The Home Racing World (HRW) 2023 Can-Am Proxy Series
The 2023 Home Racing World HO Can-Am Proxy Grid
Home Racing World (HRW) has hosted many Proxy Races. In these races entrants prepare cars to a set of rules and send them off to be raced on various tracks by other drivers. Once the cars are shipped, they typically won’t be seen by their owners till the proxy is over. Last year HRW held a series for vintage HO Trans-Am cars using the AW pancake motor platform. In 2023 HRW ran a ten race proxy series for vintage Can-Am cars based on either the JL or Auto World X-Traction or the Aurora Magna-Traction pancake motor platform.
The series rules and comments can be viewed at https://www.hrwforum.com/forum/proxy-racing/can-am-proxies/h-o-can-am-proxy-2023/168333-ho-proxy-rules.
The eighteen cars shown above made up the grid. I decided to enter the series. About midway through the series I decided to tell all about my first and third place 2023 HO Can-Am Aurora Magna-Traction cars to help other racers in future events. This was my second HRW HO Proxy. Lessons learned from the HO Trans-Am proxy were incorporated into the two Can-Am cars. The biggest lesson learned was drivability. My Trans-Am cars had some drivability issues and weren’t the easiest to drive at or near the limit. One of the goals for the Can-Am cars was that they would be fast and easy to drive on the limit in any lane at any time.
To prepare for the 2023 series, I initially rummaged in the parts box, dug up a old set of Magna-Traction cobalt motor magnets, a Mean Green motor, the red rear tires and dropped them in an Aurora Magna Traction chassis. This crude test hack was easily quicker than the two cars I ended up with. I then read the rules and the organizers comments and started over. The cobalt magnets were legal! The motor wasn’t. After I found that a legal motor wouldn’t pull the cobalt magnets around at any reasonable speed I pulled the magnets, kept the chassis and rear tires and built what turned out to be the third place car. Several months later I brought the third place car up to its final configuration and built the series winning car. Between the two cars, my BSRT McLaren’s claimed five pole positions and won all 10 races with eight one-two finishes.
The #54 (Black Tire) Car
The #54T (Red Tire) Car
The cars incorporated some of the things that were done in the 1970’s when the Magna-Tractions were first raced as well as some things I have done with my race winning Fray style T-Jets.
For reliability, both cars used Aurora Magna-Traction chassis, top plates, axles, front rims, pickups, springs and motor brushes. Aurora Super II 19 Tooth crown gears were used instead of the stock 15 Tooth as the shorter gearing provides better acceleration and braking without adversely impacting top speed. Also used were DASH 10 Ohm motors and Level 10 magnets. The motors were inspected but not worked up. The AFX McLaren bodies were chosen because they were short, light and had decent aero characteristics. The bodies used the stock mounting method. Some work was done on the body mounts and posts to allow the bodies to float on the chassis. The isolation between body and chassis reduces noise and aids handling.
Unfortunately, DASH Level 10 motor magnets are great electrical conductors. Sparks and short circuits were experienced during early testing. I blew fuses and tripped breakers but never lost a controller. Unlike some entrants, I did not lower the front magnet on either car. Initially, tape was used on the “T” car to insulate the magnets from the pickup shoes. After I finished the black tire car I updated the “T” car to remove the tape and incorporate what I learned from building the sister car. The biggest change to the "T" car was the splitting of the front magnet to prevent shorts. This modification was first done on the black tire car and copied over to the sister car.
I got the idea for splitting the magnet from my 1975 Indiana HOPRA Magna-Traction car. Splitting the electrically conductive steel flux collectors (a.k.a. shim) associated with the front magnet to eliminate the possibility of sparks and shorts from them contacting the pickups was first done on this car. Each flux collector shown below was made from AFX track rail.
My 1975 Indiana HOPRA Magna Traction car with
Lowered Magnets, O-Ring front tires, Red rear tires and Split Front Flux Collectors
To split the magnets, I made a jig out of an AW chassis and cut the magnets with a fine bladed saw. An insulated spacer model made from aircraft plywood was placed between the two halves and the magnets were glued together while mounted in their respective chassis. Both cars front magnets were left at stock height. The 54T (red tire) car’s rear magnet was not split and was mounted at stock height. The 54 (black tire) car used split front and rear magnets. The black tire car’s chassis was trimmed and the rear magnet was glued flush with the bottom of the chassis for maximum downforce. Once the magnets were set, the bottom of the chassis was sanded to flatten the rivets and allow the car to be lowered that little bit further.
I have learned that a wider car is a stable car. Front and rear track was set so that the car would just squeeze through a tech block. Spacers were used on the front axle to widen the track. The rear rim flanges were thinned to maximize the rear track. The black tire car’s rear spoiler was broken and a new one was made from white styrene. The black tire car’s radiator outlet was also opened up for weight and aero reasons. The O-ring front tires were glued to their rims for reliability.
The red tires are the 48-year-old backup tires from the above 1975 Indiana HOPRA Magna Traction car. The AJ’s Red Devil tires are fragile to install but once installed give predictable handling, wear like iron and don’t degrade. I tried several different diameter rear rims before I finalized the rear tire setup. The black tires were used when a second, brand new, set of Red Devils split during installation. The black tires came from my junk tire box. I have no idea who made them, what they are and what they were made for. What they are is the right size, gave good traction and didn’t degrade. I probably tried 10 or more sets of rear tires and different diameter rear rims before I found the ones that were used on the #54 (black tire) car.
