I got some parts back from Commercial Machine Service and put them together to see if my design would work. Well, the addage "Measure twice, cut once" came up to bite me. Since one of the goals of this design was to make the chain sprocket center distance adjustable, the plates that mount the motor and clutches slides along the joint between the upper and lower parts of the transmission. Well, upon trying to put it together, I found that I made an error somewhere and the chain was too tight; couldn't even put it together. Luckily, the joint has plenty of material and I only need about 1/8th inch. So, after MUCH grinding to lower the shelf that the Motor/Clutch plate slides on, here is the result:
Friday, January 29, 2010
Saturday, January 2, 2010
December Update - Rear Transmission
I've been working on my transmission issues for the past month and here is what I'm going to try first....
Snowmobile CVT - Basically, since I geared the car for 60+ MPH, I set the motor/wheel ratio to 4:1 (basically 4th gear), not good for driving up steep hills. However, since my initial concept was for one motor for each wheel, I went for direct drive meaning no way to change gears, hence my problem. Here is my current solution:
I'm in the process of modifying my direct drive set up with a snowmobile CVT between the small sprocket and the motors. The CVT will will vary from 2.4:1 to 1:1 depending on torque/motor RPM giving me an effective ratio of 9.6:1 (second gear). The installation requires that the center distance of the drive (motor) clutch and the driven (sprocket) clutch be very exact. In order to fix this distance, I designed a designed a plate that will mount the motor and two clutches at a fixed distance. I looked around for available software and found a program offered by Solidworks. It is very powerful and I ended up modeling my whole transmission.
And, since I'm modifying my transmission, I'm using the opportunity to fix the center distance issue. With all chain drives, a method to tension the chain is required. Most of the time, that involves a method to change the center distance between the sprockets but I didn't initially design in a way to do that. Instead, I tried to use skateboard wheels attached to swing arms and springs to keep a constant tension on the chains but I greatly underestimated the forces, which explains my noisy drive. As the chains rotate over the small sprocket, it flops around, making a lot of noise. By putting the new motor/CVT combination on a sliding plate, I'm able to adjust the center distance up to 0.5"; it isn't much but hopefully it will be enough. Commercial Machine Service is in the process of making up my pieces so I can give it a test.
On another front, I ordered a set of front struts from a BMW 328xi. It is the four wheel drive version on BMW's 3-series sedan, the descendant of the 2002. Next step there is to try to get the struts installed in my '02 and then move towards motors on the front wheels. More on that later.
Snowmobile CVT - Basically, since I geared the car for 60+ MPH, I set the motor/wheel ratio to 4:1 (basically 4th gear), not good for driving up steep hills. However, since my initial concept was for one motor for each wheel, I went for direct drive meaning no way to change gears, hence my problem. Here is my current solution:
I'm in the process of modifying my direct drive set up with a snowmobile CVT between the small sprocket and the motors. The CVT will will vary from 2.4:1 to 1:1 depending on torque/motor RPM giving me an effective ratio of 9.6:1 (second gear). The installation requires that the center distance of the drive (motor) clutch and the driven (sprocket) clutch be very exact. In order to fix this distance, I designed a designed a plate that will mount the motor and two clutches at a fixed distance. I looked around for available software and found a program offered by Solidworks. It is very powerful and I ended up modeling my whole transmission.
And, since I'm modifying my transmission, I'm using the opportunity to fix the center distance issue. With all chain drives, a method to tension the chain is required. Most of the time, that involves a method to change the center distance between the sprockets but I didn't initially design in a way to do that. Instead, I tried to use skateboard wheels attached to swing arms and springs to keep a constant tension on the chains but I greatly underestimated the forces, which explains my noisy drive. As the chains rotate over the small sprocket, it flops around, making a lot of noise. By putting the new motor/CVT combination on a sliding plate, I'm able to adjust the center distance up to 0.5"; it isn't much but hopefully it will be enough. Commercial Machine Service is in the process of making up my pieces so I can give it a test.
On another front, I ordered a set of front struts from a BMW 328xi. It is the four wheel drive version on BMW's 3-series sedan, the descendant of the 2002. Next step there is to try to get the struts installed in my '02 and then move towards motors on the front wheels. More on that later.
Friday, December 18, 2009
Long Overdue Video
Here is the video of the first drive. Took way too long to get them off the camera and into the blog but here they are. In this first one, the squeal is the brakes (need adjustment)...
In this second video, you can hear how loud the drive is which is something I am working on. On the GPS (which you can't read) the car gets up to 62 MPH. Not too bad for two 10HP, 72 V motors direct driving the rear wheels in what amounts to 4th gear. Now if I can only get motors on the front wheels.....
Friday, November 6, 2009
October.... OOPS, November update...
Kind of missed the October update for a couple of reasons; a job change coupled with not a lot progress. Basically, I spent the month working on sourcing a hub motor for the front wheels and designing the interface for the cool little embedded computer I bought.
