How to make a racing lawn mower (Updated!)

Step 4: Installing the transmission or- the RAGB

The next step is to install the RAGB ( transmission). This was a tedious task because the RAGB I chose has an unusual triangular shape and a strange bracket. Additionally, the RAGB shaft has to be far enough off the ground, yet not too far up as to protrude above the diamond plate covering it. When all the measurements were done. I had 1/4" between the top of the RAGB and the cover. The RAGB sits on two cross members welded in the frame. If you look at the pic called: "Battery bracket", you can see how it is configured. In the next pic you can see the RAGB bolted into place.

Before we get any further, you'll need to determine what your gearing ratio will be. The RAGB is a 2:1 ratio, meaning that two turns go in, one comes out of the output shaft. I suck at math, but my gear setup is as follows: Centrifugal clutch is 14 tooth. Input on RAGB is a 14 tooth. Output on the RAGB is 12 tooth, and the rear axle sprocket is a 40 tooth. That worked out well, but I have no clue what the final ratio is. The engine speed is around 4,500-5,000 RPM.

I'm using an all chain drive system. Many use belts, but I like the idea of using a chain. I used #35 chain for this build, but many use #40.

The next step is to install chain tensioners. The chain needs to be somewhat taut, but not tight. All chains will loosen and 'stretch' with use. So you need to have tensioners to keep that tension at the right level. The RAGB to rear axle tensioner was a problem because there was very little space to install one. My solution was to install a skateboard wheel that slides up and down in a 1x1 piece of steel with a slot milled along it's length. This enables you to slide the skateboard wheel up and down against the chain. You wouldn't think skateboard wheels would hold up, but they work great. Seeing as how they are designed to handle a person riding on asphalt, chain doesn't cause any damage to them at all. In this setup, I just have enough room to get into the area with a wrench to loosen/tighten the tensioner.

Comments

[McClellan41]

so which ratio has a better acceleration (power) 6:1 or 2:1??

[JOHNTHEREDNECK]

hei i have a question which transmission would be best a peerless 6spd out of a poulan or a 5spd spicer from a craftsmen ?

[mowerracer]

Are the transmissions you mention hydrostatic? If so you cannot use those for higher speeds. They simply burn up. If its a conventional Peerless 5 or 6 speed box, then that would be fine but you will need to make sure and use a steel plate to mount it as well as a hole for the output shaft of the transmission to fit through. That will reinforce it because otherwise the output shaft will snap.

[JOHNTHEREDNECK]

no theyre not hydrostatic theyre both gear drivin. put a steel plate around it on the top would angle iron work ?

[rilley1313]

hey where do i find this right angle gear box?

[mowerracer]

I found mine on Ebay. That's generally been the best place I've been able to find older parts.

[ryanhare92]

Ive been running a belt drive with my transmission and have noticed cracks are starting to appear all over my belt. What is the likely cause of all these cracks forming?

[nathansampson40]

i have a 14.5 hp briggs and stratton 7speed and i was wondering if i took the governor off if it would go faster or one of my friends said that it wouldnt go any faster because it was geared so low in the transmission and the same in the rear end

[ac-dc]

Yes if it is governed conservatively, by removing that and increasing engine RPM it will go faster - and stress the engine more. However, since the (mower?) was designed within an RPM band where the engine needed produce more torque to drive the deck too, without that it only makes sense to go with a higher geared transmission also, it is a more important change than governor increase or removal.

[the piper]

not 100 % sure but i think your gears work out to be about 1.5? turns of the axle to 1 of the engine. just off my head so :S

[ryanhare92]

Could you combine a centrifugal clutch with a multi-speed transmission instead of using a right angle gearbox? I was considering using my stock peerless 5 speed and I was just going to leave it in 5th gear with the centrifugal clutch. Think that would work? Also I noticed your sprocket on the clutch was kind of small and the one on your shaft was kind of large. I know with a pulley I have a larger one on my engine and then a small one on my transmission to produce a greater speed. How are your speeds with your setup and how does it work? Thanks

[mowerracer]

The short answer is yes you can run a centrifugal clutch to a 5 speed gearbox, but I've heard centrifugal clutches are a bit rough on gearboxes. I have a tiny gear on my gearbox output and a large axle due to general gearing. I basically have no gears for the transmission thus the output had to be tiny and the axle sprocket is actually quite small too. Most are around 45-50 teeth on the rear. Mine is only 28. My mower is sufficiently fast. Realistically probably between 28-35 MPH on the track.

[brodewald10]

do you think that a 1:1 ratio gearbox would work good. Not sure if it will produce enough speed. Or should i look for a 2:1 . I found one that is 1:1 and is preety good and will get it if i know it will work good with the speed

[spikeymikey108]

What are those right angled gearboxes called ? and im in the UK. id like to buy one of those brand new. any ideas ?

[extrememonkeydude]

I cant get the original pulley of my transmission its looks rusted to the shaft or something has anyone got any ideas for getting it off.

[mowerracer]

I had the same happen to me and my RAGB transmission. What I did was get a 4" cutoff wheel, cut through the spokes of the pulley, then cut through the pulley almost down to the shaft. I did that on both sides and it eventually came off. Be patient when you do this though. You don't want to damage the shaft.

