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 Post subject: Lawnmower racing
PostPosted: September 8, 2018, 11:19 pm 
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Location: Kamloops, BC, Canada
Hi all. I've had the itch to do some racing again ever since I moved a few years ago, and there's no autocross around here. So it's time to get in on hopefully the next best thing. They race lawnmowers at the local fall fair every year, so I'm going to get in on that for next year. I've got a few crappy old mowers collected to rob parts from, and one of them even has an engine that runs. I'm going to be doing this on the cheap as much as possible, so it should be interesting. The rules for the class I'm going to build for are basically that it had to start as a ride on mower, can't be over 36" wide, 5" minimum ground clearance, no go-kart type spindles, no internal engine mods, has to use turf tires, and the engine has to be for a lawnmower and under 17 HP. I've got almost a year to get this thing working and sorted out


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File comment: These are the most aggressive looking turf tires I could find, hopefully they work out. 18x9.5x8" rear, 15x6x6" front.
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File comment: This one has a transmission that will let me run a chain drive go-kart axle.
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File comment: This one has a 15.5 Briggs and Stratton. After I get the first one going this one might get an old air-cooled 400cc snowmobile engine for what they call the outlaw class.
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File comment: The frame will come from this one.
IMG_20180908_195636.jpg
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Last edited by turbo_bird on September 9, 2018, 7:38 pm, edited 1 time in total.
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 Post subject: Re: Lawnmower racing
PostPosted: September 9, 2018, 12:15 am 
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Joined: March 31, 2018, 5:58 pm
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They race those too in El Reno Ok. every month during the summer. They are fun to watch. Have a good time do I gotta it and keep thread going. They call them Grasscars!


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 Post subject: Re: Lawnmower racing
PostPosted: September 9, 2018, 7:04 pm 
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Joined: August 27, 2005, 1:04 am
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Location: Kamloops, BC, Canada
I found a forum for guys that build racing mowers, there's lots of guys that race them and some of them take it pretty seriously. Guys spend $4000 on their engines, but they're getting around 80 HP from an 18 HP lawnmower engine. I definitely won't be doing anything crazy like that, I can build one to run with a snowmobile engine to run with the local fast guys.
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. Thewheels 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. The guys on the other forum say they run gear oil rather than the grease they come with. I also found that they remove the chain for reverse as it can take out the cases at high rpm, so I did that too. 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


Attachments:
File comment: One of the frames I can use and the transmission.
IMG_20180909_154609.jpg
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File comment: Cleaning it up. The transmission was completely packed with heavy grease.
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File comment: Cleaned up and gear clusters back in
IMG_20180909_154717.jpg
IMG_20180909_154717.jpg [ 118.82 KiB | Viewed 1321 times ]

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 Post subject: Re: Lawnmower racing
PostPosted: September 9, 2018, 8:52 pm 
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Location: Gainesville, Mo.
We've got a group of guys here where I live called Tightwad Pullers. They do tractor pulls... with lawnmowers! they've even built a miniature pulling sled. They have lots of fun, but some guys take it very seriously. I was visiting my son one day and the "Pullers" were having a meet in the rodeo grounds next door. I heard one go off on his run, and it sounded like a fuel-burning Triumph Bonneville!

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 Post subject: Re: Lawnmower racing
PostPosted: September 10, 2018, 7:56 am 
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I have some cousins in NC that are into lawnmower racing, mostly for the kids (10-12-14 year olds) but the "Dads" do it too. Looks like a hoot! I'll try to find some of their FaceBook posts and tag you on them.
:cheers:
JDK

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 Post subject: Re: Lawnmower racing
PostPosted: September 10, 2018, 1:21 pm 
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Location: Kamloops, BC, Canada
That's cool JD. They don't let kids under 16 race lawnmowers at our fair, but 5 year olds are in the rodeo barrel racing, go figure. They use the same rodeo arena for the lawnmower races.
Kristian

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 Post subject: Re: Lawnmower racing
PostPosted: October 10, 2018, 10:37 pm 
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Location: Kamloops, BC, Canada
I've been mostly just figuring out what I can use for parts so far. I found some cheap atv wheels at Princess Auto, but apparently they're discontinued and no longer available, so I picked up some 8x6 trailer wheels with a 4 on 4" bolt pattern. They cost twice what the atv wheels were, but they came with tires that I can use on my boat trailer, so I figured it wasn't too bad. 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_ ... ts_id=1229
I posted on a lawnmower racing forum asking if they're string enough for what I'm doing. 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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IMG_20181009_191113.jpg
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IMG_20181009_191435.jpg
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 Post subject: Re: Lawnmower racing
PostPosted: October 12, 2018, 5:00 pm 
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Apparently I'm overthinking my wheel hubs, one of the guys on the other forum says he's used something similar to these and they worked good.
Attachment:
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I can make those easy enough. I've been working with some 3/4" x .065" wall stainless tube at work the last couple days, and had some leftovers, so I bent up some nerf bars as well as a couple hoops for my dash and hood. It's almost too bad I've got flights booked until February, I don't think I'll be allowed to take a bunch of tubing home in my carryon. I should get my own bender I guess.
Kristian


