I’ve been in contact with D&D Motor Systems, trying to upgrade the motor I have with something that is a bit stronger, speedier, and possibly with some regen capability.
With all of the information I had available, it just wasn’t enough without taking the engine off and going in for a look inside. I reluctantly went ahead and pulled the engine off today.
CitiCar motor on scissor jacks
It was a bit of a long drawn out process, disconnecting cables and wires, photographing and making videos of what went where. The hardest part was at the tail end where it was time to take the motor off.
At one time, I had three separate jacks that I was using. Two were scissor jacks, and I also had a trolley jack. With all of this, I still felt as if I didn’t have the correct equipment for the job. Wiggling the motor out was a fairly difficult process. After some time, the motor gave way and oil spilled out of the axle.
I now had a motor standing free on some jacks. I wasn’t able to move it back any further since the speedometer connection was still on the back. I started lifting it, but it felt as if it was catching on something. The motor is very heavy, I started to set it down, but the scissor jacks fell over. I did my best to lower it to the floor.
CitiCar motor shaft
I took a few measurements, counted 10 teeth, and then I was off to work out the gear ratio. I found a clip that I could put onto the shaft and setup my camera to look directly at it. I then went to the back of the car, marked each tire with a line of chalk, and spun both tires 10 times, calling out each revolution. It turned out to be 68.3 revolutions, which works out to be a gear ratio of 6.83:1.
Finding the gear ratio for a CitiCar
With a gear ratio of 6.83:1, my assumption is that there are 41 teeth meeting up with 6 – witch would actually be a ratio of 6.83:1, where it has an infinite number of trailing 3’s. I thought at least one of the numbers on the axle would have indicated the ratio, the number of teeth on the shaft, and what type of shaft it was.
Numbers on axle
This ratio was not recognized on the CitiCar wikipedia page. It listed earlier models with a ratio of 7.125:1, and later models with a ratio 5.17:1. The page also indicated there was a “hilly” option on the transitional cars with a higher ratio than 5.17:1 at a cost of speed, but didn’t specify what it was. A NASA article (NASA TM X-73638, October 1976, page 32) had mentioned a different ratio of 6.83:1 on their car, and a maximum speed of 32 mph.
Once I realized my gear ratio matched the one that NASA had, I was certain what the hilly ratio was, and that I had it. I’ve been in a similar situation trying to get up to 33 on level ground, but just recently found that my speedometer is four miles too fast as well.
CitiCar axle shaft
I went ahead and added the new ratio for the hilly option on the Wikipedia CitiCar page and referenced the NASA article. I may start making additional changes over time. I’ve got a treasure trove of documents, books, and links pertaining to the history of the CitiCar.
It’s been a long day. I’m tired. My goal has been completed. I’ll put the motor back on tomorrow. I had purchased a few items prior to replace the axle gear oil. I just wish I had played it a bit safer and be prepared for oil to come out. I suspect someone may have put too much inside. I’ll end up flushing it all out. I have no idea if the weight matches what I have, or how old it is.
Maximum Speed
CitiCar Speedometer
Let’s have a fun exercise to determine the maximum speed at which everything is rated.
The motor is rated for 4000 rounds per minute (RPM)
The gear ratio is 6.83:1
At 4000 RPM, tires would spin at 585.65 RPM.
I’m using 125R12 tires (the original stock size) with an overall diameter of 20.39 inches. The radius is 10.195 inches. Solving the the circumference (2 π r), I get roughly 64.06 inches.
One tire revolution would consist of traveling 64.06 inches. In a perfect scenario, this is only possible without any load, car, or gravity to make the tire… smaller.
585.65 revolutions per minute would travel at 37,516.739 inches per minute.
Unit
Per Minute
Per Hour
Inches
37,517
2,251,004
Feet
3,126
187,584
Yards
1,042
62,528
Miles
0.59
35.53
The combination of the motor, axle, and tires only permits the vehicle to drive at a maximum speed of 35½ mph.
Keep in mind, this doesn’t take a loaded radius, air pressure, or rolling circumference into account.
I’ve been talking with a few people in CitiCar and Comuta-Car groups and to someone at D&D Motor Systems to replace the motor that I’ve got. The model numbers of the motor and axle that I have do not provide enough information alone.
