Torsk (Backbone Chassis) Kart

[Functional Artist]

After a lot of cleaning
...smoothing all of the rough/sharp edges
...& removing all of the snot balls-n-such, from welding

I ran a 5/16" drill bit thru the bolt holes to "be sure" their clean
...then, used a counter sink to chamfer the edges of the bolt holes a bit

Bolted the bearings & spacers on
...just to see how everything looked

Looks pretty solid to me

 

[Functional Artist]

Installed the rear axle thru the axle housing & the bearings
...centered it & tightened the Allen screws, on the bearings, to lock 'er in place

Spins easily

Then, mounted the brake drum on the left side, the sprocket on the right & both rims

Yup, everything looks good & clears nicely

 

[Functional Artist]

Here is a quick intro/planning video (finally got around to editing/posting it)

https://www.youtube.com/watch?v=SJ9zdzrl4CA

More to come

 

[Functional Artist]

To make the motor mount plate, we need to get everything
...lined up (sprocket to sprocket)
...square (motor mount & rear axle)
...& level (motor mount & backbone chassis)

But, first we
...gotta get rid of this sprocket for #25 chain
...& install a "Power Curve" sprocket for #35 chain

https://www.youtube.com/watch?v=SMlOZ_Vch2g

So, once everything was lined up & squared up
...it looks like we need a motor mount plate that is (5 1/2" x 6")

I have some 10g. x 6" steel that will work great for this
...just gotta wack off a suitable piece

Rigged up a guide & used the cut-off tool to wack 'er off

 

[Functional Artist]

Slots

Now that we have a motor mounting plate, we need to cut (4) slots into it
...so the motor can slide (for chain adjustment)

But, first we gotta reassemble everything (again)
...& realign
...& resquare
...& relevel
for precise measurements

Now, we can mark where
...the front bolt holes are
...the rear
...& then connect them with straight lines

Drilled (3) 1/8" pilot holes along that line for each slot
...then to 3/16"
...then to 1/4"
...then to 5/16"
...& then used a small file to clean 'um up

 

[Functional Artist]

Next, we gotta do some grinding
...because (if you remember) the trailing arms are 2 1/2" & the backbone is only 2".
The trailing arms are centered on the backbone so, they stick up ~1/4" above & below.
(which is no big deal except where the motor mounting plate sits)

We need to make sure that the motor mounting plate sets level with the backbone
(across from the backbone to the trailing arm)
...which (in turn) should also ensure it's squareness with the rear axle

To do this, I made sure that
...the backbone chassis was sitting level on the workbench
...then ground the edge of the trailing arm down
...checking progress several times
....until the motor mounting plate was sitting nice-n-level

 

[Functional Artist]

I drilled (2) 1/8" holes near the inner edge of the motor mount plate
so, once the motor mount plate is where it needs to be
...I can mark the (2) spots & drill them out (to use as alignment points)
...& also to install small screws (so, I can "tack it down" in "that exact spot" for testing & then welding)

Reassembled everything again, each time adding a piece to the puzzle
...bolted the bearings in place
...slid the axle thru 'em
...installed the sprocket on the right side
...bolted the motor to the motor mount plate (at lowest adjustment)
...added a piece of #35 chain
...& adjusted/aligned everything (with the square, straight edge & the level)

After double checking ALL of the alignment points
I drilled out & added the (2) small screws to "lock 'er in place"

Gave 'er a spin by hand (gripping the axle)
Yup, spins pretty good

I also, hooked up (1) 12V battery, just to triple check the alignment of the propulsion unit (motor) with the drive unit (axle)

https://www.youtube.com/watch?v=qwh9nPT2hvM

Looks good to me

 

[Functional Artist]

This link (with some really good go kart frame info) was sent to me

https://www.witpress.com/Secure/elibrary/papers/OP07/OP07018FU1.pdf

Also, more video info

https://www.youtube.com/watch?v=gfU47WOEwSY

 

[Functional Artist]

Moving right along (or forward)

Now that the backbone is pretty much established
...& the rear axle housing
...& the motor mount

Next, would be the "Cockpit" or the operator compartment

I figure
...my signature rollbar/seatback ~40" tall
...the floor should be ~16" from the bottom of the seat to the bottom of the steering support
...& the steering support should be ~16" tall

Yup, another video
...helps explain stuff more clearly

https://www.youtube.com/watch?v=r-hz3dLTrbg

 

[Functional Artist]

Havn't done any bending yet

Been thinkin' about tires
...these Unilli 10.5 x 4.50 /6 "low rider" tires I got seem too small
(the devil is in the details)
...their only like ~1" (or so) bigger than the drive sprocket
(& that's, without the chain)

I compared one of the Unilli tires to a standard 15 x 6.00/6 tire
...& to the sprocket
(quite a difference)

I really didn't want huge 15" tires
...but, I', not likin' these 10.5" tires (not for this kart anyways)

So, I figured I'd split the difference
...I found some 13 x 5.00/6 tires (~13" tall)

https://www.ebay.com/itm/2-13x5-00-...e=STRK:MEBIDX:IT&_trksid=p2060353.m2749.l2649

Should be here Monday

I'll save the Unilli's for another project (with a smaller drive sprocket)

 

[Functional Artist]

Another reason I wanted bigger tires was "top speed"

It looked like if I used the 10.5" tires (~33" circumference)
...with the 60 tooth drive sprocket, the top speed would only be ~15 MPH


Using the "ball park equation" (MS/GR=ASxTC=IM/FT=FMxHR=FHxMM=MPH
...& a 3,000 RPM motor speed