First the motors - I found a hub motor on Alibaba.com (basically, a market place where Chinese businesses can connect with buyers) that might meet my requirements. I have ordered one that should be here early next week and I'll get a chance to see if it is going to work. It is a BLDC motor and controller rated for 6KW so it will be interesting to see how it works. The other interesting thing I found was a blog by Shane Colton. He built and mounted a couple of BLDC motors on a Razor scooter and designed the controller to power them; really cool stuff. But the main reason the oracle of the internet (otherwise known as google) directed me to his blog is that he has an idea for an axial flux BLDC motor that would be PERFECT for my hub motors. If I could get four of these motors plus the 10KW controllers......
As far as the little computer. One of my hobbies is programming little embedded computers so of course, the Electric '02 is going to have to have one (or two, or three...) And since a battery monitor is pretty much a requirement with the value of the batteries I'm carrying around, I thought it would be really interesting to combine it into a touch screen computer that could do some other things (mp3 player?, GPS?, etc). I bought a Technologic Systems TPC-TS7390 which is a Arm based computer with a mounted LCD touch screen running Debian Linux. I found the Qt Gui programming language and after a lot (too much in my mind) work setting up the development environment, I'm starting to work on the GUI. It isn't much to look at yet but it is fun. But this lead me to my other great google find: Automon. This is an application built by Donal O'Connor on the same TPC-TS7390 that interfaces with your car's on board diagnostic system (otherwise known as the thing that turns on the "Check Engine" light). Cool thing about Automon is that the OBD system is always collecting information about how your car is running and Automon is able to access that real time. Donal designed a cool interface that allows you to see engine rpm, speed, temps, etc. Really something worth while to check out.
Well I guess that is it for now. I'm hoping to have more to report next time.
Tuesday, September 15, 2009
September Update - ITS ALIVE!!!
The big news for this month is.... The car is on the road!!! Or rather I guess I should say that the car has been on the road. When I initially was planning for this conversion, I wanted a 4 wheel drive car so I sized the motors accordingly. Right now, I only have the rear motors installed (still haven't figured out how to get motors on the front wheels yet). This means that I only have half power and since I went with direct drive, I'm having some issues with hill climbing power. As for straight out flat speed, I've had the car up to 62 MPH (my goal was for 65) so I am right on track there. But when I try to drive the car back up our driveway, which is VERY steep, I can only make it up about 20% of the time. I'm guessing that if the battery is at anything less than full charge, I don't have the torque to get the last 10 feet. What is interesting is that acceleration seems fine. I can get to 60 in about 15 sec which isn't neck snapping but not horrible.
So, now it is time for a re-evaluation. My options are:
1. Figure out how to get motors on the front wheels (most desired)
2. Get bigger rear motors and figure out how to install them in the limited space (see photos)
3. Re-gear the drive to a higher ratio (difficult due to available components and loss of top speed)
4. Up the voltage from 72V to 96V or 120V (requiring new motors and controllers)
5. Rip it all out and re-install the transmission for a more standard conversion (least desirable)
Some other issues I still have to address. The chain noise is rather loud, figure out where to put the fourth battery, speed sensor, body work, battery management system, redo front battery mounts, etc..... I knew when I started this that it was a process that probably had no end. There is always something more to be done but that is what I like about it.
Anyway, here are some pictures of installing the rear drive. I also have some video of the first drives but I still need to cut it together into one video.
So, now it is time for a re-evaluation. My options are:
1. Figure out how to get motors on the front wheels (most desired)
2. Get bigger rear motors and figure out how to install them in the limited space (see photos)
3. Re-gear the drive to a higher ratio (difficult due to available components and loss of top speed)
4. Up the voltage from 72V to 96V or 120V (requiring new motors and controllers)
5. Rip it all out and re-install the transmission for a more standard conversion (least desirable)
Some other issues I still have to address. The chain noise is rather loud, figure out where to put the fourth battery, speed sensor, body work, battery management system, redo front battery mounts, etc..... I knew when I started this that it was a process that probably had no end. There is always something more to be done but that is what I like about it.
Anyway, here are some pictures of installing the rear drive. I also have some video of the first drives but I still need to cut it together into one video.
Monday, August 10, 2009
August Update
Time for an update: I've been working on lots of different things and making a little progress, the largest was the transmission. The guys at Commercial Machine Service finished up the transmission and I installed it where the rear differential used to be. Of course, I had to make the rear wheels go around using electricity so even though the batteries aren't fully mounted yet, the controller board isn't finalized and I don't have the pot box installed, I hooked everything and low and behold, I have electric motion!!! (I'll video if anyone is interested).
However, not everything worked like I hoped. I'm using a chain drive so the center distance between the input and output shaft must be such that the number of links in the chain is a multiple of two. In my case, the chain ended up needing a half link. Unfortunately, these aren't made for the motorcycle chain I'm using because the half-links are weaker. So, I had to add a full extra link to the chain, making it very loose. Since the center distance between the shafts is fixed, I'd always intended to put a tensioner in because the chain will stretch. Now, it is just going to have to take up more slack. So, I'm working on a design that will fit in the tight confines of the drive, be adjustable, and be able to reverse. More on this later.
