Race Mower Project

We had a chance to work on the project for a while today and got a few more things done. We have been trying to concentrate on the steering components and we were able to design and build a few more pieces. I know it doesn’t look like a lot was done but it all takes time and we’re sure having fun doing it. The drive system is up next.45E5C54C-9DE2-4B39-8AFF-B5B9BABA744F.jpeg14C92D2F-CA6D-4D14-B9A8-BBBB2B232023.jpeg7774AF07-18AF-41E3-9335-10F86D062FFB.jpeg
 
Well I have a little update on the race mower project. I had to put it on hold for the last several weeks do to a home remodeling project that took precedence over the mower. I gutted our master bathroom and did a complete makeover, something my Wife has wanted for a while. Anyway it’s all done and I get to play in my shop again.
We did get a chance to get several things done on the racer and I think it’s coming along quite well. We concentrated on the drive system and have that pretty well completed. I am waiting for the sprocket for the rear axle so we can compete the chain drive to the gear box. The clutch system is in and should work fine. I didn’t bother with all the keys for the shafts at this time because it all has to come apart again for painting.
The steering system is pretty well completed except for a steering wheel, which we need to find yet. All the fasteners on the steering system will have nylock fasteners when it is reassembled after painting. As the last picture shows, we are setting up the rear fenders and seat assembly, using a cad program, lol.
All the figuring and hard work is starting to show some results now. Hopefully we may have it wrapped up in a few weeks.219B8C18-F04D-49C3-BCCD-A02848A38936.jpeg204F79AB-DFBA-4A2A-AD8E-3776CDDA0A4D.jpeg2395CAD8-2E8E-4B45-A493-100A30D2A5F6.jpeg68077E88-8874-4AD8-BDEE-A77A024B62F9.jpeg5CB6E38F-AD4D-4F10-B473-636E3F3BE54C.jpeg761DE94A-E386-4F20-B504-4E1AAE3EA964.jpeg0A3BB745-4C5E-4179-949F-CBC17D1E0CB6.jpeg847AE310-3ED7-458B-967A-8B4545395C5C.jpegA9A027A7-4302-4654-9AE2-7FDCE970EAD9.jpegE4A0F1F8-08BF-4412-89B9-45753391C834.jpeg0FA51E78-5777-4670-A6FF-5E926F60F817.jpegF990971C-5CC8-4A26-95D1-897DD3B7A480.jpeg
 
Great progress Bill, i really like seeing stuff like this. Is there something in the rules against running front suspension, with the steering support there it will be very easy to mount shocks and if you get the spring rates right you'll have very big advantage in the corners.
 
Thank you for the reply. The rules that we are running under don’t allow for front or rear suspension. I agree that it would be a huge advantage in the corners but the idea is to keep it rather simple in design, so more can compete.
 
Bill, you know there is a way to cheat, you can use a truck leaf spring in the middle of the front axle and you'll get limited suspension travel that can make all the difference.
 
We made a little more progress on the racer today, getting the rear fenders fabricated and a seat back welded in. It was another great day in the shop with my Grandson.D6E8060B-ABCE-4D35-A5ED-33F59BDF2F1B.jpeg3E959995-B80C-4ED8-8F34-FAB20847954D.jpeg522A724F-C9E0-471A-8283-72BB5D6033D7.jpegE1DA698D-BC0E-4571-95B2-33609A28AADE.jpeg77C5497A-B3FC-4038-8947-89FAF7DB8E0B.jpeg
 
Dang, that looks like it's gonna be a fun machine!

What sort of speeds do they attain?
 
The machine is geared to hit a top speed of about 28mph. This can easily be changed with sprockets to make adjustments if needed. The way it is set up seems to work well for the track they are running on, utilizing the torque band of the motor.
 
A question: most cars have the "king pins" or steering knuckles close to or on the centre line of the hub. Gokarts and your race mower have the whole steering mechanism on the insed of the wheels - even some distance away from the wheels. I don't understand why. That would increase the forces on those pivots enormously and make the Ackerman steering geometry seriously ineffective, as the wheels go around an arc, rather than pivot around their centre line as Ackerman would have anticipated. Is it a fabrication issue or a racing geometry reason?
Cheers,
Joe
Having the king pin closer to the center of the wheel, is always better, but how much? In this case, there is no way to fit the kingpin inside the rim. The next best solution, is to have the line drawn through the kingpin, to meet the road in the center of the tire contact.

So what happens if the line is not in the center? A blowout, can cause the steering to pull dramatically to that side. An issue with the braking, can cause the steering to pull, as can bumps. In this case, with the small tires, and no brakes on the front, None of those are going to show much, except maybe the bumps. A big bonus of having that line meet to the inside of the wheel center, is while moving, the forces are trying to pull both wheels outward, Essentially taking any play (what we call backlash) out of the steering system.

In the end, it is all trial and error. Just look how race car teams spend the week prior to a race getting the car dialed in to that track.

You can not just angle the kingpin more, as the steeper the angle then you are causing the front end to lift when the wheels are turned. But that does add a benefit of the weight helping to keep the steering centered.
 
We made a little more progress on the racer today, getting the rear fenders fabricated and a seat back welded in. It was another great day in the shop with my Grandson.
Can I be your grandson?

Great work, something your kids, and Grand kids will remember forever.
 
Back
Top