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Discussion Starter #1 (Edited)
I am going to build an electric jr. dragster for my daughter who is 10 years old.Last year was her first year racing with a stock 5 hp Briggs with a best run of 15.77 at 40 mph in the 8 th mile.We would like to run in the 10's to 60 mph(she wants to go faster),the car weighs 285 lbs without the driver,I have not yet pulled out the Briggs -thinking it will weigh 240 with out the engine-we must stay under 400 lbs.There is more info at Nedra.com. Now for a newbie question-in knowing weight will be an issue can i get power out of a 24/36volt or 48 or do I need 72. There are some Mars motor on Ebay with controller for under $1000.00-good buy???Do I need a progammable controller? How many runs do you think we would get out of batteries before re-charge?I think I will use a DC motor.I would like to do this for around $1500-$2000 if possible.Will post some pics asap.Thanks for any advice.I own a bodyshop and have a friend who is a machinist and another who is an electrician so we can fabricate most of the parts if needed. Please give me your ideas on motor size,controller and battery.
Thank you!
 

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I am going to build an electric jr. dragster for my daughter....... Please give me your ideas on motor size,controller and battery.
Hi jr dr,

You might be able to find some example systems and build info searching in the bikes forum here. It seems like a lot of kart builds end up there as well. Here is a parts list for a kart kit (just for example). http://store.kta-ev.com/Go Kart Package (Basic).pdf

I personally would not use a PM motor (like the Mars) (and please call the electric motor a motor, not an engine). The Mars motor may be a good product, but I have seen too many PM motor parts laying on the drag strip and race track to recommend them. Stick with a series wound DC motor for great starting torque and durability. I think you should look at the 6.6 inch diameter motor. A bit heavier, but commonly available, and can provide good performance at low voltage to start and take increased voltage system as you upgrade.

With that in mind, you may wish to find a controller which will accommodate a wide range in battery voltage. WRT the batteries, this application requires power more than a large energy stored. Small Ampere hour (Ah) AGM Pb-Acid 12V batteries will work and not cost an arm & leg. Hawkers or Genesis brand are good. Lithium would be best, high C rate jobs, like A123 or Headway. Maybe even rob some Dewalt tools. You can get into the info forum here and read about energy, watt hours and Ah and such and figure out the number of runs per charge. Most such racers charger inbetween passes. You get the most power from a freshly charged and warm battery.

I think you will benefit from starting modest and working your way up in performance, meaning system voltage and power. Your mistakes will be less costly and you'll get it on the track sooner :)

Good luck.

major
 

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Discussion Starter #4
ev drives has a d&d es-10e-33 motor, 500 amp controller 36- 48 volt kit for$ 1091 its kit #5. Kit 9 has a d&d es-15-6 motor 450 amp controller 72 volt kit for $1293.with kit would you recommend to get the jr in the 10s in the 1/8 mile?? could you run the #5 kit at 48 volts then later run it at 72,or would it fry the controller?thanks for your ideas.
 

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Where you located ?? There are 2 FREE motors listed in the Classifieds, if YOU or someone you know, could pick them up. See Forklift motors, in Classifieds.
 
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Convert your photos to .jpg format if they are not yet and be sure they are not huge. 100k or so should be just fine. Much larger the server balks. No need to clog up the server with photos that are too large. Use your camera to get nice photos then reduce them in size. Then try again.

Pete :)
 

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Discussion Starter #9
does anyone know the weight of alltrax axe 7245 controller?? The d&d weighs 62 pounds,i found 12 volt 22amp hr batteries that weigh 13 pounds each about $60.00 each .car weighs 225 batteries 6 x 13= 78 d&d 62 ,so im at 365 pounds so far have to stay under 400. so will the controller,wiring ,solenoid weigh less than 35 pounds or do i have to lighten the car some how. thanks
 

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does anyone know the weight of alltrax axe 7245 controller?? The d&d weighs 62 pounds,i found 12 volt 22amp hr batteries that weigh 13 pounds each about $60.00 each .car weighs 225 batteries 6 x 13= 78 d&d 62 ,so im at 365 pounds so far have to stay under 400. so will the controller,wiring ,solenoid weigh less than 35 pounds or do i have to lighten the car some how. thanks
Go to the Alltrax site. If the info you need is not on their pages go to to the "Contact Us" page. They answer promptly.

http://www.alltraxinc.com/

Depending on length and guage of cable you are going to be close on the weight.

