Paradise Road Slotcar Raceway.com/ - Slotcar Tips and Speed Secrets

This is a new page for us aimed at making your slotcar experience more enjoyable whether you're racing or just want a little more out of your play time. These tips are by no means the definative answers. They are simply a gathering of information to point the hobbiest in a direction for improvement. Not all of these tips will apply to both drag and road course racing. It is up to you to decide if it works for you. Keeping a notebook and recording detailed test results will assist in your decision. A notebook can also save you money from trying something that didn't produce results a second time. Not all tips will produce highly noticable results, however it may compound a previous or future tip. After all, every little bit counts.

We are hoping to add tips each month. We will keep previous tips posted as long as we can before we run out of space on the page. We recommend you print or download this information for future reference. While all of these tips should help, there is still no substitute for practice on the track of your choice and making notes in your notebook.

In an effort to bring the best information possible to our racers, I went in search of an experienced racer who would share some of the speed tips and tricks so often just whispered about in dark corners of the pit areas around the country. These "Speed Secrets" are the true basics that create a solid foundation for peak performance. The truth being that the highest performance gains are created in the very early stages of a cars build up.

I would again like to thank Marty Nissen of Kahale and Martin Racing for taking the time in this project. As we talked, it was decided to use a platform similar to Hot Rod's famous Prodject "X" 1957 Chevy. From there, "Finding the Edge" took on a life of it's own.

When I approached Marty, one parameter set forth was to consider cost as a major concern. Shop resources are a huge expense to any new racer. Like any new hobby, it's the tools and supplies that weigh down the efforts of a newbie. Access through your local raceway to items and services such as tire trueing, motor service, magnet zapping, com lathe, paint and detailing are a major plus in your search for record setting runs. To that end, we sent Marty a new, still in the box Parma Edge car with the idea of building a car to run in our Edge Funnycar class. We also offered as many services to him as he needed. A few of which he took chose to use as you will see in later posts.

Step 1 Open the box and see what we have to work with. Typically, shipping was not kind to the car we sent. the body mounts were bent. Those were straightened out and we proceeded with some weights and weasures to establish a base line for the car, 108.41 grams. Not a light weight for a lexan car. The factory set the gearing at a 9 tooth pinion and 33 tooth crown, a 3:66 ratio. The tires, which are suppose to be 1" differed from eachother by .005" and were undersized by a like amount. Lastly, the car was put on a tech block to check the body height and was a bit dissapointed. The body was flat on the block but as the braid recess on the track is .010 below the surface our body was going to hit. The body could be re-pinned higher then trimmed but since the out of box body wasn't the one going to be used, we used an alternate body already at the proper track clearance height.

So there is some work to do. Equalize the tires, solder up the wheelie wheels, break the motor in, lubricate and adjust. Not a real long list.

The tires needed to be trued before the wheelie bar height can be properly set. This service can be provided by PRSR (Paradise Road Slotcar Raceway). In the interest of time, Marty chose to do this step himself. Using the smaller of the two, the tire was dusted just to get it round and then cut the other to the same diameter which turned out to be .993" While the tires were off, we should check the axle bushing to assure they are in the same orientation and correct position for the tire diameter. 1" tires should see the bushings sitting in the up and back position, which they were.

Now that a ride height has been established, its time to set the height and solder in the wheelie bars. Ours were set at .025" off the track surface. This is a starting value that was pulled from the air but has worked on other cars of this type. It may not be our final position but its a place to start. This is another service that can be provided by your raceway until a good soldering iron can be purchased.

