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'wittle 'wesistor (Mini Jeep)

6877 Views 152 Replies 6 Participants Last post by  remy_martian
For my next creation, I've been thinking about building a go kart sized jeep (mini-Jeep)
...but first, here is some Jeep info.

"The Jeep marque has been headquartered in Toledo, Ohio, ever since Willys–Overland launched production of the first CJ or Civilian Jeep branded models there in 1945. Its replacement, the conceptually consistent Jeep Wrangler series, remains in production since 1986. With its solid axles and open top, the Wrangler is the Jeep model that is central to the brand's identity.

At least two Jeep models (the CJ-5 and the SJ Wagoneer) enjoyed extraordinary three-decade production runs of a single body generation.

In lowercase, the term "jeep" continues to be used as a generic term for vehicles inspired by the Jeep that are suitable for use on rough terrain. In Iceland, the word Jeppi (derived from Jeep) has been used since WWII and is still used for any type of SUV.

Prior to 1940 the term "jeep" had been used as U.S. Army slang for new recruits or vehicles, but the World War II "jeep" that went into production in 1941 specifically tied the name to this light military 4x4, arguably making them the oldest four-wheel drive mass-production vehicles now known as SUVs. The Jeep became the primary light 4-wheel-drive vehicle of the United States Armed Forces and the Allies during World War II, as well as the postwar period. The term became common worldwide in the wake of the war. Doug Stewart noted: "The spartan, cramped, and unstintingly functional jeep became the ubiquitous World War II four-wheeled personification of Yankee ingenuity and cocky, can-do determination." It is the precursor of subsequent generations of military light utility vehicles such as the Humvee, and inspired the creation of civilian analogs such as the original Series I Land Rover. Many Jeep variants serving similar military and civilian roles have since been designed in other nations.

Development – 1. Bantam Reconnaissance Car
When it became clear that the United States would be involved in the European theater of World War II, the Army contacted 135 companies to create working prototypes of a four-wheel drive reconnaissance car. Only two companies responded: American Bantam Car Company and Willys-Overland. The Army set a seemingly impossible deadline of 49 days to supply a working prototype. Willys asked for more time, but was refused. American Bantam had only a small staff with nobody to draft the vehicle plans, so chief engineer Harold Crist hired Karl Probst, a talented freelance designer from Detroit. After turning down Bantam's initial request, Probst responded to an Army request and began work on July 17, 1940, initially without salary.

Probst drafted the full plans in just two days for the Bantam prototype known as the BRC or Bantam Reconnaissance Car, working up a cost estimate the next day. Bantam's bid was submitted on July 22, complete with blueprints. Much of the vehicle could be assembled from off-the-shelf automotive parts, and custom four-wheel drivetrain components were to be supplied by Spicer. The hand-built prototype was completed in Butler, Pennsylvania and driven to Camp Holabird, Maryland on September 23 for Army testing. The vehicle met all the Army's criteria except engine torque.

Development – 2. Willys and Ford
The Army thought that the Bantam company lacked the production capacity to manufacture and deliver the required number of vehicles, so it supplied the Bantam design to Willys and Ford, and encouraged them to enhance the design. The resulting Ford "Pygmy" and Willys "Quad" prototypes looked very similar to the Bantam BRC prototype, and Spicer supplied very similar four-wheel drivetrain components to all three manufacturers.

1,500 of each model (Bantam BRC-40, Ford GP, and Willys MA) were built and extensively field-tested. After the weight specification was revised, Willys-Overland's chief engineer Delmar "Barney" Roos modified the design in order to use Willys's heavy but powerful "Go Devil" engine, and won the initial production contract. The Willys version became the standard jeep design, designated the model MB, and was built at their plant in Toledo, Ohio. The familiar pressed-metal Jeep grille was a Ford design feature and incorporated in the final design by the Army.

Because the US War Department required a large number of vehicles in a short time, Willys-Overland granted the US Government a non-exclusive license to allow another company to manufacture vehicles using Willys' specifications. The Army chose Ford as a second supplier, building Jeeps to the Willys' design. Willys supplied Ford with a complete set of plans and specifications. American Bantam, the creators of the first Jeep, built approximately 2,700 of them to the BRC-40 design, but spent the rest of the war building heavy-duty trailers for the Army.

