Race Mower - Turnbull Garage video

As promised, here is the video that Richard put together of the Moh Canada race. It looks great! Big congrats to Andrew for taking home the win. That's all for awhile on this project, but I'm already planning a big rebuild for next year.

Race Mower - Month 3 - Race ready and Race day!

Now that we had a stout rolling chassis it was FINALLY time to get this thing moving under its own power. That problem I had with the centrifugal clutch... well here is what I did. I bought a cheap centrifugal clutch online that fit a 1" axle but it was meant to drive a chain. I then bought a cheap 1/2" pulley just big enough to fit around the clutch. I cut the middle out of the pulley, and welded it onto the clutch. 

It worked surprisingly well. I did dunk the clutch in more dirty cooling water than I would have liked to, but I managed not to warp it or ruin the bearings in it. Mounting it was another small battle. I spent the better part of an hour on my back with a grinder, grinding and hammering all the pegs and guides and things that were in my way. 

When it got to the first test fit the clutch slid on too far and rubbed on the motor case. I ground down some of the pin from the original pulley to use as a stop until it sat just right. Then I added a spacer on the bottom and bolted it all up in place. It was offset from the trans pulley by about a quarter inch but that was fine over the 19" distance. We dismantled the stock clutch pedal and utilized most or the under workings as a tensioner for our new belt drive system. 

Next all we had to do was shorten the old chain to fit our lowered rear end with the smaller sprocket and we now had a connection from the motor shaft, all the way to the rear tires. It was time to see if this thing would move!

And it did!

Reaching into the hood to operate the throttle by hand, I got it running good enough to make a couple laps around the yard. The trans did in fact work and we had the makings for a drivable machine. Now it was time to add all the controls to drive it properly.

First was the choke cable. I found a generic choke cable with a lever from the hardware store. drilled out the face plate it came with, heated and removed the knob, then mounted it through the dash where the stock throttle once was. On the carb end I utilized a mounting hole from the old governor plate to attach the end of the cable.

Next was to mount the foot pedals that would control the gas and brake. They were a nightmare to figure out as they were meant for a go kart with a tube steel chassis. I ended up scrapping their way of mounting the spring and stop as it just wasn't going to work at the angle I needed them. I mounted the pedals to 3" long pieces of 1" square tubing and bolted the tubing pieces to the running boards. 

The spring that came with them I ended up bending the end a bit in the vise so it would use the running board to spring against and screwed them down to it to act as the back stop to keep them from flopping over backwards. Lucky for me the bolts protruding through where the springs mounted to the pedals hit the tubing at just the right point to work as forward stops for the pedals. To hold the cable housing with the adjustment screws I just welded two oversized nuts to the side of the running boards and mounted it through those.

The stock air filter was long gone so I made this cool aluminum "tower of power" to hold a small aftermarket air filter. It screws onto the face of the carb from the inside and the filter can clamp on the outer diameter.

For the brake caliper it was an easy mount (also thanks to the available hoist that weekend). we used a couple long M8 bolts witch it was threaded for, along with a stack of spacers to mount it off the side of the chassis. We then set the disk inside it and clamped the disk in place on the axle using the set screw on the hub. The brake caliper had a simple screw terminal to hold the end of the cable from the pedal. After some quick adjustments we had working brakes.

We had to cut a slot in the floor for the brake disk to clear. Not my best work, but we were in a rush.

Dad was out racing so we stole his hoist for the weekend.

The final big piece was the throttle cable. I had to head back to school (off the island) so with the race under a week away my dad helped me out and figured out my throttle cable for me. He utilized the same mount point where i attached the choke. He drilled a new hole in the little plate on the throttle and used a rivet bent into shape for the pivot witch was then crimp connected to the cable. On the opposite side he mounted a spring to return the throttle when the pedal was released.

All that was left to do now were a few finishing touches. The steering wheel was a bit loose so I redrilled a bigger hole through the steering wheel and steering shaft for a new bolt. I grabbed the original seat mounting plate and fastened on a newer mower seat i had laying around. Lastly it got some fresh oil and it was time for a test drive.

