Street legal VW Sandrail dune buggy project. "Time will tell if it works" - DIY Electric Car Forums
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  #1  
Old 09-17-2014, 07:35 AM
Jayls5 Jayls5 is offline
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Default Street legal VW Sandrail dune buggy project. "Time will tell if it works"

I recently purchased a '67 Sandrail, and I'm converting it for around town travel, within a 10-15 mile range.




The meat:

30AH 74v nominal LIPO pack. ~2.2 KWh
Motenergy ME1003 Motor
Controller: Alltrax SPM-72400
Hall 0-5v throttle
Planning clutchless manual transmission.

Let me get this out of the way:
Everyone I have discussed with this so far is skeptical about this motor being so small. Yes, it's tiny and only ~38 pounds. It is a rare earth permanent magnet motor with higher efficiency than series wound motors most people use. I will not have to deal is much heat per hp, and if heat becomes a problem, I will add air cooling.
My concern is currently RPM related. I'm not well familiar with the gear ratios of my gearbox. My motor is slower turning, probably in the 3000 RPM range. While I'm sure it supplies plenty of torque, I don't know if the final drive will have it do fast enough speeds.

I got my 0-5v hall throttle working with Alltrax SPM72400, which I initially read on other forums that the throttle type didn't work. Well it seems I did. Check it out: https://www.youtube.com/watch?v=zIOJ-SL8i2w ... I have noticed that if I lose my (reference) 5v signal to the controller, it defaults the throttle signal to MAX. Basically, I don't want any "short" to result in max throttle, so I will be finding something to fix this.

I have been told my buggy weighs about 1000-1100 pounds. I plan to do clutchless manual. We will see if it works.

Last edited by Jayls5; 09-17-2014 at 07:40 AM. Reason: Typo
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  #2  
Old 09-17-2014, 06:33 PM
akseminole akseminole is offline
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Default Re: Street legal VW Sandrail dune buggy project. "Time will tell if it works"

I have a similar build in the works, though I am leaning towards series or AC. I am looking forward to seeing how this works out for you


I've searched and searched and have been astounded to find next to Nothing about Stock vw engine performance. Rpm/torque bands etc. Reading about performance builds tell me nothing about a baseline to expect and extrapolate from.

I found this and I hope it helps:

http://www.thesamba.com/vw/forum/vie...hlight=max+rpm


"A stock non-counterweighted crank is good for only 4,500 to 5,000 rpm maximum. However, as a practical matter, you will start losing power before then. If you look through the owner's manuals available here, you will find that the 40 hp made peak power at 3,900 rpm, the 1300 at 4,000 rpm, the 1500 at 4,200 rpm, and the 1600 SP and DP at 4,400 rpm. Thus, as a practical matter, there's no need to rev much over 4,500 for any stock engine, as hp begins to drop off before then."

http://www.oocities.org/eduhachek/tech.html

https://groups.google.com/forum/m/#!...ed/3GFPdU5Q2uc

http://www.thesamba.com/vw/forum/vie...r=asc&start=20

It seems that 4,000 rpm is considered 55mph territory, but at what horsepower and torque I have no clue.


I guess I'm just spoiled by looking at HPEVS dyno charts for their motors.

Anyway, good luck!
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Old 09-17-2014, 06:45 PM
akseminole akseminole is offline
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Default Re: Street legal VW Sandrail dune buggy project. "Time will tell if it works"

A thought, but idk if it will work for you. You could put taller tires on you car to compensate for your motor spinning slower than whatever the gears "think" you should be going for 4,000 rpm or whatever.

Idk, I assume that more knowledgeable people will step in soon.
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Old 09-17-2014, 08:45 PM
Jayls5 Jayls5 is offline
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Default Re: Street legal VW Sandrail dune buggy project. "Time will tell if it works"

So, I will be attaching the adapter plate and coupling the motor to the drivetrain fairly soon. Will post pictures as things progress.

I do not have a speedometer. Does anyone have a recommendation about how to implement a cheap one?

I'm planning on keeping a separate 12v system from the traction motor battery pack. It will float charge via solar. My headlights are incandescent and an unnecessary drain, so I will be upgrading them to LED. I'm debating between cree XML2 and much larger brandless LEDs. The XML's have a practical limit of 1000 lumen output max driven, which should be ok for travel. The other giant "100W" LEDs, which I will likely underdrive but might be too inefficient for my needs. Will experiment.

