Tuesday, August 30, 2011

The A/C Lines Are Installed

I confess, I expected that getting the A/C lines made to hook up to this compressor was going to be a challenge.  You could even say I was pessimistic about the whole affair.  I just couldn't envision how these lines could be made to fit in place, tie seamlessly into the car's existing system and hold pressure.  For a while it looked as if my doubts were justified. 

When I got the hoses back toward the end of last week, the technician handed them to me and began to explain how I should hook them up.  He said I should hook both ends up first, and then tighten the compression fitting in the middle.  I felt a wave of panic when he said "compression fitting."  You see, I hate compression fittings.  Despise them.  If there's a hell, it's occupied by the man that invented them and everyone else who is there is forever forced to try and make them work.  It's been my experience that compression fittings work absolutely fine, until you try to put anything in the hose they are on under pressure.  Then they proceed to leak everywhere, and nothing you do can makes them work. 

I hooked up the long, low pressure line that runs from the evaporator to the compressor, and began carefully tightening the compression fittings.  For those of you unfamiliar with how to tighten them, you are supposed to tighten them hand tight and then give the nut another 1/2 turn or so.  If you under tighten it, it leaks.  If you over tighten it, it leaks and you've ruined the ferrule inside and must replace it or the whole thing.  With that in mind, I followed the rules: hand tight, but then I did about a 1/4 turn.  I did a pressure test and it leaked like mad.  OK, 1/4 more of a turn and another pressure test.  More leaking.  *Sigh*  1/4 more of a turn and it's leaking worse than ever.  Undo the whole thing, check for dirt, debris or any other problems.  It all seems fine, so try it again. 

This went on for 3 hours or so.  It began to become difficult working through the tears of anger and frustration.  Eventually I had to resign myself to the fact that it simply wasn't going to work.  Oddly, the second hose, the high pressure side, seemed to work just fine.  Now I say that having not had the system charged.  I fully expect that when I take it down to have the shop draw a vacuum on it, and then charge it up, they're going to tell me it leaks from that joint.  I sure hope not, but if one of them is going to leak, that's the one that I can deal with.  I can reach it and remove it without dis-assembling the car.  The low pressure side requires I remove the larger battery rack under the hood to access it. 

I took it back to the shop today and explained my problem.  One of the guys, who's clearly been in this game for a while, looked at it and said, "Yeah, that will never seal.  It needs to be brazed."  That was music to my ears.  He said give us a few minutes and we'll take care of it.  They brazed a nut fitting on the aluminum tube and crimped it's male counter part on the existing hose.  I was a little irritated that I'd spent all that time on a fitting that clearly the expert felt was the wrong part for the job.  But I was so happy that it now had the right joint, I wasn't about to complain. 

I took the parts back home and began hooking them up.  It took a couple hours and I got the new dryer/receiver in place, both new hoses, the compressor mounted and the new lines attached to the compressor.  It looks terrific, but I have no way of pressure testing it apart from adding coolant to the system, which I'm not going to do until I know it won't leak.  Once the rest of the car is assembled, I'll drive it down to a local shop and they'll do all that for me.

I put together another quick (and very rough) video of what was accomplished today.  Take a look...

Another component to this is the controls for the A/C system.  They consist of an On/Off switch and a potentiometer that acts as the thermostat.  MasterFlux sells a little black box that incorporates both of those items, but I can't imagine using that in the car because it's simply hideous.  They say it's mostly for testing, and I can believe that.  I picked one up in case I needed it, but I don't think I will, so it's going back.  Instead, MasterFlux publish the specs on the device complete with part numbers and how to wire it.  I found the very same potentiometer online and bought it.  The great thing was they also had a variety of knobs to choose from to mount on the potentiometer's shaft, as well as the molex connector needed to plug all the wires into the controller board.  For the On/Off switch I'll be using the original A/C On/Off switch that came with the car.  Here's how the whole thing came out.

 Down low on the center console, just the right of the gear shift is the little silver knob that will be the temperature control for the system.  I really could think of no way to incorporate that functionality into the car's original thermostat dial above.  You see that dial just moves different baffles to control the direction of air flow, either over the A/C system's evaporator, or over the heating core.  There's no way to hook any electrical component up it.  At least no way I was willing to try.  I think that little knob will do just fine.  The On/Off switch is the top button in that two button module directly to the right of the new Link-Pro meter.

Lastly, you may recall that I was having problems keeping the Zilla controller cool in the desert heat.  I think part of the problem was the fact that I was using a radiator that was only 4"x8" in size.  Well in the video above, you saw that the new radiator is about 3 times that size.  Hopefully it will keep things a bit cooler.  But it also has a nice big fan to help suck air through it.  Well, I didn't see any point to having that fan run all the time.  After all, when I'm sitting idle in traffic, there's no heat generated in the Zilla, or when I'm cruising down the road at 40 MPH drawing only 60 amps, the air moving through the radiator is more than adequate to cool the controller. 

