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  #1  
Old 08-24-2014, 09:59 AM
Stanjo58 Stanjo58 is offline
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Default Vender Recommendation

I think I have decided to EV the Spitfire. I would like to use the AC-50 motor type. Slight fly in ointment is that I'm kinda set on direct drive. Seems a little cloudy on if that motor will do it. Car should end up at or about it's original curb weight of 1700 lbs.

Of the many venders of the AC-50 kits do any stand out in price, service or general knowledge the the forum would recommend as I would like to begin communication.

Thanks all for any help for a newbie!
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Old 08-24-2014, 08:07 PM
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dougingraham dougingraham is offline
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Default Re: Vender Recommendation

Quote:
Originally Posted by Stanjo58 View Post
I think I have decided to EV the Spitfire. I would like to use the AC-50 motor type. Slight fly in ointment is that I'm kinda set on direct drive. Seems a little cloudy on if that motor will do it. Car should end up at or about it's original curb weight of 1700 lbs.
I have seen a couple of vehicles that were direct drive using an AC-50. You absolutely need it to be lightweight. This means modest range. And if you want highway speeds it will affect your acceleration adversely. The most difficult thing will be picking a workable final drive ratio that will give you the top end you want and acceptable acceleration.

Torque from 0 to 4000 rpm at 108 volts and 650 amps on the AC-50 averages about 112 ft-lb. If you want to be able to do up to 55 mph at full torque that means a final reduction ratio of around 5:1. With tires about a foot in radius this would give you 560 ft-lb at the face of the tire or about a 0.3 G acceleration up to 55 mph and then it would drop off pretty quickly. I would guess that you could still get to 65 mph and maybe even 70 eventually. The assumption is an operating weight of 1900 lbs. You won't be setting any drag records but you won't be the slowest vehicle on the road either. If you choose the 144 volt controller then the torque remains constant up to about 6000 rpm meaning you need a 7.5:1 final ratio to be equivalent speed wise. Torque at the face of the tire goes up to 600 ft-lb making this a little better choice. The torque also does not drop off quite so quickly between 6000 and the 8000 rpm redline.

I put the 144 volt numbers into my crude drag racing sim and it shows a 60' time of about 3.4 seconds at which point you are doing about 24 mph. It indicates a 0-60 time of about 8.7 seconds but this is pretty optimistic as the sim does not yet include Rolling Resistance or air drag. It puts your 1/8th mile time at 11.4 seconds and 72 mph. And continuing the trend it thinks your top speed will be 73 mph which is redline on the motor. It predicts a 17.5 second quarter mile. Again these are wildly optimistic. The only one I would think might be reasonable is the 60' time and speed. The tires I used in the sim are the ones on my RX-7 (185/70-R13) which are 23.2 inches in diameter. What are the tires on the Spit?

A car setup with one of these motors on direct drive will be slow off the line but perfectly capable of keeping up with traffic once you get up to speed.

Quote:
Originally Posted by Stanjo58 View Post
Of the many venders of the AC-50 kits do any stand out in price, service or general knowledge the the forum would recommend as I would like to begin communication.
Any of the sponsor vendors on the right of your screen would be a good place to start.
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Old 08-24-2014, 08:37 PM
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Default Re: Vender Recommendation

Quote:
Originally Posted by Stanjo58 View Post
I think I have decided to EV the Spitfire. I would like to use the AC-50 motor type. Slight fly in ointment is that I'm kinda set on direct drive. Seems a little cloudy on if that motor will do it. Car should end up at or about it's original curb weight of 1700 lbs.

Of the many venders of the AC-50 kits do any stand out in price, service or general knowledge the the forum would recommend as I would like to begin communication.

Thanks all for any help for a newbie!
If you insist on direct drive I'd have a look at the AC75 instead. Using the 650A controller you'd have around 170ish ft-lbs (184 peak). Assuming you have limited rear end choices 3.89 or 4.11 as the common Spitfire ratio's you'd have a top speed in the 60-70 range with good acceleration. It gives similar numbers to dougingraham's calculations but using the readily available rear end ratio's.
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Old 08-24-2014, 11:21 PM
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Default Re: Vender Recommendation

Hi Stan

If you want direct drive (I love it) you will probably have to use the older technology

DC - motors

These are cheap and give gobs of torque,

AC is the future - but at the moment its either expensive or wimpy or both
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Old 08-25-2014, 03:39 PM
Stanjo58 Stanjo58 is offline
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Wow, thanks for all the comments! Just what I needed to hear.

Lets see, questions first. 185/70 R14 is as big of tire that will fit the fenders and the Diff is a 389/1. I was thinking 144V and had given thought to the AC-75 but direct hook up to the Diff that motor crowds the frame and then there is the price tag. Not insurmountable but more work as I was planning a BMW style Guibo connector, seemed the easy way to provide a shock absorber and solve any alignment problems.

Sluggish acceleration was my greatest concern. I hung up on direct drive to ditch weight and the fact that Spit' trannys are not ummmm what is the right word, robust and they leak. Diff is not exactly bullet proof either. Ah, the British god bless them. BUT! She is light, areo and handles on rails and already deiced.

As for DC motors are they not RPM limited to the degree that anything close to highway speed is out of the question. Because of where we live the car must do 70 MPH. I suppose the design criteria should be 70 miles at 70 MPH. (I know tall order) or I could be dead wrong just getting my feet wet here. What would be the DC motor recommendation? DC would be nice because I might be able to use the old controller.

