DIY Electric Car Forums banner

'wittle 'wesistor (Mini Jeep)

16919 Views 296 Replies 7 Participants Last post by  Functional Artist
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."

https://en.wikipedia.org/wiki/Jeep

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

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

Wheel Tire Wood Font Rectangle
See less See more
201 - 220 of 297 Posts
4
Test fit pics, before bending the battery box bottom, end panels
Wood Table Gas Wood stain Hardwood

*Notice the module is sitting there (actually standing & will be layed down) "au natural" without any bolts
...just a plastic Zip Tie as a temporary restraining band
Wood Gas Composite material Hardwood Machine

Test fit pic, after bending the end panels
...& laying the module down (the zip tie is now "in the way" & will have to be removed)
Audio equipment Wood Gas Machine Electronic instrument

Here is the "space" for most of the wire connections & electronics
Gas Machine Bumper Asphalt Composite material
See less See more
I may have missed it, but how thick is the box sheet you're bending up?
4
I may have missed it, but how thick is the box sheet you're bending up?
Hey Remy,
It's 18g. steel

I used the same procedure to make the top (it just has shorter sides)

Clam Shell Battery Box
Wood Gas Office equipment Machine Bumper

Test fitting the battery module
Saw Wood Automotive exterior Gas Bumper

All "buttoned up"
Wood Gas Composite material Hardwood Rectangle

Test fitting in the chassis
Wood Flooring Floor Hardwood Gas
See less See more
6
To keep the battery cables, inside of the box
...the 48V 50A Circuit Breaker will be mounted on the top, left, front corner of the battery box ;)
Digital camera Point-and-shoot camera Camera lens Camera accessory Cameras & optics

Masked the perimeter (to highlight the "cut-out" area & help protect the outer area)
...& drilled 5/16" holes (to establish the rounded corners)
Fluid Rectangle Gas Wood Automotive exterior

Cut it out (connected the dots) with a cut-off wheel, in a Dremel
Wood Rectangle Bumper Gas Tints and shades

Cleaned up the cut-out area
Rectangle Road surface Grey Asphalt Composite material

Installed the CB
Bumper Automotive tire Automotive exterior Gas Camera accessory

Pretty tight fit
Gas Font Auto part Machine Metal
See less See more
3
This battery box is designed to be like a "structural" exoskeleton
...where it helps to "maintain the structure" of the battery module
...but, also, hold (& protect) most of the electronics

It will have (5) 1/4" bolts (with lock nuts) on each side (front & back) bolting the top & bottom pieces together
...with a piece of 1" x 1" x 1/8" angle iron (in front & back) re-enforcing the bolting flange(s)
...& also, mounting the battery box to the chassis (dual purpose)

Front
Automotive tire Bumper Wood Automotive exterior Gas

Back
Wood Bumper Automotive exterior Rectangle Gas

The (2) bolts oriented upwards, initially bolt the battery box together
...& the other (3) bolts (pointing downwards) are for mounting
...but they will also, help to secure the battery box halves together

The rear piece of angle iron is welded to the chassis
...& the front piece will be bolted in
...so, it's removable

Kinda like this ;)
Handwriting Rectangle Font Material property Parallel
See less See more
You might want to pick up a few temperatures inside that box - your cells have zero cooling...not even with air.
You might want to pick up a few temperatures inside that box - your cells have zero cooling...not even with air.
Hey Remy,
I agree, "heat" (or the potential of heat build up) is an important factor when working with/using Lithium batteries
...& I'm glad/thanks for mentioning it ;)

FWIU most lithium batteries can/will create heat "if" stressed beyond a certain level
...& that's if/& or when dis-charging (drawing a lot of Amps)
...& also, re-charging (high Amperage/fast charging)

For this specific application, the motor(s) that will power the Mini-Jeep, are only rated at ~20A (ea.) (1,000W /48V = 20.83A)
...& then, it will only be re-charged with a 10A charger

So, IIUC drawing ~50A from a 2kWh 48V ~50AH Chevy Volt Lithium battery module, would be considered ~1C Amp draw
...& re-charging with ~10A charger would be considered like ~1/5C
(please, correct & explain if these assumptions &/or conclusions are incorrect or mis-leading)

So, (again) FWIU these rates should be too small to be able to create any noticeable (or damaging) heat

My personal experience, using these Chevy Volt modules, to power my ElMoto (for quite a few years now)
...which with its 8,000W motor, draws in excess of 100A regularly
...& it has NEVER even gotten warm (yes, I have checked a lot)

But also, I would think that the "close fitting" steel battery box should/would "act" as a heat sink (if ever necessary)
...& help dissipate any (potential) heat FREE BONUS :)

* WARNING when working with Lithium Batteries always evaluate your specific situation (y)

** For the record (does anyone know) how much amperage a full size Chevy Volt draws while powering it's motor?
...&/or accept while being re-charged? :unsure:
See less See more
Your steel box will do nothing for cooling unless you couple it to the plates between the cells. The air space between the battery and the box will be a thermal insulator.

