building a dirt buggy

   / building a dirt buggy #1  

Renze

Elite Member
Joined
Oct 24, 2003
Messages
4,392
Location
the Steernbos (Holland)
Tractor
Zetor 3011, Zetor 5718
Me and my friend have collected various car parts to build a dirt buggy:
The cars we used for our Dukes of Hazzard style jumps, usually lasted only a day, because the engine mounts ripped off from the bounces.. (the Dukes used about 3 Chargers per filming day... :p )

Because petrol is allmost unaffordable in Holland at 1.40 Euro per liter, i removed 2 front subframes of front wheel drive Volvo 440 1.9 turbo diesel. Diesel is about 1 euro per liter, and agricultural dyed diesel is about 70 cents per liter. The 1.9 intercooled turbo diesel engine puts out about 90 horses, and with some fuel and boost pressure adjustments its capable of 110 to 120 hp. Plenty of horses for a 500 kg dirt buggy. :p :D :D

Úsing an existing subframe means you have a complete package of wheel suspension, steering, engine and driveline mounted on a frame which can be bolted to the vehicle by 4 bolts with rubber bushings. It gives you a head start because all critical components are already aligned and all wheel mounting points are tested for durability by a few thousand cars on the road.

I saved my first 440 TD front end for parts for my second 440 TD, but when my boss took a corner too tight with the truck and semitrailer at the companies parking lot, i suddenly had 2 1.9 TD drivelines available.... :p



I have 2 weeks of holiday, with plenty of things to do. My goal is to at least get a rolling chassis during my holiday, so i am able to quickly roll it out of the workshop when i need the workshop for other things.

I took some pictures with my Nokia, so they are a bit fuzzy but you get the idea.


photo 1:

I spent about an hour walkign around, not knowing where to start, as i normally build trailers (built around 2 hot rolled steel frame beams) instead of buggies with an open cage construction.
Then i decided to start with the parts that allowed the most design freedom, which is the passenger cage, and later add the parts to mount both Volvo subframes, so i could better visualise where all the supports for the subframe mountings and spring mounts would go.
It turned out to be a good method, because within an hour or 2, i had what can be seen in photo 1.


photo 2:

I used the hydraulic pipe bender to bend a roll bar over the spot where the seats would go. Unfortunately i had only 1 pipe die, which was for a 1" pipe, not for 1,5" so i pressed the pipe oval in the bend. To reduce the effect of making the pipe oval, i bent it in 3 or 4 places to make just 1 bend.

photo 3:

an extra hoop is added to the rollbar, and some pipes from the front part of the passenger cage to the rollbar are added.

photo 4:

I've built the mounts for the front subframe, with steering housing. I had to bend the front quite a bit to work around the springs. I also had to chamfer off the front part of the passenger cage, because the front wheels couldnt sit there because they hit the lower front tube.
When i bolted some wheels on it, it really started to appeal.
several people that came around during the holiday, asked me when they could test drive it... ;)


At the rear, i'll be using the complete front wheel drive drivetrain at the back, just like Toyota used a Camry front wheel drive driveline in the back of the MR2 rear wheel drive sports car.
Photos will follow when i have time to continue.
 

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   / building a dirt buggy #2  
Looks pretty cool. Can't wait to watch this project come along :)
 
   / building a dirt buggy
  • Thread Starter
#3  
Yes, i cant wait either... But i have so many important things to do... ;)

I am wondering how well this buggy will handle, it has pretty much all the weight in the rear.... any of you drag racing experts, what's a reasonable weight distribution for a rear wheel drive ?

I think with the current setup it will take off on its rear wheels as soon as you step on the gas pedal... For safety i might have to add front ballast, but i dont want to compromise too much on the current power to weight ratio...
I think i'm going to put the battery up front, which puts about 25 kg (5%) of the weight to the front... I cannot put the fuel tank up front as well, because i didnt save an electrical fuel booster pump from the parts donors. The fuel flow must be gravity fed from a tank mounted above the engine.


Does anyone know how a glow fuse timer works, and how to re-wire it ?
Maybe i should just wire the glow fuses directly to a manual button so i can hold the button for 10 seconds before cranking it up, and forget about the complications of the standard contact lock in the steering column.

By the way, this buggy will probably keep its power steering system, because my friend (co-builder) lost control of 4 of his fingers on his right arm due to a car crash when he fell asleep behind the wheel, so he has only 1 hand to steer...
Because of his crash experience, i will weld some extra struts and trusses into the rollcage... ;)
 
   / building a dirt buggy #5  
Looks like a fun project. I really like the floor in your workshop!!!

I don't know anything about the vehicles your using, so it will be fun to follow your progress and see how it all comes together.