Dana spider axle and motor on a CitiCarv
For anyone going down the same route, here are the numbers that I see, that you can use for reference. The motor has some details on its plate, but some of the details are worn. I am unable to see the serial number at the moment:
GE 6HP Series Wound 48v DC motor plate
Manufacturer
General Electric
Voltage
48V
Wound
Series
Horse Power
6
RPM
4000
Amps
125
Class
F
Time Rating
INT
Model
5BC 49 JB 327 C
Motor plate information
Numbers 815107X and 5 on a Dana Axle
Numbers 20 and 820178-4 on Dana Axle
Numbers 820178-4, 5, and 20 appear on the axle. Another number appears as 815107X, but it may also be 8/5/07X or 8/5107X or 8/5107X.
The number five appears in the center of a circle, tilted on its side, with eight dots around it in odd positions filling eight of ten spaces.
There is also a letter “D” with a letter “W” inside of it.
I need to pull the motor off of the Dana spider axle to see inside and identify the motor coupler, spline, or shaft it will need. I’m not at all a car guy, but that’s the lingo I keep hearing. I’ll just pull it off, snap a few pictures, count things, and make some measurements with my calipers. How hard can it be? After all, I’ve watched David Brunson install a motor on his Comuta Car, so I’m certain that I am an expert mechanic now.
I wasn’t sure if removing the motor involved axle oil spilling out. I was told no, but then a few people chimed in and started offering tips on how to replace the axle geese. I figured while I’m working in that area on a 40 year old car, what bad could come from fixing something that ain’t broke? It felt like general maintenance that should be done every X-thousand miles or X-years, whichever came first. Sure enough, the owners manual had something to say about it:
The 1976½ CitiCar Owners Manual
SIX MONTHS AFTER PURCHASE AND EVERY SIX MONTHS THEREAFTER
Check differential fluid level. Use 90 weight Hypoid gear oil. Fill to top. In cold weather lighter weight fluid may be used. It is not advisable to mix different weights. When changing types of oil, flush system. Use no lighter than 30 weight oil.
I’m under the impression that the “every six months” is just topping off what’s already there, but this thing is so old, I’m wondering what I’ll find inside. I think I can just drain the fluid and fill it back in. If I need to crack it open, I’ll have everything on hand, just in case.
I previously had no clue what a differential was, but apparently it is something inside the rear axle. I watched a video by CitiCar Tom rebuilding his Terrell differential for a different axle than mine. I watched another about replacing differential fluid and ordered everything I didn’t already have, and got a nice 20% discount.
Supplies
Part #
Price
Discount
Mobil 1 Synthetic Gear Lubricant LS 75W-90, 1 Quart
26101
$13.99
$2.80
Permatex Ultra Black Maximum Oil Resistance RTV Silicone Gasket Maker (3.35 oz)
82180/82150
$8.49
$1.70
Performance Tool Multi Use Pump
W1145
$16.99
$3.40
CRC Brakleen® Break Parts Cleaner Non-Chlorinated (14 wt. oz.)
5088
$3.59
$0.72
FloTool Standard Duty 7 Quart Drain Pan
OP-112EMI
$3.49
$0.70
TEQ Correct 2 Ton Hydraulic Trolley Jack
TQ924
$41.99
$8.39
$88.54
$17.71
Order from Advance Auto Parts
DC to DC
Buck converter and 12v socket
The other night, I had a few supplies come in. One was a DC-DC Buck converter from 24/36/48v to 12v. I was hoping I could hook it up so that it would work in both the 48 and 24v mode that the car runs in.
I had two sets of wired 12v sockets. I cut one of them in half and spliced the buck converter into the middle. I ran down to the car, hooked everything up and saw/heard an unexpected spark as the wire made contact. Nothing blew up.
I also got one of the cheapest 12v car devices I could find that was still a little useful, but I wouldn’t mind having it blow up if something I did would destroy it. I found a volt meter with 2 usb ports. I plugged it in and it showed 12.7 volts. Everything worked in both the 24 and 48 volt configuration.
Given that I saw the spark, I knew this would always be on, even when nothing was plugged into it. I went ahead and placed an order for a fancy latching switch button that lights up when the power is on. It comes with a pre-wired socket, and I believe I can setup the LED to run off of the 12v supply while the 48v power only flows through the switch itself.
In the mean time, I installed the other socket onto my accessory battery.
Dual USB Car Charger 4.8A Output Cigarette Lighter Voltage Meter
$9.99
19mm 3/4″ Metal Latching Pushbutton Switch 12V Power Symbol LED
$9.99
GPS Speedometer
The T600 has connected to Skynet
I purchased a little T600 Universal GPS Smart HUD. This thing is more of a curiosity to play around with, but I got it because I needed a battery monitor, and I like some of the features it came with.
