My electric Volkswagen Sandrail (Dune Buggy).

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My electric Volkswagen Sandrail (Dune Buggy).

Postby Jayls5 » Wed May 31, 2017 10:32 am

Equipment:
90AH, 103.6v nominal, 20C LIPO battery pack. I discharge them at ~7C.
HPEVS AC-20 Motor
Curtis 1238-7601 Controller.
Power sent through 4 speed VW, no clutch.



:mrgreen:

The whole car has lots of nice tech in it. Electric parking brake (via linear actuator), Cree MT-G2 headlights retrofitted into old school headlight housing, and my watch can turn on the car & headlights. 8)

Questions/Comments welcome!
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Re: My electric Volkswagen Sandrail (Dune Buggy).

Postby footloose » Wed May 31, 2017 10:42 am

I want one.

No clutch? Shift by slipping into neutral, matching revs and sliding into new gear?
Range?
Any build documentation?
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Re: My electric Volkswagen Sandrail (Dune Buggy).

Postby Jayls5 » Wed May 31, 2017 12:53 pm

footloose wrote:I want one.

No clutch? Shift by slipping into neutral, matching revs and sliding into new gear?
Range?
Any build documentation?


Build documentation:
What I started with, and did a PMDC motor starting out
http://www.diyelectriccar.com/forums/sh ... 25425.html

Swap from ME1003 motor to AC-20:
http://www.diyelectriccar.com/forums/sh ... 169857.htm

Range is dependent on acceleration in current form, just like gas. I can get about 40 miles driving like a normal human being, but that's not as fun :twisted:

I can actually shift while moving. I just ease it in and the synchros line up. It's just slower than shifting with a clutch but I never have to worry about clutch wear or slipping. I normally just leave it in 2nd gear and it out-accelerates traffic and can pull to highway speed.

Worst case with conservative battery management (not full charge and not full discharge), I can get 15 miles of absolute racing around. 40 miles of cruising on my ~140 lb battery pack.
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Re: My electric Volkswagen Sandrail (Dune Buggy).

Postby wineboyrider » Wed May 31, 2017 1:00 pm

Super sweet! How much invested? 8)
ES IS SAVED! THANK YOU JUSTIN.
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Re: My electric Volkswagen Sandrail (Dune Buggy).

Postby footloose » Wed May 31, 2017 1:18 pm

Jayls5 wrote:Worst case with conservative battery management (not full charge and not full discharge), I can get 15 miles of absolute racing around. 40 miles of cruising on my ~140 lb battery pack.


Now I want one twice as much.
Clearly going to need to present this on the home front as an absolutely great solution for efficiently hauling groceries from the store and doing neighborhood errands... maybe I could even volunteer for Meals on Wheels delivering meals to the homebound? Or taking local kids to Sunday School on weekends? The conversation is going to be a lot like being back in my teens, explaining to Mom why it was a really really good idea for me to get a motorcycle :lol:
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Re: My electric Volkswagen Sandrail (Dune Buggy).

Postby flat tire » Wed May 31, 2017 6:09 pm

Now that's sick.

I like to shift clutchless in regular manual cars it makes the owners go crazy. And before you tell me I'm hurting their cars I did it all the time for years and 70K miles in my otherwise totally abused mk5 jetta and the tranny was still nice n smooth when I sold it.
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Re: My electric Volkswagen Sandrail (Dune Buggy).

Postby KalSteve » Wed May 31, 2017 7:15 pm

The part I would find hardest is remembering that the electric motor is happiest at high RPM whereas ICE's generally are not. I would always be shifting into 3rd or 4th when cruising where it would be better left in 2nd.
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Re: My electric Volkswagen Sandrail (Dune Buggy).

Postby Jayls5 » Wed May 31, 2017 7:28 pm

wineboyrider wrote:Super sweet! How much invested? 8)


I've invested an embarrassing amount, primarily because I kept swapping equipment and ran into other mechanical issues with the vehicle and upgrading when I wasn't happy with performance.

