Electric Mountain Board Build log

MK1

About a month ago i decided to weld up a skate board frame.
38" long , .5" square tubing with .0625 wall thickness. Mig welded together and welds ground flat on top and bottom. weight 9ish pounds.



So then I decided to add a 24 volt electric wheel chair motor (brushed of unknown wattage/working condition. I also added a 5000mah lipo pack, sabertooth 25x2 brushed motor controller and applicable RC components. It worked, barely. 15ish min of ride time 1-2 miles at about 8 mph, it was fun until I had to walk home while carrying it. When i got home after a 10 min walk I found that I had over discharged the batt (still seams to work fine though) and felt the motor it was scorching hot. My inferred temperature reader stated that it was in excess of 180 degrees...




[youtube]uTh2toq6quM[/youtube]



MK2

So I decided to order the following:
Turnigy Aerodrive SK3 - 6374-168kv Brushless Outrunner Motor
Hobbyking SS Series 190-200A ESC

I then fudged up a quick and dirty motor bracket, sorry no pic it was quick and dirty.
Needless to say I was very disappointed, using a 9:35 gear ratio all I got was cogging from a stand still, even with some moderate pushes it would not start. It would zip across my yard incredibly fast, but not with me on it. It would with my 9 year old little brother sitting on it though (after a push start.)



MK3

Well this one is in the works now I have ordered a second motor and a second ESC I also ordered 20ah of LiFePo4 batteries to keep me going once i get it all right. I also ordered 2 40 tooth sprockets for a 9:40 gear ratio.


thats a 20AH 8s setup I figure it will be fine since it is about the same charged voltage as a 7s lipo which has been my test battery.

I have fabricated some new motor mounts out of stainless, just waiting on the right wire so I can weld them up, and I will post pics of them.





I have my doubts with these ESCs I think I may end up going with the Alien Power Systems 125x2 ESC for EV vehicles. also it needs to push around some weight im 230lbs board with all batts/electronics is a beast at 30ish pounds.

More to come, please offer advise or ask questions.

Hey man, to start smoothly without pushing, there's a few things that can help as you know:
- Higher reduction for more torque but less top speed
- Settings in the ESC for 'smooth starting'

- But your best shot would be to add hall sensors to the motor. Your ESC has to support this as well.

Question: how do you feel about the welding job? It looks awesome but maybe a bit overkill to me? How's the 'flex'?

Hi, Welcome... & thxs for sharing

Quite impressed by the "safety factor" of ur built !
20Ah8s? man... seems a huge energy storage :wink:

with such work, there was a good chance to integrate the battery into the deck...
As Murfix said, play around with the settings of ur ESC to reduce cogging at standstill - reduction ratio seems low
(on mine, I could not 100% get rid of it... so, I convinced myself that it's safer to push start anyway )

so, u did ur own trucks ?

Murfix said:

Hey man, to start smoothly without pushing, there's a few things that can help as you know:
- Higher reduction for more torque but less top speed
- Settings in the ESC for 'smooth starting'

- But your best shot would be to add hall sensors to the motor. Your ESC has to support this as well.

Question: how do you feel about the welding job? It looks awesome but maybe a bit overkill to me? How's the 'flex'?

Click to expand...

Ive thought about hall sensors, i havnt decided on that just yet.

The welding job, its sound. It flexes a fraction of an inch. Before I made the board I drew it up in autodesk inventor and ran a Finite Element Analysis on it, basically a computer generated stress test, I took alot of material out during those tests.

made_in_the_alps_legacy said:

Hi, Welcome... & thxs for sharing

Quite impressed by the "safety factor" of ur built !
20Ah8s? man... seems a huge energy storage :wink:

with such work, there was a good chance to integrate the battery into the deck...
As Murfix said, play around with the settings of ur ESC to reduce cogging at standstill - reduction ratio seems low
(on mine, I could not 100% get rid of it... so, I convinced myself that it's safer to push start anyway )

so, u did ur own trucks ?

