DIY Electric Car Forums banner

1 - 16 of 16 Posts

·
Registered
Joined
·
14 Posts
Discussion Starter #1
I am a keen amateur in Christchurch New Zealand and have a donor Nissan Sunny (1986) which I intend to convert to run on batteries.
I have purchased a 48v (nominally 11kw) Hitachi forklift motor from a wrecked Nissan forklift, it weighs 85kg and spins freely when hooked up to a 12v car battery.
I intend to import Chevrolet volt batteries from the states for a 155 volt 40Ah pack and put that through a Paul and Sabrina kitset controller (144v, 500A) I will put together myself.
So far I haven't worked out the best way to manage the charging and management of the battery pack, the 155v to 12v system, the throttle assembly, the vacuum brake and reservoir, battery position or racking or the adapter plate and coupling from the gearbox to the electric motor.
Any advice or suggestions from the community would be appreciated.
 

·
Administrator
Joined
·
6,087 Posts
Hi
How much of a cheepskate are you?

I modified a Subaru TPS (throttle position sensor) for my throttle - still using it!

When I was 144v I used a simple charger using a 110v transformer, bridge rectifier, some capacitors a JLD404 and a relay to make a simple charger

Along with a "Batt Bridge" to warn me if something was going wrong with my cells

I'm currently using a 14v laptop power supply as my DC-DC
 

·
Registered
Joined
·
14 Posts
Discussion Starter #3
I have taken the petrol motor out and split the gearbox away, the question now is, do I need a clutch? the weight of the flywheel seems a bit redundant but will I be able to change gear while moving if take the center spline out of the clutch and attach use it to directly link the electric motor to the gearbox?
 

Attachments

·
Administrator
Joined
·
6,087 Posts
Clutchless
That depends on the gearbox

When you change gear the syncro cones change the speed of the gearbox input shaft so that the drive dogs can engage

With the clutch disengaged they only have to change the speed of the input shaft and the clutch disc
With the clutch engaged they have to change the speed of the engine and flywheel as well

The largest inertia by far is the flywheel

With an EV you will have to change the speed of the motor and your coupling - this is a LOT less than the engine and flywheel but more than the clutch disc

Can you borrow another Sunny? and just see what it is like changing gear without the clutch?
If it is possible but difficult then running your EV clutchless will be easy )and nothing like as difficult)

Also you will not have to change very often - I am direct drive - the same as driving in 4th with most gearboxes
If you have a 500 amp 144v controller you will be able to stick it in 4th and accelerate faster than the standard Sunny up about 110 kph
 

·
Registered
Joined
·
4,587 Posts
I have taken the petrol motor out and split the gearbox away, the question now is, do I need a clutch? the weight of the flywheel seems a bit redundant but will I be able to change gear while moving if take the center spline out of the clutch and attach use it to directly link the electric motor to the gearbox?
Yes, in an electric motor installation the flywheel's mass is superfluous; the only reason it is used is as one of the faces for the clutch (the counterpart to the pressure plate). Flywheels can usually be substantially lightened - even when used with an engine in racing applications - and with the starter ring gear not needed and no inertia required to smooth out power pulses (or desired), lightening for an electric car could be radical. I had half the mass of our Honda's flywheel machined off for competition use with the stock engine, and one could go further with an EV. Despite this, I see a lot of stock-looking flywheels in build threads. :confused:

Flywheel inertia means energy stored as rotational motion of the flywheel, instead of forward motion of the vehicle. While not a big factor in a typical EV project, it is best minimized. Some EV design discussions consider the effect of energy stored by motor inertia on performance and driving feel (and higher inertial energy storage is always bad); flywheels substantially affect that inertia.

Clutchless
That depends on the gearbox

When you change gear the syncro cones change the speed of the gearbox input shaft so that the drive dogs can engage

With the clutch disengaged they only have to change the speed of the input shaft and the clutch disc
With the clutch engaged they have to change the speed of the engine and flywheel as well

The largest inertia by far is the flywheel

With an EV you will have to change the speed of the motor and your coupling - this is a LOT less than the engine and flywheel but more than the clutch disc
I think this is a good summary. Of course shifting with the clutch engaged with an engine is not normal, and is affected by engine power and drag... which is a different situation than with an electric motor.

The real alternatives are:
  1. with flywheel and clutch, disengaging clutch to shift: shifts like the original car (assuming that in the original car you don't use an advanced technique such as double-declutching)
  2. without flywheel or clutch: shifts like shifting the original car using the clutch (no use of power to affect shifting), but with motor inertia making shifts much more difficult (vastly more inertia to overcome). Downshifts are especially difficult because the motor must be sped up by the synchro, but even an upshift is slow because the motor coasts relatively freely compared to an engine, and the synchro much slow it down.
The rotational inertia of some electric motors is very high, particularly the larger-diameter, higher-torque, lower-speed designs. Others are much lower. Flywheel inertia varies, too, although any engine with few cylinders will have high inertia (an 8-cylinder is usable with no flywheel, but a 4-cylinder absolutely needs substantial inertia). Motor specs (for serious modern EV motors, not so much for the updated-forklift brushed DC units) often state rotor inertia; engine specs don't but a rough inertia value can be calculated from diameter and thickness. So I don't know if "the largest inertia by far is the flywheel", but maybe it doesn't matter much...
 