Thanks a million for everyone's help!
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Old 08-25-2014, 05:58 PM
Canadian Electric Vehicle Canadian Electric Vehicle is offline
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Default Re: Vender Recommendation

Our shop truck is a 2005 Ford Ranger.
It uses a 5 speed trans which was locked in second gear limiting speed to 45 MPH with an AC50 and performed quite well.
We had one of the first pre production AC75's and swapped it into the truck a couple of years ago.
Changed it to third gear and it would top out at about 60mph and good performance, not tire smoking but good.
Your Spit is a LOT lighter than a Ranger truck so the 144V AC50 should have no problem direct drive as long as your not loading it up with lead acid batteries or wanting tire smoking performance, that's AC35X2 Territory.
My first EV conversion was a 63 Spit and I used a Nissan trans for the reasons you stated.
I have had a few customers with English cars use Ranger or S-10 trans in order to use one of our off the shelf adapters.

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Old 08-25-2014, 06:33 PM
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Default Re: Vender Recommendation

Hi Stan

DC motors are limited by
Max rpm
Voltage

A 9 inch motor will do 6000rpm - easily
an 11 inch motor will do 4000rpm - easily and 5000rpm with an element of risk

You will need 144v - more would be better

My car has an 11 inch motor and a 4.1:1 diff will definitely do 70 mph

I would recommend a 9 inch motor and at least 500 amps

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Old 08-25-2014, 11:06 PM
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dougingraham dougingraham is offline
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Default Re: Vender Recommendation

Quote:
Originally Posted by Stanjo58 View Post
Lets see, questions first. 185/70 R14 is as big of tire that will fit the fenders and the Diff is a 389/1. I was thinking 144V and had given thought to the AC-75 but direct hook up to the Diff that motor crowds the frame and then there is the price tag. Not insurmountable but more work as I was planning a BMW style Guibo connector, seemed the easy way to provide a shock absorber and solve any alignment problems.
A 185/70 R14 has a diameter of 24.2 inches so torque at the face of the tire will be decreased by 12/12.1 which is essentially negligible.

WarP 9 at 1000 amps and 144 volts (unsagged) will deliver 266 ft-lb (my dyno run at EVCCon) up to about 4000 rpm. So the 3.89 final drive would give 1026 lbs at the face of the tire. Better than 1/2 G acceleration up to about 4000 rpm. Speed at 4000 rpm would be 74mph. Your top speed would probably be a little over 100 mph. A bit smaller tires would probably help you out by giving you more torque and with this setup you should not have any problem making your 70 mph highway speed.

Surprisingly my RX-7 has a final drive of 3.909 and with smaller diameter tires is not all that far off of what you are thinking about. However my car weighs 2600 lbs with me in it so if the spit ends up weighing 1900 lbs with you in it this would be a big difference. I would call the 4th gear performance from zero sluggish in my car and it just feels like the WarP 9 is working hard. But it does do it.

Quote:
Originally Posted by Stanjo58 View Post
Sluggish acceleration was my greatest concern. I hung up on direct drive to ditch weight and the fact that Spit' trannys are not ummmm what is the right word, robust and they leak. Diff is not exactly bullet proof either. Ah, the British god bless them. BUT! She is light, areo and handles on rails and already deiced.
What I would expect your direct drive performance to be is going to be like my third gear performance. I consider this acceptable on my car and is what I use around town all the time.

Probably the best place to put the motor would be in the transmission tunnel with a short drive shaft back to the diff. The diff is going to be fine for being directly coupled to an electric motor. You feed it a lot more torque with the ICE motor when you are in first gear than you will with a typical EV arrangement.

Quote:
Originally Posted by Stanjo58 View Post
As for DC motors are they not RPM limited to the degree that anything close to highway speed is out of the question. Because of where we live the car must do 70 MPH. I suppose the design criteria should be 70 miles at 70 MPH. (I know tall order) or I could be dead wrong just getting my feet wet here. What would be the DC motor recommendation? DC would be nice because I might be able to use the old controller.
DC motors are plenty capable of highway speeds. I would not expect a long life if you try to go long distances at highway speeds with a Brushed motor. There is too much heat to get rid of long term. If the car weighs 1900 lbs and you have get a mix of driving conditions you should see around 190 wh/mile. This means you need a minimum pack size of 13.3 kwh to make 70 miles. This is going to weigh something over 315 lbs unless you go with the CAM cells.
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  #9  
Old 08-26-2014, 04:23 PM
Stanjo58 Stanjo58 is offline
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Well what do ya know. I did figure something right. I had planned on a 14KW pack. E-mails I have received from AC motor venders seem reluctant to live without a transmission. One told me the AC 75 torque curve was all wrong.

I must say though that if I were in their business I would prefer selling tranny adaptor plates and such and no angry customers about poor acceleration. Not exactly sure what to think about all that.

I don't need tire smoking performance but I need to leave red lights without annoying people. I think I would prefer an AC motor due to less maintenance and the 70 MPH top end is a must for safety without killing the motor.

I guess I just haven't found the correct motor if there is one, very confusing.

Thank you all for trying to help!
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Old 08-26-2014, 04:48 PM
Canadian Electric Vehicle Canadian Electric Vehicle is offline
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Well what do ya know. I did figure something right. I had planned on a 14KW pack.
We have built quite a few Geo Metro's over the years (about 1900lbs) and in real world driving with hills, lights, wipers (it rains here) and heater running we see about 2ahr/km on a 96 volt pack or about 200wh/km or about 300wh/mile?
I always build for worst case consumption, nothing worst than getting left at the side of the road in a snow storm because you didn't factor in wipers and heater consumption.
Those of you in warmer climates don't need to worry about this but for a lot of us its critical.
Using my calculations you would only get about 50 miles on your 14kw pack.
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