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IMG_20181012_133232.jpg
IMG_20181012_133232.jpg [ 99.24 KiB | Viewed 895 times ]
IMG_20181012_132843.jpg
IMG_20181012_132843.jpg [ 207.84 KiB | Viewed 895 times ]

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 Post subject: Re: Lawnmower racing
PostPosted: October 29, 2018, 8:59 pm 
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Location: Kamloops, BC, Canada
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.
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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. Grinders and paint make me look like the welder I ain't.
Kristian


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IMG_20181029_174251.jpg
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IMG_20181029_174214.jpg
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IMG_20181029_174128.jpg
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 Post subject: Re: Lawnmower racing
PostPosted: October 30, 2018, 10:31 am 
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Location: Carlsbad, California, USA
Hey Kristian, what is the make/model of that tubing bender in your photo above. It looks simple and seems to do a nice wrinkle-free bend. I need to find something to do the bends on my rear kick-up shortly. They will be 3/4" mild steel tube.

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

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 Post subject: Re: Lawnmower racing
PostPosted: October 30, 2018, 11:14 am 
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Location: Kamloops, BC, Canada
Hi Lonnie. The bender is a Ridgid #368. It's a 3.75" centerline radius, and they don't seem to ever wear out, so buying a used one shouldn't be much of a risk. Our version of Harbor Freight has a bender on sale this month that I'm thinking of picking up, it uses interchangable dies to go from 3/8" to 1", and the reviews are decent. You might be able to pick something like that up too. I'm only really interested in it for 3/4" and 1", but the other sizes might come in handy once in a while too. https://www.princessauto.com/en/detail/ ... -p8708067e
Kristian

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 Post subject: Re: Lawnmower racing
PostPosted: October 31, 2018, 11:52 am 
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Joined: October 24, 2008, 2:13 pm
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Location: Carlsbad, California, USA
Thanks, Kristian.

Interestingly, Princess Auto has a selection of benders, but Harbor Freight does not. It only has the hydraulic ram type, which is not good for what we want. That Princess tool looks like a very good deal from down here. A new Rigid tool for only 3/4" is almost $400 US. Baileigh has a somewhat similar tool to the Princess version for $295 US. It lacks the degree indications of the Rigid tool, however.

Lonnie

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

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 Post subject: Re: Lawnmower racing
PostPosted: October 31, 2018, 1:50 pm 
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Location: Kamloops, BC, Canada
You're talking about the old hydraulic pipe kinker. Yeah, those aren't real useful for stuff like this. I used one for the forward supports of the roll bar on my locost, but it wasn't great. Good thing I only needed about a 50 degree bend, and I used 1" pipe. I've seen the Ridgid benders on eBay, and would probably buy one, but shipping to Canada kind of kills a lot of deals on heavy stuff.
Kristian

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 Post subject: Re: Lawnmower racing
PostPosted: October 31, 2018, 8:15 pm 
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Location: Holden, Alberta, Canada
turbo_bird wrote:
Our version of Harbor Freight has a bender on sale this month that I'm thinking of picking up, it uses interchangable dies to go from 3/8" to 1", and the reviews are decent. You might be able to pick something like that up too. I'm only really interested in it for 3/4" and 1", but the other sizes might come in handy once in a while too. https://www.princessauto.com/en/detail/ ... -p8708067e
Kristian

Thanks for the find Kristian. I just texted my son back home to pick one up for me, can't complain about the price. :cheers:

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 Post subject: Re: Lawnmower racing
PostPosted: November 1, 2018, 9:25 pm 
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Location: Kamloops, BC, Canada
No worries Perry, glad I was of some help. I picked one up today and it actually looks pretty decent. I haven't tried it out yet though, so it might not be that great. I think some kind of marks for degrees will probably get added to it as I figure it out though. It even came in a nice molded plastic storage case to keep everything together.

Sounds like the rules for mower racing are changing to a more standardized set from ARMA (American Mower Racing Association). Nothing is changed yet, but I talked to one of the local organizers about it today, and was told if I build to the ARMA rules they'll let me race. There are also a couple other clubs nearby that use those rules, so I'll be able to do more than just one race weekend a year if it all goes well. The big changes for me are I can run a lower ride height (4" vs. 5"), my seat has to be from a lawn tractor, I have to keep my engine governed at 3650 rpm, and my gear ratio has to be 8:1 in high gear. It's a bit more restrictive than the old rules were, but I'll go with it. It will simplify things a bit I guess.
Kristian

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