Final production version jeeps built by Willys-Overland were the Model MB, while those built by Ford were the Model GPW (G = government vehicle, P = 80" wheelbase, W = Willys engine design). There were subtle differences between the two. The versions produced by Ford had every component (including bolt heads) marked with an "F", and early on Ford also stamped their name in large letters in their trademark script, embossed in the rear panel of their jeeps. Willys followed the Ford pattern by stamping 'Willys' into several body parts, but the U.S. government objected to this practice, and both parties stopped this in 1942.

The cost per vehicle trended upwards as the war continued from the price under the first contract from Willys at US$648.74 (Ford's was $782.59 per unit). Willys-Overland and Ford, under the direction of Charles E. Sorensen (vice-president of Ford during World War II), produced about 640,000 Jeeps.

Jeeps were used by every service of the U.S. military. An average of 145 were supplied to every Army infantry regiment. Jeeps were used for many purposes, including cable laying, Sawmilling, as firefighting pumpers, field ambulances, tractors, and, with suitable wheels, would run on railway tracks."

I came across this drawing
...& it seemed like a pretty good guide

So, I'm thinking maybe ~50% should work for a mini jeep, I'll just have to calculate a ~2:1 reduction ;)

Wheel Tire Wood Font Rectangle
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Discussion Starter · #2 ·
FWIU the US military started using mechanized vehicles toward the end of WWI
...but, what was available, at the time, was inadequate for many "war type" situations
...& what "was available" was only available in small numbers

What they ended up with was a bunch of different vehicles
...from different manufacturers
...that all required different parts
...& then, the mechanics (or soldiers, out in the field) had to learn/figure out how to fix all of these different vehicles.

Going into WW2 the military wanted (1) "simple" vehicle, that was more capable to use, where there weren't any roads
...would be easier to "stock" parts
...& (1) common vehicle for the soldiers to learn how to fix

The Bantam BRC design kinda "won" basically because it was the only one to submit a working prototype
...but, because Bantum was a small company, the military submitted the design to Willys (the only other company to respond to the military request) & Ford (probably due to their manufacturing capabilities) & they were encouraged to enhance the design.

Fords most notable contribution to the design seemed to be the extensive use of low cost, easily produced "stamped" parts (like body & grille)
...& for Willy's, it was the powerful "Go Devil" engine.

Another important acclimate of the BRC design, was the use of already available "off the shelf" parts
...with tested designs
...already available inventory
...& also, easily increased manufacturing capabilities

So, once the military approved a design (M38) "Jeeps" started infesting our planet (~650,000) just of this designation

The ones built (here in Toledo, Ohio) by Willys were designated MB's
...& the ones Ford's built were GPW's

Then, after WW2 Willys started building a civilian version of the M38's that many soldiers relied on daily
...& had so much experience with.

So, the CJ (Civilian Jeep) was "born"

"The CJ series were literally the first "Jeep" branded vehicles sold commercially to the civilian public, beginning in 1945 with the CJ-2A, followed by the CJ-3A in 1949 and the CJ-3B in 1953.

These early Jeeps are frequently referred to as "flat-fenders" because their front fenders were completely flat and straight, just as on the original WW II model (the Willys MB and identical Ford GPW).

Then, beginning with the CJ-5 (in 1955) they featured rounded fenders and hoods, first introduced as the military Willys MD (or M38A1). The (slightly) restyled body was mostly prompted to clear the taller new overhead-valve Hurricane engine."

A few other "Jeep fun facts" :p

* The Jeep CJ (built from ~1945 - 1986) is one of the few vehicles that has had over a 30 "production run" (with very few changes)
Its replacement, the conceptually consistent Jeep Wrangler series, has remained in production since (1986 - present)

So, remarkably, it still looks pretty much the same. (for over 75 years) OMG

* The Wrangler is one of the few remaining four-wheel-drive vehicles with solid front and rear axles.
These axles are known for their durability, strength, and articulation.
Another benefit of solid axle vehicles is they tend to be easier and cheaper to "lift" with aftermarket suspension systems.
This increases the distance between the axle and chassis of the vehicle.
By increasing this distance, larger tires can be installed, which will increase the ground clearance, allowing it to traverse even larger and more difficult obstacles.

