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Mini-Vee: 1/3 scale Humvee, go kart and yard mule (now with 450HP diesel)

dremu

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dremu submitted a new Build:

Mini-Vee: HMMWV (Hummer) go-kart

I've always wanted a HMMWV (the military Humvee, like the consumer Hummers but even less comfortable.) After careful consideration, however, I concluded that if I wanted an oversize topless impractical vehicle on large tires, with GM powertrain better suited as a conversation piece than a daily driver, I could just as well have a Blazer. Which, coincidentally, I already do. :doah:

And even after finishing my mini bulldozer-backhoe, I find I enjoy building small things. (As you'll see later on, being able to carry and move a winch bumper in one hand is priceless.) So I put on my thinking toque

Read more about this build here...
 
First, the finished product:

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Hopefully it bears more than a passing resemblance to the real ones. For size reference, during construction:

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that's a six-foot-and-a-bit lanky 19-year-old with a shit-eating grin.

-- A
 
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First up was the design. I put on my thinking toque and dug up my stash of reference material

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of course, now with the Google, you can find all kinds of pictures and drawings on basically any internet.

The end size was decided in part by what parts were available (ie seats), and then laying out the components on the shop floor:

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Engine is behind the passenger seat, 6.5hp gas, smallest I could find with electric start. I hate pull start.

We've talked about Cardboard Aided Design; this is Duct Tape Aided Design.

I basically scaled the thing down so that I could just barely fit two adult Men Of Stature (ie me, the fat man) inside. Really it's for one such person, or one fat man and one kid, inasmuch as two fat guys would have to be very good friends to sit that close. I tell people it's 1/3 scale, but in actuality it's like 1:3 in width, maybe 40% in overall length, and like 1:2 height. Kinda sorta. Length is fudged obviously by cutting out the rear seats. Tires are 18x9.50 on an 8" wheel, which is more like 1:2 scale, but I find that they appear about right. Height is, well, whacked, as you can see in the second pic below with the stick figure man. After a bunch of squeezing and stretching photochop work, this was the closest I could do, so that it resembles a HMMWV while still fitting my legs inside. Mostly. I didn't think it was possible, but I believe my end result to be even less ergonomic than the full-size version :haha:

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I'm still playing with seat height, but you end up with your right leg basically flat out inbetween the front wheels. I find it's easiest to fold up the left leg and hang the knee out the door. No idea how that'll work with the doors on, but that's not a big deal as they're easily removed (one hand, yay!)

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I finally photochopped a set of graph paper-like grids onto the drawings, marks every inch and every foot, for use in the shop. "Blueprints" (using that term loosely) thus created, I set to work.
 
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The first thing actually fabbed was the front axle, as the rear axle is an off-the-shelf item from my go-to supplier, www.gopowersports.com. These guys have freaking everything for go-karts and mini-bikes and the like. Traditionally on a kart, the front tires are much smaller than the rear, so the front axles and knuckles tend to be smaller in scale. Though this one is 2WD, it still has to be mechanically symmetrical front-to-back, so the wheels are all the same and the front axle is similar to the rear. The stub shafts are ends cut off of a solid axle and a washer welded on the inside end

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which is then stuck inside a spindle (2.5"? tube, turned on the lathe for bearings), and a steel round welded on the end.

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The rounds were bought on Ebay 'cuz I can't cut round for shit and cuz they're so damn cheap to have someone else CNC cut 'em. The one welded to the spindle has a hole cut on the center to access the inside, and the other one is just welded to the knuckle.

The knuckles are fabrication sleeves and tabs from www.diy4x.com, thank you Kert @cybrfire . I think I have as much of his stuff NOT on a truck, e.g. gate hinges and go-kart parts, as I do actually on a truck :haha:

And the axle proper is just a piece of square tube with more tabs and some channel for the C's. A lot of this project uses scrap, leftovers from the dozer project and such, so don't get too caught up in trying to find logic in why I used that size/shape material in any given place. Oftentimes it's just 'cuz it's what I had. Run what you brung, right?

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Assembled, with a very temporary tierod until I got the steering column placed.

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At this stage, the frame and axles can be moved by one person as long as the tires are off. With the tires it was just a bit more than my chiropractic bill could withstand.

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I hate sheetmetal welding, so I decided on an old-school steel ladder frame, and then a wooden body. As my wife says, wood is not my favorite medium. This is a polite way of saying I am not a fine woodworker. Even with good tools, the result is at best ... passable. But it's fun, and a definite hoot.