3,000 MS (motor speed) / 6 GR (gear ratio) = 500 AS (Axle speed)
500 AS (axle speed) x 33" TC (tire circumference) = 16,500 IM (inches per min.)
16,500 IM (inches per min.) / 12 FT (foot) = 1,375 FM (feet per min.)
1,375 FM (feet per min.) x 60 HR (hour) = 82,500 FH (feet per hour)
82,500 FH (feet per hour) x .000189 MM (mile per hour multiplier) = 15.59 MPH


But, if I use 13" tires, having ~40" circumference
...& the 60T sprocket, the top speed should be closer to 20 MPH

3000 MS / 6 GR = 500 AS
500 AS x 40" TC = 20,000 IM
20,000 IM / 12 FT = 1,666.67 FM
1,666.67 FM x 60 HR = 100,000.20 FH
100,000.20 FM x .000189 MM = 18.9 MPH

 

[Functional Artist]

The 13 x 5.00 / 6 tires showed up yesterday (a couple days early)

They are a bit shorter than the 15" tires & taller than the 10.5" Unilli's (like I wanted) but, their kinda narrow

The sprocket to tire ratio looks better

I got one mounted on the rim
...just gotta see if I can get the bead to seat

 

[Functional Artist]

While waiting for the air compressor to "fill up"

I figured I could work on the "cockpit"

So, I got the bender out
...& a 10' piece of water pipe

I started off by measuring & marking the piece of pipe right in the middle, 60" from each end
(this will be the top of the rollbar)
...& also @ 40", each way, from the center mark
(these will be where the seat back will curve into the floor)

So, it's marked at 20", then at 60" then at 100"

Then put 'er in the bender, lined up @ the center mark & bent 'er to the max
(to help bring the bottom, seat back area, as close together as possible)

When the pressure is released it springs back pretty good
...but, we can work with that

 

[anickode]

I would imagine the narrower tires will be an advantage in the handling department, as it will likely not NEED the grip of wider tires, which would become a hindrance without a differential, unless the plan is to power slide every corner.

 

[Functional Artist]

I would imagine the narrower tires will be an advantage in the handling department, as it will likely not NEED the grip of wider tires, which would become a hindrance without a differential, unless the plan is to power slide every corner.

Yup, I agree
...kinda why I originally went with the smooth & now ribbed tires
...to (hopefully) compliment the live axle & not work against it

I have never used ribbed tires on a kart so, I wanted to give 'em a try
...& they may even have a bit less rolling resistance
(riding up on the ribs) than a turf tread or the smooth tires

* Power sliding every corner is a good plan too

 

[Functional Artist]

Once we had the rollbar/seatback next, was the (2) side bends
...one @ the 20" mark
...& the other @ the 100" mark

Before each bend, I angled one side up a bit & the other side down a bit

The idea was to get them to angle inwards, toward the backbone because, the bottom of the seat back (rear part of the cockpit) should be ~16" wide

Where as the steering support (front part of the cockpit) should (nearly hug the backbone) only be ~8" - 10" wide (quite a bit narrower)

They didn't angle in as much as I had in mind but, should be able to work with 'em

 

[Functional Artist]

Steering support (front part of the cockpit) is next

I had a ~48" piece of water pipe

Measured & marked it in the center (~24") then, marked it @ ~14" each way from the center mark
...which should leave ~10" going back, on each side, from the lower bends

Put it in the bender, lined up @ the center mark & bent 'er to the max

then, bent each side (~35 pumps) @ the 14" from the center marks

but, only this time, with each side angled outward away from the backbone
(to be able to (hopefully) meet up with the (2) ends of the rollbar/seatback bar)

 

[Functional Artist]

The floor of the cockpit needs to be ~16"

Set the backbone on the workbench, positioned the cockpit over it & aligned the floor bars @ 16" apart
(just on one side for now)

First thought about splitting the difference & just cutting them both @ 8" (8" from the front & 8" from the rear)

The front section is about where it needs to be, it's the rear section that needs to be worked a bit

I figured that I should leave a few inches more, on the rear section
(longer arms should give additional leverage, for workin' it)

So, I wacked the rear sections arms off @ 10" & @ 6" for the fronts

 

[Functional Artist]

There is gonna be some pressure on these "floorboard" connection joints
...not really structural but, more from my bends being a little off
...& having to do some "tweakin" to bring 'em together

So, I'm not gonna just butt weld 'em together
...I'm gonna pin 'em
...then, butt weld 'em

5/8" rod (like for steering shafts) fits nicely inside this water pipe & will make good strong "splints"

I wacked off a couple of 3" pieces (should give us ~1 1/2" inside each end)

Drilled an 1/8" hole ~1" from the end of each pipe end (on the inside edge as to not be so visible)
...then inserted a "pin" ~1 1/2" into the ends of both of the front sections pipe ends
...then, drilled an 1/8" hole about 1/4" into the 5/8" rod & inserted a small screw to "pin" the pin in place

 

[Functional Artist]

Slid the left end of the front section onto the alignment pin of the rear sections left side
...still a bit off

Wrapped a ratchet strap around the lower part of the rollbar/seatback
...to help draw the sides together (in a precise & controlled manner)

It took a little tweakin' but, I got 'er together

Inserted the front pin/screws to lock 'er in place
...& double checked everything

Looks pretty good
...all of the bends came out deicent
...all of the rails (seatback, floorboards & steering support) are mostly even
...& it even sits nice-n-level