I got the Chassis for $1500 + a year membership fee agreement at a local maker space.
I got the controller, chill plate, contactor, and motor used for $2000 shipped.
Batteries averaged about $25 a piece... and there are 126 of them... so that's $3150 not including shipping. (They're 5000 mAh 4S1P Turnigy hardcase packs)
The adapter plate and balanced clutchless coupler was around $750 if I remember correctly.
1500w Charger was around $225 shipped

Those were the main components, and I'm sure all the other little pieces add up to a lot as well. It's been my money pit, lol.
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Re: My electric Volkswagen Sandrail (Dune Buggy).

Postby oatnet » Sun Jun 04, 2017 9:53 pm

Excellent job! :D

I have particular interest in your build - I don't know if you have seen my B.F. Meyers Towdster dune buggy build (CLICK HERE for the long build thread), but it looks like we think along the same lines. I finished it a few years ago, and it is monster fast, but I've been thinking it would be fun to swap an 8" AC51 for my 9" ADC - less torque but lighter and more efficient. It looks like you are doing pretty well with an AC20 so maybe I can go smaller... Do you know how much it weighs now? I'd love to see more, do you have any build pics?

-JD
Last edited by oatnet on Sun Jun 04, 2017 9:56 pm, edited 1 time in total. View post history.
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Re: My electric Volkswagen Sandrail (Dune Buggy).

Postby Jayls5 » Tue Jun 06, 2017 1:45 am

oatnet wrote:Excellent job! :D

I have particular interest in your build - I don't know if you have seen my B.F. Meyers Towdster dune buggy build (CLICK HERE for the long build thread), but it looks like we think along the same lines. I finished it a few years ago, and it is monster fast, but I've been thinking it would be fun to swap an 8" AC51 for my 9" ADC - less torque but lighter and more efficient. It looks like you are doing pretty well with an AC20 so maybe I can go smaller... Do you know how much it weighs now? I'd love to see more, do you have any build pics?

-JD


I've seen your build before I was building mine; yours is awesome with nice fab work - better skills than me. I just put mine on the scale at a scrap metal yard the other week, and it was 1240 lbs. Check the comments in this thread earlier on for the build thread, it's on the DIYelectriccar link.

The Curtis stuff is pretty awesome for the amount of adjustment you can do (with a hacked programmer), but the output for any single controller setup just won't be fast like a high end Zilla controller. The peak current and voltage just isn't there, so you really would need the AC35x2 with two controllers to make it fast (I currently have one in my garage awaiting use :mrgreen: )

I actually just took the 1238-7601 off my Buggy to be used on the AC35x2 (another project). I've downgraded controllers in the past few days to a 1238-7501 on the buggy, 550A instead of 650A. It's really not as big difference on the smaller AC-20 if you go by the graphs (magnetic saturation reducing returns?). I felt the difference in torque, but the AC35 seems to gain more from the extra current. AC-20 goes from 83 tq peak at 650A to 69 tq at 550A... so 14 ft*lbs difference. The AC-35 goes from 128 tq at 650A to 108 tq at 550A, 20 ft*lbs difference.

If I had the option knowing what I do now, I'd probably do the AC-35 and a 144v nominal Curtis controller. While I've never had a thermal cutback yet on the AC-20 motor, it's definitely on the high end of what kind of weight it should be pushing. It's toasty racing around on flat terrain. I'm 100% confident doing 40-50 mph indefinitely without overheating the motor, but continuous highway speeds (70mph+) would probably overheat it eventually. In addition, regen braking continues to heat the motor, so I turn it off entirely when I'm racing around on my AC-20. You could keep regen on with the AC-35.
Last edited by Jayls5 on Tue Jun 06, 2017 1:46 am, edited 1 time in total. View post history.
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Re: My electric Volkswagen Sandrail (Dune Buggy).

Postby litespeed » Tue Jun 06, 2017 6:47 am

Super cool car and a nice job.

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Re: My electric Volkswagen Sandrail (Dune Buggy).

Postby kiwiev » Sat Jun 10, 2017 7:07 am

oatnet wrote:Excellent job! :D

I have particular interest in your build - I don't know if you have seen my B.F. Meyers Towdster dune buggy build (CLICK HERE for the long build thread), but it looks like we think along the same lines. I finished it a few years ago, and it is monster fast, but I've been thinking it would be fun to swap an 8" AC51 for my 9" ADC - less torque but lighter and more efficient. It looks like you are doing pretty well with an AC20 so maybe I can go smaller... Do you know how much it weighs now? I'd love to see more, do you have any build pics?

