Do I use the Clutch?

July 18, 2008
Let me talk about the motor/transmission adapter for a moment:  There is a lot of controversy in the industry about whether to use a clutch type or a clutchless type system.  As typically most driving is done in 2nd gear up to about 45 miles per hour, and 3rd gear above that, and there is no need to use a clutch to start up (the motor stops completely when the car does) many say the clutch is not necessary.  The extra weight of the flywheel and the clutch parts merely slow down the acceleration and reduce the efficiency of the vehicle.  They say that for the occasional shifting required it is easy to do without a clutch, you just pause a second or two and the transmission will easily go into the next gear.  Shifting between forward and reverse is always done at a full stop, so no clutch is needed there.

The proponents of the clutch system say that using no clutch will put an excessive strain on the transmission, and that the clutch provides added utility and safety as an additional way to disconnect the motor from the drive train.

I decided to use a clutch system for two reasons: 

First, I feel more comfortable having a clutch, as I have no experience yet with an electric vehicle.  I know the clutch system will work for me - a clutchless system would be an unknown.

Second, if I change my mind and decide to go to a direct connect system, it is easy to modify what I have to eliminate the flywheel and clutch pressure plate.  In place of the flywheel I would make an aluminum plate to which I would bolt the existing clutch plate.  The transmission shaft would fit into the splines normally and I would have a direct drive, clutchless system.  If I started with a clutchless system, there would be no way of adding a clutch.

For the time being, at least, I will have a clutch.

Assembling the Motor, Adapter, and Transmission
 

The adapter which mounts the flywheel is securely attached to the motor shaft using the taper bushing.  This shrinks onto the shaft as it is tightened, and makes a very secure attachment.

Here the bell housing, flywheel and the clutch assembly have been installed onto the motor.

The motor, adapter, and transmission are now assembled and ready for installation into the truck.

Here the motor and transmission are installed in the truck.  The front motor mount is the strap around the motor body supported by a pair of Chevy engine mounts.  The third mount is the standard one under the tail shaft of the transmission.  The large gold color bolt prevents rotation under high torque conditions.

Do I need the Engine Computer?

One of the concerns I have had is whether or not I need to keep the original engine computer.  I went through all the signals going into and out of the computer and decided the only ones performing functions I still need are the VSS (Vehicle Speed Sensor), which drives the speedometer, and the air conditioning controls.  I should be easily able to bypass the computer for the A/C, but I know nothing of the VSS.  Once I had the motor installed, and the back of the truck up on stands, I could run the motor, driving the rear wheels.  Of course I only drove it with 12 volts, but that was enough to get me to about 8 miles per hour in first gear.  As I was already overloading the 12 v. power supply, I decided not to try any higher gears.  A rough measurement showed the motor pulled about 100 amps initially, dropping to about 50 amps after getting to speed.  My power supply is good to about 40 amps, but seems to take the overload quite well for short periods.

Back to the VSS and the speedometer.  I attached pigtail test leads to the VSS signal from the transmission sensor into the computer, and to the lines that drive the speedometer head.  I was hoping that the computer only changed the wave shape, but not the frequency.
 

Here is my scope showing the sine wave output from the transmission speed sensor. The waveform really goes clear across the screen.  I just used too fast a shutter speed!

I set up my oscilloscope and first looked at the raw signal from the sensor to the computer.  It was a sine wave of about 15 v peak to peak, at about 294 HZ (at about 8 mph).  I then reconnected the scope to the output of the computer and saw a square wave, from 0 to 12 v at about 10.6 HZ.  So much for being the same frequency!  There is about a 27/1 ratio from input to output.  I'll keep the computer for the time being.

8/6/08
I placed an ad on Craigslist for my engine, radiator, exhaust system, fuel system, and all the other now-unneeded parts.  Within several hours I received a call from a man in Phoenix who said he would like it all!  I quoted him an extremely good price on everything, and he drove up here and bought it all.  I can now once again turn around in my garage!

Throttle Assembly Mounting

I decided to install the new throttle assembly next.  This is a dual Hall effect electronic throttle which interfaces with the speed controller I have on order.  I had no idea how much of a problem it would be to mount it properly with the pedal in the correct position.  It turned out to not be bad at all.  The original throttle was on a bracket mounted on three studs protruding through the firewall.  It turned out they were welded to a plate which was on the engine (now motor) side of the firewall with the studs extending through.  Positioning the new throttle, it appeared that one of the studs lined up exactly to keep the throttle in the same place as the original.  The new unit mounted on only two studs or bolts.

I removed all the original parts, fabricated a new doubler plate with two pieces of threaded rod threaded into tapped holes and locked with nuts on the back side.  I drilled a new hole in line with the 2nd mounting hole and put the new doubler studs through the firewall.  I mounted the new throttle on these studs.  I also bolted the backing plate to the firewall using one of the now unused holes.  Placing a rubber grommet in the hole where the throttle cable originally went through the firewall and feeding the electric cable through this hole, and plugging the connector into the new throttle completed this installation.
 