What I need is some way to monitor the temperature of the controller and turn the fan on when it starts to get too warm.  I started looking and found what I think would work.  It's a switch that will close a contact when it hits 122 °F.  It opens up again at around 115°.  That is well below the point the Zilla begins to complain about heat, but high enough that the fan won't run unnecessarily.  The switch itself is just a little button style switch that has to be in contact with the item you're monitoring.  The place I've noticed seems to get hottest on the Zilla is the top, right in the center.  It may get hotter else where, but I don't have access to where ever that might be.  So the question became, how do I mount a small dime-sized switch to the top of the Zilla without it moving around or looking too hideous.  Here's what I came up with, you be the judge...

That piece of aluminum is pressed and held down tight to the top of the controller.  The switch is held down tight to the aluminum strip.  I used some thermal paste left over from my last CPU purchase to help heat conduct into the switch.  The switch drives the relay you see at the bottom of the screen, which will then turn the fan for the radiator on.  OK, it might not be the sexiest of solutions, but I thought it was pretty clever and should do the trick nicely. 

Wednesday, August 17, 2011

Mounting the Compressor

The last two weeks have been exceedingly busy and it's only been these last two days that I've actually had the opportunity to begin working on the car again.  Very frustrating!  But I've made some progress, and I thought I'd share what's been done. 

I finished building and installing the motor mount, which meant that I could finish making all the connections to the transmission; drive shaft, clutch slave cylinder, gear shift linkage, and reverse light connection.  Incidentally, I was able to find the proper Bosch female connector to go with the male connector used for the reverse light switch mounted to the transmission.  That was not an easy item to locate.  To make it worse, apparently Bosch only manufactures them in lots once every so often because they were unavailable at every place that carried them for months, and then in a weeks time everyone had them. 

At any rate, the drive line is complete, and the motor is safely tied down.  It is resting on and held down to a solid piece of hard rubber designed for motor mounts.  The original cross members that prevent the motor from spinning while under torque are still there, but I've added some rubber cushioning that will absorb shocks from upward travel as well.  So to recap, I have hard rubber pads set to absorb any vertical bumps or vibration, and braces to keep the motor from spinning.  It's not going anywhere, and it should be nicely isolated from any sharp bumps the chassis receives.

The last couple days I finished building the tray and the supports that will hold the MasterFlux A/C compressor.  It's a tricky fit, just like everything else in the car.  It will be suspended from the front battery tray as mentioned in previous posts, but it can't be directly under, or there would be no room to hook the pressurized coolant lines up.  So it has to hang below and slightly behind the rack.  Maybe a video will demonstrate it a bit better.  Take a look.

I'm not sure that the shaky camera and rambling dialogue help clear things up, but hopefully you get an idea of what's involved.  Afterward, I took some careful measurements of where the new hoses needed to run, and disconnected the existing hoses.  I took them down to a local shop and explained what I need.  I was worried that they'd want to finish the hoses on the first visit, and I'd run into problems when tying to put them in the car.  Not only do the hoses need to be the correct length, but the new fittings that I need for the new compressor have to be crimped on at the proper angle so there's no twist in the lines.  Apparently this is not an uncommon problem. 

What they intend to do is cut the old hoses off the fitting end that I need to keep and crimp new hoses on that are a bit longer than I need.  Then they'll call me in and hand me the half completed hoses and the new fittings.  I can then bring the whole lot home and mount it up, cut the hose to length and mark the proper angle to crimp the new fittings on and return it to them for the final crimp.  Of course I still need to find a place to mount the compressor's controller and all the supporting electronics.  Truthfully, that has me worried.  I have an idea of where it might go, but I won't know for certain if it will fit in that space until both battery racks are mounted back in the car. 

With the addition of the new meter, and it's larger shunt, I thought I'd take this opportunity to hook things up in a cleaner way.  The old set up had all of the negative lines from the high voltage side running to one side of the shunt.  There was the 2/0 cable from the controller, the 6 AWG from the charger, a 10 AWG from the heater core, a 12 AWG for the DC to DC converter and a small 18 AWG for the negative lead to the meter.  That's a lot so squeeze onto one terminal.  So instead, I'm adding a bus bar.  The bus bar I got has 4 leads, three of which will hold all those cables and wires mentioned above, and the last remaining one will be reserved for a new cable that will run to the new shunt. 