I would still run a thermometer lead into the box so you can catch a problem in the making.
  • Like
Reactions: 1
I would still run a thermometer lead into the box so you can catch a problem in the making.
Oh, Remy...Remy...Remy
I'm not against overcomplicating things (well, I am but, lets say I'm not) :p
But,
I'm also not against having more info
So,
I know your SUPER busy & all
...but, could ya...
...maybe...
...please...
...elaborate (like, give an example of something that would be adequate for this situation) ;)
DC 12V LED Digital Thermostat Controller Temp Sensor Control Relay Gauge ToolsDC | eBay DC 12V LED Digital Thermostat Controller Temp Sensor Control Relay Gauge
you could wire it just as the temp display or use the relay to control the ksi circuit
Mini F Digital LCD Thermometer Temperature Meter Gauge Sensor Indoor Outdoor US 708624426304 | eBay Mini F Digital LCD Thermometer Temperature Meter Gauge Sensor Indoor Outdoor US
The second one is just a temp sensor.
Perhaps a couple top of pack, middle of pack.
later floyd
  • Like
Reactions: 2
Just a thermocouple and a temperature guage will do...maybe attach it to one of the aluminum plates between the cells.

Do you have any power for stuff like your brake lights at 12V or is it all at the pack voltage?

I'll take a look when I get home later this evg. unless someone else jumps in beforehand, which won't hurt my feelings.
  • Like
Reactions: 1
Just a thermocouple and a temperature guage will do...maybe attach it to one of the aluminum plates between the cells.
I've noticed that you often mention the KISS concept
...but, you don't seem to "practice what you preach"

When you've asked about
Frame materials or Switches or BMS & even Pack cooling, I've explained the (my) entire thought process
...that led to each decision (that I made)

Define the parameters of a situation & then, work within those parameters ;)
&
Now, it's Battery temperature monitoring (on a low voltage, low power, go kart) 🤪
No - it's temperature monitoring of a NMC lithium battery. Nothing to do with what it's going into.

Any build is ultimately the builder's set of choices.

You can choose not to do it, just like you chose not to liquid cool it, then chose to put it in a closed box like the big boys do, but with no conductive heat path out. You unintentionally insulated an exothermic chemical reactor.

Your motorbike had 50mph air cooling - this has nothing at all because of the choice of using a closed, air insulated, box.

KISS is Floyd's temperature guage and your eyeballs. It's your choice of not using a BMS to watch the temperature. It's your assets that might burn up, not mine.

With 1C discharge in a closed box, temperatures will rise. On a 110 degree summer day, you don't get much margin for that rise.

1C is a substantial discharge rate for a completely uncooled sandwich of cells that you have unintentionally coupled, vs isolated when they had coolant flowing, with aluminum plates between them. The cells will heat each other.

Your choice on thermal monitoring, or not, but I think you've increased the cell heating with the way this pack is being used.

Your build here is brilliant, just that some of your "simplifications" for this pack and its box may be complications.
See less See more
No - it's temperature monitoring of a NMC lithium battery. Nothing to do with what it's going into.

Any build is ultimately the builder's set of choices.

You can choose not to do it, just like you chose not to liquid cool it, then chose to put it in a closed box like the big boys do, but with no conductive heat path out. You unintentionally insulated an exothermic chemical reactor.
Does the Lithium battery in (most) Nissan Leaf(s) have (any) pack cooling?
...& are they mounted "in an enclosed box"?
...& they power full size (highway driven) cars?

* Concept,
Enclose the battery pack
...& most, if not all, of the high voltage stuff "safely" inside of a metal box (like most OEM EV's do) :)

1.) So, most (if not all) of the high voltage "stuff" is safely "sealed away"
...& isn't easily accessible (accidentally touchable) by you, family, friends etc. while on display
...or showing
...&/or even during general vehicle maintenance

2.) Again, so most (if not all) of the high voltage "stuff" is safely "sealed away"
...& isn't easily accessible by you, family, friends, first responders etc. in the event of a collision

3.) As a "Fire Wall" to help shield the vehicles occupants from "the battery pack"
...& (hopefully) give them a bit more time to exit, the vehicle, in the event of a fire :cry:

So, I thought this build would be a good example, to show folks, how someone "can" evaluate "a" situation
...& then, (how I went about) build an enclosed box
...that can hold the battery (pack) & associated "stuff"
...& then, (how I went about) mounting it, to the vehicle
&/so,
I intentionally put "this" NMC Lithium battery module, in a closed box "like the big boys" should do (but, not all do)
...for the reasons listed above ;)
&
I intentionally chose to eliminate the liquid cooling system
...because IMO it's not needed, for "this" specific application
...will ultimately "serve no purpose"
...& just unnecessarily complicate "the build"

