We Need To Talk About Front Tires

 The tires I want to use are 20" fat tires. I also have 16" rear tires from a lawnmower, but they don't have brake mounts. Weight is one of my biggest concerns. The fat tires are about 18lbs each. The lawnmower wheels weigh 5lbs more each. 

The CV joints that I got have 21 splines. I can't find axle hubs that fit. Everything I found uses 23 or more splines. And the axle hubs would add more weight. Ideally, I'd like to mount the wheel/brake directly to the CV shaft, if I can.

I removed the axle bolt from one of the 20in Fat tires to see how it's constructed.

It looks solid. The center hole is 12mm and the inside of the flange is 25mm. If I turned down the spline on the CV axles, the diameter of the CV axle would be around 20mm. I think the 12mm hole could be widened to 20mm.

I'm waiting on an aluminum front wheel hub that I want to study. It would be great if I could modify an existing hub to fit on the CV shaft. Maybe I could turn a custom wheel hub for the fat tires on the lathe? 

Rudy February 11, 2023

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A New Idea For The Front Axle Hub

I've reimagined the front axle hub, keeping our machine shop captain's advice to run the axle directly into the hub of the front tire. Instead of one, solid machined piece, the bracket is now 5 plates welded together. The bearing that supports the CV would be pressed into the outer plate. The outer plate includes mounting holes for brake calipers. An eye bolt is positioned at the necessary pivot point.

The bracket would sit on head bearings (from bicycle necks) and secured to the wheel frame.

I added rabbits to the mating parts so that everything self-aligns when it's clamped together for welding. Here it is with the tire on:

Mounting the tire hub still needs more research. I need to see if the hub has enough material to cut splines into, which would mate to the CV joint's spline shaft.

If all that can work, it'll still need a long bolt to clamp everything together. That would need to be turned on the lathe.

Rudy February 06, 2023

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A Place To Hang My Differential

I worked on the brackets that will secure the front differential to the main truss. They would be made out of flat plate (probably fabricated on the Tormach CNC Mill at Lowell Makes) and welded together. They would be bolted to the frame in 3 places.

The space between the brackets where the sprocket is located is the width of the differential that I measured from the housing, minus the difference in the thickness between the original ring gear and the sprocket that will replace it.

Cleaning the differential is going to be a messy job that will require a pressure washer using hot water. I'm going to wait until it gets warmer to do that job in our driveway. After it's clean, the pins that hold the ring gear to the differential will be drilled or pressed out. 

Hopefully, the holes can be reused to attach the front drive sprocket to the differential. The differential axle will be attached to the CV axle with universal joints. Universal joints should work, since the angle between the two axles will always be small.

In the meantime, I am working on the last front-end issue: where the CV joint meets the wheel. 

This first idea would cost way too much to fabricate and would probably be too heavy, even in aluminum. 

I'm thinking about using some kind of C channel or bracket. The CV joint would sit on a bearing mounted to the back of the bracket. The legs of the 'C' would be bolted to the frame with thrust bearings (or maybe headset assemblies from mountain bikes) supporting the hub.

This is the area with only the required pieces showing:

The eye bolt attaches to the tie rods used for steering and has to be at a specific angle to the CV axle. The CV axle is supported by the bearing. To use headsets from bikes, the frame ends would have to be tubes. But if we use thrust bearings, it could be a plate (probably gusseted).

Rudy January 28, 2023

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Exploratory Surgery On The Transaxle

 I opened up the transaxle! The layout of the parts inside is a little different than I imagined.

The ring gear is a largest spur gear and it's riveted to the differential housing, acting as an endcap.

It will be difficult to remove that gear to replace it with the 36 tooth sprocket. But if I can drill out the rivets, I think I can use those holes to bolt the sprocket to the differential housing.

The shifter plate has square slots, so I'll have to make my own shifter plate to interface with the pins I want to press into the drive pulleys. At least I will be able to use the arm that slides the shifter plate along the shaft.

There are also bevel gears in there that I need for the water jet project. All in all, a pretty good haul.

I also measured everything inside the casing, so I can now work on finalizing the front end.

Rudy January 22, 2023

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We've Intercepted a (Rebel) Transmission

 I removed the rear axle from the lawnmower! 

Two bolts were the only thing holding it on. Once I took those off, I was able to get the belt off without too much trouble. 

The tires still have to come off. The bolts holding them on did not loosen on the first try. I'll take another shot tomorrow from the comfort of the sealed garage. Then, it's time to crack open the case to retrieve the differential, the shifting mechanism, and the bevel gears inside. The front end can be finalized once we have these pieces.

I also fit the 28 tooth sprocket onto the hub-conversion brackets. 4 of 6 fit easily. But 2 of the holes were not on the same bolt circle. I enlarged those 2 holes enough that I can now secure all 6 bolts.

I've been finalizing the rear mounts. I think we're close to making the parts that will secure the rear wheel to the main truss.

Rudy January 21, 2023

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IRL Parts!

 I got the new rear hub yesterday! It's pretty.

I also received today a single speed conversion kit and a 28 tooth wide sprocket.

I need to confirm if the sprocket actually fits. Otherwise, I'll have to find a sprocket that I can modify.

Rudy January 18, 2023

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So That's How a Lawnmower Works

 I spent 2 hours on saturday studying the lawnmower frame and how to detach the rear transaxle. I found and removed 4 bolts that attach the transaxle to the frame. 2 came off easily. I had to cut the other 2 off. There's a belt that goes from the engine to a pulley clutch and another belt that goes from the clutch to the transaxle.

I can loosen the big belt with the clutch, but I haven't figure out how the belt comes off in one piece. There are tabs acting as guardrails that keep the long belt in place. I can't seem to remove the belt without bending the tabs out. Seems like there is another way. I'm going to do some youtube research before I do anything with that. I might not have to touch that anyway. Other than detaching some springs, I think the transaxle is now only attached by 2 more bolts.

I think if I undo these bolts, I won't have to mess with the belts at all.

I spent the rest of Saturday fixing my virtual model of the center truss. The IRL frame has 9 cross-members. My model had 10. I spent most of Saturday taking measurements and trying to make my model match. It's tricky, because I can't measure to the center of anything. I have to estimate based on the distances at the intersections. 

I'm glad I did, though. I already have to shift some things around in front because of the slightly different geometry.

Rudy January 16, 2023

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