Electric Flexboard Project

[addicted2climbing]

Hello All,

I have been spending quite a bit of time on this forum learning as much as I can for a project to electrify a Flexboard. For those that don't know what a flexboard is, its similar to a mountain board but its much more stable since its wheels tilt as the turn is initiated rather then how a skateboard works. It is said to be free of speed wobbles since the forces are in line of the wheels but I will have to test that out myself. http://www.flexboardz.com

Anyhow, I am going the R/C component route and have most of my components in route from HK and Leaders Hobby. I am using 2 aolean 6354 250KV motors that I plan to add external hall sensors. Since I have been waiting for the items to arrive from china I have been working on the design in Solidworks. To make room for the motors I have had to design a new set of swingarms which allows me to also add any other features I need to mount the motors or hall sensor mounts. Unfortunately since the motors have yet to arrive this is as far as I can go since I don't have the motors hole pattern. If anyone knows or has a 3D model of a 6354 please let me know?

Marc

[addicted2climbing]

Today I worked on some speed calcs for various battery packs and it has some interesting results that make me question which batteries to buy. I had originaly planned around 2ea 200KV motor and 2ea 6S packs, but with HK out of stock on most motors and the new SK3 motors not being released (until now..dooh) I gave up waiting and bought an Aeolian 6354-250 KV motor which now has me dealing with more RPM per volt then I had planned. But I am unsure if that is not a good thing in some way.

I ran the calcs with various battery packs and gear ratios and it looks like I can go with one less cell then I had planned and possibly even 2, but I am unsure if that is a good idea as my EE knowledge is limited and usualy based on propellors for R/C aircraft so unsure what the pros and cons will be on my board. Anyhow I have room for a 70 tooth rear sprocket and I can get motor sprockets in ranges from 11 to 15. I can even bump up the rear a little as well but probably no more than 5 teeth due to diameter constraints.

Anyhow what I found is as follows. These are just voltage to ratio to RPM to MPH and I am unsure what amount of losses to add to this equation... I was thinking of taking the resultant MPH and figuring 80%, but unsure... Below is 100% no losses figured. These also figure in raw 6S/5S/4S voltages and do not take into account that freshly charged packs read more then nominal either...

At 6S (22.2) with a 70/12 sprocket (5.833 ratio) I get a rear wheel speed of 25.47 MPH

At 5S (18.5) with a 70/12 (5.833 Ratio) I get a rear wheel speed of 21.23 MPH

At 4S (14.80) with a 70/15 (4.667) ratio I get a rear wheel speed of 21.23 MPH (same as 5S at above ratio)

So my question is what will I gain or lose by choosing to go with 5S over 6S? And if I can get the same speed at 4S why would I choose 5S?

I plan to start with 1 pack for each motor at 5000 MAh and then at a later date buy another set and run them in Parallel. However if I go 4S I can afford to just buy all 4 packs at once. Buying the batteies is an investment which has me leaning toward the 5S or 6S since I would hate to buy the 4S only to find I do need the added voltage. I am using the HK 150 amp R/C Car speed controlls rated for 6S that also have the hall imput connector.

Now about me, I am big at 6'4" and 235lbs so curious if higer voltage at a larger ratio is better then lower voltage at a smaller ratio.

Can those in the know explain what the tradeoffs are for higher or lower voltage with ratios that bring the overall speeds down to close to each other? SInce I will be standing on this thing 25mph seems like max I would be comfoprtable ever going and even then I would limit the throttle travel anyhow. And if I plan to limit the travel anyhow, why bother and just use lower voltage instead and more throttle travel... Oh my I am confused...

Help....

Marc

[EBJ]

http://www.youtube.com/watch?v=Dvd09FKa ... _embedded#!

second board in video.
Perhaps you should post a question on the video attempting to contact the builder.
Or contact flexboardz for the contact info.
I imagine the builder could answer many of your questions.

[EBJ]

also: I believe the reason you will want to use the higher voltage (and also gearing it down lower) is due to the fact that these RC motors tend to lose sync at start-up. So by gearing it down you are decreasing the zone in which you may get motor cogging. I think it always helps to look at the extremes: How would this motor perform if you bolted it directly to the wheel and ran just 1 volt across it? Vs, running the max voltage and gearing it as low as possible. I think after picturing those scenarios it becomes clear you will want to run it at a high V with more gearing.

