Slingshot dragster

I figured I would get this build thread started. I am still in the parts finding/ design stage of this one, but snapped a pic of the mock up for a teaser. I have alot of parts coming in for the gilson build and will try to get that one done before getting too deep in this.

This will be like the old school slingshot dragsters of the 60's with GT/LT parts and alot of custom fab stuff. 6' wheelbase, 27" rear tires on 15" rims, 20" cart tire front tires with 3/4" bearings, 19.5hp briggs twin, 3x2 transaxle and manual CTV from a MTD shift on the go. It will launch with a gear ratio that is around 15mph top end, then the CVT can be smoothly changed to top out at 60mph.

Looks pretty awesome!! Planning on doing any performance upgrades to the twin? I imagine your aren't going to run it governed and these engines are known to seize at high rpm

With the CVT, it shouldnt take much HP to hit 60 once it gets rolling. The 19.5 twin should have enough power to get off the line without any up grades. The 60 mph top end was calculated at 3600 rpm and I dont plan on bypassing the governor. grenading an engine at 15mph is bad enough, I dont want to see what happens at 60+.

Cool build! Just wondering, what is a 3x2 transaxle?

It is the 3 speed hi/lo tx used in alot of the sears GTs. 1.25" axles with 5x4.5 bolt on wheel hubs

Are the 633s even capable of 60ish?

wont know until we get there. The larger tires will help. If it is screaming too much, I may change the ratio and back it off to 40. The bad part about this set up is the driver sits behind the diff and legs are right over the axle. Back in the day they wore a cup incase the rearend blew up. That is part of the reason they went to a rear engine dragster, that and Garlits headbutted an engine when the frame broke.

Ah right. Pretty good test for those heavy trans doing 60mph! Esp with 27" wheels. May grenade quite quickly but who knows

Yeah that was what the math came out to with the pulleys that are on the parts I have now. The fastest LT I have modified was clocked at 32 (gps) with only a pulley swap. That TX had bushings where this one has needle bearings. Not sure I trust 30+ year old needle bearings in this thing. I might do a rebuild before I get too serious about running balls out.

from what I have found, needle bearings are rated at 2x the rpm these should see. These TXs were built for ground engaging equipment and pulling a 14" plow would be more stress than pushing a 500# rocket (and my fat ass counts for half of that)

I got some new tools in this week and started on the fuel tank. Rolled some rusty scrap for the tank. Inside will be cleaned and sealed and the outside will stay rusty. I'm gonna go rat rod on this one too. The end caps are domed and waiting for the bead roller to make a flange so I can get these welded up. The bung will be scavenged from an old rusty tank and the port will be a 1/4" pipe union welded about 3/8 off the bottom so it wont be sucking up water and crusty junk at the bottom of the tank. With the new equipment, I will be able to make custom tanks, mufflers and body parts.

Picked up what I expected to be a organ donor for this thing today. GT18 gear tractor for $30. It is in too good shape to hack up for parts. Needs rear tires and battery and it sounds like it may have starter issues, but the deck turns free and is in good shape. I have some used parts I can slap on it. If it runs good, I will probably flip it in the spring for an easy $400 profit.



the GT18 came with a pretty kickass seat that will get moved to the Gilson rat rod.

It will hit and run with the solenoid jumpered and carb primed. Looks like a good deal so far.

Wow that's a steal for $30! Even the decals on the hood are in perfect shape!

After a few hours of poking around, it starts and runs good. I could fire it up right now and go mow with it. Need to change the oil, swap the rear tires and waiting on a new key switch.

I decided to enter this in the next build off and in the process of doing that, the body concept got changed. I am scribbling out some frame designs and some real bad photoshop renderings of the finished product.

I planned on using the CrastsmanII front axle. It looks good upside down, but I dont trust the E clips on the spindles to hold the front end up. It could get ugly if one pops off at 60mph. If I use it right side up, the frame needs to be bent up 8" in the front. That would look wrong with the mower hood on it, so it looks like I will be doing a custom 5" drop axle.
I might be getting the cart before the horse, but I got bored at work today and made some 46" "JOHN DEERE 116" hood decals.
Getting some scrap steel rounded up to start the mock up for the frame. Thinking about doing a sheetmetal box over the ladder frame with lightening holes made with the dimple dies. That will probably be some dress up stuff that gets done at the end of the build.

Here is how we dropped the front end on the dynamark. This widened it at the same time.



We cut up some C-channel steel and put some go kart spindles on. Still has good camber and just the right amount of caster IMO

A custom front axle is definitely the best for doing 60mph. Stock axles are dodgy even at 15-20mph.

Personally I would never, ever flip a front axle. Think caster angles, it will make steering really bad, it will actually fight to stay centered and always will be pointed one way or another. You would be better off mounting the stock axle on top of the frame, or even better yet making your own front axle, and adding more caster angle making your steering self center easier and much more stable at speed. Just sayin'

I was thinking a tube axle any way. I grabbed the C2 axle for mock up and liked the way it looked.
I cant post pics here from work, but here are the hood decals

well crap. here is an off topic question... how do I rotate pic here? It is right side up on my pc

back on the axle flip, I saw a guy do that on a Cub Cadet pro stock Gt puller. He said it steers good even with the extra weight in front of the axle. Pullers dont steer much, especially with the front end off the ground, but you still have to get to and from the pits

KPI works in reverse too. Sorry for multiple short posts.. I am multitasking. Cleaning the shop, smoking some pork butts and this

RichieRichOverdrive wrote:

Personally I would never, ever flip a front axle. Think caster angles, it will make steering really bad, it will actually fight to stay centered and always will be pointed one way or another. You would be better off mounting the stock axle on top of the frame, or even better yet making your own front axle, and adding more caster angle making your steering self center easier and much more stable at speed. Just sayin'

Agreed. The axle flip completely rapes and murders the steering geometry. Between the KPI (which makes the camber and caster go nuts when you steer) and the scrub radius, it's a total nightmare.

What's more, if yours is the type where the spindles are retained by a C-clip, now the entire weight of the front of the machine is being held off the ground by two lousy little C-clips. No bueno, and downright dangerous at speed.

Neat idea for a build! Nifty front wheels.