# Connecting directly to the driveshaft?



## madderscience (Jun 28, 2008)

You don't say what kind of car you have, but given your battery size plans, direct drive is probably a bad idea. 55 T-145s is nearly 4000 pounds of weight which means the vehicle (gotta be a pickup or van) is likely to end up around 7000 pounds.

Unless you idea of a hill is significantly less serious than the seattle hills around here, you will need lower ratios to get going on the hills.

As an example, I leave my car (a 1985 toyota MR2 with 21 T-105s) in 2nd gear for all driving under 40mph, and it will get going on about a 15% grade from a dead stop in 2nd gear (but it doesn't like it). 2nd is an 8:1 ratio in my car and I have 22" diameter tires. My car weighs 3400lbs.

You are planning a vehicle with double the weight of mine and basically the same motor and controller and a gear ratio equivalent to about 4th gear in my car. Your tires would probably be larger further reduciing your effective gear ratio.

If you must go DD with a 7000lb vehicle, find the highest ratio diff you can get (like 6:1, ORV places sell stuff in that range for offroaders) and use a 11" warp for the torque (bonus, it comes with a driveshaft yoke), and a Z1K controller to get the amps you need for starting. 

YOu could also find a divorced transfer case like an NP205 to get you two speeds. Still no adapter plates needed. 

Still, I think the best plan is to find yourself a manual transmission and use that. (your mention of a flex plate makes me assume you have an automatic, bad idea: less efficient, harder to make work in an EV.)

Good luck.


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## TheSeeker (Mar 19, 2008)

55? that's a 330 volt system! 

The car is a 1985 3 series BMW. started off at about 2200# I was thinking more along the lines of 144v, but you seem to be implying that I'd need a LOT more juice than that to get the thing moving.


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## TX_Dj (Jul 25, 2008)

TheSeeker said:


> I can get !50 miles at 55 with Trojan T145s, a Curtis 1231C and a WarP9 motor


I think this sentence is where the discrepancy comes from. If read quickly, that could lead the reader to believe that you are planning 55 Trojan T145s 

Nonetheless, direct drive needs a lot more grunt to get moving, which means more amps from a dead stop, which means you're using an even faster Ah rate than someone with an equivalent setup who retains a transmission, which means the same pack will give you less range overall.

If you have an auto in the car, swap it for a manual. If a manual isn't available, pick another donor unless you want the hassle and inefficiency of converting an automatic, or have lots of money for better technology overall.


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## TheSeeker (Mar 19, 2008)

Sorry, that was supposed to be ~50 miles at 55 MPH with Trojan T145s. corrected.


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## madderscience (Jun 28, 2008)

Ah, OK. I was confused.

144v with T-145s is about 1700lbs of batteries.

The car will probably weigh a bit over 4000lbs fully built then.

Should be doable but you need a big amps controller and you still want to find the highest ratio diff you can get. That part is critical. Most cars have a 4.7:1 ratio available. I know the BMW 1600 I had a while back had a 4.7:1 ratio diff and something like that would be what you would want. From what I remember about beemers it is possible to swap diffs back and forth between many cars so you ought to be able to find a higher ratio diff somewhere and swap it in.

YOu might want to consider T-105s instead of T-145s. You will sacrifice some capacity but you will also lose 250 pounds (10lbs less per battery) with the same operating voltage. That means noticeably better performance. If you still want the same weight in batteries, add more T-105s (assuming they will fit) for higher voltage and better performance than a same-weight pack with T-145s.

Use a warp 9" motor and make sure it is tuned to handle the amps from the Z1K or bigger controller. 

Sigh.

I read things 10 times and still misread stuff.

Sorry


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## rankhornjp (Nov 26, 2007)

http://www.high-impact.net/transmission_and_gear/extreme_underdrive_divorced.htm

reduction gearbox made for 4x4s, available in a 2.7:1/1:1 and a 4:1/1:1 ratio. Shift on the fly, using planetary gears. 3.63*2.7=9.8:1 and 3.63*4=14.52:1

Kinda pricey ($1900-$2300)but it would be a good replacement for a transmission.


James


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## Tristar500 (Jul 9, 2008)

My TR7 is dirrect drive. I use two 7 inch motors, Works sweet! 

http://www.evalbum.com/preview.php?vid=1793


Lawrence Feir
*Innovation Robotics*


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## TheSeeker (Mar 19, 2008)

Hmm, siamese 7s... interesting idea. What kind of cooling (if any) does that need? What depth of discharge are you going to for your 25-30 miles?

I'd want a bit more range, so would it be better to go for 6v batteries at 72 or 96v (12/16 x 6v) or for a beefier 72v system with 2 strings (18 x 8v) ... *ponder*

You say "reverse via contactors" ... from what I've read reverse can be bad for series wound motors... are you running at neutral advance? or is there anything special about your setup that prevents arcing?


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## Tom Thomson (Jun 11, 2008)

My previous conversion ( Dodge Ram 50 pickup ) was direct drive and performance was ok but it only weighed 2000#. Reversing was accomplished with an Albright reversing contactor and I had no problems at all. That said, my current conversion ( 924 Porsche ) has the original transmission and so far I prefer shifting ( the motor seems to prefer it too ) .
tommyt


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## Toby B (Aug 10, 2008)

> I'm having considerable trouble trying to even get my transmission disconnected from the flex disk that its bolted to ...


The secret is to put a big hose clamp (or 2 shorter ones screwed together) around the disc (the 'guibo') and squeeze it as tightly as you can.
Then you usually need very thin walled sockets to get onto the nuts..

I'd leave the trans for a first- time heavy car.
Really, all most of us need are 2 well- chosen ratios, 
but that takes just a bit of engineering and luck-
and most ICE transmissions don't have the right ratios easily available.

hth,
t


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