When setting up tire sizes, I have learned that it is better to start tall and come down rather than starting low and coming up. This applies to all car types. The front O-rings were selected to allow the pickups to move to accommodate high rails. The rear tire height was set to provide a small air gap between rail and chassis. On high rail spots the magnets should just skim the rail. You can see a bit of rubbing on the outside edges of the black tire car’s rear magnet so the tire height is about right.
Since we had no knowledge of the tracks ahead of time and no changes were allowed once the cars were entered it was important to set the cars up tall. As the cars were set up differently the tire sizes were not the same. The black car’s tires sizes were 0.395” Front and 0.460” Rear. The red car’s tires were slightly taller at 0.400” Front and 0.465” Rear. The two cars were set up months apart and I didn't measure tire heights as part of the builds. Didn't fire up the lap timer either. The cars were set up on my home track (Magic Raceway) using the old noise, trigger finger and Mk. I eyeball techniques.
Pickup tension was minimized to aid handling while retaining speed. As a result of current flow through the pickups one pickup will show signs of wear and the other pickup will show signs of arcing or burning. Brush tension on the “wear” pickup can be reduced to improve handling with no impact on motor performance. Brush tension on the “arcing” (or burning) pickup should be higher than the other to minimize arcing. Pickup travel was also limited.
Motor brush tension was increased to boost speed and acceleration while keeping motor temperatures below 150°F. The black tire car used stretched stock Magna-Traction motor brush springs. The red tire car used cut down pickup springs. If I were to do it again, both cars would use cut down pickup springs. When changing motor brush springs from stock to aftermarket you have to be careful to not compress the springs so far that they bind. Coil bind occurs when the spring is compressed such that the coils touch each other and the spring cannot be depressed further. Coil bind will result in increased motor heat and accelerated brush and commutator wear. Coil bind is probably the failure mode for at least one of the two motors that failed during the series.
Gears were not lapped but were selected and installed to minimize noise and rolling resistance. Noise is wasted speed and time was spent with each car to make them as quiet as they could be. The top plate was lubed with a light grease. The axles and the bottom of the car were lubed with Habby’s T-Jet Oil as it is a proven product.
Both cars were set up to be easy to drive, fast over an entire segment and to be consistent in both outside and middle lanes. During the series both cars consistently received comments like being easy to drive, find the limit or push. I have driven many cars (built by myself and others) that have won races or dominated series. None of them were difficult to drive. I have also driven cars that were fast but difficult to drive. Those cars rarely won.
Not only must a car be fast and easy to drive it also must also be reliable. The #77 Porsche 908 lost a motor in qualifying for the first race and was withdrawn. The Black UOP Shadow suffered a motor and chassis failure during the first race. It continued after receiving a new motor and chassis. A front end came apart and ended up all over the track during a race but the car was also repaired and continued. One way to prevent this type of failure is to countersink the pin head side rim to allow the pin head to be flush with the rim. This allows more of the pin to be inserted into the opposite rim. By the end of the series several cars were missing body parts as a result of racing incidents. Then there is fate, fortune, karma or luck. For example, the red tire car came home with a steel washer stuck to the bottom of its front magnet. Fortunately, the washer didn’t seem to impact the car’s performance.
The Shadow's Well Done Motor
My expectation was that both McLarens would survive and finish in the top five. Things were going well until the seventh race. During this race the “T” car retired and finished last as a result of a crown gear failure. I was given the option to retire or repair the car. I chose to repair it. The car was shipped home where it was discovered that both the gear and the splined axle were stripped. A new rear axle and crown gear were installed and the car returned to the series in time for the next race. The replacement Super II crown gear was pressed and bonded to the splined axle for maximum reliability. The repair was completed immediately after the car was received. The car was track tested and shipped back the following morning having spent less than 24 hours in the shop.
As a result of the retirement the “T” car slipped from second to fourth, eight points behind the Chaparral. In the final three races the “T” car battled back to third overall, three points (and one short lap) behind the Chaparral having taken two poles, a second place finish and two first place finishes.
Being consistently quick is king and without any problems, the #54 (black tire) car won the series going away. Also quick and running without problems, the #66 Chaparral claimed three pole positions and took the runner-up spot. The two Ferrari 512M’s were consistent and quick as well and finished fourth and fifth overall. Each Ferrari claimed a pole and the white Ferrari made the podium on those occasions when one of the top three cars had an off day. The cars were not slow. A short video showing the eighth, seventh and first place cars taking some practice laps for the final race can be seen at https://www.youtube.com/watch?v=kRm0ai0kPeY.
First, Second and Third Overall
The above is a summary of the results. A spreadsheet with all of the details can be found at https://docs.google.com/spreadsheets/d/14_zofAgfjXpwwUhUBlSmvqVZ3nqdrqqPtctuKwUTjqg/edit#gid=0.
Last, but not least, both of my cars utilize a concept that I have been using with pancake motor cars for many years. It is known that pancake motor cars swerve one way under acceleration and the opposite way when slowing down. To counteract this, both cars used different weight front rims. One rim is stock AFX. The second is dimensionally the same but heavier. The force applied by the heavier rim opposes the rotating force applied by the armature when the car changes speed. I have found that this setup aids handling and minimizes tire degradation with pancake motored cars. On both cars the left side front rim is stock. The red cars right side front rim is metal. The other car used a modified stock AFX front rim with a metal doughnut attached to its inside. With the exception of painting the “T” car’s rims black I didn’t hide what I did and why I did it. However, few (if any) have adapted the concept.
Chassis Top View Showing Front Rim Details
Hopefully the above will benefit all. It was a fun series and I wish to thank the organizers, drivers and marshals for their hard work. I also want to thank all of the racers who participated.
Created October 24, 2023