KMX Cobra

[Pure]

So why are you filing down freewheels? Is because the chain has funky spacing?

[Ypedal]

Update Time !!

With pictures this time.

So here is the situation....

kmx31-chain.JPG (67.8 KiB) Viewed 585 times

No.3 is the original cheap chinese i been messing with..
No.2 is the mess i made yesterday from a no.3
No.4 is an ACS 14t i picked up today at the local bike shop
No.1 is a no.3 that i fixed !!!

* The tape on 1 and 2 is just to keep dust and grindings from the insides of the units....

So after a dissapointing day yesterday not being able to resolve this.. i had to go to my nephew's 3rd birthday party across town at my sisters, so i used the RC bike to get there and on my way home i swing by the local bike shop with a piece of chain and my problem freewheel..

Here is the problem :

kmx32-chain2.JPG (35.14 KiB) Viewed 585 times

Above, see how high the chain rides on the teeth.. ( the picture actually makes the problem obvious, i should have taken pictures yesterday... )

[Ypedal]

Here is how the chain should fit.. on an ACS claws 14 tooth..

Problem here, is that neither did i or the bike shop owner guy realize that the threaded inside of the units are not the same diameter, this will NOT fid a crystalyte thraeded collar.. it's to small.. wtf this is supposed to fit i have no clue.. but mofo it dont fit what i needed ..

[Ypedal]

This is no.2 i mangled yesterday, trying to grind down the teeth a step at a time with no luck.... this is where i gave up..

[Ypedal]

so here is the problem.....

the ACS = 2.34mm :

kmx-35-acs235.JPG (42.29 KiB) Viewed 584 times

vs

cheap chinese 16t freewheel = 2.85mm :

[Ypedal]

Solution, for now, was to take the angle grinder and shave the thickness of the 2.85 down to 2.3x , put the fw in a bench vice and carefully worked it down until :

[Ypedal]

Now, after all that work, i spun the modded cheap chinese fw on the hub, bolted the motor back onto the KMX, ran in the house grabbed a 48v 5ah lipo pack in a hurry and taped it to the bike..... slapped a CA on there ( thank god ) and off i went..

As soon as i got going, i noticed my 12S pack voltag was a curiously low 40v, should have been 50v.... but in the heat of the moment i throttled on with a shit eating grin from ear to ear

Then i hit me.. oh jezus.....i picked up the wrong lipo pack..... I had a pack ready to go, ballanced and fully charged, but the other ( idential looking was right next to it with a less than 3v cell in it !! while the other 11 were at 4v + !!!!!!

Pedaled home, see, good reason i got the pedals working as a priority !

cut it off the bike, ran into the house.. grabbed the right pack. set the previous one in the middle of the driveway far away from anything flammable, deal with that after.. strapped the full charged pack on the bike and put on a helmet and gloves.... !

OMFG..... this is so much fun, it's even better than i expected, even with a puny 48v 35 amps this X5305 in a 20" rim is smoooth as silk..

I went up the road alongside 80kph traffic, a few figure 8's in the honda/ harley davidson dealership parking lot, zipped back home and up the dirt track alongside the CN rail service road .. ( BBbBbbbbBbUuuuuMMmmMMmPpPPppPP YyyYyYY ) .. but still fun !!!.. these KMX's are sturdy machines.. i weigh 185 lbs atm and got properly bounced around, will have to repeat this a few times before i declare it " tough " .. but it's certainly not flimsy,.,..

So, after all that disaster, it's a running machine ! and ready for upgrades !

[Doctorbass]

Nice!!!

So much past problem.. fun MUST begin!!!

Doc

[kevo]

It looks and sounds like major fun, glad you worked through all the issues. I'm green with envy!

[wojtek]

I could not agree more.

Drifting a trike is not only fun, it is really, really easy. You will feel like a proper rally driver in no time.

I am glad you are going with a 20 inch rear wheel. 20s are much stiffer generally and easier on the frame.

Matt

depends what you want to do i guess...

i think in the end im going to run my cobra in 2 versions..
20'' front 26'' rear with 5405 [ as Kenny could not provide 24'', but fortunately there is enough clearance for 26 vrim with big thick hookworm 26x2.5!!!!

second one will be 16'' front and 20'' moto rear wheel with 5403...

[wojtek]

what type of thottle is your preferred for trikes?

i like thumb throttle, as there are a lot of forces going on both handlebars when cornering, i rather keep my hands of firm handebar grips than throttle!