Hope that helped.

[addicted2climbing]

Hello EBJ,

Thank you for your post. I did see that video shortly after I started this project. I am in contact with the designer of the Flexboard and he has been kind enough to send me the original swingarm in Solidworks and I used it as a basis to design a new one with an added wheelbase and width to make room for the motor and sprocket. He contacted the kid in Germany to put me in touch with him, but he has not replied yet. The kid in Germany made his own swingarm as well but went a different route than I did for coupling the sprocket to the wheel. I chose a much simpler method to keep costs down but should that not work I can always redesign it the more complex way.

I see your point in regards to minimizing cogging issues by having the higher gear ratio. I am looking at a few different batteries in 6S and based on my application will either go the standard pack route or the long pack route since they are thinner to minimize the height of the packs under the board. However my height will be decided mostly by the speed controlls which are the tallest items under the board. I was also looking at LifePo batteries as well, but they are a bit more pricey then the Lipo but it looks like they last longer and are safer. However 3.3 volts versus 3.7..... I am capable enough to make my own packs if needed, but I hear that the cells sold on ebay are not worth buying. I can get some prismatic Life packs from HK, but most in my application are out of stock and their single round cells are pricey... Anyone have a good source for Life cells worth lookign at? Or should I forget it ansd stay Lipo since its what I am familiar with?

Marc

[ChristianR]

Hi Addicted2climbing,
A 6S 5Ah 30C LiPo battery works very fine on my electric mountainboard (custom, with 2 motors brushless Turnigy C63-64-A 280kV, 2 BEC and 2 bat.).
I can run fast, and climb slopes in mountains or forests with it !
A LiFePo4 is much more expensive compared to a LiPo battery, but it may have a longer life span (more charge/discharge cycles).
But low cost LiPo are excellent for your purpose. 6C is a good choice.

And if I can get the same speed at 4S why would I choose 5S?

Battery capacity (Watt.hour) = Voltage (4s or 5s or more....) x Ampere.hour
You will ride a longer distance with 6S !

[addicted2climbing]

Hey Christian,

Thanks for the reply with a similar project. I did more searching and found these as well for $28 each. I coul buy 7 or 8 ea of these and have one single pack at 10000mah feading two motors and as I can afford it buy more. What I like about these are that they bolt together as a pack and can be configured in different ways and I could then tear them down and also use them in an E bike project as well. They claim 2000+ cycles with them. Anyone use these? I suppose I need some way to monitor them during use so I dont discharge them too far....

http://www.batteryspace.com/lifepo43812 ... roved.aspx

I would have liked to use 63-64 or 63-74 motors, but the spacing between the swingarms would only fit 2ea 6354..

What kind of range do you get with your setup? I was hoping for 10 to 12 miles or so to be able to commute on one charge... Or I keep a charger at work as well.

Marc

[ChristianR]

Rider 85 kg + mountainboard 15 kg = 100 kg
I ride in the Alps in a mountainous area.

I have made some measurements with a Wattmetter. Battery LiPo, 6S, 2x 5Ah


-With 2x5Ah I can ride about 12 km (I stop before complete discharge, near 11.5 km) on a 900m circuit for car race in mountain, with slope, flat parts, up and down hill all the time.
- On a completely flat way (not for cars, farmer only) about 11km, (soil covered by little stones, gravel).
- On mountain forest roads and paths, with strong slopes >8% and a good climbing speed (15 - 20 km/h but it can go faster) it is possible to ride 5km if you climb all the time, and 9 or 10 km if you came back by the same way (regenerative breaking).

-> Range from 5km to 11km according to soil / slope / road / speed ... with 2x5A 6S. I will buy more batteries soon...

[addicted2climbing]

Hello Christian,

Thanks for the great reply. What great information... I do still have some questions...

You mention regenerative braking which makes me think your not using an R/C style speed control. Also are you using an R/C style Transmitter to control it or are you using some other wireless control or wired?

I am still on the fence between Lipoly or the LifePo4 Headway cells. I found them much cheaper than the link I mentioned above, but I have no experience with Lifepo4 so I need to spend more time reading.. Unsure how the BMS stuff works as Lipoly has it built in to work with hobby chargers...