Click to expand...

I want massive range/ride time, and a batt pack capable of powering future projects aswell and since LiFePo4 has such a great life expectancy it was my only choice.

I actually thought about integrating the battery into the deck, but I had built the deck before I made the batt back.

My basic ESCs have very few settings so I may end up trying more reduction or experimenting with hall sensors.

the trucks are MBS I really debated making my own, and then decided to use their trucks.

JBallard86 said:

The welding job, its sound. It flexes a fraction of an inch. Before I made the board I drew it up in autodesk inventor and ran a Finite Element Analysis on it, basically a computer generated stress test, I took alot of material out during those tests.

Click to expand...

Awesome! Using FEA, you get exactly the flex you wanted! I like that approach

Sick! Love that tubular frame and the shape you chose. It seems the perfect size, not too bulky, Very nice.

So tonight I finished up the new motor mounts, they are made from 304 stainless tubing cut down just a bit.

Since I already had one ESC ready to go I decided to give it a try with the new gear reduction with just one motor. Still wouldnt, but It felt a lot better than with the 9:35 reduction. I have hopes that with the second motor it might actually start moving with very little input from me. If it doesn't ill move up to 50:9 reduction, as I would really like to have a step on and go board without having to invest another 500$ for sensored ESCs.

BTW the only sensored ESCs capable of 30v 7s-8s configuration of at least 100 amps are from Alien Power Systems, Google has not been helpful in my search, and recommendations?

BTW new pic

hey

really nice build so far planning on makeing a mountainboard. sorry to ask a qu but how much did you get the mbs trucks for? (1st post on Endless-sphere! yay)

BShady said:

hey

really nice build so far planning on making a mountain board. sorry to ask a qu but how much did you get the mbs trucks for? (1st post on Endless-sphere! yay)

Click to expand...

I actually ordered an entire board from Amazon: http://www.amazon.com/gp/product/B002ZFBYYY/ref=oh_details_o03_s00_i00?ie=UTF8&psc=1

It was a damaged product and was less than 100$, ended up just cosmetic damage to the packaging, and free shipping w/amazon prime. The deck is now just a garage ornament until I decide what to do with it.

So to answer your question I got the trucks, wheels, bearings for lets say 100$

I was going to order all of that from MBS but it was going to be double than just buying the board, But I do believe I need to order some "roadie" tires.

hey thanks

btw a place for tires i found is http://www.partsforscooters.com/. i know that some peopl also get tires from http://www.harborfreight.com/.

BShady said:

hey thanks

btw a place for tires i found is http://www.partsforscooters.com/. i know that some peopl also get tires from http://www.harborfreight.com/.

Click to expand...

Yeah, they have tires right now for about $4.99. What kind of mountain board would you use with them?

So yesterday I finished up the mounts, so I thought, I had to weld a brace from mount to mount. By the way, stainless is a PIA to weld with mig, even with the right wire, my stainless welds are not pretty but they will do the job.



I am just barely able to start without cogging, but when I do its a one way trip, because the ESCs heat up to the point where they will not get me going again. I even think they have a thermal cut off, because one started beeping at me.

While i was able to ride it I have to say a few things about it, remember we are talking 250lbs board + Driver.

1. Acceleration is intense, I have to lean way into the board to keep from being thrown off. Acceleration is actually to intense, and will get worse when my new sprockets arrive.
2. Throttle is a little jumpy, the trigger has to be used very gingerly. Im hoping that an ESC setting will help this.
3. Punching it while moving fast already, is dangerous, you have to be ready for it.
4. I have the ESC brake setting set to medium, wants to stop way to fast.
5. No way would I let someone else ride this, its way dangerous. aka fun
6. I really need to buy a helmet.

