Heymow - Lawnmower Racing Forum
Mower Building / Setup Help => Project Builds => Racing Mower Builds => Topic started by: turbo_bird on September 08, 2018, 10:38:41 pm
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Hi all, I've been wanting to build a racing mower for quite a few years now, but never really had anywhere to race one, but I moved a few years ago and the local fall fair runs a race every year. Time to get off my butt and get building. They don't really follow any official rules that I know of, so things will be different from a lot of other builds on here. I'm not allowed to run a centrifugal clutch on the engine unless it's a snowmobile type, only L shape spindles are allowed, 5" minimum ground clearance, turf tires only, and no engine mods. I've got a few old mowers to scavenge from, and I'm trying to do this for as cheap as possible. I've got an old Toro that I'm going to rob the 3 speed transmission from, an MTD that's going to donate it's 15.5 Briggs, and an old Craftsman for the frame. The local guys run two mod classes, up to 17 HP and up to 22 HP. I haven't got any building done yet, just reading and taking stock of what I've got for parts. For tires I've got a new set of the most aggressive looking turf tires I could find, 15"x6x6 for the front and 18"x9.5x8 for rears. I was planning to use the Foote transaxle out of the Craftsman, but reading about them being weak I think I'll switch to the transmission out of the Toro. That will also let me get my seat lower. That's about all for now, I better pressure wash some of this junk and start tearing stuff apart.
Kristian
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The Torro that's donating it's transmission. It's an old 3 speed, but that should be ok for what I'm doing.
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I got a couple of my donors tore down today and had a look at what parts I have. I'm going to have to pick up a piece of 1" round for my rear axle, and somehow adapt my wheels to fit it. The wheels I have are for a 3/4" axle with a square key. I may just turn down the ends of the 1" to 3/4", that would probably be the simplest solution. I should be able to make them nice and tight too. The 3 speed transmission I have is going to be belt driven from the engine with a tensioner as my clutch, seeing how I'm not allowed to run a centrifugal clutch on the crank. Then it will be chain drive back to my solid axle. I pulled apart the transmission today to check it out and clean the grease out, as well as take out the reverse chain. It's a Foote with bushings instead of bearings, but it should hold up a with a bone stock 15.5. I'm not sure what frame I'm going to use now, the one I was originally planning to use is only 12" wide, but will give me a 42" wheelbase. The other one is 17" wide at the rear and tapers to 12" at the front and will give me a 40" wheelbase or so. The rails are parallel for about the half the frame, then taper in. It's also just a pair of stamped c channel rails, where as the other one is one stamped piece and very flimsy for the weight. I'm leaning towards the wider one because the axle will be better supported.
Kristian
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Are talking about Barriere? Or does Kamloops have a race too?
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Are talking about Barriere? Or does Kamloops have a race too?
I'll be racing in Barriere. I live in the middle, Kamloops is just the nearest city. Are you one of the Barriere racers? I think they do some racing in Armstrong too, I might head that way as well.
Kristian
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I'm from the West Kootenays and I race with the North Okanagan Lawn Mower Racing Club. This past weekend we were in Salmon Arm Friday/Saturday and Grand Forks Sunday. Busy weekend! Armstrong race is our club, Thanksgiving Saturday.
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Cool, I didn't know there was any racing in Salmon Arm. My in-laws live there, maybe I'll have to visit them more often. If I have something put together for Thanksgiving I might try to get to Armstrong for the race. What classes and rules do you guys run?
Kristian
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I'm going to have to pick up a piece of 1" round for my rear axle, and somehow adapt my wheels to fit it. The wheels I have are for a 3/4" axle with a square key. I may just turn down the ends of the 1" to 3/4", that would probably be the simplest solution. I should be able to make them nice and tight too.
I have reservations about this. From personal experience, on an old racer I built, I had a jackshaft that was 3/4" and had the ends turned down to 5/8". The one end that gave me problems a couple of tiies was the end that had my drive sprocket on it, as the chain was spring tensioned. It broke right at where i had turned it down. I went to straight 3/4" and never had any problems afterwards. The axle diameter your using is a larger, but I'm worried that the shoulder where you stop your cut will become a stress point.