I have been running a small pulling tractor. Weight was/is a problem for us as well. Finally went to Headway batteries. We now have a (Edit change this to 99 pound from 65) pound battery that can produce over 100 (EDIT change this to hp from kW) for over 30 seconds. Check with some of the others like Yabert that have gone this route. Slightly:eek: more expensive then the lead you are looking at, but you will probably end up there anyway.

Jim
 

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Finally went to Headway batteries. We now have a 65 pound battery that can produce over 100kW for over 30 seconds. Check with some of the others like Yabert that have gone this route.
The Headway are rated 909w/Kg (10 Ah) or 1500w/Kg (8 Ah).... so the max power you can produce with 65 lbs of cells will be : 65 / 2.2 = 29.5 x 1.5 = 44 Kw

But 44 Kw is 310 lbs-pi of torque at 1000 rpm or 62 lbs-po of torque at 5000 rpm.

To Jr, the D&D is a great motor, so start with 5 or 6 lead batteries and later if you decide to go with lithium your motor will be good enough...
 

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The Headway are rated 909w/Kg (10 Ah) or 1500w/Kg (8 Ah).... so the max power you can produce with 65 lbs of cells will be : 65 / 2.2 = 29.5 x 1.5 = 44 Kw

But 44 Kw is 310 lbs-pi of torque at 1000 rpm or 62 lbs-po of torque at 5000 rpm.

To Jr, the D&D is a great motor, so start with 5 or 6 lead batteries and later if you decide to go with lithium your motor will be good enough...

I'm not all that good with math, and those of you out there that know this stuff better then me please point out where I'm wrong

The 38120P battery is rated at 8 ah and 25C for at least 30 seconds. That equals 200 amps. I'm hoping that voltage drop at 25 C in a 50S/3P battery will not exceed 2.75 to 2.5 volts per cell. (Still waiting for the batteries to arrive so I can test this volts per cell premise)

So here is what I came up with

2.5 VPC under 200 amp load times 50 batteries per series string equals 125 volts.
3 parallel strings at 200 amps per string equals 600 amps total.
600 amps times 125 volts equals 75 kW battery output for about 30 seconds.
75 kW equals approx 100 horse power.
150 batteries at 300 grams per cell (I goofed here:eek::eek:) is 45 kg equals 99 pounds.

At approx 100 lbs of battery your math and mine are not too far apart.

Would you please post the formula that you are using to convert kW into torque. It would be a big help.

I also went back and edied my original post.

Thanks,
Jim
 

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Hi

Kw = hp x 0.746 or W = hp x 746

And HP = (Torque x RPM) / 5252.

So 75Kw = 100 hp and 100 hp @ 2500 rpm = (100 x 5252) / 2500 = 210 lbs-pi
If you start from other side, a big 11" motor give 300 lbs-pi of torque @ 3000 rpm, that give 171 hp ((300 x 3000) / 5252).


When you will got your cells please give the result... I'm interested to know the internal resistance difference between Headway 10Ah and 8Ah cells!
 

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Discussion Starter #14
i will go with lead to start with to keep costs down.How would you recommend i buy my kit from ??? ev drives?? or from d&d ?? or any where else? i have read some horror stories on this forum and dont whant to get ripped off. im going to order one in the new year.i emailed alltrax for the weight of cont.
 

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jr dragster,

I bought my ES15-6 and Alltrax 7245 from D&D Motors.

D&D is an Alltrax dealer. They gave me a fair price and good service.

You might shop and get a motor or a Alltrax 7245 on eBay for a better price, but they don't come up often. I've also seen used, prices vary.

