KMX f-8

epower-1

100 mW
Joined
Jan 28, 2019
Messages
35
Used KMX f-8 Tornado
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By no means my trike is at this point is no ERT Death Trike or recumbents.com Yeller wright your name in the black top trike, but they were my inspiration
they all started out life as a KMX frame. and with some time and dough I can achieve that kind of performance.
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https://www.youtube.com/watch?v=CkZK1cVHyMk
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https://www.youtube.com/watch?v=WKAMus3oSdw
Thanks to Alan from ERT and Matt from recumbents.com for having the balls to build their trikes and giving me the inspiration to build mine.
Alan @ERT for his great motors and controllers all his stuff is awesome.
Barent from West Coast Electric Cycles who has built some pretty mean bikes himself for His great batteries motors and controllers and always continuing to improve on what he sells.
Justin at Grin for just about anything that you could want for your builds and the genius behind the Cycle Analyst and innovator of new and better stuff.
Luna Cycles for their in stock most of the time Great 52v 50 amps continuous 70 amp burst 24 and 28 ah battery selection.
Spinning magnets for his educational articles that have provided so much great information, master creator of the early archives of ebike stuff.
Albe's BMX shop that carry quality BMX rims and tires and answer the phone when you call
Stacked BMX for rims and tires
yo jimbo's garage for his great spokes and fast service. Quality Spoke maker.
Maaxxis, Cult and VEETIRE for great rubber
Alex,Cult,Weinmann,Eclat for their nice selection of Rims

Back Story: My KMX is a used f-8 tornado SN# KMX0003666 it's a early model with 16 inch front wheels and a 20 inch rear, the lowest frame height for a KMX except for the kiddie trike (perfect) for what I wanted.
I prefer the smaller 16 inch wheels up front and I like a 20 inch in the rear, the 20 inch rear wheel gear ratio delivers extreme acceleration with the right battery even with the small 35mm motor.
I bought this trike as a Amazon return paid $500.00 and that is about all it was worth if that,
It was cheap but the frame was tig welded steel which is very workable for chop cut grind and welding on.
Which motor battery and controller to start out with was a no brainer for me I use the same motor controller combo that I have used on a lot of my builds it is a proven starting point for me that I know does the job.
I first read about this motor in one of Spinning Magnets articles https://www.electricbike.com/edge-1500w/ it sounded logical to me so now the shop has three of them that are used for different test scenarios.
My motor's are, one from LA ebikes and two more from ERT.
What I have found is that all EDGE motors aren't created equal, after close inspection they were different, In china they don't know what a edge is to my understanding, that is a name that was given to it in the USA, if you try to order one from the manufacture they only know it as a 205 35mm V2 and when you place a order you can have them made up in different ways, for example the Edge motor that I got from ERT had temp sensors in them, (you want this if you are going to run Hi amps), The one that I bought from LA ebikes did not come with a temp sensor and the faze wires were of a lighter gauge wire than the ones from ERT, I have not tried out Westcoast Electric Cycles new edge as of yet but Berent orders them with heavier gauge faze wires and these newer curved magnets which is supposed to have benefits, I will for sure give one of those a try if for nothing else than to satisfy my own curiosity, what I have done in the mean time is just up grade my motors with a motor harness from Grin Tech, 12 AWG faze wire, and put a temp sensor in the one from LA ebike.
Just a side note when all three of the motors were set up different one with very small faze wires LA ebike's, one with a
little bigger faze wires ERT, and the third ERT modified with grin's motor cable running the same wheels amps volts on the same trike the one with the Grin 12 AWG faze wires out performed the others, it would be sweet to snag one wright out of the box with all the bells and whistles a V3 version with dual set of Hall sensors would be the icing on the cake.
Bring it on Alan and Berent.
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The controllers that I use are from ERT, 18 fett 100v 100 amp sine wave programmable.
The battery is a Luna 52v 24ah that I have used on other builds it does a great job, with the GA cells giving up 50 amp continuous and 70 amp burst.
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First Battery motor and controller set up. I kept it simple on/off switch and a throttle
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The battery was mounted on the side of the seat, zip tied to the seat frame with two bottom support brackets in a luna bag and the controller mounted on the main frame.
This combo worked out well for a V.1 set up, 50 mile range with out peddling impressive acceleration. You could call it quits right here and have a great little trike to have fun on. At this stage the setup cost around $2250.00 to build and about a weeks time
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I rode the trike for the first part of the season and found that for me a old man it was too hard getting in and out of, I made a 5 inch riser for the seat which made it very easy to get in and out of, it puts some weight higher up, but with speeds of only 30 mph it was manageable.
I also added a bar to the front of the seat to extend it and dished it up to create more of a bucket type seat to hold me in and keep me from sliding out.
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I took the seat cover to a interior guy and he added some material to the bottom seam of the cover about 2 inches and provided a new dense three inch foam pad which made it cushy and more comfortable.
After I raised the seat I had to loose the mounting the battery to the side of the seat thing, up that high was to much weight up top, I put the battery in a bag on the frame behind the seat, moved the controller to the back of the seat
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This set up worked well I rode it the rest of the summer and the following summer that way.
Getting the seat set up for you makes a huge difference it is no fun doing a long ride on a seat that sucks,
The final version of the seat will have a latch for multiple position seat height low to hi, low for speed high for comfort at the flick of a lever, that will be further on down the road.
 