-JD


JD I would go the AC50 cheaper and more torque

Cheers Kiwi
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Re: My electric Volkswagen Sandrail (Dune Buggy).

Postby kiwiev » Sat Jun 10, 2017 7:15 am

viewtopic.php?f=34&t=74081 run a twin AC35 in my Hilux

The trick to Regen is the same as driving for getting rid of heat keep the rpm up I live in the hills and don't touch my brakes at all coming into town I can put 120 amps back in for about 3 miles.

Cheers Kiwi
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Re: My electric Volkswagen Sandrail (Dune Buggy).

Postby Jayls5 » Wed Aug 09, 2017 7:28 pm

Ever since I downgraded from the 650A to the 550A model controller, it hasn't been able to keep up the continuous power handling with no water cooling. I happened to have some PC liquid cooling parts lying around, so I thought I'd give them a whirl. The radiator is hilariously small, but it's better than nothing.

First, the tube diameter was not the same for the chill Curtis chill plate and my CPU cooler, so I had to adapt it:

Image

Image

Image

I'm zip tying things in place for now while I test to see if it's even worth it:

Image

Image

I the pump has a nice mini built in reservoir, and it is supposedly rated at 0.4A at 12v, so ~5 watts of power consumption. It seems to move the water pretty fast for what it is. I hooked it up to my 30w solar panel on top of my battery box, and it runs it full speed even in intermittent sun. At night, I have a 12v aux switch hooked up to run it off my aux battery.

I took it out today, and it's night and day difference. I imagine most of the improvement comes from doubling the surface area on the heatsink. I had the controller bolted up to the chill plate with nothing running through it before, and now it's got water contact as well as actual flow. For now, the mini radiator is doing passive cooling and gets its airflow from driving.

Not having to worry about controller limits as much, I adjusted some controller parameters for improved acceleration rate and doubled my regen. I also discovered that I never set the RPM limit to 8000 when I downgraded controllers... it was set at 7500. So now I can hit 50 mph in 1st gear, and I hit 70 mph going up hill in 2nd. I rode around beating the piss out of it starting in 2nd gear doing max throttle runs repeatedly for a stress test. While I never hit thermal cutback on the motor, I got home and hooked it up to the monitoring software and discovered the motor was at 108C :shock:

The controller was sitting at 45-50C.

So... let's just say that the AC-20 motor is not sized for a 1240 lb car to do continuous highway driving. The power is definitely there, but I need to cool this thing. Since I already have cooling running in the back, I was thinking about getting some copper coil pipe, wrapping the motor with it, and then sending the coolant through that. I'd obviously need a way bigger radiator and a powered fan on it, but I'm thinking I might boost the motor's capability to handle continuous highway driving. Thoughts/comments welcome.
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Re: My electric Volkswagen Sandrail (Dune Buggy).

Postby kiwiev » Fri Aug 11, 2017 4:28 am

Good work mate, what way does your motor face? Because on my ute the air comes from the gearbox end and blows forward into the radiator and against the air coming in.
108 deg is not bad btw they tend to get hotter after a run because there is no air being sucked thru.

Cheers Kiwi
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Re: My electric Volkswagen Sandrail (Dune Buggy).

Postby Jayls5 » Fri Aug 11, 2017 5:25 am

The driveshaft is facing toward the front of the car (side with the fan is in the back). You can kind of see it in the pic above, attached to the rear transaxle.

I realize the fan is designed to pull the air through the motor, then redirect it over the case. I'm not sure how great the air movement is while driving even though it's all in the open.

You really don't think I should worry about the high temp? I know for a fact i'm going over the motor plate rating at highway speed. My choice is either air duct for more flow, or copper coil wrap and liquid cool the case.

I just looked up the CPU pump I have, and it's rated at 300 L/h... which comes to ~1.3 Gallons/minute if my maths is correct. The recommendation for the curtis chill plate I saw was 2-3 G/m, so i'm getting like 65% of the recommended flow. Not bad for free! :mrgreen:
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