Thanks,
Eddie
 
   / building a dirt buggy #6  
So far, it looks good. Only thing I can add to your basic structure is to remind you that TRIANGLES are strong, boxes are not. Small triangles are stronger than large triangles. It is stronger to pull a tube than push a tube, but your weld is more stressed in tension than compression, plus it's usually not feasible given things like ground clearance. If force pushes a tube (for instance the upper spring mounts) have tubes direct that force into the main structure. See attached pics for examples of triangles transmitting force to main structure (main hoop of roll bar).

"Ideal" weight distribution would be 50/50 given your short wheel base & intended use.
 

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   / building a dirt buggy #7  
Renze said:
Yes, i cant wait either... But i have so many important things to do... ;)

Snip

By the way, this buggy will probably keep its power steering system, because my friend (co-builder) lost control of 4 of his fingers on his right arm due to a car crash when he fell asleep behind the wheel, so he has only 1 hand to steer...
Because of his crash experience, i will weld some extra struts and trusses into the rollcage... ;)

You might consider creating a glove typ. of the one Mel Kenyon, his Bro. and Father created for him after a horrific crash where he his fingers were burned off of his left hand.
Good luck
L*S

From : Mel Kenyon: The King of the Midgets
Miraculously Mel survived and after series of operations at the San Antonio Burn Center and a lengthy absence from auto racing, Mel returned to auto racing the next year missing virtually all of the fingers on his left hand. Together with his brother Don and his father Everett, they designed a special glove in which a rubber grommet was sewn into the palm. This was to fit over a stud on the steering wheel so that he could grab the wheel with his right hand and steer with the palm of his left hand.
 
   / building a dirt buggy
  • Thread Starter
#8  
Eddie,

the floor in my workshop are concrete pavers, sized 10x20x8 centimeter. This is a very common way to pave surfaces in Holland, all of our property is done this way. I dont know why, but Americans seem to pour concrete everywhere, and i havent seen a single paving brick when i was in Canada...
the main advantage of paver bricks is that you can re-pave when the dirt has settled over years, or get acces to the underground utility network under our streets, without hiring a concrete saw...


DBdartman,

i know about them triangles... i just need more 1 3/4" (42 mm) pipe to finish the rear end, and then 33mm (1 1/4" ??) pipe to make the triangles. Grinding a radius to every pipe to connect to the other is just way too much work, so i only do that for the main construction.
I dont want to ease the job by compressing the ends of the pipes either. I think i can weld the gaps between the radius of a 42mm pipe, and the open end of a 33mm pipe.
I had in mind to add several meters of pipes for various supports and extra bars, i'm not half done yet ;)

On the other hand, i only want the passenger cage to be stiff, not the front end as it should absorb the impact by crumbling, in case it might happen...


LeonS,

my friend isnt "missing" 4 of his fingers, he just cant use them anymore because a nerve was ripped loose in his shoulder when his arm slung forward at the moment he hit the tree... He can use his palm to steer, but not use both hands to grab and take over the steering wheel in a drifting slalom...


Does anyone have an estimate of the weight of a European 1.9 diesel (steel crankcase, aluminium head) with an aluminium transaxle ? I dont have scales that go higher than 120 kg, and neither a clue about what the rear end may weigh...

Sure 50/50 weight ratio would be ideal, but i am not intending to add 400 kg of ballast to the front to get to 50/50... is 45/55 acceptible, or does it get very tricky then ?
 
   / building a dirt buggy #9  
Renze, do you have a chop saw? Making a "fish-mouth" (to fit end of tube to side of tube) can be fast or slow, very precise or "close enough" depending on the result you want. When I worked in the fab shop I used a hole saw in an old milling machine to make fish-mouths if I wanted them tight. There are cutting jigs available (around $100-$200 USD) available that also use a hole saw. I have, after very little trial & error, learned to make reasonably tight fish-mouths with a chop saw & 4" or 4.5" (roughly 100 or 120mm) grinder. Once you figure it out, it should only take a couple minutes with the chop saw & grinder method. It's nearly impossible to use words to tell how to do it, but if you're interested I can take & post a few pictures showing how it's done. I built such roll bars from 1986 - 2000, so I know a thing or two about it. The car above I built for a friend. He's been drag racing it for almost 20 years now. It's heavy, at 2900 lbs (around 1400 kilos) but is over-built (safe!), fast, & consistent (9.0-9.1 seconds in the quarter mile at 148-149 MPH). Attached are a couple pics taken 2 years ago, above post pics were taken about 7 years ago.
 

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   / building a dirt buggy #10  
I would look at the vw sand/rail buggies. They do not have anything close to 50/50 balance. They do jumps fine. Steering may be light, but you can use independent rear brakes to help with understeer.
 
 
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