I took it over to my buddy Nik's family farm for a test rip. It flew, but we lost gears, 1,2,3, and 5... Ooops. I guess i never did take a look at that transmission. A quick look inside and the fluid within had a color that could only be described as baby poo. With the race tomorrow morning there wasn't enough time left to dig into that. I added some heavy gear oil to the baby poo mixture and hoped that 4th gear would take this thing to the finish line. Or at least 1 lap, heck, id be happy if it pulled away from the start line.

Lined up at the start line (Nik's mower to the left)

That little mower did all that and more. Though we didn't place well we sure had fun, and we weren't even last. Part way through lap 1 of the first race we lost 4th gear, but seemed to regain 5th. It took me awhile to figure out how to get it up the hill in 5th, but after a couple running starts we were back in the race. We completed 5 laps and were still running at the end of the race. Race 2 we got 1 real good lap in before the transmission gave in altogether. 

It was a ton of fun, and I hope to be back next year! I took the go-pro camera along for the ride and sent my footage to Richard from Turnbull Garage, who is putting together a video covering the event. Ill post his video on the blog when it is ready!

Race Mower - Month 2 - The rear axle.

 Now it was time to make this thing move... or not. I wanted to change to a centrifugal clutch, and thought id just pull off the stock pulley to check the shaft size. It was seized on good! After I spent over an hour with pullers and hammers I had the stock pulley off the motor shaft. I was not about to put it back on. 

The motor turns out to have a 1" shaft and unfortunately for me a 1" centrifugal clutch with a pulley is not common and would run me about $200. It was time to work on something else while I figured out the best move on this issue. Time to tackle the rear end.

There were a few tasks involving the rear end of this mower. One was to get some new tires on it since the old ones no longer held air, another was to lower it to match the front end, and since this was a race mower a smaller rear sprocket was certainly in order to get some more speed out of this thing. With that gain in speed it seemed only natural to add some stopping power somewhere (since it barely had any brakes in stock form) and upgrade the bearings.

*This bushing sandwiched between two plates was the stock bearing*

First I pulled out the old axle and dismantled it. The stock sprocket on the rear end had 55 teeth, and it was HUGE, in fact, it was the lowest hanging part on the mower so it was best to get a smaller one on there for that reason too. 

I went into my shed and was blown away to find an old mobility scooter differential that was almost identical to my mower differential. It may make a fantastic spare in the future, but for now the most interesting part was the 27 tooth sprocket attached to it. It would effectively double my speed and by the looks of it was the smallest sprocket you could fit on that diff. PERFECT! well,... almost perfect. The chain and sprocket on the old mower was a #41 and this sprocket was a #40 witch is a thicker chain and sprocket. Luckily though the two sizes share the same pitch and overall profile so all I needed to do was make this one thinner. I took it to the lathe and turned it down to the correct thickness and re-chamfered the freshly machined side. The bolt hole circle to attach it was also different so I had to drill another set of holes in it to fit the mower diff.

Next were the brakes. The axle only has a keyways on the ends for the tires to attach to so I was not going to be able to use a hub with a key. I found a brake disk from an old ebike and turned a custom aluminum hub for it. 

To attach it to the axle I ground a flat spot on the axle and used a set screw in the hub to hold it in place. I bought a cheap mini bike caliper and turned down the ebike disk to fit it. Probably would have been best to just buy the matching disk with the mini bike caliper, but I'm cheap and had the means to utilize a free one.

I disassembled the differential and regreased it before reassembling with the new sprocket and brake disk.

Now it came to mounting the rear end. The original bearings were nothing more than a couple bushings with some grease so we definitely needed an upgrade. I also planned to use some narrower tires so we could now mount the new bearings a little further out to increase support for the axle and allow us to run a standard pillow block bearing. I cut two pieces of angle iron to hold the bearings and mounted them up as far as they could go. 

The rear end ended up a tiny bit lower than the front but I may eventually run larger tires in the back so this is no issue and was barely noticeable. Next was to test fit the axle and figure out some spacers. It turns out the matching rear tires from the same scooter I used for the front end fit the rear axle perfectly so it seemed only natural to use them. Now I would have 4 matching rims and tires. OCD very satisfied. 

For spacers we ended up finding a set of cheap bushings that worked perfectly for us. Two on each side put us almost perfectly to the end. A couple washers to take out the slack and we had it sitting on 4 wheels again, now fully lowered.

That's all for this post. Next post its time to tie this all together. Belts, Chains, clutches, pedals, cables.