* In addition to higher ground clearance, many owners aim to increase suspension articulation or "flex" to give their Jeeps greatly improved off-road capabilities.
Good suspension articulation keeps all four wheels in contact with the ground and maintains traction.

* Other useful features of Jeeps are their short wheelbases, narrow frames, ample approach, breakover, and departure angles, thus enabling them to traverse through places where full-size four-wheel drives have difficulty.

* AMC (American Motors Company) carried over the practice of using "available" & "off the shelf" parts when building the CJ's.
So, some Jeeps came, from the factory, with Ford engines & some with Chevy engines
...some had ford style steering columns & others had Chrysler style columns
...& power steering pumps
...& brake boosters
...& all kinds of other things too ;)

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Discussion Starter · #4 ·
"GP" - General Purpose (vehicle)

Does JC Whitney still sell body panels, etc for them?
It wouldn't surprise me.
It seems like there are more aftermarket parts available for these Jeeps, than most any other vehicle ever made
...but, most of them probably won't be much help, with my 50% endeavor.

I've been "playing" with some numbers (going off of the pic in the first post)
...& it looks like just 50% is just a bit too small
...but, if I (divide by 2 (50%) & then multiply by .1 & add them together) seems to work better :cool:
Handwriting Font Rectangle Parallel Writing

So, maybe ~33" wide
...with a ~45" wheelbase
...& ~72" long overall ;)

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Discussion Starter · #6 ·
So...55% scale, according to book lernin' 🤓
Well...while thinkin' about "names" for my mini-Jeep, Watts-n-Learn was (1) of them
...but, thought some folks might take it personal :unsure:

Speaking of "names" it seems like folks have named their Jeeps, just about everything under the sun
...even Magic Smoke, which I thought would be a really kool name for an electric powered Jeep

My criteria for a name was 1.) mini- 2.) electrical 3.) Jeep
...& "if" I could "hit" (2) I'd consider it a "double bonus" ;)
...but, also, something most ordinary folks would easily recognize

I really liked Amplitude, Capacitator &/or Recifier
...but, does the average "Jo" know what those are (probably not)

Just for "giggles", here are some of the names, I came up with :p
Handwriting Font Material property Writing Paper

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Discussion Starter · #9 ·
I took the drawings & measurements (from the notebook)
...& started applying them (in the real world) to a piece of ~1/4" plywood (using a ruler, a square, a pencil & a sharpie)

First, I tried a 48" wheelbase
...but, it didn't seem right/proportionate (the wheels seemed too far apart)
Tire Wheel Automotive tire Motor vehicle Tread

So, I tried the 44.5" WB
...& IMO it looked much better ;)

* One of the "visual markers" I like to maintain is the "look" of the frame, where it curves up a bit, just in front of the rear wheel.
Like this:
Tire Wheel Automotive tire Tread Synthetic rubber

Then, after everything was drawn out, maybe something like this ;)
Automotive design Wood Flooring Floor Automotive exterior

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Discussion Starter · #12 ·
I like the way you're mocking it up.
More ideas for you:
Thank you sir :)
I just don't like that "seat in the cargo area, look"

Actually, I was kinda waiting for you to ask, "what you gonna do with your feet?"
...& I was going to say, Flintstone the firewall ;)

* There won't be an engine up there
...thus no need for a "firewall", let's try & take advantage of the situation

As for getting your knees under the dash

It looks like it "should have" ~14" from the floor up to the "dash bar"

So, think about it from a go kart, Corvette or even a Formula 1 "point of view" are going to have to "climb in" :p

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Suggest you get yourself an adjustable stool and crank it to the compressed height of your seat. Mark the bottom of the dash panel and your pedals. See if your bent knees will fit in there.

I'm not concerned about entry (if you can get into a kayak, you can get into this thing), but the seat back to pedal distance with the dash as a height constraint on your knees which you did not have in your kart builds. In a kart, your butt is an inch or two off the ground, which lowers your bent you have the seat a lot higher up relative to the pedals.