·
Registered
Joined
·
14 Posts
Discussion Starter #6 (Edited)
Thanks Duncan and Brian, My engineer brother is going to have a look at it and see what he can do tomorrow, the easiest thing to do would be to mill out the current spline from the forklift coupler and weld or otherwise attach the female spline from the center of the clutch. I have read that a lot of people end up leaving their car in 4th gear and just relying on amps and torque to get moving, the car will mostly be used at city speeds around Christchurch.
 

·
Administrator
Joined
·
6,087 Posts
I don't know if "the largest inertia by far is the flywheel

But I DO know - I have designed drivelines for engine test systems used all round the world (not in NZ!)

The rotational inertia of the flywheel on something like the Sunny will be a factor of 10 larger that the rotational inertia of all of the other engine bits put together!

Going back into the depths of time the old Ford gearbox would have no problems at all shifting without a clutch - but the BMC gearboxes would be a bit more of a problem

Now is the Sunny gearbox a nice robust changer like the Ford?
Or is it a more marginal shifter like the Mini?

Besides for a Sunny with an 11 inch motor you really won't need the gearbox - My car weighs about the same - but I have 55% of the weight on the driven wheels and a bit more grip than the Sunny
With 500 amps the Sunny would be able to chirp the FRONT tires in top gear

As it is I drive the Device on the road with the current limited to 570 amps - it is plenty fast enough to leave almost anything in the dust
1200 amps is a bit scary

In the Sunny the only reason to use a lower gear will be if you want to smoke the tires
 

·
Registered
Joined
·
14 Posts
Discussion Starter #8
The car will probably end up being used by my 16 year old son so the smoking of tires is almost a dead cert. I think the government calls it 'sustained loss of traction' in a frowny way.
 

·
Registered
Joined
·
4,587 Posts
I don't know if "the largest inertia by far is the flywheel

But I DO know - I have designed drivelines for engine test systems used all round the world (not in NZ!)

The rotational inertia of the flywheel on something like the Sunny will be a factor of 10 larger that the rotational inertia of all of the other engine bits put together!
Yes, of course - the flywheel exists to add inertia; I can certainly accept that it has a far greater moment of inertia than the other engine bits. I only meant that the inertia of the flywheel might not be so much higher than that of the electric motor... which is why I discussed rotor inertia, and not the inertia of engine parts.
 

·
Registered
Joined
·
4,587 Posts
With the right electric motor (is the 11 kW Hitachi a big 11-inch motor?) the transmission would not be needed for gearing...

But this a front-wheel-drive Sunny, and that transmission is a transverse transaxle, right? If the transaxle is not used, in a car without a separate final drive unit (differential), you would need something else to provide reduction gearing and a differential. Although hauling around a 4-speed or 5-speed (plus reverse) transmission seems redundant, it might not be bad compared to buying a specialty EV gearbox with differential, and equipping the motor controls for reverse.

Another alternative (without a multi-speed transmission) would be to convert to rear-wheel-drive; apparently some variants of this model were all-wheel drive, so it should be possible. The motor would be entirely in the engine compartment (there's no transmission tunnel, unless you want to build one), and you would need a suitable final drive (diff) and rear suspension bits compatible with being driven. It would likely be easier and cheaper to just start with a more suitable car. ;)

If you end up using the transmission but you do not need to shift it, you could go without a clutch: if you do want to use a different gear, even if you need to stop to shift comfortably you can get that alternative engine speed range. You could also shift for reverse, rather than adding a reversing contactor and running the motor in reverse.
 

·
Registered
Joined
·
14 Posts
Discussion Starter #11
So, the adapter plate is half made, I whittled away at a 12mm plate with my angle grinder and marked through with a home made punch to get the bolts all lined up for the gear box face of the plate, now I need to get a coupler machined which will pass through the plate to from the keyed shaft of the motor to the splined shaft of the gear box. My plan to get them to line up is to set up the gear box vertically then sit the coupler on the spline, the adapter plate bolted down with a hole large enough for the coupler to pass through on the gear box, a ring of the right size for the female register on the electric motor placed loosely on the adapter plate then the motor sitting on coupler and resting on the plate. if I run the motor up to 12v speed will it center itself on the plate enough for me to mark the correct position for the register ring?
any advice on lining it all up much appreciated.
 

Attachments

·
Registered
Joined
·
14 Posts
Discussion Starter #12
P&S 500 Amp 144V controller has arrived as a kit set, time to brush up on soldering skills, haven't soldered for 30 years but have YouTube, will travel!
 

·
Administrator
Joined
·
6,087 Posts
What I did wrong!
With the big joints either use a non corrosive flux or be very careful about cleaning afterwards
Don't leave the unit uncovered in a dirty and dusty shed for a year

Other than that it's easy peasy - the instructions are really good
 

·
Registered
Joined
·
14 Posts
Discussion Starter #14
Adapter plate and coupling all put together, I am yet to weld the register ring into place but it runs smoothly at 12V.
 

Attachments

·
Registered
Joined
·
14 Posts
Discussion Starter #16
Motor mounts fabricated to attach to the same flexible suspension points as the old ICE. many cut off discs later...
 

Attachments

1 - 16 of 16 Posts
Top