I'm not actually all that mechanically inclined, so I'm playing a lot of this by ear.
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Old 09-18-2014, 01:36 AM
Duncan Duncan is online now
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Default Re: Street legal VW Sandrail dune buggy project. "Time will tell if it works"

Hi your car is "similar" to mine

And I will join the chorus saying - motor too small - mine is 102Kg (maybe a bit on the large side)
http://www.diyelectriccar.com/forums...ghlight=duncan
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  #6  
Old 09-18-2014, 06:29 AM
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Yabert Yabert is offline
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Default Re: Street legal VW Sandrail dune buggy project. "Time will tell if it works"

Please anticipate to change your motor by a 8'' or 9'' DC motor (maybe forklift) in a close future (consider simple modification on adapter plate for other motors).
It's simple, if you drive your car like it's possible to drive it (enjoy the torque and the speed) you will destroy your tinny motor soon...
Oh! Keep in mind that a 8 or 9'' motor will give you better performance (more torque).

About speedometer, I suggest you a cheap way to know a lot of good infos: http://www.ebikes.ca/shop/ebike-part...-analysts.html

Hey, by the way, nice buggy
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Old 09-18-2014, 07:43 AM
akseminole akseminole is offline
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Default Re: Street legal VW Sandrail dune buggy project. "Time will tell if it works"

I know that not everyone has the budget for these, but I'll put it out there all the same.

I'm pretty seriously considering the 4x6 lights as they are street legal driving lights, only pull 40watts between the two of them and are already set up to just bolt on and wire in.

The 7" lights (DOT/FMVSS certified) are more likely something that I will put in my Jeep, but I know they make 7" external light mounts. Also they only pull like 20-25 watts each at 12v with a high and low beam function.


http://www.amazon.com/gp/aw/d/B00HSG...&pi=SX200_QL40

http://www.kchilites.com/catalog/pro.../category/381/

Housing to mount 7" light.
http://www.pacificcustoms.com/ac941411.html

http://www.amazon.com/gp/aw/d/B003LJ..._SS115&simLd=1

I've actually owned the 1st gen of these trucklite LED lamps and also this generation of them as well. I much prefer the 2nd gen design over the first. The light pattern is superior. The light color is just perfect. White, no yellow tinges or blues, just white.*

There are some artifacts(a slight "x" pattern from each lamp) in the light pattern on the road caused by the optics and reflector which Can be annoying if you let that kind of thing bother you. I just ignored it and enjoyed the superior(to halogen) light.*

I like that they work on a range of voltage from 9v-33v so even if your battery is low, they can still put light out or if your system runs (for whatever reason) at 24v.*
12.8v low beam 1.8 amp
12.8v high beam 3.6 amp

Also, they are DOT/FMVSS certified, which for a street legal buggy could be a thing to consider.

http://www.amazon.com/gp/aw/d/B007K8..._SS115&simLd=1

In a bit more affordable category, I've ordered a set similar to these and for the money, it was actually pretty decent light output.
However, Not street legal. "Off-road" only.

http://www.amazon.com/gp/aw/d/B00E0K...&pi=SY200_QL40


These seem like they would be the easiest way to get speedometer functionality in your rig as long as you don't routinely travel underground or in concrete jungles where you can't get a good gps signal. I don't know what the legality of using them as your only speedometer is, that's up to you to determine.

The first two would just "look" right at home in your buggy. The others are cheaper.

GPS speedometer selection from amazon, most expensive to cheapest:

http://www.amazon.com/gp/aw/d/B00B0Z...110_SY165_QL70

http://www.amazon.com/gp/aw/d/B00B0Z...110_SY165_QL70

http://www.amazon.com/gp/aw/d/B005X4...&pi=SX200_QL40

http://www.amazon.com/gp/aw/d/B00KZP...110_SY165_QL70

Last edited by akseminole; 09-18-2014 at 08:45 AM.
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  #8  
Old 09-18-2014, 08:00 AM
ga2500ev ga2500ev is offline
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Default Re: Street legal VW Sandrail dune buggy project. "Time will tell if it works"

For the speedometer I'm sure that nothing would be cheaper than an old cell phone with GPS and a speedometer app. Would'm even need cell service to use.

ga2500ev
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  #9  
Old 09-18-2014, 09:09 AM
akseminole akseminole is offline
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Default Re: Street legal VW Sandrail dune buggy project. "Time will tell if it works"

^Cheapest, most likely.
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  #10  
Old 09-21-2014, 09:07 AM
Jayls5 Jayls5 is offline
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Default Re: Street legal VW Sandrail dune buggy project. "Time will tell if it works"

Thanks for all of the suggestions so far!

Minor update, acquired a clutchless coupler and adapter plate to mount this thing. I still have to cut out my key to size. I might also try to bolt the coupler directly to the threaded center of my motor shaft. It might require a little turning on the lathe to fit a bolt in. It might not be necessary at all, since the key and 2 set screws seems more than enough to keep it in place. I'm also highly considering doing forced air via this bilge blower in the pic that pulls ~110w.

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