I finally got some time to start my build thread. I’m currently a mechanical engineering student and between going to school and working my free time is very limited. I have been wanting to build an eskate for a while now and over the past couple months I started gathering parts for my build. I am calling this build the experiment because I have no Idea what to expect when its done, could be awesome or could catch fire. This mostly due to my battery choice. I have decided to make a 8S pack out of recycled 18650 cells from dead laptop batteries. I know these are not the correct batteries for an application like this, but they were free and I’m curious to see how the pack performs. I have not decided the exact size of the pack but it will be 64 cell minimum, possible even up to 80 cells. Even with this amount of cells the pack will still have a low discharge amperage leading to intermittently pulling 3C or more. Obviously this is no good for the cells, but lets see what happens.
Onto the build. The part I’m most excited for with this build is designing my own truck hangers. I purchased a set of caliber clones before I realized that they were not wide enough to run dual 6364 Tacon motors. An old friend of mine is a machinist and has recently purchased his own 3-axis CNC mill. He agreed to help me out with the trucks as well as the motor mounts.
I sill have a lot of work to do to get this board done, but I hope to finish for the summer. Anyway here is the build list and some images.
Deck: Ebay Kicktail downhill deck
Trucks: Homemade 200mm CNC hangers on caliber 44° base plates
Wheels: 90mm Flywheel Clones
Motors: 2x Tacon 160 245kv
Motor Mounts: Homemade version of Torque board mount
Gearing: 15T motor / 36T 3D printed Wheel pulley
ESC: 2x Axle VESC
Battery: 8S8P or 8S10P Laptop 18650 cells
Remote: GT2B with 3D printed case
Enclosure: 3D printed
Thank everyone and yes, the 3D printed parts are just design samples. I want to be sure that my design is perfect before machining. I am even trying to run a stress analysis on the truck and axles in solidworks just to make sure.
Ron, I checked on ebay for the deck I purchased but it looks like they are not listed anymore. The sellers name was decoysupply and it was titled Longboard Downhill top mount quality skateboard blank 9.75 x 37.5" SPEEDBOMB C03.
I haven’t had much time to work on the board, but I did get some parts in. I also was messing around in solidworks and made some new truck designs. My plan is to make several designs and let my machinist friend choose the best option. I almost have all 64 cells for the 8S8P pack. Still have a bunch of cells to test and since I have the time I will to go through the rest to find the highest capacity cells. Most of the cells in the pack so far are between 2400 and 2200mAh according to my cheap Chinese testers and my balance chargers.
Just FYI,
The stress analysis on solidworks isn’t perfect. My boss only lets me use it to verify deflections, but no real engineering can be based on it…
Hangers are made out of 4140 Chromoly Steel which has a tensile yield strength of 65KSI, 6061-T6 aluminum on the other hand only has 30KSI. People bend hangers all the time, so make sure you pick out a good material to machine them out of, and make sure that your friends CNC mill can actually handle said material.
Very nice work so far. I think there may be several people interested in a wider caliber hanger. Im looking for a 215mm hanger to fit dual 70mm long motors and 15mm belts. Be interested to find out how much CNC ing the hanger cost?
PXSS, I do agree with you with the solidworks analysis. This will be my first time messing around with the analysis side of the program so I thought I would give it a shot. I am trying to over build the hanger to be safe. This includes using 10mm axles, which I did not want to use but I think it will be necessary, and using 7075-T6 aluminum.
These hangers are around 205mm wide. I was wondering if I should just make them 215mm in case I wanted to get 70mm motors in the future but I can’t make up my mind. I feel my board is not that wide and might handle a little weird with that wide of trucks.
Maybe someone can give me some advice on the truck axle. I keep going back and forth between the 8mm axle and the 10mm axle. I was set on using the 10mm axle, but after printing my latest hanger design I am a bit worried about the amount of material around the axle. This is because I am sticking to the same hanger profile as the Caliber II and there is not much material around the axle to spare. My main question is would it be better to have the stronger 10mm axle or to have more material in the hanger and use the 8mm axle.
I would say go 8mm only because I love to use skateboard bearings with extended race. It eliminates the need for a spacer and shim washers and allows me to really tighten the wheel nuts. With 10mm you will have to use an industrial bearing and I have not seen much selection in the 22x10x7 size. But to your question about not much material being left with a 10mm axle, how much material is left there like 3mm? I think it would work but may ovalise over time. How much thread extends inside the hanger?
Irdesigns, bearing selection is another reason I would like to use the 8mm axles. With the 10mm axles there would be about 3.8mm on the sides of the axle, the top and bottom have more. Using the 8mm axles allow another mm of material. Another consideration is the 10mm axle uses 8mm thread and the 8mm axle has 6mm threads. The shoulder portion of the bolt will slide about 34mm into the hanger.
With 34mm inside the hanger I think both will work perfectly. The M6 thread should be fine provided your not changing wheels every day, then it could wear out a bit faster than the M8 thread.
Although 7075-T6 has enough tensile strength, it’s fatigue strength is lower than chromoly steel which means that it’ll fail sooner seeing the same amount of impacts. The Aluminum in this case is also the stiffer metal which won’t be as smooth to ride over bumps and might lead to fatigue.
If you’re ok with these trades, then I’d suggest go with an 8mm axle. No need to go larger
Been busy with school, but made some progress. I decided to try the “boosted style” VESC enclosure from Thingiverse. Its a tight fit for two VESCs but should be able to fit them if i move the capitation location. I also started soldering the battery and should have it completed soon.
