Build a Lawn Mower Caster




About: Engineer, Critic-at-Large

Casters are no longer available for my electric lawn tractor. Here's how I built a replacement.

Some History:
GE designed and built several models of Elec-Trak electric lawn tractors in the '70s. Mine is a 36 volt model built in 1971 (more pictures below). It has a front-mounted mower deck with casters.

I broke the right hand caster. There are a few people making parts, like the Electric Tractor Store, but I needed to mow the back yard this weekend. Off I went to the farm supply to see what I could piece together.

If you want an electric lawn tractor, your choices are limited.
(1) There are many of these 1970s Elec-Traks still going strong, but people don't seem to like to part with them until they die (either the people or the tractors). They seem to be most common in the Midwest -- you might pick one up there for less than a grand (eBay or Craigslist). Kansas Wind Power sometimes has one. Check out for tons of information on these durable machines!
(2) You can order a new Electric Ox. from Canada. Sweet electronics, no mechanical transmission. You may need a loan though.
(3) You can wait for Modern Electric Tractor Inc. These folks are setting up to build updated versions of the Elec-Trak design, as well as improved models. Word is the prices will be similar to those of professional mowers, not consumer models.
(4) You can mod a consumer gasoline tractor. Later, you will weep as all the expensive parts you added lie among the rusty ruins of the crummy donor tractor.

Step 1: Root Cause

Some idiot drove a 1000 lb. lawn tractor into the ditch and jammed one of the casters into the ground. It broke at the weld, just like they warned us in school.

Step 2: Bits and Pieces

The farm supply store is a den of temptation. Aisle upon aisle of bits of machinery. Only the farmers know what everything is.

There were about 30 bins of casters. The only one with a long stem was for a bush-hog type mower, and it was way too big. I finally found one designed to go on a trailer jack that was held together by nuts & a bolt, so I could disassemble it and put in a bigger bolt for the stem. See photo 1 below for details of the hardware.

Total cost: $20. The nuts alone would have cost that much at the home improvement store, except they don't carry anything that big. Farmers have bigger nuts, and they buy them by the pound.

Step 3: Tools

Beyond basic hand tools, you need:
(1) a small drill press with clamp
(2) 15/16" and 1-1/8" wrenches or sockets and a big adjustable wrench or another 1-1/8"
(3) a 3/4" drill bit. Big twist drills are pricey, try Harbor Freight or Big Lots. Next time I'll try a step drill from Harbor Freight. In a pinch you can use a Dremel or die grinder, but it'll take f o r e v e r
(4) a bench vise. Locking pliers (Vise-Grips) could work if you have a third arm to hold them.

Wear your safety glasses!

Step 4: Make New Stem

We want the threads to go through the yoke so we can attach it and we want the smooth, unthreaded part to push up through the bushing on the mower so we can adjust it. Too bad the head is on the wrong end.

First we'll drill a hole for the clip near the head of the bolt.

Then . . . off with the head!

Step 5: Diassemble the Caster

Take the hitch pin off.

Unbolt the wheel.

If there's a tricky part, this is it: the head of the bolt is welded into the cup. Don't mess around trying to get a wrench on it, just clamp the cup in the vise.

The jam nuts have been deformed a bit to keep them from vibrating off, so you'll have to wrench them all the way. You only need one wrench or socket since you're only removing them.

Step 6: Open the Hole

Here we have to open the hole from 5/8" to 3/4". Next time I'll try a step bit, my 3/4" bit is dull dull dull.

Clamp the yoke to a block of wood and feed it slowly. Wear your safety glasses!

Clean up the EXTREMELY SHARP edges. I used a file, but a Dremel tool would have been easier to use and done a better job.

Step 7: Assembly

Doh! The nut hit the wheel!
Omitting the wheel-side lockwasher fixed that.

When you get everything the way you want it (i.e. when the nut don't hit the wheel no more), take the wheel back out and clamp the stem in the vise. Using the adjustable wrench on the stem side nut and the 1-1/8" wrench or socket on the wheel side nut (see the second picture below), tighten the living daylights out of them. (Pocket Ref says you can go to 257 ft. lbs. on a Grade 5 Bolt. Good luck with that.)

Grease up the outside of the cheap axle bushing, push it into the wheel, and put the wheel back on. Tighten the axle bolt until the yoke clamps down on the axle bushing.

Viola, the caster, she is done.

Step 8: Installation

The deck height is adjusted by adding or removing spacers from the stem of the caster. Grease your stem, stack up washers and spacers to get everything even, and put it back on the mower. Stack the extra spacers and washers on top (always use a metal washer on the very top to protect the plastic) and secure with shiny new hitch clips.

Now we're mowing without gas!

Also we're mowing without much noise or pollution, and with a 37 year old machine that is still going strong with a minimum of care and maintenance.