Next thing that cropped up was I was popping spokes on the front wheels
The stock kmx rims are nothing to write home about the 16 inch fronts have a one cross lace pattern
they were swapped out for a set of 16 inch alex rims with spoke eyelets I laced them up with a radial spoke pattern
since then I have not popped any more spokes doing many hard turns
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before and after
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All our stuff is equipped with the Grin cycle analyst V.3 but It was a drag having to stop bend forward to push the buttons
to change screens to see all the data that I needed to see, I contacted Justin at grin and he made us up some special CA's with a remote 3 button switch which allows me to look at different screens on the fly (sweet)
The Cycle Analyst V.3 is set up for max speed 999 mph and 99 amps so nothing is limited
It will allow what ever the battery will put out to put out. you will have to reprogram the controller for the same amp values to make this all work or the one will fight the other the controller takes precedence over the CA, the ERT 18 fet controller is good for 100v and 100 amps, set up like this I see 74+ amps with one 52v battery.
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The trike stops ok with the two front disc but I wanted a little more
so it was on with a rear disc set up the KMX is already set up for adding a rear disc brake it is a direct bolt up sorta thing
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Here is where things take a turn
The shops EEB endure bike is powered by a 72v 30ah 30q Battery with a 100 amp BMS from West Coast Electric cycles
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I just had to try it out on the trike.
It was a game changer
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At almost 100 amps the acceleration was spooky and on the edge of out of control.
As much as I enjoyed that whole thing the battery had to go back into the enduro bike, it gets used as transportation the trike is for fun and a test bed, I decided I wanted the 94 amps. So I started thinking that the shop has two of the 52v 24 ah batteries if I hooked them together in parallel they made 100 amps continuous and 140 amps burst where a single 52v made 50 amps continuous and 70 amps burst the beauty was they both fit in the bag behind the seat, (the difference between the 52v 94 amp set up and the 72v 94 amp set up was the 52 set up would rocket up to 30 mph before I would let up but the 72v 94 amp set up accelerated much faster and harder) ( the 30q cells in the 72v has less sag and more amp output per cell than the GA cells in the 52v) it shot past 30 mph so fast and was still climbing to 40 mph before I shut it down the trike was very squarely.The 72 volt spins the hub at a higher rpm than the 52v faster top speed.
I rode the trike for the rest of our season with the two 52v 48 amp hour range out the wazoo batteries I could go out and test ride for 60 miles plus with battery to spare with out peddling.
Then reality sat in (hey yall watch dis), while goofing around in the fall out in the street in front of the shop doing donuts on a damp leaf covered road throwing up rooster tails I crashed the trike, it slid side ways hooked up and threw me out of the seat sending my 67 year old ass sliding down the street bloody arm now with a scare (Kids don't try this at home)
So in the shop it went until after the holidays and things settled down, I was thinking about the crash and what happened, what I figured was all my weight was up front, and the rear skinny tire was easy to break loose.
I moved the seat back to the rear as far as I could to get some weight on the rear wheel, but my feet would not reach the peddles I have a 32 inch inseam, I cut the boom down 10 inches, now the bottom bracket is all the way against the frame perfect
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I can set in the seat and my feet reach the peddles and instead of peddling with my legs sticking up in the air I am actually pushing more in a downward motion more like riding a bike shorting the boom also eliminated all the boom flex while peddling, it is comfortable and the weight now is in the rear, I also had to make some 5 inch extensions for the handle bars so my hands could reach them I had to moved the battery bag in front of the seat and moved the controller to the side of the seat riser.
cause their was no room behind the seat now in it's new position.
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After all of that work it sucked, I did not like the battery up front and decided to make two battery supports to go under and behind the seat and set the battery weight lower to the ground.
While all this was going on I decided to address the skinny tire thing
I scored some 20 inch three inch wide 36 hole rims and laced them on and wrapped it with a 20 inck 4 inch wide fatty slick
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FYI the three inch rim fits in the KMX frame like it was meant to be
The 4 inch tire takes some work with a acetylene and oxygen massage.
 