New items ordered:
2x 8 tooth #35 sprockets current ratio 5:1, new ratio will be 5.625:1
Alien Power Systems 125A dual motor controller
Alien Power Systems Program Box
Alien Power Systems 35v 1200mf cap bank

Now for what still needs to be done:
1. Switch from the 5ah testing battery, to the 20ah battery. This means I need to finish the battery enclosure, and design some mounts for it.
2. Permanent solution for holding electronics.
3. Add a fan to ESC for increased dependability.
4. Thinking of making some .5" risers from UHMW plastic to give my feet a little room, they like hitting the tires. Or i cut the board in half and make it about 5" longer.

Im really hoping that the new ESC will allow me a broader range of selections to fine tune the motors. I also hope that with the program box it is easier to program, I really hate that morse code BS. Im hoping that the new ESC with the right settings will allow me to use the 5:1 ratio, so I will have a higher top speed. That way when im just cruising ill possibly get better battery usage.


As always comments, tips always welcome

Not to harp on such a nice build, but why didn't you read up on the gear ratios for all the other builds on here? On 8" wheels you need like a 45-55 tooth sprocket and an 11-14 tooth on your motor. You are not alone in doing this, but there are plenty of working boards could have saved yourself all the hassle. You obviously know what you are doing, besides that.

dirkdiggler said:

Not to harp on such a nice build, but why didn't you read up on the gear ratios for all the other builds on here? On 8" wheels you need like a 45-55 tooth sprocket and an 11-14 tooth on your motor. You are not alone in doing this, but there are plenty of working boards could have saved yourself all the hassle. You obviously know what you are doing, besides that.

Click to expand...

You are entirely correct.

When I found this forum I had already built my board and had it working with a brushed motor. I incorrectly assumed that the brushless motor would work the same.

I also wish I had not purchased the hobbyking brand ESCs.

You live and you learn.

JBallard86 said:

You live and you learn.

Click to expand...

... and you'll work it out I'm sure

Since it looks like the project is going to come together here soon I decided to go ahead and make a battery box for my 8s 20ah LiFePo4 battery pack.



It is made from Smooth On Smooth-Cast 321 Urethane resin. I applied it like fiberglass, I added milled glass fiber and used fiberglass mat in its construction. The "handles" on the ends are red oak then glassed over. Bondo is used to level it all out. I am not going for perfection in the box, just something that looks decent.

Cool!
What material is the mold made of?

Murfix said:

Cool!
What material is the mold made of?

Click to expand...

I used the batteries themselves to make the box. I put a cork spacer on the terminals and some cardboard on the sides to give me room. I then wrapped it up in a few layers of bags. I then taped it up in a layer of aluminum tape used for hvac work since the resin won't stick to it. I then use a sprayable adhesive to put the first layer of fiberglass mat on.

That's a nice approach. I'm planning to use bags/kitchen plastic foil as well and then, believe it or not, just olive oil as releasing agent. I hope it'll work =D

Been using cling foil, the stuff that you put around food to stay fresh in the fridge, for my longboard building with epoxy resin and it didnt seem to stick to the foil at all even without any additions. Something you could use to get a nice outer finish is the stuff you get self sticking foil and such on I think. It is usually coated with a thin layer of silicone and you could get it for free anywhere someone prints on that foil I guess. Havent tried that yet, so use it with caution tho.

Ok so my new gear ratio works with a little cogging but its acceptable.

I will say this, This thing is dangerous. Im really debating going sensored if I cant calm the acceleration down with the new ESC. Currently here is how starting off goes:
1. you start to minimally cog
2. tires start to spin
3. tires hook
4. hold on for dear life, or fall over backwards, riders choice.

Now if I start off in grass the same thing happens, but when the tires hook it is much easier to control.

If I decide to go sensored, do you guys feel it will make initial take off smoother, and more controlled?

My motors can are rated at 75 amps @ 44 volts. I am running them around 24 volts Id like to use this controller: 12 FET 4110 MOSFET Extreme Modder Controller LYEN Edition $129 it seems it limits current at 45 amps and with modifications can run even higher.