This thing feels and looks cheap. It simply gives you the bare bones of features it advertises. The most fancy display has a round swoosh below your current speed.
I had to configure it first to bring the speed adjustments down to 100% and offset to 0 mph. I also played around with the three colors that it shows text in.
Speed
Speed Alarm
Distance
Voltage
Voltage Alarm
Duration
Cardinal Direction
Altitude
Clock
The features I like of the T600 Universal GPS Smart HUD
Leaving Home
CitiCar at Advance Auto Parts
Teddy and I started our trip to pickup some supplies to change the cars axle oil, and to pull the motor off to take a closer look at the spline for the shaft of a new motor. As we pulled into the parking lot, there was a police car strait in front of us. Sometimes I think they are going to make up an excuse to pull me over just so they can have a closer look.
Teddy waits to take off on another ride
We wern’t at the store for too long, as it was an online order for pickup. It started to rain a little when we took off. I took Teddy over to Gertrude Miller community park on the way home. It got really dark, windy, and rainy very quick. I started wondering if the wind was strong enough to blow the car over.
Our first trip in the rain
The trip home was… interesting. The roads were wet. The rain was pretty hard. I had the wiper running along with the lights. I saw my voltage on the accessory battery was down to 12.0v. I even tried the defroster to see if I could defog the window. When I turned on the fan, I didn’t feel any air coming through the window vents. The simple fix was to use my hand to wipe down the window. I’ll have to look into what I can do to defog the windows later.
Dead after arrival
As we pulled into the garage, I turned off the lights. Since I was playing with the GPS HUD, I flipped the switch for the lights back on and see how much they impact the accessory battery.
Nothing.
I suspected that a fuse had blown. I grabbed my multi-meter and tested all seven for continuity. I found the bad apple. When I matched the position up to the cover plate, it was labeled as a fuse for the break, turn signal, and horn. I turned on my turn signal and it worked. I pulled out the fuse… still works. I’ll need to re-label these fuses later. Even if I was reading the panel upside down, the other label indicated it would have been the controller.
Luckily for me, one of my first investments in the car was to purchase a variety of fuses and throw them in the back of my car. The cover plate indicated a 20 amp fuse would be adequate for the lights. I replaced the fuse, and all was well with the world.
I took a look at the burnt out fuse and noticed it was rated for 30 amps! My speculation is that the previous owner put that in there because they got tired of replacing 20 amp fuses. Since this happened at the tail end of the trip, I’m guessing that the wiper motor had too much trouble as I entered the garage. Since it wiped away all of the rain, there was a great deal of friction to continue.
In the meantime, I have a DC fuse block on order with sticky labels and LED’s that light up when a fuse is blown. I’ll add the lights and windshield motor to my list of things to upgrade later.
Accuracy
Regarding the GPS HUD, there were a few things enlightening about it. The speedometer on the car was reporting 4 miles faster than what I was actually traveling at. I was able to set my phone next to the GPS monitor and confirm its accuracy. I thought I was going amazingly fast the other day pushing the car to 33.5 mph, only to realize now that I was going under 30.
On a related note is that the distance I have driven on the odometer is much higher than this new gadget is reporting. There seems to be a large discrepancy in just a few short miles. When I punch my routes into Google Maps, It’s sitting in the middle of the other two.
Waypoint
Odometer
Distance
T600
Google
Home
1,088.9
Advanced Auto Parts
1,093.0
4.1
3.5
3.7
Gertrude Miller Park
1,094.2
1.2
1.0
1.1
Home
1,097.4
3.2
2.8
3.0
Total
8.5
6.3
7.8
With the battery voltage meter, I felt better to see how the lights and a wiper affected the voltage with a general idea of the batteries health. I would still prefer to see a capacity meter of some kind with a percent, colors of red/yellow/green, and a bar showing how much is left.
I used the altitude feature to get an idea about how high the hill is to get out of my little neighborhood. The top of the hill is at 648 feet above sea level, and the lowest point is at 508 feet. Every time I go on a little trip, I’m starting out with a 140 foot tall hill.
I know it’s super cheap, but here are some other things I wish it had
A separate set of leads to connect to your battery – monitor 48v battery voltage while connected to a dc-to-dc 12v converter
A switch to turn it on
Buttons on the front
Better sticky pad. It keeps pulling up from the dash
The Chez 