Hoping to button this thing up in the next couple days just have some wiring work to do
then hurry up and wait for some good weather to go out and see what it is.
Mocking up some wiring
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Dudes Ready for a test ride building it was a hoot
Their needs to be some final adjustments and tweaking done
I usually spend the day on the bike path with tools and do all the fine tuning
I will post up a final cost sheet so you can see what it is
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Used trike 500.00
motor 350.00
controller 225.00
Batteries 1800.00
rims tires spokes 400.00
Cycle Analyst 150.00
misc. 200.00

Total 3625.00 Give or Take
 
I will ride the trike like this for the summer put some miles on it and have some fun
do some more mods as needed to better soot me
 
Test ride the YIN YANG
The new rear tire specked out at 22.9 inches (tall)
this slight difference took away some of my hole shot which I expected
A 45mm motor and the 72 volt battery should compensate for that

Peace Bill
 
Jonboy said:
your trike looks amazing, i did skim your thread and question your seat hight.. LOL I'd creak a bit getting low in the original.. I was only talking of a similar build this week ... but i only have mountains to ride on.. cracking job :bolt:
Thanks for the feed back, the seat height is around what a standard trike would be it just looks high cause of the 16 inch wheels in the front
but in the stock form it is slammed on the ground It was a bit much for me to get into and out of
I use this pretty much for bike paths and it is a blast a little rocket chair
 
Great looking KMX!
What are those front rims and tyres? Would you mind sharing a link? Thanks!
 
wojtek said:
Great looking KMX!
What are those front rims and tyres? Would you mind sharing a link? Thanks!
Those are alex DM24 16 inch rims I bought these from a friend and he got them off ebay
their were advertised as cart wagon rims 32 hole with spoke eyelets
the tires are cult 16 inch BMX tires https://www.albes.com/cult-juvenile-tire/
 
Thanks a lot!
 
Impressive build. I'm glad it didn't kill you.

By shifting your weight primarily toward the rear, you've greatly increased your likelihood of tipping over during a turn, especially with the small wheels. The advantage of having had your weight primarily on the front is that you can take corners with more lateral Gs without tipping because the center of gravity is less inclined to shift above the rear axle line.

On this site, adam333 makes a front suspension kit that can widen your front track and makes the trike much more ridable over rough roads, and also has a rear suspension in the works but I haven't tried it yet(it may help fix the problem of what happens when the rear wheel loses traction and then hooks up again while cornering sharply). Unmotorized, and without suspension, I found my KMX to be nearly unrideable over 20 mph on anything but the most perfect roads.

Awesome build. It looks like a lot of fun to have that much power in a KMX. Did you use anything for torque arms? I'd be worried about destroying the rear dropouts without them.
 
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