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Post by motorguy on Oct 24, 2012 19:48:52 GMT -4
Well our driver being nine ten soon it looks like Junior is where we belong! So now getting a plan and trying not to build a tractor that is not legal is a concern.I have a selection of tractors and vertical shaft motors all Briggs.I have a good Briggs 12 IC that should power it? So here is the question What would the best steering, drive system and rear axle.for junior and still allow the same tractor to be used later in faster classes in the future.I also noticed no minimum weights in the rules? I'd appreciate any advice.Thanks Motorguy
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Post by happyhab on Oct 28, 2012 8:25:49 GMT -4
Hi there. My son started to catch a few GH races last year and we too have caught the bug and will be building two new racing mowers over the winter (a year behind schedule to to a '62 Cub Resto-Mod). Glad to hear of another Junior racer!
I have spent a considerable amount of time (off and on for 2 years) researching many proven racing mower designs. There is a ton of info on the net. Definitely checkout the links section of the GrassHogs website and Heymow forum.
Regarding your Junior build, my humble opinion would be to recommend building a super-modified chassis, if for no other reason than safety. I am sticking with the 'frame-rail' style tractor chassis' found on Murray and Toro mowers (and also used by many 'professional' mower racers). You can strip it right down to the bare rails and then build it back up adhering to the club's build rules and your specific safety concerns. As far as I can tell from the rules, a super-modified chassis will allow you to run in all classes except stock-modified as long as you meet the other class-specific rules (motor, transmission, etc).
For Junior class, you would have to run a vert shaft motor of the appropriate size and either a shiftable transmission/transaxle or right angle gear box coupled to a live axle. Peerless right angle shiftable transmissions are a popular choice for this purpose. They are small and very robust once race prepped. I think most people find them in rear-engine riders.
Good luck with your build!
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Post by motorguy on Oct 28, 2012 20:48:34 GMT -4
Thanks a bunch.Exactly the info I needed..Now I can get started.Thanks again....Motorguy
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Post by Storms Racing 77 on Nov 5, 2012 16:42:47 GMT -4
Motorguy, To start of with your first post, yes a 12 hp IC briggs would be the motor to start in your junior build and most likely the most commonly used one throughout the class, once the governer is removed those little engines will pull a junior around fast enough for the time being . As for your questions about steering, drive systems and rear axles, If your concerned about using that machine to move up in classes build it strong and ready for harder faster racing for later, the more you move up in classes the bigger the power which means your going to start finding weak spots if you dont prepare for the kind of power you can eventually get too. I have to agree with Happyhab, start your build as a supermod frame, this is a huge safety benefit for your driver being lower to the ground and more stable. And by doing so you are at a headstart for moving up in classes and having the right frame setup. As for steering goes, as another safety and racing benefit, I myself would eliminate the stock steering that is in a normal cutting machine and make your own design ( or copy ) someones direct steering design. From personal experience I've had my stock steering break apart from getting jolted in corners or bumps.. direct steering elimantes that problem significantly. As for your driveline, my personal preference is a 90 degree 1-1 gearbox, reasoning for this, there's less gears to worry about coming apart and breaking with them, you dont have to worry about shifting, and with the less amount of rotating gears with just a 1-1 instead of a shiftable 5-6 speed your power from your motor isnt being robbed as much from it. As for rear axles, A solid 1 inch steel axle or 1 1/4 would do fairly well, or if you want to go light and strong you can buy a chromoly hollow axle. Hope this helps with starting your build, feel free to ask questions. Steve.
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