Print PDF
Favorite
Email
Notice:
I've recently completely turned this mower into a new build. If you've read this before, proceed to step 12 for the latest updates. Otherwise, start reading below for the original build. Thanks to everyone who has commented before. As always, feel free to ask questions and I'll do my best to answer. Click Here to proceed to step 12.
In this demo, you'll get some ideas of how you can make a real racing riding mower used in national events. Have fun turning what used to be the family lawn mower into a fire-breathing high speed racing machine. Also- I'm constantly making changes and modifications to the final machine so check back to see what I've done. The next plans I have include steering upgrades.
Please read the following paragraph before proceeding.
Before we start, there's a bit of safety to discuss.Yes, racing lawn mowers from an outward perspective is sort of funny ( which it is!)But its important to realize that racing mowers such as these are heavily modified to handle much greater speeds than the original mower was designed for. Many of these mowers go 50MPH or more.Making a race mower isn't as simple as taking a stock tractor and making it go fast without any alterations. So its important that the frame, brakes, steering, engine, and wheels are modified or altered to handle this additional speed.So to make this point doubly clear, it is NOT a good idea to take a bone stock mower and make it go fast. You can, and will get hurt if you do so, and trust me- I've seen enough people wreck due to this very reason. So play it safe. Secondly, if you do plan on racing, make sure and check out the rules for your chapter and wear appropriate safety gear such as a helmet ( motorbike), gloves, boots, and long pants.My mower is built using ARMA ( American Racing Mower Association) rules and regulations. Lastly, your mower must have an approved jet ski/snowmobile style safety tether switch. If you fall off ( which we often do) the mower must automatically shut down or it'll keep right on going! Racing mowers might seem silly, which it sort of is, but you can get hurt if you're not careful. So be safe!
Ready, let's get started! The 'victim' I chose for this build is a late 60's Grants mower. Tiny little mowers like these were produced back when riding mowers were still deemed a luxury. They're little more than a seat sitting on top of a mower deck. Most used smaller engines. The advantage of using such a little mower is that you can reduce the weight dramatically by simply having a 'legit' riding mower complimented with a larger engine, hence a higher power/weight ratio. Don't get attached to it. When its done, there won't be much left of the original.
The first step is to strip the mower down to the frame. Modern mowers usually have a single stamped piece of steel. Older mowers like this one have frames made of square tubing or slabs of steel. This will give you an idea of how much of the mower is actually usable and how you can lay out the drive, steering, and brake components. Besides the hood, what's leftover to use isn't much. The rest are worthless such as the stock wheels, steering wheel, and transmission.
I've recently completely turned this mower into a new build. If you've read this before, proceed to step 12 for the latest updates. Otherwise, start reading below for the original build. Thanks to everyone who has commented before. As always, feel free to ask questions and I'll do my best to answer. Click Here to proceed to step 12.
In this demo, you'll get some ideas of how you can make a real racing riding mower used in national events. Have fun turning what used to be the family lawn mower into a fire-breathing high speed racing machine. Also- I'm constantly making changes and modifications to the final machine so check back to see what I've done. The next plans I have include steering upgrades.
Please read the following paragraph before proceeding.
Before we start, there's a bit of safety to discuss.Yes, racing lawn mowers from an outward perspective is sort of funny ( which it is!)But its important to realize that racing mowers such as these are heavily modified to handle much greater speeds than the original mower was designed for. Many of these mowers go 50MPH or more.Making a race mower isn't as simple as taking a stock tractor and making it go fast without any alterations. So its important that the frame, brakes, steering, engine, and wheels are modified or altered to handle this additional speed.So to make this point doubly clear, it is NOT a good idea to take a bone stock mower and make it go fast. You can, and will get hurt if you do so, and trust me- I've seen enough people wreck due to this very reason. So play it safe. Secondly, if you do plan on racing, make sure and check out the rules for your chapter and wear appropriate safety gear such as a helmet ( motorbike), gloves, boots, and long pants.My mower is built using ARMA ( American Racing Mower Association) rules and regulations. Lastly, your mower must have an approved jet ski/snowmobile style safety tether switch. If you fall off ( which we often do) the mower must automatically shut down or it'll keep right on going! Racing mowers might seem silly, which it sort of is, but you can get hurt if you're not careful. So be safe!
Ready, let's get started! The 'victim' I chose for this build is a late 60's Grants mower. Tiny little mowers like these were produced back when riding mowers were still deemed a luxury. They're little more than a seat sitting on top of a mower deck. Most used smaller engines. The advantage of using such a little mower is that you can reduce the weight dramatically by simply having a 'legit' riding mower complimented with a larger engine, hence a higher power/weight ratio. Don't get attached to it. When its done, there won't be much left of the original.
The first step is to strip the mower down to the frame. Modern mowers usually have a single stamped piece of steel. Older mowers like this one have frames made of square tubing or slabs of steel. This will give you an idea of how much of the mower is actually usable and how you can lay out the drive, steering, and brake components. Besides the hood, what's leftover to use isn't much. The rest are worthless such as the stock wheels, steering wheel, and transmission.
Remove these ads by
Signing UpStep 1Configuring the build.
The next step is probably one of the more difficult parts of the build: configuration and finding parts. Building one of these is sort of like building a small car with all its various systems. Since all of these racing mowers are one-off type builds, finding the parts that will work can be a pain. I've had a lot of questions about where the tires, clutch, and right angle gear box ( transmission) comes from. the gear box can be found on ebay. The tires are go cart tires and can be found online on any site that sells go cart parts. The same is true for the brakes and rear axle components. The front axle is a custom unit built by a company called Acme Mowersports.
