittle fracture).

The alloy wheel is actually fairly flogged out where the key engages when assembled. I expect the action of the quick forward/reverse changeover is fairly harsh on the drive components.
I was actually thinking of putting a key in and filling either side with arc weld and then grinding excess back. This still doesn't solve the flogged out alloy wheel hub issue. Another thought is to leave the key out and drill two holes through the wheel hub to pump some epoxy liquid steel in. If I get a flat I'll just have to fix it on the rim.
What do you think of a through drilled pin?

hi all,
i agree with grumpy that if you can find a mill and have it precision cut it would be a pretty permanent repair. even if you have to take it to a shop its only a 5 minute job, probably cost $50. then to enlarge the hub to fit the wider key a file could be used fairly easily and accurately.
as to the drilled pin idea you would need to use a very hight tensile material for the pin,at least 1/4 inch thick stainless to sustain the pressures of the sharp change in motion (theres that bloody inertia again). so if you drilled it as close to the start of the taper you may be OK for the short / medium term, but in the end i would reckon that the high tensile pin needed would strip the alloy rim and mild steed axle causing real problems.
alternatively try mower shops for second hand bits. if you live near hastings, try hastings mowers as they have quite a bit of junk laying around.
welcom to the forum!
regards jay

You can calculate the cross sectional area of the Woodruff key - it is just the thickness of the key times its diameter. A pin would be in double-shear instead of single shear as the key is, so you need the cross-sectional area of the pin to be half that of the key. I don't know the dimensions of your key, but most likely you can achieve sufficient area to be able to transmit the torque. However you require a good fit between the shaft and the hub; neither a key nor a pin can work unless all of the fits are tight.
A way your problem might have been fixed in the old days would be by fitting two tapered pins of suitable diameter, at right angles to each other and about 10 mm apart axially along the shaft. If there is a small engineering workshop in your area they may have the pins and the special tapered reamers you have to use to fit them. It is a very simple job for someone with experience.
Most amateur-fitted parallel pins fail. This is because they are not properly fitted. To have any hope the holes have to be drilled through both parts simultaneously (that is, with the axle and shaft pre-assembled), then with the parts still assembled, the holes have to be reamed to the exact size of the pins, and the pins driven in and then riveted neatly on both ends. I've never seen a successful job where the holes were not drilled through both parts simultaneously, and precious few where the holes were not reamed to fit the pins exactly.

I'll be pulling the shaft out to replace the sprocket so I will probably do what basic repairs I can do to improve the keyway issue. Then fit the wheels and try drilling a pin in. Will probably have to remove the tyre and drill through the rim to get a clean shot at the hub. Wonder what a new shaft costs?.

What do other brands of ride ons use to attach drive wheels to the shaft?.

Pity they weren't steel rims....a strategically placed bead of weld would have sufficed.

Finding some second-hand replacement parts at the right price seems like the best solution. If that isn't possible, why not look around for some steel wheels? If the axle size is too small you can bore them out, and if it's too large you can sleeve them. (I don't recommend turning the axle diameter down to fit smaller hubs: the axles might break.)