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Thanks MOWtaku, I was thinking about that too. With a radius at the end of the cut it should be ok, but I might be better off modifying the wheels instead. I have to run steel wheels, so no go-kart stuff here. I could get some 8x7 trailer wheels though, but they're pretty heavy.
Kristian
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May I suggest 3/4/5 bolt wheels say off a golf cart, being 8" and running the appropriate hubs with 1" bore and setting your width and locking them in place? Might be a more simple solution and you can still run your 1" axle with no modifications
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I don't golf, so I hadn't thought of golf cart wheels, thanks. I also just realized I've got a crappy little chinese quad out back that has 8" wheels, so I might just rob those for now. I should be able to use the rear brake too. I won't be able to get anything done for a couple weeks though, I'm away from home two weeks at a time for work. I might also see what I can find for some 1.25" tubing locally for my rear axle, might as well go straight to the good stuff. I think I'm going to pick up some 16x6.5 tires for the rear too. They're only $23 at our version of harbor freight. They'll let me get my butt a bit lower between them. The same place also has 8x7 atv wheels for $30, those should do the job.
Kristian
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Sounds like you're on the right track , cheers from Canada's east coast!
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Sounds like you're on the right track , cheers from Canada's east coast!
Thanks, good to see there's a few Canadians on here too.
Kristian
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I've been mostly just figuring out what I can use for parts so far. The ATV wheels I was going to buy are apparently discontinued and no longer available, so I picked up some 8x6 trailer wheels with a 4 on 4" bolt pattern. They were way more expensive, but they came with tires that I can use on my boat trailer, so figured that was worth it. I picked up bearings for a 1" axle, and some other stuff like sprockets and hubs for them and my brake rotor. I was thinking of building my own wheel hubs using split tapered hubs to keep them tight on the axle, but then I found these go-kart hubs in Canada for what looks like a decent price.
http://www.kartworks.ca/index.php?main_page=product_info&cPath=198&products_id=1229
Would they be strong enough for racing on a fairly rough surface? They'll certainly be lighter than what I was thinking, and require less fabrication. I mounted one of my new tires to check the diameter, and they're 15.5" inflated to 15 psi. I need 5" of clearance to the chassis, which is 2" tall, so this means I'll run my axle above the chassis and not have to notch anything. If I ever switch to smaller tires I'll have to change things up, but I'll cross that bridge if I ever get to it. I've decided I'm going to use the chassis pan from the Craftsman. I can reinforce the frame in basically any way I see fit, so I'm going to weld some reinforcements to the outside rather than the inside like most do. I got the pan all cleaned up today and came up with a bit of a plan at least.
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Double check on those hubs, they look like only 3 bolt, and the studs are too small anyway. http://www.kartworks.ca/index.php?main_page=product_info&cPath=198&products_id=1690 (http://www.kartworks.ca/index.php?main_page=product_info&cPath=198&products_id=1690)
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The hubs are 3 bolt, but welding new centers into my wheels or making adapters wouldn't be hard. Do people use the other style ones and they work good? I was concerned with something like that wobbling on the axle because it doesn't clamp on. I would think that that any movement would quickly destroy the axle and hub. Maybe I'm overthinking it though.
Kristian
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On one of my mowers I cut out the 3/4 center and welded in a 1" shafting coupler, it's not perfectly true, but neither are stock rims, haven't had any issues. Also reinforced the rim by welding a plate from the coupler to the outside diameter of the rim
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Cool, thanks. I was thinking of building hubs like you linked to, but was worried they wouldn't hold up. I can whip a couple up with some couplers and my dad's lathe easy enough. If it doesn't last I can just try something different then. I'm going to use the stock front wheels, and I'll probably reinforce them with some plate like you did. One of the local racers i talked to mentioned that too. Having a wheel center come apart during a race would probably be pretty exciting. I was working with some 3/4" x .065" wall stainless tubing at work today and had some scraps, so I bent up a couple nerf bars and a dash support. The problem is I work away from home and have flights booked until February, so I might have to see if they'll fit a suitcase. I'll probably get some funny looks at the airport with them. It kind of sucks, I have lots of scrap tubing at home but the bender for 3/4" is about $1000, and I only have access to it when I'm at work.