Motor break in comes next. I had to think about this for awhile and in the end called Monty Ohren at Best O’ the West for some advice. Monty has been at this a very long time and is a great resource. See, the thing is that I haven’t broke in a motor by the “dry method” in decades but wanted to start this project with this method as it is what the a new to the hobby person will likely do. It’s also a great opportunity to show off the differences that can be made by the wet method

As it turns out there are a couple of ways to approach this. The simplest is to run the motor in at 2.5 to 3 volts for about 45 to 60 minutes AFTER you apply a drop of oil to each bushing. The factory brushes have a shallow recess in the center of the brush to start the process assuming the brush hoods are well centered, which they nearly never are. What we are trying to accomplish here is to mate the brush to the commutator to arrive at the exact same radius to the full width of the brush to provide the largest current path possible and to seat them deeply enough to maximize the armatures timing. This can be by your raceway owner. The important thing is to prevent brush arc during the process

At this voltage and time the brushes will not be fully seated. Too fully seat the brush may take up to 4 hours but it will get you a running motor that won’t tear itself up. During the break in you need to move the gear back so the motor can turn with no load on it.

After 60 minutes at 2.5 volts, the most voltage I could use and remain spark-less, the full width of the brush track could be seen in the commutator, a good thing. At this point I carefully remove the brushes one at a time and mark each for orientation. Looking from the end bell side of the motor the right brush is the positive brush. I place a small dot with a Sharpie on the top of that brush. The negative brush is the left brush and it gets two dots. This assures you get the same brush in the same hood and in the same orientation each time. This is very important in sealed motor work. The commutator is never round nor without taper so each will mate differently.

     The positive brush on this motor was well centered but the negative bush was not. We will live with this for the initial testing and will correct later. It is hard to correct in a sealed motor but not impossible. We note a bit of COM taper as well as evidenced by the V shape of the wear pattern.

     At this point I removed the pinion, you wont. I ran the motor on the dyno to get a base line and found we had a peak of 58 watts of output and a maximum of 54,000 rpm, pulled 25 amps maximum and just under 10 amps at peak rpm. Not exactly what I would call a stump puller.

     Back to the break in stand. This time I ran it for 3 hours at two volts keeping close track of temperature. Never even got warm. At the end of the run we give the brushes a look and find we now have a nearly complete wrap and most of the taper is gone. Yes the COM wears in as well as the brush.

     Back to the dyno stand with good results. 74+ watts peak and 56,600 rpm pulling 32 stall amps and 9.9 peak rpm amps. On a percentage basis that is huge, 27.5% power increase and an extra 2,600-rpm on tap.

     Few tracks have a dyno and even fewer privateers. I’m lucky to have one. Don’t worry about this, as we will test from time to time. Your results should mirror directionally. The absolute numbers will vary from motor to motor.

     After reinstalling the pinion I put the motor on the power supply to check unloaded amp draw at 3 volts and find it to be not quite 1 amp. This is a useful point of reference while we set the gear lash.

     Okay we reinstall the motor in the chassis. Before we set gear lash we’re going to set the axle end play. Loosen one wheel and adjust so that you can see or measure about .003” between the hub and the bushing with the other wheel snug to it’s bushing. You can use a piece of notebook paper if you like. We need a bit of clearance to not only prevent axle bind but to “feel” the gear as we lash it.

     With end play set and motor installed bring the crown gear “just” up to the pinion and snug the set screw. We want the teeth fully engaged but not bound up. This is sort of a feel thing and may take a few attempts to get it perfect. You want to be able to feel some clearance but not see the clearance and you want that to happen at the tightest point in the gear train. Nearly all gears have a bit of run out or wobble which will make the gear tighter in one place than another. Find the tight spot and set the lash there. Put a drop of oil on each axle bushing and hand rotate a few turns to work in. Now put the motor on the power supply and again look at the amps at three volts. It will draw a bit more but if it is drawing more than a quarter amp more you’re too tight. With a bit of practice you can get this down to about a tenth of an amp and not have a sloppy feel to it. Mine was 1.2 amps perfect. Again, your track owner can help here. Once you feel that perfect spot you can do this by feel.

     Notice I spent zero time lapping gears and didn't oil them. Nylon gears will not require this.

     We assure the braid is laying flat and the guide is straight or inline with the centerline of the car, mount the body work and off to the track for a bit of base line testing. Final weight, 107 grams. We lost 1.41 grams from our inital out of box inspection.