On another note, Where in France are you? I just spent 3 weeks in france with a week in Paris, a week with my girlfriends family in the Gers and haute pyranees and then a last week in the south near Carcassone and a few days in Collioure...

Take care,

Marc

[EBJ]

Hello Christian,
I found them much cheaper than the link I mentioned above,

post the link please.
Some ppl on this forum could share their good/bad experiences w/ purchasing from a particular place.
Sometimes there are reasons batteries are way cheaper on one site and not on another.

[ChristianR]

Yes I use a R/C speed control, for both acceleration and breaking.
This model : http://www.hobbyking.com/hobbyking/stor ... duct=10608
Electric breaking is not necessary on a e-bike (since you have mecanical brakes), but it is extremely usefull on a mountainboard or a Flexboardz.

I use a LiFePo4 battery (36V 12Ah) on my electric Dirtsurfer (no regenerative breaking but a mecanical brake) and a LiPo battery (6S 22.2volts, 2x5Ah) on my e-mountainboard (with regenerative breaking and wireless).

Both batteries works fine, LiPo is cheaper, but LiFePo4 will probably last longer.
I will tell you more about this in a few years !
I am located in the french Alps (near Grenoble, south eastern France).A nice place to ride with mountains all around .

[addicted2climbing]

Hello Christian,
I found them much cheaper than the link I mentioned above,

post the link please.
Some ppl on this forum could share their good/bad experiences w/ purchasing from a particular place.
Sometimes there are reasons batteries are way cheaper on one site and not on another.

Hey EBJ,

Here is where I found them. They seem reputable.
http://www.manzanitamicro.com/products?page=shop.browse&category_id=29&vmcchk=1

Do you have any experience in using this type of battery?

Marc

[addicted2climbing]

Hey Christian,

The link you sent me was the transmitter not the ESC... I ordered the 150 amp car ESC with sensor imput from HK as well as many other things. Are you using an outrunner motor? And if so did you add halls? Do you have a link to your projects I can look at?

On your LifePo4 pack do you use a hobby charger from HK or one dedicated to LifePo4? Also what do you use for Ballancing of these packs.. I am so use to using liPos that I am trying to understand how these are charged and what I would need should I go this route. I really like the idea of investing in say 20 Lifepo4 cells and the using them in many differnet projects and configs... I can only ride one at a time anyhow...

As for Grenoble, I was hoping we would end up in the Alps, but we only had 3 weeks so we went to the pyranees since we had to go there anyhow for a family reunion at a mountain refuge. I could easily live in the Luchon / Vallee du louron area... When I did my planning for the trip, I wanted to go to Gap for some soaring which is not too far from you. I use to fly sailplanes years ago and wanted to fly in france... I currently fly Hangliders (deltaplane) since its much cheaper to fly then sailplanes....

Maybe next trip.

Marc

[EBJ]

Hello Christian,
I found them much cheaper than the link I mentioned above,

post the link please.
Some ppl on this forum could share their good/bad experiences w/ purchasing from a particular place.
Sometimes there are reasons batteries are way cheaper on one site and not on another.

Hey EBJ,

Here is where I found them. They seem reputable.
http://www.manzanitamicro.com/products?page=shop.browse&category_id=29&vmcchk=1

Do you have any experience in using this type of battery?

Marc

Sorry i dont.
I went Lipo.
much more complicated than I thought it would be.
wiring took me forever, but I did add a bunch of the safety features mentioned all over this forum.
Needed a battery that could output up to 200 amps.

[ChristianR]

On my electric moutainboard I use this motor Turnigy 63-64 280kV 65a brushless motor with this ESC HobbyKing brushless car ESC 150A, without hall sensors, x2 ( on left and right rear wheels).

My lifepo4 battery, bought on ebay, was sold with a dedicated charger.
But I unscrewed its aluminium box, there is a 11 pin balance connector inside, but it is not used by the chinese basic charger

A video of my e-MTB during a first test in the french Alps e-MTB
You can find much more details about it on the french forum dealing with electric skates e-ride-earth (or the google transation )

[Kin]

If it's not to late, I'll add, setting up your motor system for a higher voltage input will require a lower current for equivalent power application, so overall there should be less heat in a wiring system. (wire resistance is dependent on current, not voltage. As current increases, resistance increases).

