Ok
So, we have some goals
...& an idea, of what we would like it to look like
...but, where do you actually start?
The driver is the heaviest, most awkwardly shaped component in a racer
So, I usually start with the ****pit
Driver Accommodations
First, think about a Seat
I like the plastic racing style seats
...they kinda "wrap around" the driver & provide some side support
Then, think about things like:
Steering
...what kinda steering wheel
...how far should it be from the driver
...& how to mount it
Pedals
...what kinda pedals
...where are you going to put them
... how far should they be from the driver
...& how are you going to mount them
Roll over protection
...roll bar(s)
...or a full roll cage
Side impact protection
...what need to be where
...in what direction (vertical, horizontal, angled)
...& how high etc.
...& also, egress
...how does the driver get in & out
...& how easy is this to accomplish?
So, far this is all in thought or on paper
Now, actually set a seat up
...set a driver in it
...& start "mocking" things up (steering, pedals etc.)
Mapping things out, around an actual driver helps give a "real world" perspective of everything that's involved
...& the room that's required
Then, do lots of measuring
...& adjusting
...& making notes
...& even pics
Then, with this info
...you can start planning
...& building the rest of car (around the driver)
After lots of trial & error, here are some of the specs that I have come up with.
Keep in mind that
...I'm ~5'5" tall & ~150 lbs.
...& these dimensions are based "around" a driver my size
...but, at this "planning stage" everything is adjustable
Chassis overall height: ~34"
Side impact protection height: ~18"
Dash bar/Steering support height: ~16"
C**kpit side to side: ~20"
Distance to pedals: ~34" - 36"
Leg Tunnel: ~14" x ~14"
Base frame rails: ~14" (apart)
* An easy mock up method is to use "real world" CAD (Cardboard Aided Design)
...just get a refrigerator box (or any big card board box) & re-configure it
Maybe something like have a ~14" x ~60" bottom
...leaving a ~24" area, for the seat/driver
...add a ~14" x ~14" x ~36" leg tunnel
...then, add some sides
...& go from there
* Also, keep in mind, the EA rule book (page 6.) requires a max overall width of 48" & a max overall length of 12" for all race cars
So, with the measurements ...& the diagram posted above, I started measuring, marking & cutting pieces
I started at the top, making the roll cage ...(2) pieces 1/2" Schedule 40 water pipe (actually 5/8"ID x 7/8"OD with ~1/8" wall) ~60" long ...marked at 3" intervals ...& then, bump bent
* When making "stuff" where (2) matching pieces are required, I usually try to make both pieces, at the same time (it's easier to make matching pieces)
If I may ask, how does the "weigh in" work, at EA races?
Does the driver actually hold the ballast weights
...& then, gets weighed, to make sure that they (together) weigh at least 180lbs.? (as per the rule book)
Then, the ballast (weights) get secured, in the car
...& the car then, gets inspected, just before the race?
Chassis overall height: ~34" (check)
Side impact protection height: ~18" (check)
Dash bar/Steering support height: ~16" (check)
C**kpit side to side: ~20" (check)
Distance to pedals: ~34" - 36" (check)
Leg Tunnel: ~14" x ~14" (check)
Base frame rails: ~14" (apart) (check)
& also,
In the very last pic (in the last post) notice that the available area, for the battery box is
...~8" from the (front to back)
...the lower frame rails are ~13 1/2" apart (side to side)
...& there is at least 12" of vertical space available (up & down)
After most everything checked out "within specified parameters", I went ahead & made up & installed, a front seat mount (which also doubles as a mid-chassis, cross member)
Started working on & installing the "truss bars"
* Notice the "truss bars" that "run" next to the seat, needed to be curved a little bit (to "clear" the seat)
I also, made up & installed a curved cross member, in the rear, that will also help support the driver's weight, while entering & exiting the car
I found a (3) wheel hydraulic disc brake system, for Hammer Head go karts (~$75.00)
It has heavier duty (more properly sized) components (thicker rotors & bigger calipers) ...& also, provides braking for all (3) wheels (for better control)
It comes with the Master Cylinder
...(3) Rotors
...& (3) Calipers (already plumbed & the system bled)
* A couple of extra bonuses are
...the rear caliper has a parking brake feature incorporated
...& the Master Cylinder has an automotive style brake light switch, already built in
FYI: this video shows, this type of brake system, being mounted on a kart
* A couple of important factors to pay close attention to are:
1.) Check out the cast front wheel hubs, that are "normally" used with this brake system
2.) Notice where the master cylinder is mounted ...& how that mount is fabbed & installed
3.) Also, take notice of the size of the front rotors, compared to the size of the tires, they will be controlling ...& the size of the rear rotor, compared to the size of the rear tires, that it has to control
The wheels that I'm going to try, on this racer, are normally used on golf carts.