I want to mention that there are other equivalent name brand motors out there as well. ADC, Netgain, Warp and others

If you buy a new motor, plan on spending a lot of time running the motor on 12 volts to seat the brushes. I have run the motor I have for over 6 hours and it just keeps on getting better the more I run it.

Before you read below get used to the fact that good batteries cost a lot and cheap batteries cost more.

If you are going to go with lead I recommend 16 ah Hawker (Enersys) Oddsey batteries, you will probably pay over $100.00 each. They are not cheap but you get what you pay for. They weigh 13 pounds apiece and are about the size of a motorcycle battery. You won't find many, if any, other batteries that will give the kW they will. Look up the specs on the OEM site. you will be imppresed.

You can probably draw twice the amps from the Hawkers, while still maintaining good voltage, then you can from the cheaper lead batteries.

Last gasp on the Headways.

Yabert has had a set of Headways in service for a while in his bike. He might have a bit of info to throw in here as well. So might Frodus.

I went through 2 years of pulling with lead, and that experience tells me that high output lithiums are the way to go. At the Power range you need the price difference isn't that bad.

A 72 volt Headway system would be minimum of 20 batteries. You can pull 200 amps (25C) from a single string of 38120P batteries for around 30 seconds and expect it to sag to 50 or so volts at that load.

At the $19.00 each price that I paid (you might do better) thats $380.00 for a single string and a double string of 40 would be $760.00.

A 6 battery set of Hawkers would cost a minimum of $600.00.

A double string of 40 Headways weigh 12 kg 26.5 pounds. Six Hawkers weigh 78 pounds.

My 72 volt Hawker pack saged to around 40 volts when I pulled 400 amps. The double string of Headway's (According to Headway) should hold to about 50 volts at 400 amps. As soon as we get our batteries we will put them through some tests to see how they will hold up.

Hope he above helps you decide.

Jim
 

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i will go with lead to start with to keep costs down.How would you recommend i buy my kit from ??? ev drives?? or from d&d ?? or any where else? i have read some horror stories on this forum and dont whant to get ripped off. im going to order one in the new year.i emailed alltrax for the weight of cont.
Lead is the easiest way to learn.... no complex charger and balancing. But it's a fact, many cheap batteries come more costly than few good Headway.

Pay attention to the real price.... that including shipping, custom and taxes!

Watch your PM.
 

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Discussion Starter #17
i found a d&d model 170-501-001a 48 v for 250 +shipping do you think it would have the power i need to move the 400 pound dragster fast enough? it rated at 13hp is that peak power? what controller would you recomend for this motor.also looking at an advaced dc motor lighter than than the 15-6 d&d by 25 pounds ,but more money. to many decions to make LOL
 

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i found a d&d model 170-501-001a 48 v for 250 +shipping do you think it would have the power i need to move the 400 pound dragster fast enough? it rated at 13hp is that peak power? what controller would you recomend for this motor.also looking at an advaced dc motor lighter than than the 15-6 d&d by 25 pounds ,but more money. to many decions to make LOL
That motor is a made to be used on a golf cart axle and does not have a front bearing and DE cover and has a female output connection.

I'm afraid it is a very poor choice unless you have access to machine shop equipment.

Probably not a good first time, starting out motor (ask me about the door stop I bought).

I would need to look up the model number of the Advanced DC motor to tell you if it would be good. But a lighter weight then an ES 15 may mean a smaller diameter motor. Get pictures and specs and post them. Many people on the forum will help out.

D&D has a series of motors that start out with the ID code of ES. Like ES 15 and ES 31, those would be good.

Don't buy until you ask. I didn't and paid the price of an unusable motor for my task.

If price is important look for take out and reman lift truck (Hi-Lo) motors. Read through the the Sticky posts about chooseing a good Hi Lo motor in the Motor forum. It's a long read but invaluable.

Hope this helps.
Jim
 

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Discussion Starter #20
motor??????????????? amd a000-4009 at kta services for $605 ,50 pounds .or D&D es-15-6, $669 at ev drives 62 pounds with one would you guys recommend?????price is so close that ethier way, 12 pounds in weight is more important .give more your ideas thanks
 
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