Introduction: Electric Mountain-board (UK)
This is the first project I have created a step by step for, please be kind.
As of right now i have most parts bought / made and the wheel assembly complete, when i complete an element i will update this post.
I am doing this project as part of the Duke of Edinburgh's Diamond challenge; it is a great program set up by the DofE for a way of inspiring drive, creativity and challenge. There is 3 categories which you can challenge your self at, Physical, Skill and Personal. In an attempt to avoid the (great but) predictable hike up Ben Nevis I thought I would make something that I would need to research for and something that I would have to learn skills for, in this case, Skateboarding (mountain boarding), mechanical and electrical assembly along with a plethora of smaller techniques. If what you see is of any use and you are in a position to please check out my JustGiving page to donate to the DofE charity: http://www.justgiving.com/Electric-skateboard
If you think you would be interested in the back story and my decision making please go here: http://electricmountainboard.weebly.com/
As i will be making this over a period of time i will be uploading different elements of the build at a time and then an assembly guide.
This guide is not the best way to do it but it is my way, the budget for this project is around £300.
Step 1: Parts List
For all of the below items I am using a board I already own, it is an Exit mountain board that obviously has a deck, wheels and trucks here is a link to a similar board :(Amazon link) https://goo.gl/pSV77Z . I have also given links to the closest individual parts i could find.
Connection plate: For my connection plate (which i would not recommend) I have used 18mm plywood cut into a circle just under the size of the wheel hub. If you have the facilities or means to make a metal alternative with much higher tolerances and precision then do. This will be used to transfer the drive from the sprocket to the wheel, hopefully evenly and prevent warping to the wheel... maybe!
With hardware buying more than you need is always the way to go, it is often difficult to get the exact number anyway and they will more than likely come in use for something else.
Bolts: M6 x 30mm Hex x 3
Washers: M6 small washers x 8
Nuts: M6 nyloc nuts x 8
Bolts: M6 x 80mm Hex x 5
- Chain: This is a great set that seems high quality, I had to do a bit of research and make some mistakes before settling with this.
- Motor sprocket : As of writing this I haven't quite figured this part out yet I have got the pinion from the casing and it fits the chain but whether I can connect it to the motor, I don't know!
- Shaft connection: Not sure this is going to be strong enough, the motor is powerfull...
- Truck connection plate:
This is basically a piece of 50mm x 50mm x 3mm angle aluminium with a section cut out for the truck pivot bolt. It adds workable surface area to the truck face. My current design has this plate only attached by two bolts, this might have to be improved.
- Angle bracket:
This is a small section of the same materiel used for the truck connection plate, 50mm x 50mm x 3mm angle aluminium. This allows to motor to be mounted in the correct location.
- Motor plate:
This is a piece of flat plate 3mm aluminium that attaches to the angle bracket allowing for slight adjustments and it's what i had lying about.
Bolts: M6 x 30mm x 2
Bolts: M6 x 20mm x 8
Nuts: M6 nyloc nuts x 8
Washers: M6 small washers, as required.
Step 2: Wheel Assembly
Wheel assembly parts list
Wheels - The wheels are from the old mountain board i bought around 5 years ago, it is nothing special and I have never used it... properly, here is a link to a similar board: (Amazon link) https://goo.gl/pSV77Z Sprocket - As i have discovered buying the right parts especial online can be tricky and I have had to buy different chains and sprockets before getting it right, here is what I found: (Amazon link) https://goo.gl/pSV77Z connection plate - I made the connection disc out of wood, I did this because I have the tools to work with this material far easier than metal however during assembly I discovered that this is not a great idea for a few reasons. Firstly I made the disc by using a circular cutter around the same/ less diameter to the wheel hub. It is not a great material as the tolerances needed to install the wheel to the sprocket need to be tight as any movement will cause the chain to tighten and slacken whilst operating. Hardware - Nuts, bolts and washers. 3 x m6 x 30mm + 5 x m6 x 60 - 80mm hex bolts. I suggest buying nyloc bolts as pretty much every connection will be under a lot of vibrations whilst riding. We will also need some small washers, everything m6 (6mm).
See step 1: Parts list for more information and links to parts.
Step 3: Wheel Assembly: Step 1
Cut out a circular piece of ply wood.
I used 18mm thick good quality ply.
the connection plate will act as not only a drive plate but also to create distance between the sprocket and wheel.
My connection plate is 74mm diameter but ideally you would want it to be tight in the wheel, the inner diameter of the wheel is 80mm, in my case. I have cut a connector plate with a jigsaw also that fits snugly in the wheel but it isn't as accurate regarding the hole in the middle.