The axles thus started, I grabbed a coupla chunks of channel for the frame, and started mocking up the tub.

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The floor is 1/2" ply (or whatever thickness resembles that, 15/32 or 29/64 or whatever mathematical abomination the lumber people foist off on us.) The seats are angled back an arbitary "some" degrees, with a ~2x2 with one side cut at that arbitrary angle to provide the back slant.

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Set up the firewall area and one layer of the sides. I had this bright idea, of which you'll see more later, that I'd do two layers of ~1/4" ply, glued together for the sides and tailgate. One layer would have cut out areas to give an embossed look. This turned out to be a bunch of work, though I still don't see how I coulda done what I wanted with a router, so maybe it was worth it.

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As part of the tub, there are ~1x1 wooden crossmembers under the floor, at the ends of the tub and under the seats. The tub then bolts to the frame at the steel crossmembers.

And then a mockup of the steering column, both seats, and the doors cut out, so it starts to look like a thing. (Not a Volkswagen Thing, mind you :D )

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Aaaand that's the first two months of work. More to come.

-- A
 
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Thanks for the good words! The next-door neighbor is kinda to blame, as he asked me "So, what's your next project?", as if it was, you know, to be expected that Emu is always in the shop building *something*. Which, in retrospect, I guess that IS to be expected.

I knew the hood was gonna be a challenge; on the full-size HMMWV/Hummers it's a fiberglass piece with a million weird angles and asymmetries and curves and generally obnoxiously shaped. I absolutely LOATHE working with fiberglass, plus I'd have to make a positive to make a mold anyway, so I figured I'd try my hand at wood.

Shades of The Holy Grail: "Why do witches burn? ... Because they are made of wood?"

If it turns out utter crap, I can at least use it as a positive for a 'glass mold. In any event, the end result is not exactly what I had envisioned, due to both poor craftsmanship (or as we say "learning experiences" :D ) and also having to streeeeetch the thing vertically to make the wheel wells look remotely right as compared to the rest of the tub. Remember earlier when I said the scaling is not even across the axes, i.e. it's 1:3 or 1:2 or 2:5 or whatever, so it's distinctly taller than it should be, but has to be to fit people inside that have, you know, legs.

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The curved parts are made with realllly thin lauan, less than 1/8". There's tons of jigsaw work, and more than a bit of my trademark wildly inaccurate measuring. Hopefully, however, car guys will look at it and say "Oh yeah, that's a Hummer". I suspect not-car people will look at it and say "That's a Jeep", but for those who know the AM General history that's actually not far off.

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Jeep nerds will count the Right And Proper number of grille slats (again with The Holy Grail: Seven shall be the number thou shall grille, and the number of the grille shall be seven :haha: ) Daimler-Fiat-Chrysler-whatever they are this month actually has that trademarked, I gather, but AM General retains a license because they made postal jeeps at some point.

Lighting will of course be all LED to avoid overloading the tiny generator. Gotta love the Chinese cheap stuff you get on Amazon and Fleabay these days.

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Here you see the design process and how often it changed (red Sharpie! black Sharpie! green Sharpie! Use ALL the Sharpies!) and inside are the aforementioned amazing "blueprints" (again, term used very loosely.)

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For the front and rear markers, I 3D-printed cases to make the lights look less like round trailer lights and more resemble the military lights. Again, not perfect, but a fun touch. The red thing on the driver's side is also 3D printed, a (nonfunctional) blackout light. With a bit of masking and paint, I think it'll look right.

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Though I'm striving for detail here, I have had to take some liberties. The airlift shackles that protrude through the hood, for instance, don't actually go to the tub for lifting. They do, however, mount solidly to the hood ribs, which make them a very convenient and comfortable way to shift the thing around. All told the hood weighs a bit short of 30 pounds, but it's a bit unwieldy due to the stupid shape. And yeah, there is a certain amount of wood filler (Bondo for wood.) That's the pink stuff there; I got the fancy one that goes on pink and then dries brown, so you know when it's ready to leave alone until tomorrow before sanding. (Just because it SAYS it's dry, doesn't mean it's ACTUALLY dry.)

Unpainted but installed, the hood ends up like so

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and

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with the doors. I've had fun with the hardware; got little rubber latches for the hood on Amazon, and the door latches are for like a truck toolbox. I'd have preferred to have them parallel to the ground, i.e. square to the door top, but I couldn't figure out a way to have them actually latch unless they're square to that back angled edge.

