Going to post some pictures of the details tonight with a basic intro and update on where I am in the project.
Cheers,
Chris
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curiosity peaked
A few picture below. waiting on parts in the mail to start assembly. I will post more as I get parts in.
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Are you sure that dinky car ESC will survive?
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Nope. It might not survive. We will see. I will upgrade to a VESC eventually.
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Yeah, that ESC’s not going to make it more than a few hours (I’m being generous)
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@Chris22 I love to see this creativity, and the liquid-cooled concept is awesome! However, with 10S and a 730KV motor you’re looking at a top speed of around 116 MPH… you won’t have any torque at ridable speeds (in theory, by all means test it!)
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I would kind of like to see that…
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He’s planning on gearing down 6:1 by way of a 2-stage reduction (spur & chain).
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dont those water cooled motors need a resivoir or more so a lake to work with? Is he going to add a fish tank to the build?
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I’m looking at pictures of a big radiator on the back…?
Subscribed for the radiator
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Interested to see how she turns out!
Seems like a lot of torque for a single wheel. Have you done any calculations on the static friction of urethane on asphalt? When I was designing my board, I used the torque calculations to derive a maximum force. This force needs to be less than the force of static friction, or you’ll get wheel slippage
My motor is about 1/2 as powerful as your T20, and it already has enough torque to run over small mammals and climb vertical walls. This thing is gonna be a monster! Good luck
P.S. HobbyKing lists a max voltage of 11S, but perhaps yours is a different model?
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I am going to put a huge heatsink and fan on it. I also am keeping the cable length between the batteries and ESC as well as the ESC to Motor as short as possible.
I notice that not everyone realises how important this can be. I have noticed that if you keep the cable lengths short the ESC is fine. I think its because the voltage spikes being higher in longer cables.
By the time I am ready for testing I will likely have already purchased a VESC already in the event I blow the ESC i am using now.
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HTownBomber is right I am going to post something about it now.
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No I have already tested it with a previous project using only a closed loop system. Basically a small radiator with a fan on the back that pulls the heat out of the water. If i have to I might add an inline electric chiller using small 12v chilling plates. It will depend on season as well. In fall and spring I will be okay for sure because the air going through the rad is so cold. In the dead of summer I probably have to avoid riding it hard.
I plan on installing a temperature sensor. I will program it with an Arduino Nano to control the water pump speed and fan speed to regulate the water temp. As well as an alarm when it hits a dangerous number.
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I have built a few E-vehicles and I am currently working on my first electric longboard.
For my electric skateboard I decided to use a higher KV motor (720kv) that pulls 128A and runs 12s. This will give me a lot of RPM. I have started to design a reduction system to drop the RPM from 30,000 rpm to around 5,000 rpm. With my gear reduction I should get around 7.5 ft-lbs for torque. The motor is over 6000 watts, and water cooled. Turnigy T20 . I am going to use Turnigy k force 120A hv esc that I have used to run this motor in the past. Mostly because I have it lying around. I will eventually switch to the VESC because of the improved start up torque and more advanced setting for regenerative braking. The motor I am using is a 4 pole motor with a ERPM of (720KV)* (12S * 4.2V)*(2 Pole pairs) = 72,576 Max ERPM We will see if it this ESC can handle the load, might not. I will work out the electrical and mechanical efficiency to see how bad it is. I know with the added reduction I will have some mechanical losses but hopefully not a ridiculous amount. I am running 90mm wheels. I would have liked to go to a 7:1 reductions but I am starting out with a 6:1 due to space limitations. I am using a two stage system. A pulley mounted on the wheel will be driven by a pulley mounted to a small 3/8" OD jackshaft bolted to the rear truck. I am using roller bearings to hold the shaft, which are rated at 650 lbs and 29,500 rpm. I will use a hardened shaft so it can take the load. The other side of the jack shaft will have my second reduction which I have already purchase. This reduction is a set of high load 20 degree pressure angle spur gears at 2:1 reduction (24 to 48 tooth). The 24 tooth is mounted to my motor; the 48 tooth is on the jack shaft. I have to make sure I can still adjust the belt tension, or alternatively add a belt tensioner as an add on. That’s basically my gearing plan. I might weld a small SS box around the gears after I am happy with it and fill this with grease or oil; otherwise my only concern is that the gears are going to get HOT. The motor I think i can keep cool with the water jacket. I have used this motor on a BAJA 5T before and I still have the small radiator/fan and water pump i used as a closed loop cooling system on that project. I am going to use a similar system here. Preliminary results from my spreadsheet I used for speed Calcs below.
The Board I am using is a Step Deck that is very big. I wanted it to be stable. I added ½” rubber risers because I like how they smooth out the ride. The radiator will be mounted as I show in the pictures on top of the rear truck with the fan drawing air out of the back side.
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Yes that is the radiator. I am going to use the read truck bolts as mounts. I also don’t want it too far from the motor so I dont have long water lines between the two. This will help the pump.
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Jmasta,
I know it seems like a lot of torque. I have the startup set to super soft. I am hoping that is enough to not spin the wheel. I also have very very sticky wheels. They are not hard urethane. I think they are 83a hardness.
Correct the Turnigy T20 is an 11S motor, but I have ran in with 12S in the past and never had an issue. Most of the engineers will design a motor with a safety factor. They can take slightly more voltage most of the time. 1S more is not enough to kill the motor in my experience and lowers the amp draw.
11S is such as strange battery size to find anyway. I would guest most people not wanting to test the limits of the motor would run 10s.
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