A list of parts needed for this build are:
A: Engine
B: Transmission ( right angle gearbox)
C: Centrifugal clutch
D: sprockets
E: Front axle and spindles
F: Rear axle and axle hangers
G: steering wheel
H: Brake system
I: chain
J: electrical components
K: Wheels, tires, and hubs
M: Gas lever
N: high endurance engine components
Many of the others need to be made by hand. One thing that's helpful is that many of these components such as the rear axle and hangers,wheels, hubs, spindles, and brakes are basically go-cart components. Some golf cart and motorbike components work as well. Sprockets and such can be had from sites such as Mcmaster -carr.
Once you get all the parts, the build actually goes pretty quickly.
A list of parts needed for this build are:
A: Engine
B: Transmission ( right angle gearbox)
C: Centrifugal clutch
D: sprockets
E: Front axle and spindles
F: Rear axle and axle hangers
G: steering wheel
H: Brake system
I: chain
J: electrical components
K: Wheels, tires, and hubs
M: Gas lever
N: high endurance engine components
Many of the others need to be made by hand. One thing that's helpful is that many of these components such as the rear axle and hangers,wheels, hubs, spindles, and brakes are basically go-cart components. Some golf cart and motorbike components work as well. Sprockets and such can be had from sites such as Mcmaster -carr.
Once you get all the parts, the build actually goes pretty quickly.
| « Previous Step | Download PDFView All Steps | Next Step » |
thanks
Engine/clutch 14tooth -> 14tooth on RAGB=Same ratio.
RAGB has 2:1 ratio. Now engine turns twice for axle turning once. RAGB has a 12tooth and rear axle has a 40tooth.
40tooth / 12tooth = 3.33 ratio x 2 (from 2:1 ratio in RAGB) = 6.66:1 over all ratio.
Tires are 11 inches in diameter.
With that ratio your speed will be:
5000RPM=24.56MPH and
6000RPM=29.48MPH.
Changing ANY of the numbers changes the MPH. If you change to a 36tooth rear sprocket then the ratio becomes 36/12=3:1x2(RAGB)=6:1 total.
Then the speeds become:
5000RPM=27.27MPH and
6000RPM=32.72RPM.
These are TRUE numbers, IF the clutch is locked up and not slipping. Using belts, there may be belt slippage, making your speed a little slower.
With a 40/12 ratio, changing rear tire from 11 inch to 12 inch diameter changes speed at 6000 from 29.48MPH to 32.16MPH.
It would be easy to put all of that into a spreadsheet to show speeds for every 1000RPM and what happens when changing sprocket ratios or tire sizes.
I made a formula over 35 years ago to figure numbers like that out, the formula is:
RPM÷RearRatio÷TransRatio×TireDiameter÷336.13524=MPH
Nice Instructable.
Ken Chevy
080810 1316
Either way, good luck with your build.
If you hook the engine driveshaft up to one of the shafts, the other shaft will either turn 8 times faster or 8 times slower than the engine is turning.
You will probably be using it to gear the engine speed DOWN, so divide the RPM number by the larger number, that will tell you how fast the output shaft will be turning then.
Input RPM = 4,500 / 8 = 562.5 RPM output speed.
Ken
122810 2127
I can't read minds (yet - LOL) and can't see the parts you have in front of you.
So, you have to give me numbers.
Make a mark on the input shaft of the transmission and another mark on the output shaft. Then put the transmission in 1st gear and count how many times the input shaft goes around to the output shafts ONE time. If the 5 speed goes around 10 times to one time for the output shaft in 1st gear, then that is 10/1, and 7 times in 2nd gear it would be 7/1 etc.
You HAVE to have the numbers to figure out the ratios.
So you will HAVE to get both transmissions, mark the shafts and count the turns to get the ratio for each gear...OR that info (transmission ratios) may be available from a dealer.
But you MUST have:
Engine RPM
Pulley ratios
Transmission ratios
Rearend ratio
and, last but not least the Tire Diameter.
Once you have those numbers, then input them into the formula I furnished:
EngineRPM÷RearRatio÷TransRatio×TireDiameter÷336.13524=MPH
If, for example, you have 4,500 Engine RPM/8=562.5 engine RPM
562.5/6
Rearend ratio of 6/1
Transmission ratio of 5/1
and a Tire Diameter of 12 inches
then we would do 4500/8=562.5
562.5/6=93.75
93.75/5=18.75
18.75*12=225
225/336.13524=.6694 MPH
Less than ONE MPH @ 4,500 RPM engine speed.
So, get rid of the 8/1 and make them 1/1 pulleys.
Then the MPH would be 5.355 MPH
Change the rearend ratio from 6/1 to 2/1 and then you have 16.065 MPH @ 4,500 RPM engine speed.
Then change the transmission ratio to 1.5/1 and your MPH would be:
53.5499 MPH @ 4,500 RPM's of engine speed with a 12 inch tire.
4,500 RPM engine speed (w/1/1 pulleys) + rearend ratio of 2/1 and transmission ratio of 1.5/1 with a 12 inch tire = 53 MPH
Put different numbers into the formula, John. It will work every time. It is simple, 2+2=4 every time.
EngineRPM÷RearRatio÷TransRatio×TireDiameter÷336.13524=MPH
I used to use that formula a lot when I was drag racing years ago.
You can use a regular calculator, use the one in your computer works fine, and just do them one step at a time. Try it, figure out some ratios, John.
And, like mowerracer said, 45 to 55 MPH is pretty improbable without having an engine putting out a LOT of horsepower!
And it would take so long to get up to speed too, because of lack of HP.
You might try it with a 3.5 rear ratio to start with and that will be about 30 MPH and see what that is like.
Ken
122910 1438
If you change your axle sprocket to a 24 tooth, which would make it 2:1, then you could obtain 50MPH at 6,111RPM if you had enough power.
It looks like it would be fun.
Ken
080910 0820