 

This is the new throttle backing plate.  The two studs are threaded rod screwed into tapped holes in the plate and locked with nuts on the back.

This shows the backing plate installed into the firewall.  The two studs extend through into the driver's compartment.

The finished throttle installation looks just like the original one.  The electrical interface is a connector at the very top-left corner of the assembly.

Initial Look at Instrumentation

I decided that since I now have the voltmeter and ammeter, I should look at how to mount these in the original display panel.  I started pulling panel after panel loose, and finally got to where I could remove the gage assembly.  I will eventually mount my gages here in place of the fuel, oil pressure, and temperature gages.  The 12 volt meter should still be useful.  I will also have to disconnect several of the indicator lights from the logic network in the gage display and run them out on separate wires.  That will come later when I have a delay in other areas.
 
 

I have pulled a number of panels out to gain access to the display panel.  It now removes by just disconnecting a connector on the top.

Determining the Battery Configuration

At this point I still do not know what battery configuration I will be using.  It's time to fix that!

I contacted my motor supplier with 4 possible battery configurations.  They offer a service to run your data through a program which predicts the performance of the finished vehicle.  By comparing my different possibilities, I can see just what the pros and cons of each configuration and then balance that with the final cost.  The possibilities I am considering are 2 120 volt systems using twenty 6 volt batteries of different capacities, and two 144 volt systems.  One of these uses 18 8 volt batteries and the other uses 24 smaller 6 volt batteries.

After carefully reviewing the results of these calculations, I eliminated the two 144 volt systems.  The 18 8 volt batteries just had too little capacity for use in hilly Prescott, and the 24 battery system would be a nightmare trying to place all the batteries.

Battery Boxes

I have tentatively selected the 120 volt system using the largest (and most expensive) batteries, but it has the best performance of the 4 systems.  Using either this system, or the one with lower capacity batteries makes no difference in the battery boxes, as the two batteries are the same size except for about 1/4 inch of height difference.  My plan shows two 4 battery boxes in front of the rear axle, and a 10 battery box behind the axle.  There will also be 2 batteries under the hood.

Now it's time to start getting my hands dirty and build some battery boxes!  I have done detailed layouts of my battery boxes and now know exactly what size and shape to build.  The boxes will be frames of 1 1/2 inch angle steel.  These will be lined with plywood on the bottoms and the sides.  I will use thin spacers between the batteries at the base to keep them about 1/4 inch apart.  This allows for the normal swelling of the battery sides and prevents them from becoming so tight they cannot be removed and replaced.

I am now about two months into this project (about 1 month since I started pulling parts from the car).

I cut all the angle pieces for the bases of the two "front of the axle" battery boxes and welded them together using my new MIG welder.  Boy is it easier to get a decent weld with this machine!  I am not saying that my welds are particularly pretty, but they sure are much better than I ever was able to do using my "stick"  arc welder.  I still have the problem of not always being able to see where I am welding as my bead continues.  Some of my welds wander off to the side and have to be redone in the correct location.  All in all, I am very happy how it is going.
 
 

Here is the start of my battery boxes.  Each of these frames will be suspended in front of the rear axle along each side the drive shaft.  Each will hold 4 batteries, and will have many appendages before completion.

Before getting too far into making the battery boxes, I decided to make a dummy battery of cardboard.  It is exactly the same size as the batteries I will be using.

Frame Clearance

One problem I encountered was trying to avoid interference with the bottom of a cross member over the batteries.  The bottom curved downward quite a ways from the frame, and would have required the battery boxes to be located lower than I wanted, or so far toward the center of the truck that other interferences occurred.  My solution was to modify the cross member.  I torch cut a fairly large bottom section of the cross member and welded on a reinforcing plate.  The net result was much more headroom extending within a couple inches of the frame.
 

The bottom of the cross member has been cut away.  The original curve continued down at about a 45 degree angle from the end of the cut near the center of the picture.  It then curved toward the frame and connected to the bottom rail.  I left a little of the bottom still riveted to the frame.  That is what the bottom of my stiffener plate is welded to.

Front Battery Box Supports

I used 1 1/2 square tubing to support the battery boxes.  I have one piece going across the frame at the front of the battery boxes and another at the rear.  The front one is welded to a pair of brackets which then bolt to two of the bed supporting brackets.  The rear rail merely bolts through the top web of the frame.  Where ever I bolt through the square tubing I either weld a pipe into the tubing which the bolt passes through, or I use a 1/4 inch doubler the full width of the tubing.  Each of these methods ensures that the bolt will not collapse the tubing.
 

The front bar is welded to a pair of brackets bolted to a bed support bracket.

The rear bar is bolted to the top rail of the frame.

Beefing up Box Supports

8/22/08
As originally designed, I was going to use just 1 1/2 inch square tubing, as many other EV conversions have used.  I did some stress analysis on various members, including these cross members.  As they were planned, I have a static stress safety factor of about 5 to 1.  This is to the yield point; to the ultimate strength the safety factor would be about double that.   I would like to increase this for safety in an accident.  I did a number of stress analysis of different scenarios.  I looked at using a heavier wall tubing, doubling up on the tubes and adding additional material to what is there.