     You have started your notebook, right? Kept track of everything you did and the results? Good, you can't race without a book.

     I checked track voltage when I arrive. We have a battery powered track so this varies a bit from week to week. 16.2 volts right on the money. This is also an 1/8th mile venue.

Paradise Road is 13.3 volts and a 1000' track. The 660 time is of comparison, but this is a good reason to keep your notebook. Voltage and track length will affect your gearing choices.

     I give the car a few swipes of glue on the glue board, card the excess off the track set it and have a go at it.

     60 foot time is .1794, 330 foot is .5249, ET registers .8510 at 30.55 mph. The car is smooth and unruffled the entire pass. A slow start but a good one. We play with the glue up a bit and get a best pass of:

     60-.1746, 330-.5018, ET .8162 at 31.10 mph. This is an item where both your track operator and experienced guys at the track can be invaluable. Glueing up is an art that is hard to teach in pictures and even harder to explain in words. It will change as we progress. Point is that we have improved the ET by half a tenth with nothing more that glue up.

     I notice that the motor, by sound, is not fully wound up by the time it hits the finish line and I want it to be. This means that this car on this track and power is geared too tall. I swap the 33 tooth crown for a 35 and make a few passes to yield: 60- .1612, 330- .4773, ET .7775 at 31.80 mph, a pretty nice improvement. It might seem strange that the mph went up on a shorter gear but it is not really. All that meant was the first gear was taller than the motor power could pull. Still it doesn't seem wound out fully so we repeat with both 37 and 39 tooth crown gears. Not until the 39 is installed does the mph drop and the motor seems wound out. Both of these gears were Cox and only the 39 is still available.

                           9/37 gears 60’ .1555, 330 foot .4699, ET .7696 at 31.80 mph
                           9/39 gears 60” .1539, 330 foot .4661, ET .7678 at 31.57 mph

     Note the exact same mph for both 35 and 37 tooth gears? Running slower with both 33 and 39’s? Note as well that the 33 tooth was 1 mph slower than the 39 tooth? The motor is pulling nearly 10,000 more rpm with the 39 than the 33 and, again, to a higher mph.

11/16/2009

We do some chassis tweaking. We add two pieces of .062 piano wire to the wheelie bar spot soldered in. Yes, I have some cleaning to do. We added an up right support to prevent axle bearing binding. This is just a piece of SS tube I had laying around in the scrap box. Measuring the width of the bottom of the channel I cut a piece the exact same width and soldered in place after assuring the side plates were square to the base with a small machinist square. Almost never off in these cars.

  Two items of note in this photo below. A motor plate brace made of some .0625 SS welding wire and the upper rear body mount.

      While I tried to capture it in a second photo below I failed to show that when using the adjust-a-bush set ups and a D can motor that with the motor flat against the floor of the chassis a line drawn down the center of the motor does not intersect the center of the axle and falls below the axle about .060". This is a bad thing and there really is no cure for it due to the motor size and the rules we are working with the prohibit chassis modification and/or use of centered bushings. The best we can do is solder in the motor support after motor installation and assuring the bell end of the motor is in contact with the floor getting as much angular correction as possible. This condition will tear up metal gears faster than you can buy them.

      The body mount is a simple piece of brass .062 tubing and two Parma ferrules. Note that the ferrules are soldered to the tube on the inboard side and not to the chassis proper. Nor are they actually snug against the chassis side rails. This permits a bit of side to side and quite a bit of for/aft and up and down movement.  What it is, is perfectly centered and just wide enough to touch the body with out drawing in or pushing it out when pinned. The front axle which is also the same tubing and the front mount is likewise custom cut to length but fit more snug to provide a more fixed support.

      Personally, I do not consider a floating mount and absolute requirement with such a stiff chassis while using a Lexan body. I also wish that Stainless tubing would be allowed and brass this length unsupported means we will replace mounts more often that I would care to do so jot down all critical dimensions in you note book.

Below is a list of past articles we have covered. Click on the title you wish to view.