Your motorbike had 50mph air cooling - this has nothing at all because of the choice of using a closed, air insulated, box.
The (2) Chevy Volt module(s) on my ElMoto are "butted" right up against each other
...& almost completely wrapped with (the same) 18g. steel (except top & bottom)
...&/so, "if" your claim "Your steel box will do nothing for cooling unless you couple it to the plates between the cells. The air space between the battery and the box will be a thermal insulator." is true
...then, my ElMoto doesn't have 50MPH air cooling
...& still doesn't (ever) warm up
...even when ~50A (~1C) steady & sometimes well over 100A (~2C) are being drawn from it
See less See more
Do you have any power for stuff like your brake lights at 12V or is it all at the pack voltage?
All functions associated with "this" Speed Controller operate at (48V) pack voltage
...except, for the throttle, which operates at (5v)

The plan "was" to mount the Circuit Breaker, right on the battery box (done) :cool:
...& both speed controllers, inside of the box
...so, all of the battery cables, would be kept "safely" inside of the box

This way the only wires outside of the box were
...the control wires (On/Off & Reverse)
...the wires for the power meter
...& also, the motor(s) power cables

But now, thinking it thru (a bit more) Remy has brought up a valid concern (heat in the box) o_O

I still don't believe (from my experience) that the battery module will ever encounter, any heating issues
...but, I know (again, from experience) that these YK-31 speed controllers can & do get warm or even hot sometimes
...& "if" mounted inside of the box, they could/would increase the temperature inside of the box
...which could/would affect the battery module :confused:
Circuit component Motor vehicle Electrical wiring Gas Engineering

Re-evaluating...re-evaluation... ;)
See less See more
DC 12V LED Digital Thermostat Controller Temp Sensor Control Relay Gauge ToolsDC | eBay to a 12V fan such as NZXT RF-AP140-FP Static Pressure Fan 815671013095 | eBay or two one intake and one exhaust. This vehicle is for use in a parade it most likely see less than 100A? draw max but with multiple start and stops. this is assuming a 12V circuit is available.
Later Floyd
  • Like
Reactions: 1
DC 12V LED Digital Thermostat Controller Temp Sensor Control Relay Gauge ToolsDC | eBay to a 12V fan such as NZXT RF-AP140-FP Static Pressure Fan 815671013095 | eBay or two one intake and one exhaust. This vehicle is for use in a parade it most likely see less than 100A? draw max but with multiple start and stops. this is assuming a 12V circuit is available.
Later Floyd
Hey Floyd,
Thanks, for the helpful suggestions :)
...& "That's the spirit" ;)

This SC doesn't have any 12V available
...but, something like this (48V fan) may work (or 2) (y)

NEW 120MM DC 48V Fan NMB 108 CFM 0.15A 2950 RPM (~$12.00)
NEW 120MM DC 48V Fan NMB 108 CFM 0.15A 2950 RPM | eBay
2
Your build here is brilliant, just that some of your "simplifications" for this pack and its box may be complications.
Thanks! I always appreciate it when the craftsmanship gets noticed :)

Think of it this way, after building a couple of mini-EV's you (or anyone really) would start incorporating things learned from the previous ones (research & then, development leads to improvements & sometimes simplifications)

So, after you/me (or anyone really) built several mini-EV's using mainly the same components (small motors, controllers & Chevy Volt modules) over & over again (& not "jumping" around between different technologies)
...you sometimes notice "situations" where you can "potentially" simplify things
&
That's where Define the parameters of a situation & then, work within those parameters ;) comes "into play"

Let's move on, for now (we'll get back to the electronics) (y)

Front section of floorboard
Cut it out of, the top section, of the piece of 18g steel
...same as the battery box (bottom section)
Brown Wood Rectangle Handwriting Font

Drew it out on (the steel) using the CAD template

* Notice, the differences between the left side & the right sides?

I was leaving my options "open"
...while trying a couple of different ideas
...until I could actually "fit" it on the frame

Spoiler Alert: The left side is "the winner" ;)
Rectangle Wood Flooring Wood stain Hardwood
See less See more
3
After getting the front section of floor board cut out
Table Wood Tool Line Composite material

...& then, (kinda) dry fitting on the frame
Fixture Gas Wood Composite material Metal

...& then, after settling on the "left profile" did a "final" trim (& deburring of the edges)
Rectangle Wood Tints and shades Symmetry Font

Then, went to the bender & started thinking about the bending sequence

So, going across the piece, we will need a "kick up" (~45*) in the lower front (solid line middle/top)
...& also, another (~45*) for the ~1" "lip" in the upper front (solid line near the top)
But then,
I realized that the side "bolting flanges" are on multiple (~5 different) angles
&
No matter/which ever way or section, that I bent first
..."that bend" would end up being in the way, of other bends
So,
Re-calculating...re-calculating :unsure:

* I tried clamping the piece to the edge of the work bench
...& then, clamping a 1" piece of steel to (1) of the flange(s)
...& manually "hand bending" it
...but, (quickly) found this 18g. steel is too thick/ridgid/tough for me to bend it "by hand
So,
Re-calculating...re-calculating :unsure:
See less See more
Buildhenge:
Table Wood Tool Pneumatic tool Line

Now you need to wait 6 months before you can use that solar measuring table for 6"-spaced layout again.

Glad you got it done on the one of two days a year that you could 😂
See less See more
  • Haha
Reactions: 1
201 - 220 of 297 Posts
Top