Step 9: Post-Mortem

Thanks to my no-measuring build technique and some inevitable geometry, the new caster won't let the mower cut grass as short as it used to. Maybe half the difference is due to wear in the wheel, so it's really only about 5/8" taller than the original mower. Fortunately, I don't need to cut that low, but you might.

You could probably get it to within 1/4" of the originally designed height by omitting the other lockwasher, using the thick nylon washer from the trailer jack caster assembly in lieu of the 1/2" nylon spacer (there must be at least one nylon part on top of the metal part of the caster assembly), and trimming the thread end of the bolt to keep it from hitting the wheel. If you really wanted to get it to the SAME height, you would also have to find a thinner nut for the stem side.

Upgrades: for $15 I could buy another caster that has a heavier solid wheel and a hollow axle with a grease fitting that I could swap with the wheel and axle here.

As always, there were some parts left over.

I know there's kind of a limited audience for this Instructable, but it was fun to make and it might actually help someone. Hopefully it will spark a little more interest in electric lawn tractors and mowers as well. Thanks for reading!



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    16 Discussions


    6 years ago on Introduction

    This is really cool! I hope to do something similar here shortly. :)

    BIL Castors and Wheels manufactures and supplies castors, casters and pneumatic wheels. Great deals on casters, big savings on pneumatic wheels. Huge selection of castors for all applications


    9 years ago on Step 7

    You probably would have been better off omitting the flat washer and keeping the lock washer to keep it from vibrating apart (it is a lawnmower after all). You could also either grind the nut down so it's not as thick or used a jamb nut (not as thick as a normal nut), since you don't have the bolt fully threaded into the nut that you're using anyway (in steel 3 threads at 50% depth have are full strength). For that matter, you would have been better off just welding it.

    3 replies

    Reply 9 years ago on Step 7

    Alas, I did not have access to a welder and I could not find a jam nut in that size. I did not think of grinding down the regular nut. My logic for keeping the flat washer was that it would be better at spreading the load at the joint while the lockwasher on the other side would still provide tension. Its not a constantly rotating joint and there's not a lot of torque load being transmitted since the top is free to rotate in a sleeve. It's been about a year with no problems. Corrosion will eventually lock them together


    Reply 9 years ago on Step 7

    (oops -- I hit the "post" button too quickly!) Corrosion will eventually lock them together better than any lockwasher. If I do the mod to get more height adjustment (see step 9) I'll grind down a nut like you suggested if I can't find a jam nut. Thanks!


    Reply 9 years ago on Step 7

    Heh, that's probably the best approach... if it works let it all rust together and worry about it in 20 years when the next part breaks. ;-)


    Reply 10 years ago on Introduction

    Thanks! It was pretty strong to start with. If it lasts another 37 years I will be very happy!


    10 years ago on Introduction

    Hoorah! Somebody who fixes old (or new) equipment rather than just slinging it away, modern society has created a breed of utter morons! Nicely done repair that, economical too -- didn't cost a fortune did it!?! I like how you sought out a part to do the repair with and the fact that it was an ingenious bit of bodgery to make a completely unrelated part fit, using simple tools and a bit of the old grey-matter in your noggin'. What's more is that the design is modular (within reason) to allow (or hinder slightly less anyway) the facilitation of repair to some degree. Take a look at more or less anything now and they all have completely unmodular wheels and parts, unique to the given device -- it would also seem that parts are no longer manufactured to do repairs with, what a to-do!

    2 replies

    Reply 10 years ago on Introduction

    Thanks! It was less than $25 US for the parts, maybe 2-3 hours of steady work to build & photograph. I probably spent more time wandering around Lowes & Agricultural Supply Co. looking for parts than I did actually building, but that's more like a vacation. I know I spent more time putting the Ible together than everything else combined! I'm with you, things ought to last longer & be rebuildable/upgradeable. That's one reason I bought the ET -- I went to buy a new Infernal Combustion mower and EVERY one of them had a plastic ring gear on the flywheel side of the starter -- guaranteed to wear out. I had recently repaired the same thing on my previous mower, and the replacement part is aluminum. I'd love to to be the guy that sells every family in America ONE inkjet printer that takes generic ink and lasts forever.


    Reply 10 years ago on Introduction

    Your welcome. I'm glad that I can add one more person to my do-not-hitlist. This world needs a little chlorine in the gene pool. It seems that everybody these days is rather self-obsessed and nobody is truly happy, the rat race and all that -- it just steals your soul and locks it away in an impenetrable fortress -- but.. locks can be picked and security bypassed. Happy modding!

    Phil B

    10 years ago on Introduction

    Your's is a good solution for anyone who does not have access to a welder. A welder or a friend who has one would open more possibilities.

    1 reply
    ScubabubbaPhil B

    Reply 10 years ago on Introduction

    Yep. GE actually made an arc welder to plug into the battery pack on the tractor, but I don't have one. I could have had the stem welded back but the yoke was badly worn from the wheel rubbing on it. A good welder could have fixed that too, but it would have cost more and taken longer. That grass needed mowing immediately!