Is this a single seater? If not, wheel wells may be another leg problem.

It's good that you're constraining the design...just need to double and triple check you can get an adult (or two?) accommodated.

Wide mower tires and rims might be a consideration as well.

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Discussion Starter · #15 ·
Suggest you get yourself an adjustable stool and crank it to the compressed height of your seat. Mark the bottom of the dash panel and your pedals. See if your bent knees will fit in there.

I'm not concerned about entry (if you can get into a kayak, you can get into this thing), but the seat back to pedal distance with the dash as a height constraint on your knees which you did not have in your kart builds. In a kart, your butt is an inch or two off the ground, which lowers your bent you have the seat a lot higher up relative to the pedals.

Is this a single seater? If not, wheel wells may be another leg problem.

It's good that you're constraining the design...just need to double and triple check you can get an adult (or two?) accommodated.

Wide mower tires and rims might be a consideration as well.
Appreciate the input

The dash bar in my Aerial Atom kart is ~14" above the floorboard
...& I believe the dash in the Slingshot is about the same height

I did a quick drawing this morning to "double check" the seating & foot accommodations

Here are the "basic" numbers
...but, this is art so, everything adjustable ;)
Rectangle Font Parallel Triangle Slope

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Discussion Starter · #17 ·
Checking another "guide" that I sometimes go by, the FSAE RULES 2022

* See, sometimes I go by "the book" (or at least "check it" for reference) ;)

In the F-Chassis & Structural section, I notice it has instructions for a 2-dimensional driver template "used to represent the 95th percentile male"
Font Material property Pattern Paper Monochrome

...& an illustration too
Font Pattern Circle Number Rectangle

It specifies 915mm (~36") from pelvis to foot
...but, the bottom of the seat is about the same height as the feet/pedals

Additionally, under T-Technical Aspects they have specifications for the cockpit opening
...& also, an Internal Cross Section Template

It specifies a 350mm (~14") requirement from top to bottom
...& 300mm (~12") from side to side (for a single driver)
Art Font Gesture Rectangle Pattern

Just more info/food for thought :)

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Yup - but that is for reclined seating.

What you are proposing is a bench seat, so I think you need an "anthropomorphic" model that has the knee joint in it, not a straight line hip to ankle model the FSAE cars use.

From Henry Dreyfus's book "Designing for People" (which is on sale on Amazon right now), if you don't want to squint at this lame scan:

Human body Font Parallel Elbow Rectangle

Or a stool up against your plywood sheet where the seat is and maybe a footpeg to see where your knees wind up when projected onto the plywood model's dash to floorboard opening. Don't forget the knee and foot positions traveling to a pedal from the floor or dead pedal and actuating it, unlike a kart where it's mostly ankle action.

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Discussion Starter · #19 ·
Thanks, great response
...& very informative :)

I evaluated the situation a bit more
...& agree it's going to be tight
...but, this "is" a "mini" vehicle so...:whistle:

Now, let's talk about the frame & suspension

Many "replica" or "bodied" go karts use a simple Ladder style frame
...& the body is just a facade (or outer cover)

I'm thinking, since I'm designing & building a frame, from scratch, I'd like to incorporate a few features
...which may even strengthen it as well

Here is kinda what a "stock" jeep CJ frame looks like (top of pic)
...& below is kinda what I'm thinking for a rear trailing arm

* Notice it would be "curved" to "mimic" the look of a leaf spring

It would connect to the frame in front of the rear wheel (like a CJ)
...& use (2) coil-over shocks (1) on each side (not shown)

The rear of the trailing arm would curve upwards a bit
...& then "cross-over" to the other side
...but, would not be connected (to the frame)

The rear axle
...& brake system would all be mounted on this trailing arm

* Thinking about using this concept for the front axle/suspension too
Font Wood Parallel Art Pattern

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You could just raid a golf cart for leaf springs, frame, front suspension and steering, etc...basically that 125cc mini-Jeep, de-iced.

You can also go plywood unibody with a front subframe....think about using wooden boatbuilding techniques (including a layer of fiberglass) for everything back from the front tires.
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