I decided to add a 1/8 thick strip, welded to the top and bottom of the front cross member.  This will increase the safety factor to over 10 to 1.  This is the best method for beefing up this member as the bolts holding the battery box run through the square tubing vertically, limiting what I can do above or below the bar.. 

For the other cross members the racks bolt through horizontally.  This allows me to weld a spacer to the bottom center of the tubing, then run a strip along the length, welded to one end, passing over the spacer, and then on to the other end.  This will add significantly to the stiffness and the load carrying capacity of the beam.  A very simplistic, conservative check shows a yield safety factor of over 14 to 1.

I stiffened the battery boxes considerably by welding diagonal strips on both ends, and along the length from the center up to each end hangar.  This has always been in my plans, and keeps the stress to about 1/18 th of the yield stress.

It looks precarious to mount the front rack rear cross members with only one 3/8 bolt at each end, but the stress here is only about 1/89 th of the yield.
 
 

Here are the front box cross members.  The front one has 1/8 in. plates welded top and bottom. The rear one has a truss arrangement on the bottom.

The cross member mounts for the rear battery boxes will not require any stiffening, as the front will be what is left of the factory cross member, and is easily strong enough.  The rear mounts to another 1 1/2 inch square tube.  The stresses are much lower in this member, as all the weight is hung from an area very near the supported end.  No stiffening will be added to this member.

After completing the supporting cross members for the front boxes, I completed the box frames by adding angles in the corners to use in hanging the boxes, as well as diagonal stiffeners and hangars to support the middle of the longer pieces.
 

The frames for the front battery boxes are complete, ready to be lined with the wooden box members.

Lining the Battery Boxes

I then cut 3/8 plywood to fit the bottom and sides of the boxes.  After painting these, I installed them.  This completed the front battery boxes and I installed them in the truck.
 

Here the front battery boxes are installed complete with the wooden liners.

The same two boxes viewed from the side.  Each box will hold 4 batteries.

Cross member Modifications

I then started looking in detail at the rear battery box.  This will hold a total of 10 batteries behind the rear axle.  The rear factory cross member is a massive thing.  The front half mounts the upper end of the rear shock absorbers and has brackets to prevent twisting of the frame rails.  The rear half primarily mounts the cable mechanism that holds the spare tire up tight under this cross member.  I decided to remove the rear half in the interest of providing much easier access to the batteries.

I torch cut the rear half out and finished the cut areas with my angle grinder.  There was a flange on the rear side which presented a potential interference when changing batteries.  I heated this area with a torch and hammered it straight down.  The location of the rear side of the remaining cross member is located within 1/8 inch of the front of the main portion of the rear battery box.  This is ideal for mounting the box.  I added a rear cross member at the extreme rear end of the frame rails to support the back end of the box.  This member will also support the hinges that will allow the bed to be raised somewhat like a dump truck, to allow battery access..
 

This is the factory installed rear cross member.  Note the front half mounts the shock absorbers and the rear half held the spare tire tight to the bottom side held by a crank-up winch.

I have cut out the rear half of the cross member to allow easy access to the batteries which will be below.

Rear Battery Box

I then concentrated on building the rear battery box.  It is also a weldment made mostly from 1 1/2 inch angle steel.  I reinforced it using 1 inch bar stock.  There were several challenges in mounting so that I could still install or remove batteries.  The rear 4 batteries extend slightly under the rear cross member.  This means I need clear vertical access to the front batteries.  I can install the rear ones first by sliding them back under the cross member and letting them settle into the rack.  The front batteries then simply drop into place.

The small 2 battery rack in the front was a little more difficult.  These batteries rest about 1/3 of the way under the factory cross member.  To change these batteries, I needed to make the front of the box easily removable as well as providing structural strength for safety.  I solved this problem by cutting the corner rails so the space between them was at least as wide as the two batteries.  I then made it so the wood panel would drop into slots and rest in the correct place.  To the top of this panel I fastened an angle which drops over the corner rails.  The end result is a panel which simply drops into place, with a top structure that is very strong for loads toward the front. 
 

Here is the finished framework for the rear battery box.  8 batteries are held by the large portion to the left, and an additional 2 batteries by the small box to the right. All these batteries are mounted using the 4 long upright angles on the main rack.

The rear battery box is now completed and mounted in the truck.  Note the easy access to the 8 batteries in the rear after removing the section of the cross member.

It looks very intimidating having so many batteries located so far to the rear.  I did a center-of-gravity check, and weight of the full compliment of batteries will be centered about 1 foot ahead of the rear axle.  This is just about where the truck was designed to carry its payload.
 

The two batteries on the front of the rack mount partially under the cross member. To install or remove the batteries the front wall lifts out so the batteries can be removed through the front.

The lift out front wall is topped by a length of angle for structural integrity.  It is notched to drop over the corner angles.  Also note that the corner angles were machined to provide clearance for installing and removing the batteries.

This is the progress through the end of August 2008
 

To go to the next section, click here.