The door hinges are fabbed up, just flat stock, tube, and a solid round down the middle. To remove, you unlatch the door, then just grab at the front of the door and pull up. I'll say many times during this build, but it's nice to have components you can carry with one hand. Especially since this is like a @Greg72 build, where you install and remove any given component what seems like a hundred times while you're making it.

You can see the "embossed" idea on the doors here, where the outer layer has the pattern cut through, and then is glued onto the inner layer. The back of the tub has the same thing above the wheel well. The doors have had the "corner" created by the cut filled in with wood filler and sanded (soo ... much ... sanding...), which is why they're lighter in color, and the tub hasn't had that done yet. (The tub isn't glued yet, just screwed together temporarily.)

Here you can sorta see the two layers of the tub sides

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My poor Blazer, spending much of her time as storage for wood :haha:

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Then the two pieces are glued and clamped. And yeah, that piece is warped a bit, as 1/4" plywood is finicky, even as two pieces together. I actually finished gluing them on the welding table, not seen here, so they should be mostly flat. And once it's glued into the tub the corners will be straightened with 1x1's, keep it fairly flat/straight.

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Finally, we see that primer covers a great many sins. Discovered that B-I-N makes their primer/sealer, my go-to fave for woodwork, in a rattle can, so there's no brush marks. Of course wood is so much more porous than metal, one can doesn't go remotely as far as I'm used to with metal, but it does seal nicely and should help protect all of that wood filler and glue from getting wet.

And that's another month's work in one post. How easy it seems... and how much sweat and sawdust it really was :D

-- A
 
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Looks like a Hummer to me. What's the powertrain plan? Sorry if I missed it, I was skimming at some points due to being at "work". LOL
 
A certain amount of time on this project is spent just sorting out in what order pieces must be completed, i.e. motor has to be in place for the roll bar, axle has to be in place for the motor, this has to happen before that but after this other. What work is actually done also depends on my mood, i.e. whether I feel like cutting up wood or welding on metal, whether I have a whole Saturday or just a couple hours of an evening, and how badly my back hurts and what's on TV tonight :haha:

I found real early on, pushing the thing around the shop, that it was gonna need both forward and reverse. Traditionally, smaller go-karts often just go forward; to reverse, you just pick up the ass end and drag it, with the front free-wheeling. This contraption is too heavy for that (and wide, like a Hummer!) so I sourced a reverse box for a mid-size kart. The trick then was to mount this to the motor, to which I'd already added a "torque converter" (a really small belt-driven CVT).

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This is a foam-core template of the adapter from the motor to the CVT clutch. It came with a cast aluminum piece, which I decided to redo in steel to then adapt the reverse box onto.

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Crappy pic in the sunlight, but the original aluminum piece on the left, with the bearing on it right where I'd want the gearbox to be. Rather than cut that down and try to machine it, I figured I'd just fab my own.

Then a plate for the gearbox (box itself in upper left)

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The adapter combines the flat plate of the CVT with an adapter on the output for the gearbox, much like the adapters on our trucks from transmission to transfer case.

Cut those out of 1/4" steel plate, and then wrap a piece of 1/2" wide flat bar around the outside (tack weld the end, beat with hammer, tack an inch or two down, beat with hammer, lather, rinse, repeat...) for extra strength, and nobody notices that it was cut with an angle grinder, no plasma cutter here.

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The pulley at the motor is the trick to the CVT. Basically, there's a spring-loaded slip pulley inside that tightens up at higher RPM, increasing the effective pulley ("gear") ratio of the belt arrangement. I think this one varies from about 3:1 to about .9:1, so it's like an overdrive tranny, sorta like a TH700R4. The gearbox, seen here under the exhaust behind the bottom pulley, selects forward, reverse, or neutral. It has a little filler pipe for gear oil (all 250mL of it!) and a little breather tube, the works

The square tabs on the adapter mate up to holes on the original cover, thus

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to protect the belt from debris.

Speaking of debris, and remembering that this is the dry season when much of California is a tinderbox (think of those wildfires in the wine country, not far from here that killed dozens and destroyed thousands of acres, etc) ... some of my grinding sparks went through the window screen...

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Took me a coupla minutes to notice, had my earmuffs on, so it was the smell I first noticed. Once I stopped work, I could hear the crackling, but I looked all around the shop, no flames, nothing. Was only when I stuck my head outside that I saw the flames, foot plus tall and starting to billow smoke. Photo doesn't do it justice, that's like a 20' diameter circle and the paint on the shop wall is bubbled.