Step 4: Wheel Assembly: Step 2
The wheels I am using have 5 holes in them which hold the two parts of the hub together. I lined the two pieces up and drilled through the wheel holes with a 6mm bit.
Counter sink the holes on one face so that the head of the bolt is flush with the ply. The bolt can’t be allowed to rotate in this countersink, glue can be used.
Step 5: Wheel Assembly: Step 3
The sprocket I am using has 3 holes in it I lined the two pieces up and drilled through the sprocket holes with a 6mm bit.
Countersink the holes on the opposite face you countersunk the 5 holes, making sure that the head of the bolt is flush with the ply. The bolt can’t be allowed to rotate in this countersink, glue can be used.
Step 6: Wheel Assembly: Step 4
Insert the 3 bolts in the ply disc so the head of the bolts are sat in there countersink. Bolt the piece to the wheel using 5 bolts and washers on the nut face. The tight countersink will allow you to tighten the nuts.
Step 7: Wheel Assembly: Step 5
Drill a hole in the center of the plate so the wheel can spin freely around the truck (mine was 19mm).
Bolt on the sprocket using the three protruding bolts, the tight countersink will allow you to tighten the nuts.
And you have finished this element
This is not the best method as the accuracy is too low but it is a very easy material to work with.
Step 8: Electronics: Step 1
The electronics are not overly complicated but was one element I spent a lot of time researching; mainly because this is where most of the expense is.
· ESC – Electronic speed controller. With a brushless motor you need an electronic speed controller, it basically chops up the electricity going to the motor causing it to rotate… The ESC I am using is for a boat, I chose this one because it can take a lot of Amps and is cheap. There is an ESC designed for electric skate boards but it is around £120. The boat ESC will do the job but it is a bit sudden when the motor first starts up.
· Battery – If you are hoping to buy a load of bits and go riding the next day you are probably going to hurt yourself. Batteries are dangerous or can be if mistreated and you will need a big one. I chose mine because it can output 240amps (max), the motor can pull 70 Amps so I am well within my limits. Here are a couple of things I learnt. Lipo batteries may not say what voltage they are but they will say how many cells the battery has, denoted with a “S” for example 6s (which is what I have; the motor can take 12s) each cell is 3.7v. The other important thing to take is the discharge of the battery or current, this is denoted with a “C” the higher the discharge of the battery the more Amps you can draw. How you calculate the total amps = Amp hours x discharge, the battery I chose is 12Ah x 10c = 120Amps or 12Ah x 20c = 240Amps (max); never good to rely on the max.
· Motor – These motors are great! I will cover ratio calculations for sprockets in the drive section. Here is what you need to know, motors have a KV number this is the amount of revolutions per volt, so the one I have is 149KV meaning every 1 Volt will make the motor turn 149 RPM (revolutions per minute) I am currently putting 23v (because new battery) through the motor meaning the shaft will spin at 3427 RPM. All so the lower the KV number the greater the torque, seen as I don’t want to go silly quick I chose this one.
· Wire – You can use 12awg or 10awg (lower the number thicker the wire) 12awg is a lot easier to work with.
· Connectors - XT90-s connectors with spark protection are great as I read that sparks in a circuit with Lipo batteries are a big no no; which makes sense.
· Heat shrink – This will stop any stay wires short circuiting.
You will need a soldering iron and some solder but that is pretty much it.
Apologies for the big step and a lot of information, as I said I learnt a lot on this one.
Step 9: Electronics: Step 2
Making the safety loop
Instead of buying a spark proof switch; which is expensive, you can make one using the XT90 connectors.
Cut a piece of wire about this long |--------------------------| or long enough to fit your figure in when it is looped around, mine was around 70mm.
Strip the wires on both ends
Twist the inner wires together and apply solder to the wire this will hold the wires together and hold the bond to the connector. Take a male or female connector (doesn’t matter which) and apply a very small amount of solder to the terminals.
My connectors came with an end cap so if you have that make sure you don’t forget to put that on the wire before closing the loop, same goes for the heat shrink.
Solder the two ends on the connector apply the heat shrink and end cap.
Loop switch safety cut off thingy complete.
Step 10: Electronics: Step 3
Now we have made the safety loop we need the opposite connector to be in the circuit. Take the opposite connector and using the same techniques mentioned in step 2 attached one of the terminals (does not matter if it is the positive or negative) to the negative ESC power cable. Cut off another piece of wire and attached it to the over side.
Step 11: Electronics: Step 4
My battery came with an XT90 connector so I just attach the opposite connector to both ESC wires (one being from step 3); if your battery doesn’t have an XT90 connector then cut off what it has and attach a new connector or buys the appropriate connector. Most people buy two batteries and wire them in parallel to get more Amp hours or in series for more volts, I just bought one big one and I can upgrade to two if needed.