Controllers - I laid out the controllers on a piece of Plexiglas and I've gone through a couple of iterations, but I'm still not satisfied. I figure that I will mount them above the motors but I don't want to take up too much room in the trunk, so I'm still adjusting. One thing that is coming together is the method to keep the controllers cool. Again, to keep the cable runs short, the controllers are going to be in the trunk and I was having a hard time coming up with a way of providing enough air flow. A couple of people have used water cooling but mine aren't designed for it. However, I found these: http://www.alliedelec.com/Search/ProductDetail.aspx?SKU=6190228&MPN=416501U00000G . Secure them to the bottom of the controller with some heat sink compound in between then route the antifreeze to a radiator in the slip stream and Voila, cool controllers.
Battery Mount - I finished up a battery mount for the front batteries but I'm not super happy with it. I've said before, metal fabrication is NOT my strong suit and the mount looks like it. However, it is functional and I figure that since this project probably will never be totally finished, I'll add a professionally fabricated mount to the list of things to be redone.
Batteries - I was part of the group buy from EV Components. I was heading over to Seattle towards the end of July and I thought I would save myself some shipping cost by picking them up myself. Unfortunately, a customs snafu delayed the batteries and they weren't available for my trip. So now I'm having them shipped but that means that I still don't have my full pack. Soon.... hopefully soon. When they get here, I'll have all the components and then it will be time to get this thing driving!
Guess that's all for now. When I get something finalized, I'll post some pictures.
However, not everything worked like I hoped. I'm using a chain drive so the center distance between the input and output shaft must be such that the number of links in the chain is a multiple of two. In my case, the chain ended up needing a half link. Unfortunately, these aren't made for the motorcycle chain I'm using because the half-links are weaker. So, I had to add a full extra link to the chain, making it very loose. Since the center distance between the shafts is fixed, I'd always intended to put a tensioner in because the chain will stretch. Now, it is just going to have to take up more slack. So, I'm working on a design that will fit in the tight confines of the drive, be adjustable, and be able to reverse. More on this later.
Controllers - I laid out the controllers on a piece of Plexiglas and I've gone through a couple of iterations, but I'm still not satisfied. I figure that I will mount them above the motors but I don't want to take up too much room in the trunk, so I'm still adjusting. One thing that is coming together is the method to keep the controllers cool. Again, to keep the cable runs short, the controllers are going to be in the trunk and I was having a hard time coming up with a way of providing enough air flow. A couple of people have used water cooling but mine aren't designed for it. However, I found these: http://www.alliedelec.com/Search/ProductDetail.aspx?SKU=6190228&MPN=416501U00000G . Secure them to the bottom of the controller with some heat sink compound in between then route the antifreeze to a radiator in the slip stream and Voila, cool controllers.
Battery Mount - I finished up a battery mount for the front batteries but I'm not super happy with it. I've said before, metal fabrication is NOT my strong suit and the mount looks like it. However, it is functional and I figure that since this project probably will never be totally finished, I'll add a professionally fabricated mount to the list of things to be redone.
Batteries - I was part of the group buy from EV Components. I was heading over to Seattle towards the end of July and I thought I would save myself some shipping cost by picking them up myself. Unfortunately, a customs snafu delayed the batteries and they weren't available for my trip. So now I'm having them shipped but that means that I still don't have my full pack. Soon.... hopefully soon. When they get here, I'll have all the components and then it will be time to get this thing driving!
Guess that's all for now. When I get something finalized, I'll post some pictures.
Wednesday, July 1, 2009
Front Battery Mounts
Spent some time last night working on how I am going to mount the batteries in the car. Since I'm going to have the rear wheels driven by motors in the trunk, the logical place is up front where the ICE used to be. Since I'm planning on having four packs, I need to find a place to put the 96 batteries and no matter how I try, they aren't all going to go in the front. Still, I think I can get three up front which will nicely replace the weight (~360 pounds) and I won't have to monkey with the suspension. I'm thinking the fourth pack is going to go where the gas tank was but I haven't made up my mind about that yet.
Since I'm trying a bunch of different configurations, I came up with a different way to simulate the pack rather than the cardboard box method. I got some foam insulation from Lowes and cut it up into 96 LiFePO4 battery analogs. This made it very easy to pack (pun intended) the batteries into the front of the car to determine the best way to get most of them up there.
Now I just have the job of fabricating what I came up with. I tried a little gas welding and let me tell you, it is HARD!! Metal fabrication is definitely not my strong suit so I'm probably going to end up with something that will at least initially, be bolted in. Not my preferred solution, but you gotta work with what you have.
Since I'm trying a bunch of different configurations, I came up with a different way to simulate the pack rather than the cardboard box method. I got some foam insulation from Lowes and cut it up into 96 LiFePO4 battery analogs. This made it very easy to pack (pun intended) the batteries into the front of the car to determine the best way to get most of them up there.
Now I just have the job of fabricating what I came up with. I tried a little gas welding and let me tell you, it is HARD!! Metal fabrication is definitely not my strong suit so I'm probably going to end up with something that will at least initially, be bolted in. Not my preferred solution, but you gotta work with what you have.
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