Wednesday, September 23, 2009

Mounting the motor-transmission assy, Part 2

Completing the motor-mount and installing it took a lot longer than I expected. More than 4 hours last night, but it's done and it seems to work. The culprit was the bracket to hold the driveshaft support. Here's a picture of the mount as of 2 days ago.

The two studs pointing toward the camera were supposed to mate with the driveshaft support bracket. In order to make it easier to attach the bracket we welded the bolts to this mount. Unfortunately, with the driveshaft installed there wasn't enough clearance to swing the bracket into place. So, I had to grind off the bolts. Even with loose bolts, there was still not enough clearance. Besides with loose bolts it was going to be difficult to align the driveshaft properly.

That left only one other option: weld nuts in place on the motor mount. This will allow the bracket to be swung in place and still align the bracket properly. So, we installed the mount onto the motor, pushed the driveshaft into the transmission, and attached the driveshaft support using some short bolts (3/8" x 1" long).

Two problems arose:
1) Somehow the entire driveshaft/mount assembly needs to be taken off the motor so the nuts can be welded in place.
2) The driveshaft support bracket, even though it looks beefy enough, actually flexes quite a bit when lateral force is applied.

For #1, our first thought was to slide the bracket off the mounting grooves on the motor, which will also pull the driveshaft out of the transmission at the same time. That didn't pan out - the bolt heads are so snug in the grooves that they don't really slide. So we ended up disconnecting the transmission from the motor (again) to free the driveshaft. Once they were separated, we could take the mount off with the driveshaft attached.

To solve #2, we added a gusset to the bracket. The freshly painted part of the mount in this picture is the gusset. You can see the newly-welded nuts on there, too.

Here are a couple of pictures of the finished mount and motor installed, with driveshafts intact. Finally!

As you can see by these pictures, the driveshaft bracket can actually be attached in 3 places. We chose to ignore the top one and are only using the middle 2. That top bolt hole was actually in a different plane than the middle 2, so it had to be ground away so that it wouldn't interfere with the motor.

Lower Transmission Mount
This was quite simple. A block of aluminum with two tabbed bolt holes in the top which mate up with the transmission and a single bolt through the center pointing straight down which locates the mount through a hole in the cradle. This is a picture of it before the driveshaft was reinstalled.

Upper Transmission Mount
This is the main torque rod for the transmission. Not yet finished, the plan is to use a piece of angle, some bar stock, and a couple of spacers. More on that later.

Monday, September 21, 2009

Mounting the motor-transmission assembly, Part 1

Now that the motor orientation is set, the next step is to design the mounts that will keep it in the right place. I'm trying to do a better job with pictures. Hopefully I didn't go overboard.

Rubber or solid mounts?

Most EV converters use the rubber engine and transmission mounts. Since I won't have to deal with the vibrations of an ICE and since the AC24LS doesn't have the torque of the ICE, I've decided to mount the motor-transmission solid to the frame. If something bad happens, or the drivetrain sounds bad, I should be able to convert it back to the rubber mounts.

Motor mount

Since the motor orientation is such that the mounting face is in the down position, it would be unwieldy to use the upper engine mount. Instead, the plan was to mount the motor to the engine cradle, in approximately the same location as the original lower engine mount. The design of that mount was done in a step-wise fashion.

Step 1: Attach angle-iron brackets to the motor mounting grooves. Basically, cut 12" pieces of angle (1.5" x 1.5" x .125" thick) and drill a couple of .407" holes (clearance for the M10 bolts which fit in the grooves) in each one. Once attached to the motor it looked like this.

Step 2: Place a piece of angle perpendicular to the two brackets at the back face of the motor, and tack it in place. This view is from the top.

Step 3: Bolt a short piece of angle to the cradle and tack weld the assembly made in Step 2. As you can see, the cradle is not level at all but it doesn't matter using the method employed here.

Step 4: I am so fortunate to have a friend with a welder. The next step is to remove the bracket and weld everything together solid. Yes, that's right. We're using an old hollow-core door with a galvanized plate bolted to it as a welding table. Nothing is too good for this project!