Kristian
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Here's the tube parts I made, and the bender I used. I made the second hoop today so I've got my grill support too. I don't have a good for this mower, so I'm going to cut one out of aluminum sheet.
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Finally back at it, and it feels good to be welding and grinding and actually building something again. The first step was to reinforce the stamped sheet metal chassis. Turns out these things have almost as much torsional rigidity as the proverbial wet noodle. With the chassis sitting on my very crappy build table I could pick up any corner about 1/2" without any others lifting up. That just won't do, so I welded on some old shelf brackets to reinforce things a bit. Without adding any cross members it's already a lot better.
(http://www.locostusa.com/forums/download/file.php?id=62033&mode=view)
(http://www.locostusa.com/forums/download/file.php?id=62034&mode=view)
(http://www.locostusa.com/forums/download/file.php?id=62035&mode=view)
(http://www.locostusa.com/forums/download/file.php?id=62038&mode=view)
(http://www.locostusa.com/forums/download/file.php?id=62037&mode=view)
(http://www.locostusa.com/forums/download/file.php?id=62036&mode=view)
I used a piece of 1" tubing to mock up my rear axle. I squared it to the chassis and put shims under each side, then tacked it to the chassis so I can mount my bearings. I'm using bearings with 4 bolt flanges, but I think I'm going to only use 3 bolts and trim the extra one off the bearing carriers. The dowels are welded to the brackets, and should help keep everything aligned. The hole through the frame rail also has a tube welded in so the bolt won't collapse the frame when I tighten it. Good thing grinders and paint make me look like the welder I ain't.
Kristian
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Not sure if you talked with anyone during the Barriere race but it sounds like they may be adopting ARMA rules or becoming a chapter.
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I didn't talk to anyone this year. I did ask on their Facebook page if adding steel outside of the original chassis was allowed though, and someone responded saying it's ok. If they go with some official rules does that mean what I've done to reinforce the frame won't be allowed?
Kristian
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I had a look through the ARMA rules, if they go with them it totally changes what I need to build. I'm waiting on a call back from the organizer of the Barriere fall fair races to see what's going on before I get too far into this. It's still pretty easy to change things at this time. Hopefully I'll be allowed to run with a homemade hood, as none of the mowers I've managed to scavenge had one.
Kristian
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Looks like you've added it on the inside? In that case you should be fine. I don't see how they could not allow machines built to previous rules, there wouldn't be very many compliant machines. our okanagan rules are almost identical to the current Barriere rules. We are discussing rule changes as well as potentially adopting ARMA as well.
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No, I added steel to the outside of the frame, but it doesn't extend past the original stamped flange more than 1/16" (thickness of the steel I used), and it looks kind of like it belongs there. Switching to ARMA rules means I can drop my ride height an inch though, and I'll have to change the way I was going to do my steering and seat. I was planning to build it like a supermod with a kart seat and steering running straight to the front. The ARMA rules would mean I have to go with a mower seat and leave the steering column in the stock location. Not a huge deal at this point in time, but it would suck to have it built and then find out. Thanks for the heads up on the potential rule changes. I haven't heard back yet to see if the changes are going ahead, hopefully I can get some info in the next couple days.
Kristian
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I talked to one of the people that's in on organizing the local races, and I was told if I build to the ARMA rules I'll be good to go. So I guess I'll drop the ride height an inch, and build it according to the Superstock rules. I guess that takes any of the gearing questions I might have out of the equation too, and the engine should last a long time with the governor still being used.
Kristian
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So did they say definitively that they will be adopting ARMA rules for all new builds? Or just you should be ok? It’s going to be interesting to see what they decide for all existing builds, if they will allow them to be grandfathered in with new builds or have to run on their own.
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I don't think if switching to ARMA rules has been decided yet, but I was told if I built to them I'd be allowed to race at Barriere as well as elsewhere in the province. I might as well build to the ARMA rules then, it gets me 1" lower and 2" wider than the old rules. And if they're not going strictly by the ARMA rules, I can probably disconnect the governor and play with my gearing at the Barriere races if I feel the need. I don't know what they'll do with guys that have built other stuff, but I would guess they'd probably still be allowed to race at least at Barriere.
Kristian