[Sacman]

Cool Gaston! Now we just need video of you fishtailing that thing.
(make sure we can see your egrin)

[JohnC]

Is your problem the wrong chain size? The plates look to long. Copied this from a bike site.

“Bicycle Chain Size
When buying a new bicycle chain, you do not really have to worry about the length of the new chain. Bike chains come in a length that is longer than needed, so you have to use a chain tool to shorten the chain to the right length.
It is important to know the bicycle chain speed or width that your mountain bike requires. Bike chains come in different speeds, generally ranging from 5 to 10 speed. The way they are different is by their width, which is usually determined by the length of the pins. The speed of the bicycle chain is simply the number of cogs on your rear cassette. For example, if you have 8 cogs on your cassette, you would need an 8 speed mountain bike chain.
Often, the width of 6, 7, and 8 speed bicycle chains are similar enough to be interchangeable. 9 speed chains are narrower, and 10 speed are narrower yet”.

Put up a video of your machine in action Shrub.

[Ypedal]

Thumb throttle, yes, as discussed by Knoxie this is pretty much the only way to fly with these side steer type controls..

Fishtailing will require a bit more power, right now it just " grabs " and i've had one of the front wheels way up in the air near tipping point lol... ( and yes.. i was leaning far over.. )

To pull a proper donut required enough power to break the tire loose and spin fast in relation to vehicle speed.... i'll get there !.. have faith !

[Ypedal]

The original 24" rear wheel had 8 speed cassette, so the inner links of the chain are thin, see calipper numbers above..

My next step is to remove the rear shifter and lock the derailler in place with a short cable, this will free up valuable space on the bars..

[wojtek]

yes i went to the bmx bike shop where they had only 14t freewheel. luckily i took the hub motor wheel and realized that it doesn't fit.

apparently there are 2 sizes of freewheel smaller and larger. so anything from 16t should fit the hub... not sure you can get less than 16t in the larger diameter size..

the freewheel i got was cheap chinese, thicker than standart 9 / 10 speed but it seems my 2010 kmx cobra does use thicker chain... i needed to add a bit of chain and that is where i noticed that some of my chain didnt fit and some did [8 speed chain, sram PG850 was good]

[Sacman]

Fishtailing will require a bit more power, right now it just " grabs " and i've had one of the front wheels way up in the air near tipping point lol... ( and yes.. i was leaning far over.. )

To pull a proper donut required enough power to break the tire loose and spin fast in relation to vehicle speed.... i'll get there !.. have faith !

You probably could... maybe not on asphalt but you could on a gravelly road.

[JohnC]

Ypedal and Sandy sighted in his new machine tear-assing around neighborhood.

[Ypedal]

Nice !!...

I been at this a long long time.... but not quite " that " long !.hehe.

[Ypedal]

Yesterday, removed disk brake, cable and lever...

Perfect spot to bolt up a monster torque arm once the high power controller lands..

[Ypedal]

Also removed rear shifter from right side handle and removed cable..

I cut an old brake line short and locked the derailleur into the single speed freewheel... no more accidental shifting and loosing chainline.. and one less thing on the handle near the throttle !

[Ypedal]

Got a red roll of 3M safety reflective tape.. and needed to seal up some PSI filled polycarbonate boxes..... time to put these cells to use !

I like tape..

[Ypedal]

Cut a piece of black ABS, heated and bent to match the frame angle, will double side tape it and zip tie to the frame.. then tape the 2 packs on top of this.. one is shifted to the left so that it does not interfere with the chain line, then the 2nd pack on top can be centered with the seat and secured up there somehow.. that's a tonight plan.

[Sacman]

Nice!
A rear fender would be nice too... to keep the rear wheel from slinging muck onto your beautiful battery packs and controller.

[wojtek]

Cut a piece of black ABS, heated and bent to match the frame angle, will double side tape it and zip tie to the frame.. then tape the 2 packs on top of this.. one is shifted to the left so that it does not interfere with the chain line, then the 2nd pack on top can be centered with the seat and secured up there somehow.. that's a tonight plan.

any reason why you have not decided to place the battery packs in front of the trike? with RC motor it does make sense to put some weight at the back to have more grip on the rear drive wheel but with heavy hub motor at the rear, placing battery in front would significantly imrove handling and balance.. that is what most of the KMX users are saying.