They are 8" steel rims that are 3.75" wide & have 4.80 x 4.00 x 8 Diamond Pattern Turf Tread tires
They are brand new "take offs" (meaning that the golf cart buyer wanted fancy wheels/tires installed)
I found a set of (4) of them on eBay for ~$75.00 & that's ...~$18.75 per wheel ...or ~$9.38 per rim ...& ~$9.38 per tire
* These are probably not the best tires for racing ...but, we have endless options available for 8" rims (when we get to that point) ...& for ~$9.00 ea. they are perfect for initial testing
FYI: these steel wheels weigh ~8lbs. (ea.) w/tires ...as opposed to ~3lbs. (ea.) w/wheels, that the plastic bicycle wheels on Polaris weigh
So, this "upgrade" comes with a ~15lb. "weight penalty" ...but also, has a (4th) wheel ...so we have a spare tire, that's all ready to go
For comparison, here is (1) of the (~16") golf cart wheels next to (1) of Polaris's (~20") wheels
* Notice the golf cart wheel is only a few inches shorter, than the bicycle wheel
...but, has almost double the width
Plus = better traction
Minus = higher rolling resistance
-- Edited by Functional Artist on Tuesday 2nd of January 2024 03:11:07 PM
"* Notice the golf cart wheel is only a few inches shorter, than the bicycle wheel
...but, has almost double the width
Plus = better traction
Minus = higher rolling resistance
I do not think this is correct. Oddly, wider tires seem to have less rolling resistance. It has been discussed before in the tires section and there is some good test data comparing wider and skinner bicycle tires on the Internet. Here is what I posted:
The wider tire having lower rolling resistance is counter intuitive but it makes sense to me. Most rolling resistance comes from the tire deforming to create the contact patch-going from a round tire to a flat spot on the road. The more the rubber has to move, the greater the energy loss. This is why a larger diameter tire should have less rolling resistance than a smaller diameter tire. The greater arc of the larger diameter tire is closer to the flat line of the road and changes less.
The wider vs. thinner tire is due to the shape of the contact patch and geometry. The skinny tire contact patch is long and thin while the wider tire contact patch is short and fat. If everything else is equal, than the rubber in the center of the arc of the skinny tire has to move further than the rubber in the middle of the wider tire.
The key, of course, is 'if everything else is equal'. Different tire construction such as thicker rubber or inability to run higher pressures are going to weigh in too. We get our lowest rolling resistance just before the tire wears through. This makes sense since the rubber is very thin and it takes less energy to deform it. Not ideal for finishing the race though.
1.) The fact that the way the front Halo support, was attached to the center of the dash bar, that there was a potential for the dash bar to buckle.
Which could cause the steering wheel & column to collapse ...potentially injuring &/or pinning the driver in the ****pit, "if" the vehicle ever rolled over or flipped. Not good
2.) A center windshield support could/would be irritating to try-n-look around &/or thru for an hour
Plan B: Let's try some A-Pillars
Another angle/view
Notice how this concept would transfer the "load" or force (in a roll over) down to the upper side frame rails
...& also/then, down to the lower frame rails (lower supports to be added)
&
How the dash bar & steering are now totally separate from the "load path"
4 ROLL BAR 1. The roll bar must protect the driver's head/helmet in the event of a roll-over. It must be tall and wide enough to do this considering the full range of possible movement. 2. The roll bar structure must be triangulated with at least three legs or panel equivalent. Triangulated bracing can be either forward or rearward. With three legs bracing must extend from the top of the roll bar and securely attach to the vehicle structure, with four legs, each of the braces must extend to within 4" of the top. Any roll bar that is constructed from more than one continuous piece must be reinforced and braced triangularly from all junctions/joints in addition to the top. 3. The roll bar structure must appear to be sturdy enough to withstand the vehicle being dropped, upside down, from an altitude of one foot, with the driver inside without failure. 4. The drivers helmet must be below a straight line drawn from the top of the roll bar to the top of the highest structural point when the driver is securely belted in driving position. P A G E 6. E L E C T R A T H O N A M E R I C A
Before
After extending the rear
...& adding a "leg" or brace
T
Another view
I also, added a 4" x 8" gusset
...across the 5-way junction for additional strength
...& to "lock' everything together
It looks to me like it will meet:
3. The roll bar structure must appear to be sturdy enough to withstand the vehicle being dropped, upside down, from an altitude of one foot, with the driver inside without failure.
Motor Speed/Gear Ratio=Axle Speed x Tire Circumference = Inches per Minute traveled/Foot (12) = Feet per Minute traveled x Hour (60) = Feet per Hour traveled x MPH Multiplier (.000189) = Miles Per Hour
5,000(RPM's) / 4.8(GR) = 1,041.67 (axle speed) 1,041.67 x 51 = 53,125.17 (inches per min traveled) 53,125.17 / 12 = 4,427.10 (feet per min traveled) 4,427.10 x 60 = 265,626 (feet per hour traveled) 265,626 x .000189 = 50.20 MPH
Keep in mind that the Ballpark Equation doesn't factor in things like: rolling resistance, Aerodynamics, overall weight etc. ...it just gives us an idea of what "may be" possible with a specific set up (motor RPM's, gear ratio, wheel size etc.)
I used a straight edge to align the motor & wheel sprockets
...marked where the motor needs to go
...then, installed (4) 5/16" x 1" slots in the motor mount
I used (4) 5/16" x 1" Carriage bolts to mount the motor
* Notice how the "square" under the heads "fit in" the slots
...so, the motor can be tightened down with just (1) wrench
I used the straight edge again to double check sprocket /chain alignment
...Another view (straight "down the line")
* Notice (after alignment) I used a couple of pairs of Vise-grips, to "lock the motor mounting plate "in place" for welding