[extrememonkeydude]

so does this thing only have one gear or is it like a 5 speed

[mowerracer]

Its just one gear, so its really simple.The reason I have this is because the engine shaft is vertical and in order to get the chain to the rear axle, the output from the engine needs to be horizontal. If you use a centrifugal clutch and do your gearing right, you can avoid a multi-speed transmission and a foot clutch. Makes it a lot easier to control on the track.

[cowboy720842000]

i'm looking at using a mower that is hydro staic any tips or should i just find a different one?

[mowerracer]

Unfortunately you can't use hydrostatic transmissions for racing mowers. At that high a speed it is unable to force enough fluid through and it burns itself out. You need to go with either a regular 4-5 speed transaxle or a 5 speed gearbox. Look for a peerless 500 or 700. That's the better quality 5 speed gearbox.

[razor2258]

were can i buy the transmissons

[mowerracer]

I've bought all of mine off of Ebay. I'd also look around and see if there were any mower repair shops in your area. The "good" ones will have a nice junk pile out back. Probably sell you one pretty cheap.

[razor2258]

what do i need to get for my engine i want to run just a staight chain to the back but my engines shaft runs striaght to the ground what do i need

[mowerracer]

That's why I am using a right angle gear box because you can't run a chain straight from the engine to the rear axle. You're also going to need to get some sort of centrifugal clutch because without it you'll kill the engine when you press the gas.

[derekonderdonk]

What kind of sprockets did you use? How do they stat put on the shafts?

[mowerracer]

They are just regular 5/8" ID sprockets that I bought from www.mcmaster.com. Just look up "sprockets". They use set screws that you tighten after they are slid onto the shaft, and that it what holds them in place.

[mrdelaney21]

I was wondering if anyone has a 1:1 90 degree gear box for sale with 3/4in shafts if not where can I get one and will a split box with 2 out puts work. please email me [e-mail] thanks

[AHolland]

were could I get a axle like that at a reasonable price?

[mowerracer]

The front axle is made by a guy in TX who runs a company called Acme Mowersports. The whole front axle with components for the steering was around $125, which is really reasonable given the cost of all the components and having to set your own inclination and caster. http://www.acmemowersports.com

The rear axle and parts can be had from any go cart supply seller. I got mine from Acme as well because his prices are decent, plus he is a good guy to deal with. Go for the 1" 1/4" size axle because it is the most common size thus you will have an easier time getting things like brakes, bearings, and sprockets to fit it.

[jboy14]

where can I get a chep Right angle gear box. and what are the age classes

[mowerracer]

The cheapest right angle gear boxes are the gear boxes used on mower decks. These are cheaper because they typically come with two mounting holes versus 3 or 4. Mine are the three hole variety. Unfortunately, these seem to be getting more and more expensive. My first gear box was $30. I bought a second spare and it cost double that. Look around on Ebay. Either that or see if anyone in your area repairs mowers and has a pile of them in the back to rummage through.

[jboy14]

what about a 7 speed forword

[mowerracer]

You can use a transaxle, which would be what most mowers come with. Those are the cast transmissions with the rear axles sticking out. BUT you cannot use a hydrostatic transmission since they won't hold up at all and burn out. You can also use one of the 5 speed gear boxes. Look for a Peerless 700. They work well.

[Merkatroyd]

What would be a good ratio to use with a 12 hp motor? Thanks for all the help so far, I 'm coming along pretty good in this project.

[mowerracer]

Well... unfortunately I sort of suck at ratios. I can tell you what I did and it might give you a ballpark idea. I used a centrifugal clutch on my engine. It is a 14 tooth sprocket. The RAGB is a 2:1 ratio. I used a 14 tooth on the input and a 12 tooth on the output. The reason for the 12 on the output on the RAGB is to partially compensate for the 2:1 ratio. From the RAGB I used a 40 tooth rear axle sprocket. It uses 6" rims for the wheels. That combination worked out well and I could probably run an even smaller axle sprocket if need be. Hope that helps!

[Merkatroyd]

How wide should the back axle be? I have a craftsman mower, the width of the original back axle going thru the transmission is 29 1/2 ". thanks

[mowerracer]

The maximum width in most organizations is around 38" max. I am using a 40" solid axle for mine. The wheels can be slid inward a bit to meet the requirement. The idea is to try and get the mower as low to the ground and as wide as permitted to lower center of gravity. I'd say that on yours, the wheels "dish" outwards from the axle centers, which would probably give it some extra width. I had a Sears before this one and what I did was buy 3/4" 4 on 4 welded hubs from a site called Acme mower racing. They fit golf cart wheels and it also pushed the width out to 38".

[fool1a1a1a]

where did u get that right angle gear box all ive found is expensive offset ones that are big and bulky email me with the answer on that aand also where did u get u get that back axle [e-mail] is my email

[mowerracer]

The Gearbox is actually a used International RAGB used on their snowblower attachment. The one I have is probably 40 years old. I got it off of Ebay. I found that typing "right angle gear box" and "Right angle GEARBOX" got drastically different results. I paid $40 for it. Look up lawn mower racing forums too. Lots of those guys will have junk laying around. The axles and its hangers, along with the brakes, tires, wheels, bearings, etc came from a combination of Acme mowersports ( Acmemowersports.com and A site in Nebraska called Turk Brothers. All I got from Turk was the tires/wheels, which tend to be expensive. But they had a good price. You can also get all of these from Ebay.