Step 5: Build a bracket for the passenger-side driveshaft (this long shaft is in two sections so that the CV joints are in the same location for both wheels). It's amazing what can be built with pieces of angle and flat bar. Here's a picture of the location of the driveshaft support (sorry it's a little dark - that's the steering rack to the left).

Here's a picture of the finished bracket, nicely painted. The two bolts pointing at the camera are spaced to mate up with two holes in the driveshaft support.

Next... installation of the motor mount, and the transmission mounts.

Sunday, September 20, 2009

Connecting the motor to the transmission

I've been very remiss about updating this blog, so I'm going to do my best to "catch up" a bit. It might take a few entries to do it, but if I don't do it now it might never get done.

Attaching the AC24LS motor to the Saturn transmission

The motor-transmission adapter that comes with the ElectroAuto kit is quite impressive.  Very professional machining job, and I especially like the elegance and strength of the flywheel adapter which uses a taperlock design. The flywheel adapter is a special 2-piece unit that converts the keyed output shaft of the AC24 motor to a flange with the proper bolt pattern so that the Saturn flywheel can be attached to it, the same way it attached to the ICE output shaft.  Sorry to say I have no pictures of this, though. I was so excited to actually be putting something together that I completely forgot about documenting it!  And at this point I'm not going to take it apart just to take pictures. You'll have to take my word for it. (or look at other websites where they actually remembered to take pictures)

Anyway, after following the directions and installing the flywheel adapter so that the "magic distance" is correct (the magic distance is a measure of the location of the flywheel relative to the end of the motor output shaft and is important so that the clutch will work properly), a friend and I muscled the transmission onto the adapter and bolted it together.

A little background here.... the front face of the AC24, where the output shaft exits, has four bolt holes in it which serve to allow the motor to be attached to whatever it is powering, whether it be a conveyor belt, lathe, or electric car. So the motor can be installed in any 1 of 4 orientations.  A typical DC motor is cylindrical in shape and so doesn't really have a top or bottom side to worry about during installation.  The AC24 motor, on the other hand, has cooling fins which basically turn it into a rectangular prism, with a definite top, bottom, left, and right side. One side, which I shall call the "top," has a large electrical box on it where the main power cabling is attached. Looking from the back face with the electrical box on top, the right side has 2 grooves cast into the casing which are designed to accept the head of a 10-mm hex bolt. These are how the motor is supposed to be mounted. (I actually have a picture of this! Though as you can see the motor has been turned 90 degrees - more on that later!)

The other two sides are basically blank, though supposedly one of those sides can have a lifting eye installed (mine didn't).

Ok, where was I? Oh yeah, the four mounting positions. So, because of the 4 bolt holes in the front face, the "top" (with the electrical box) can be mounted either in the up position, right (toward the front bumper), down, or left (toward the firewall). My initial thought was that it would be easiest to mount the motor with the mounting side in the up position (electrical box to the firewall), and construct a simple bracket made of angle iron to secure the motor to the existing upper engine mount. It would require the least amount of metal (less weight) and it would be easy to access the mounting bolts in case I needed to pull the motor out. Too bad I didn't think about the driveshaft. As soon as the transmission was attached I immediately saw the problem. The driveshaft to the passenger side wheel runs alongside the motor, and very close to it. So close, in fact, that the electrical box will interfere with it. I have a picture which sort of shows where the driveshaft exits the transmission, but it's hard to see from this angle that it will interfere. Trust me, it does. Bummer. Ok, plan B.

If I rotate the motor 90 degrees clockwise (when viewed from the back face) there will be a "blank" side toward the firewall, which is good for the driveshaft, but now the mounting side is toward the bumper, which makes a motor mount design tricky. More complicated, more metal required, and worst of all the electrical box is now "up", which means it is unlikely that I'll be able to install components above the motor. Not a good Plan B.

If I rotate the motor another 90 degrees clockwise, another "blank" side is toward the firewall (good again) and the electrical box is toward the bumper (good, since it frees up room above the motor), but the mounting side is now "down." This basically rules out using the upper engine mount, but it was possible that I could instead use the lower engine mount. It seemed the only way to go, so again with the help of my friend we disassembled the motor from the transmission and re-installed it in the new orientation. Yep, no pictures of the assembly process, but here's a picture of the assembly in the engine compartment.
Next, the motor and transmission mounts.....