My question is:
1. Is this controller rated to low for my use, or should decide to go the 16 FET version.
2. From my limited reading of the linked thread for the controller, Im assuming it will work with RC motors modified with sensors. Any Input?

If i do go this direction I will probably only buy one if its still available and see if the board will work with one sensored motor.

Sadly if the new ESC doesnt work i will have to wait until after the new year to continue working on this project.

Then you are still geared too high. 55-65 tooth on the wheel and 12 or so on the motor. Thats 4.58/1. You could try your current setup on the salt flats though. Fastest Eboard ever produced and ridden! Take some vids for us. Joking aside what is your top speed so far though? Each one of those motors is over 50cc. The chinese gas skateboards only have one motor and they are pretty fast. You have two of them on that board. That's 100cc. 100cc and geared up kind make that board pretty intense. Geared right you could give up one of the motors and still have plenty of fun. No speed records that way. I also just noticed you are running 8s - even higher speeds than I thought!

What is your current gear setup?

Sorry, I don't know of a source for #35 size sprockets. Ebay has some 55 tooth for $10, but they are split sprockets. I'm sure you can figure that out, you've got the skills.

As to the sensored version, I wanted to do that at first, but you'll run into a few issues. First the controllers are too big and 2nd you can't use a remote control - you have to be wired for your throttle. Again, you won't need to be sensored if you have lower gearing, there will be less cogging the lower you go. If you have the alien ESC your acceleration should be setup better than an ebike controller.

Crazy, I didn't know a 6374 SK3 Motor is 50cc comparable. Pretty crazy.

dirkdiggler said:

Then you are still geared too high. 55-65 tooth on the wheel and 12 or so on the motor. Thats 4.58/1. You could try your current setup on the salt flats though. Fastest Eboard ever produced and ridden! Take some vids for us. Joking aside what is your top speed so far though? Each one of those motors is over 50cc. The chinese gas skateboards only have one motor and they are pretty fast. You have two of them on that board. That's 100cc. 100cc and geared up kind make that board pretty intense. Geared right you could give up one of the motors and still have plenty of fun. No speed records that way. I also just noticed you are running 8s - even higher speeds than I thought!

What is your current gear setup?

Sorry, I don't know of a source for #35 size sprockets. Ebay has some 55 tooth for $10, but they are split sprockets. I'm sure you can figure that out, you've got the skills.

As to the sensored version, I wanted to do that at first, but you'll run into a few issues. First the controllers are too big and 2nd you can't use a remote control - you have to be wired for your throttle. Again, you won't need to be sensored if you have lower gearing, there will be less cogging the lower you go. If you have the alien ESC your acceleration should be setup better than an ebike controller.

Click to expand...

Im actually running 5.625:1 gearing, 45 teeth on wheels 8 tooth on motors, the problem with going lower is it will accelerate even faster. Im 230lbs my 150lb freind can get on it and not have any cogging issues. Im really hoping that the alien ESC is just more efficient and more programable than the hobbyking branded ESCs. I could still try to go with a 50 tooth sprocket, but with my current ration I have a possible. top speed of 20.1 mph with a 50 tooth sprocket i have a possible top speed of 18mph. id like to go back to my 5:1 ratio which i took up to 25mph, but it was 2 hard to start, lots of cogging.


Another option I see is going 4wd with slightly higher gearing.

Ive been getting my sprockets on Amazon using my mill to add clearance for the trucks and for the bolt circles. Also ive been using .375" bore sprockets for the 8mm shaft motors and using my lathes to make adapter bushings.

Here are my sprockets with bushings:



Also all of my testing has been with 7s lipo final board will be using 8s lifepo4 which ends up being pretty much the same voltage

Have you tried the EzRun Pro 150A ESC's? They seem to work better than HK 150a ESCs.