The only problem is that the bus is only rated for 400 amps.  As we all know, I'm looking to put 1000 amps through it.  Well the reason it's rated at 400 is that there is only one 1/8" thick piece of copper tying all the connectors together.  To over come this, I've made 3 new strips of copper totaling 3/16" to stack on top of the existing one, for a total of 5/16" of copper.  That is more than enough for 1000 amps.  That's nearly twice the thickness of the battery straps. 

Speaking of battery straps, I'm taking out the original copper straps that came with the Sky Energy (CALB) cells and replacing them with the braided copper straps from EV Works.  While I'm at it, I've gotten rid of all the old washers and split ring washers in favor of Nord-Lock washers.  These changes will allow for two things.  First, as the chassis moves around and the batteries jostle about, those braided connections will flex the tiny amount needed and not put any strain on the connection point at each battery.  This will help to ensure that there is always a good connection at each terminal.  To further ensure a good connection, I'm using the Nord-Lock washers.  Once you've tightened down a bolt with one of those washers on it, it does not back off.  Vibration or the usual expansion and contraction due to temperature changes simply won't affect them.  Consequently, no loose connections, no fires. 

Monday, August 1, 2011

The A/C System Has Arrived

Last week, the Masterflux A/C system arrived from Revolt Electric, a full 3 weeks ahead of the initial 6 week wait they said I was in for.  Fantastic news and time to get cracking on mounting it.  I opted for the Sierra Model 06-0982Y3, and the 025F0140-03 controller.  The controller can be driven with anything from 120V to 420V DC, and the compressor is capable of putting out over 15,000 BTU.  Of course, that's when it operates at over 300 V DC.  Since my pack voltage is 160, it will be putting out roughly 10,000 BTU.  Should be plenty adequate for a two-seater car that has slightly more cabin space than the inside of a microwave.  At full power, it will draw about 6 amps, just shy of 1 kW. 

First things first.  In order to mount the A/C compressor, I need to know how much room I have to work with.  It's going to fit right behind the condenser for the A/C system and the new radiator I'm installing for the Zilla.  But before I could measure how much space I needed to build the frame that will hold radiator and then mount it in place.  Here's a shot of the radiator in it's frame:

Essentially what I built is a frame made from various angle aluminum stock.  The radiator doesn't have any screws or brackets that you can use to mount it to anything.  All it has is three pegs meant to hold rubber bushings that would then be pushed into some mounting bracket.  Try as I might, I could not find any bushings that would fit the posts.  What I did find where rubber stoppers at the local hardware store.  I bought three of them and drilled a hole through each.  Then I constructed the frame, drilling holes to accept the "bushings" I made and then fastened the whole thing together.  It turned out pretty well.  The radiator is suspended in that frame via those bushings which provide a little shock absorption for the assembly.  It will be suspended from the front battery rack by those two tabs you see sticking out of the top of the rack.

Once that was complete, I put the assembly in place and just clamped it so that I could start figuring out how to position the compressor.  I was very worried that I'd have little to know extra room, but as it turns out, I have loads of space.  I think there may be as much as a full inch in either direction for me to play with.  That may not sound like much, but trust me, that is huge.  I've had a difficult time fitting very nearly every component since I started the build, running short by 1/16th of an inch here or there was way to common.  Very frustrating.

The A/C compressor will rest in a tray I've made, that will then be suspended from the front battery rack as well.  Here is a shot of the tray I made today:

Notice the three large holes in the middle.  They are for the rubber feet that hold the compressor, which cushion vibration while it's running.  The tray is 1/8" aluminum plate surrounded by 1x1 inch aluminum angle stock.  It is light yet remarkably stiff.  The compressor weighs about 20 lbs, so it needs to be sturdy. 

At this point, I'm very glad I made that rack out of steel.  It will end up supporting 12 batteries, the power steering pump, the Zilla's radiator and the A/C compressor.  Fortunately it's more than sturdy enough to support all that weight, as are the brackets it mounts to in the car. 

My recent experience working with steel and aluminum for all the different support structures that I'm adding is not too dissimilar than my past experience.  I've found that building an EV is an endeavor that requires a great deal of care and attention to detail.  You decide how and where you're going to mount something, and measure the space.  You measure even more carefully, and even build cardboard models.  Then you begin cutting the metal you need.  Once everything is cut, you start drilling and bolting and/or welding it into it's final shape.  You then go back to fit it in the car, and discover that it won't work for some completely unexpected reason.  So you scrap the whole thing and start over.  Maybe it's just me, but this seems to be an ongoing theme. 

Next I get to build the structure that this tray will be suspended from.

On a final note, I did finish installing the new Link-Pro meter in the car.  It fit perfectly, replacing the Link-10 effortlessly.  I still need to find a new place for that shunt, but I'm not too worried about that.