Anyway, my fire extinguisher habit has again been justified, three of them around the shop. Took a good chunk of the big ten pounder to put this one out. Narrowly avoided destroying my shop, never mind my other neighbor's two acre vineyard, etc. Scary.

As a stopgap, I'm only metalworking with the windows closed, but long-term I gotta figure a solution with a big welding curtain or a movable sheet of plywood or something. The windows are old & crappy, so I don't mind that they're getting etched by the sparks, but if I replace them I don't wanna damage the new ones.

-- A
 
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Looks like a Hummer to me. What's the powertrain plan? Sorry if I missed it, I was skimming at some points due to being at "work". LOL

Woot! I did something right! :D

Powertrain is a 6.5hp gas motor, Chinese knockoff of a Honda GX200-something.


That was a coupla weeks back, so the battery was loose next to me, the shifter wasn't mounted, and the steering ... well, that "woohoo" part-way through isn't the good kind of excitement so much as fear I was gonna drive straight into a wall :D

But it moved under its own power!

-- A
 
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These little home fab projects you’re doing are more interesting than most of these truck builds.

Thanks! I don't know if that's fair though. If I posted on Tractornet or something there'd be more guys that have done this sort of thing, though total customs are still infrequent.

Plus, did I mention how much easier it is to do a winch bumper, when you can carry it in one hand? And I don't need a rotisserie to flip the tub, just a helper.

Also, there are more people building mini-whatevers, especially semi trucks. This one is one of my faves


The reveal when the guy gets out of the cab is epic. I couldn't do that as (1) I don't have the space on my lot and (2) I get claustrophobic, but it's an amazing piece of work.
 
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Now that the body was sort of designed, certain minor details like pedals and controls, could be set up. Helps to drive the thing when you can stop and start dontchaknow.

There are two pedals, one throttle and one brake, which mount to flat channel

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You'll note a bolt tacked in each corner, which goes down through the floor. Much easier to put nuts on from the bottom when the bolt is captive. These in turn have a series of holes in the floor

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here going up-down, steering column on left and front of the vehicle at top of pic. This allows for adjustment for height in driver, should we have midgets or children wanting to drive.

The pedals then mount onto this fixture

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with return springs, and then control cables will hook on the pedals, and mount to the tabs in front. These things are small enough that my feet, at least, pass right over the cable, so there's no interference. The midgets might have trouble, I'll hafta burn that bridge when I cross it. While they're set up like a regular car (brake on left, gas on right), I color-coded them too, as a hint for anybody too young for a driver's license. If we get colorblind midgets I'll be in double trouble.

Got one of these Chinese control panels, Because Race Car!

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For how cheap it was, it's actually halfway nicely made, good switches, albeit labeled ACC1, ACC2 and ACC2 :haha: It'll get scrubbed of the labels and the faux carbon fiber as a race Hummer this is not. It does give a nice obvious set of engine controls, plus switches for lights, winch, etc.

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Switch panel, choke lever, and pedals all mounted up.

The gearbox came with a control lever for forward-neutral-reverse. It's set up in that order, i.e. lever points forward to go forward, which is intuitive and all. Except on regular car prundles, you push the lever forward to go back and back to go forward. (Forgotten about prundles? Your car might have one. It says "PRNDL" right on it.)

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Welded some tabs onto a piece of square tube and put it down the center. The various control cables run through it and it mounts the mini-prundle (because "FNR" sounds rude.) The neutral is very handy for pushing the thing 'round the shop, and either of the gears are low enough that they act as a parking brake.

Turned out that to fit the drivetrain over the axle, I had to do a jackshaft, an intermediate shaft between transmission output and axle.

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(front of vehicle to the left)

You can see the drive chain coming off the transmission just right of the belt in this pic; that's I think a 12:15 reduction there. Not remotely enough to drive the thing, but it acts as an underdrive -- think doubler in low gear. The jackshaft is the one to the rear of the axle, to the right in this pic. It has like 10:80 reduction driving the axle, giving me about 1:10 overall from tranny to axle. The solid disc on the jackshaft is the brake. I put it there for additional grabbing power, since it has that same 1:8 reduction, which is also torque multiplication (or division, however you want to look at it.) It means I get eight times the clamping power versus mounting it on the axle proper. Which, given the weight of this vehicle, is A Good Thing.

Having two chains means that adjusting tension is a bit complicated. The axle is stationary, but the pillow blocks for the jackshaft mount to slots in the frame, so that adjusts the axle-jackshaft tension. The motor is also on an adjustable slider, so it can be adjusted after the jackshaft is adjusted to the axle.
 
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