[addicted2climbing]

Hello All,

Well I have made some progress on the design and all of my purchased components have arrived aside from my batteries. I worked on the battery box design and now I can verify that the 4ea 6s 5000 lipos will fit with 2ea HK 150 amp speed controls and receiver. The battery box shown is still work in progress as I would like to add some fans as well as some louvers to the sheet metal lid. I may test run the board without a box to start so I can get all the wiring done as well as any switches which I then can add to the box once I have all the electronic items finalized. Anyhow I have attached a jpeg of what it looks like so far...

Marc

[addicted2climbing]

Hey Everyone,

I have been working on the design for a while now and I am finally done. I found a huge error in my swing-arm where I managed to design a left at one point and switched over to thinking it was for the right so I ended up with something that did not work well for either. I had to scrap it and start over and this one is much better and also easier to machine so hopefully the cost will come down a bit. Now I start detailing the parts and get them to a shop to make. I fear the parts are going to be pricey as I sort of went all out on the design.

Anyhow I have attached some jpegs of the motor/swing-arm assy as well as the battery box.

Batteries should be here on Friday and I can then finalize my battery tray and velco strap locations and then that's it...

Marc

[sk8norcal]

looks great!!

here's the other flexboardz thread..
viewtopic.php?f=35&t=28406&p=409519&hilit=flexboardz#p409519

I am still hoping to test one of these boards some day...
I did test rode a Zuumer scooter which have a similar tilting wheels rear truck...

[addicted2climbing]

Hey Sk8norcal,

Thanks for the link. I am familiar with that one as well as its on the flex-board sitetoo. Before I started, I had considered the Hub motor route as in all honesty it is a better option since it is a more sealed system and does not have the issues of chains. However, they had to use a larger wheel and also had to design a "U" shaped swing-arm since they could not cantilever mount the hub motor and I wanted to keep it as simple as possible and also use as many of the original parts as possible. I think it could be an amazing option if the hub motor wheel size was smaller or if all 4 wheels were larger.

Take care,

Marc

[sk8norcal]

btw, how do u like the flexboardz ? (vs a carveboard)
do u use it for kiting or just carving ?

[addicted2climbing]

Hey sk8norcal,

I have never ridden a carveboard so i cant make the comparison. I bought it with the intention of adding motors. I have ridden it on a pavement hill and it does carve and feel much safer then a mountainboard. What i like is its CG is lower. I bought a used kitewing and it came with a mountainboard and i tried the mtn board on some long grass hills and it was fun but i felt sketched a bit due to the higher CG. The flexboard feel more like a large skateboard then the mtn board felt. I may sell the mtn board to fund the machining of these parts or to buy another non electric version tomuse with the kiteboard if i find that the electric version feels heavy when used with my wing and no power

[sk8norcal]

which mtnboard ?
this guy flips the trucks mounting for lower deck height..
http://www.bgsurf.blogspot.com/


btw,there are smaller hub motors, shown here on myway..
viewtopic.php?f=35&t=22409

(click hub motor)
http://www.goldenmotor.com/

[addicted2climbing]

The Mtn Board is an MBS pro model from a few years ago. If you rlooking for a used MBS board let me know? If your ever in the los Angeles area look me up...

As for the hub Motor, I did find a few small ones, but they were from golden motor and when I looked at the specs they did not seem ideal. I wonder if the ones on the scooter are a different brand or one designed by them for their application? For now the R/C stuff will work for me since comming from the R/C electrip plane world its what I am familiar with. If after this project is done, there are smaller hub motors out there that look better I may try and retrofit them to my board. I would just have to design another set of swingarms and my battery box would probably still be good unless I had to change controllers.

Marc

[sk8norcal]

ya, i hit u up when i go to LA, been wanting to try the flexboardz for years...

rc seems like the way to go,
but my knowledge of rc stuff is minimal,
hoping to do a rc standup scooter someday...


btw, there are some guys racing e-skateboards in velodrome down in LA area...
i want to test out that 5th wheel setup..
viewtopic.php?f=35&t=18964&p=309896&hilit=skateboard+racing#p309896