Step 12: Electronics: Step 5
Coming out of the motor is three wires and the same for the ESC, I have bought a MT60 connector to attach these two and allow me to dismantle it. It doesn’t matter about what leads connect with which but if the motor spins the wrong way during testing you can swap any two leads over and it will then spin the other way, seen as I haven’t mounted the motor yet I just wired it up and I’ll attach the motor to the relevant side depending on the rotation of the motor.
Step 13: Electronics: Step 6
Attach your ESC to your RC receiver (my acceleration trigger was on channel 2)
Make sure everything is connector and the motor is braced and way to go. Test that all components are functioning.
These components can me dangerous if not treated with respect.
Step 14: Drive - Chain
The chain is obviously a bought part that came with the sprocket I need
to adjust the length of it. I can adjust the length after all the mounts are installed to achieve the correct length for tensioning. The chain is stronger that bicycle chain but weaker that motorbike chain, so a very god bike chain breaker might do the trick, I had to buy a motor bike one.
Step 15: Drive - Pinion
part was so hard to research. All I had seen online was custom parts using inaccessible tools. I seriously considered scrapping the chain drive and going for a much easy belt drive approach. I decided to persist with one idea to cannibalise an eclectic scooter pinion and get it custom made. Luckily I know a guy, who knows a guy that could do this relatively cheaply at £30, for comparison I had an engineering firm quote me £90 - £120 for the same work. I am a little disappointed I could not find an alternative because the spirit of this guide is that anyone can make this with standard tools and well no skill. Never the less I had the pinion drilled out at 8mm to fit the motor shaft and add 3 holes drilled and tapped in the collar to fit grub screws.
Step 16: Mount - Truck Plate: Step 1
This attaches to the truck to give a greater working platform to bolt from to connect the motor. We will be bolting this plate onto the truck. The tracks will have to be removed to attach these parts.
Cut your piece of aluminium angle to the correct width for your trucks (if your trucks are suitable for this technique).
I chose the distance by measuring the distance between the inner wheels and taking off around 50mm, this will allow for wheel clearance and sprocket clearance, if it does not further down the build then more can always be cut off.
Step 17: Mount - Truck Plate: Step 2
My trucks have a pivot bolt that connects the two halves of the truck. Clearance for this moving part will have to be cut so the plate can be securely fixed to the lower truck section. The reason why we need the plate on the same part as the wheels is so the motor chain and sprocket are set and don’t move from each other during turning.
Firstly I cut a “V” but found this took away too much material to then bolt with.
I cut out (using a girder or hacksaw) enough material dead centre of the plate to clear the pivot bolt and to allow clearance when pivoting, making sure to remove the sharp burs.
Step 18: Mount - Truck Plate: Step 3
Lining up to drill holes are tricky, I found it easier to mark where my two holes on the truck can go, measuring the distances and checking the plate to see if there is enough material.
So as to prevent nuts working free I will add two more bolts to the underside of the trucks to stop potential twisting.
I drilled the holes in the truck and then drilled through those holes into the plate, whilst having the plate clamped to the truck.
To attach to the truck I used 6mm machine bolts and nyloc bolts. Because I only cut enough material off to clear the bolt the piece catches on the top truck section. Insert a bolt between the plate and the truck as a spacer.
Step 19: Mount - Motor Plate: Step 1
The parts for this plate are made out of material reclaimed from a cheap steady cam rig, the aluminium just happened to be suitable for the job (50mm wide x 100mm long).
To prevent the torque bending the plate I doubled up the thickness
Drill out 4mm holes for the motor, I lined up the mounting plate that came with the motor and drilled through the holes.
Step 20: Mount - Motor Plate: Step 2
Cut out a hole for the motor shaft, i used the mounting plate that came with the motor as a guide.
We now have to attach to the angle bracket but first we have to make that.
Step 21: Mount - Angle Bracket: Step 1
This piece will allow the motor to be in the correct orientation.
Cut a piece of aluminium angle 50mm long; making a piece 50mm x 50mm x 50mm.
Drill holes and bolt it to the outer face of the motor plate.
Step 22: Mount - Angle Bracket: Step 2
Attached the motor plate with the motor and pinion attached use the chain or a straight edge to line up the pinion to the drive sprocket. Clamp the angle bracket the truck plate, drill and bolt.
Step 23: Mount - Angle Bracket: Step 3
To tension the chain add spacers in-between the angle bracket and truck plate.
Assemble and bolt all parts