Project 908, My new fastest car? Options

[cydewaze]

This is a project that's been quite a while in the making. Ever since acquiring my SCX Peugeot 908 HDI, I've been wanting to fit it with the full line of SCX Pro parts to see how much of a difference they really make.

But before I get to the Pro parts, a little history.

I have a fairly small track, 65-ish feet of lane length, full of tight, twisty turns and not much straightaway. To make things worse, I did sadistic things like adding an R1 "bus stop" chicane, a flat R2 turn at the end of one of the longer straights, and deliberately off-cambered an already decreasing radius turn. There are numerous places to spin off and lose body parts. It's like when NASCAR does Watkins Glen.

The circuit favors cars with lots of grip and a low center of gravity, which is why my Pug 908 excelled from day one. In addition to urethane tires, I've made a few other mods. Those include:

- re-wrapping the braids to improve contact
- performing the "Dave Kennedy" guide flag mod
- taping the motor pod to reduce movement
- fine-tuning the magnet height

All this tuning combined with the Pug's already excellent handling made the car the fastest stock non-Slot.it in my collection, with a best lap of 5.378 seconds. The only non-modified cars in my stable that were faster were my Slot.it Audi R8C (5.037) and Slot.it Rothmans Porsche 962 (4.957). The Pug was also only around a tenth behind some of my other heavily modded, high-RPM project cars. Pretty impressive for a stock SCX.

Recently, I made a few changes to my track. I expected times to come down a lot, but it wasn't to be. Even though I made the track more stable, I also tightened up a couple of the turns, and removed some guard rails in favor of aprons. Where before you could "cheat" your way through a turn by riding the back corner of the car along the armco, the new design left you with smooth apron to contend with. Go too fast and you lose the rear end completely. It made the track a bit more challenging. Some of my cars did better, some did worse.

Eventually I started posting new times for all my cars. Fastest again were my Slot.its, with the R8C now the fastest at 4.935, and the Rothmans right behind it at 4.937 (yes, only .002 apart). But a few days ago I was amazed with a Scalex Porsche Spyder RS that I picked up. Completely stock with urethane tires, I managed to pull a time-bending 4.898 out of the car. It's an amazing time that I can't touch with either of my Slot.its, and it shows how handling is more important than power on my track.

During the past week, my Pro parts have started to arrive by post for my SCX Pug. Among the changes were Pro braids, a 54mm rear axle, a Pro crown gear, and the all important Pro Speed motor. I had also ordered rear wheels, but they were out of stock, so those are yet to be tested.

Tonight I installed what I had, and after some strategic dremel work, I got the car running smoothly. Since the 17mm SCX wheels were out of stock, I had to settle for a spare set of slot.it wheels I had lying around. After mounting up the tires, I found the car with its belly resting on the track. It seems that the slot.it wheels are smaller in diameter than the stock SCX Pug wheels. Since I had sanded the tires down based on the SCX wheel diameter, they were now too short when used on the slot.it wheels.

So I threw on a new set of 1408 Yellow Dogs, and put em to the sandpaper. After playing around a bit with the rear track, I finally got something that would lap smoothly.

Here's the rear end, with Pro Speed axles and gears:




Pro braids:




Looks pretty mean this way, eh?




I eventually got to a point where I could turn a few laps in anger. I'd turn a few laps, do some tweaking, do a few more, tweak more, etc. Right away I could tell the car was considerably faster than it was before the mods. Not just from power of the the Pro speed motor, but also from the smoothness added from the other Pro parts. The car just felt (and sounded) smooth and effortless, and my first few laps in the 5.0 range proved that the parts were paying off.

After some more tuning, and actually raising the magnet, I broke into the 4's. I pulled the car off the track, pulled the old, flaccid tape off the motor pod, cleaned the chassis, and replaced the tape with two new pieces. My next two laps each sounded the fastest lap chime, and after a few more I was able to squeeze out a 4.856. Yes, that's faster than BOTH of my Slot.its, and faster than my "factory freak" Scalex RS Spyder.

Needless to say, I'm quite pleased with the car's performance, but it goes beyond that. You see, I put 30 more laps into the car after that lap, and 20 of them were sub-4.9 second laps. By contrast, my Scalex Spyder dies off quickly after around 10 laps, settling into the 5.3 second range. If you don't pull off a fast lap in the first 6-8 laps with the car, you've missed your window.

SCX has definitely hit a home run with this car, but I'm not finished yet. Still on my list are the proper SCX rear wheels (with inserts) and the Pro bushing kit for the rear. Who knows, I may be able to squeak another few more hundreths out of the car.

[LDFan]

Cydewaze,

Quite an impressive bit of work I must say. Sure wish I had my Pug delivered but it's being held up @ this time.

Dave

[cydewaze]

It'll be worth the wait, trust me!

[LDFan]

I do have the Audi R-10 which I would think would be similar in performance to the 908.

What are your thoughs on it?

Dave

[cydewaze]

Dave, while I've been wanting to pick up an R-10 of my own to test, I've not gotten around to it yet. The only Pro R-10 I've ever put my hands on had been boogered up by one of the guys in our local race league, and one of the wheels kept falling off.

Whenever I get around to getting an R-10, I'll do some back-to-back testing. But it makes sense that the R-10 should be as fast or faster than the Pug, since the R-10 should be less top-heavy (no roof). The R-10 also has alu front wheels I think, so that should make the front end a bit more stable since the alu wheels are usually more true than the plastic ones.

[Pittman]

Very interesting work on the 908 project. The Scalextric motors lose torque as they warm up, so the lap times increase. Same thing happens to my cars (no magnets). The SCX motors increase speed as they warm up, it can take 25 laps or more to hit the best performance. And, your SCX Pro Speed motor should get faster after hundreds of laps, as it breaks in. You may find that as the gears wear in you go faster, too. Keep trying and you can be sure that 908 will hold the track record by a good margin.

[DaveKennedy]

Interesting work up on the Peugeot. I really love the Peugeot I've worked on but I haven't done nearly that much work on mine.

How was the crown gear clearance under the body? I see you've put a 27-toother in there. Good choice for a track with short straights. The 10-tooth pinion on the Pro motor meshes well with the Pro gears. I usually switch all my 9 pinions to 10's just because I prefer the feel of the mesh with that pinion.

[yellowdog6769]

Paul you will find that the Pug will be faster around your track than the Audi R10 because the R10 is a longer car. On our big track at Ace we run the box stock LMP's both mag and no-mag. The mag cars are raced at 14v and the Scaly Porsche spyder rules. No-mag at 12v and the tables are turned. The Pug just plain out handles the Scaly LMPs.
Right now I'm working on my RAA LMP car which is a SCX Audi R10. It will have the new 25k motor, Super Wheels and of course Yellowdogs.
I'm trying a little tweek on the guide to get rid of the dreaded wobble. If it works, I'll pm ya.
Dan
Team Super Tires

[cydewaze]

How was the crown gear clearance under the body?

It required some dremeling, but now that I've done it once, I know exactly what to dremel if I ever do it again. I took away a bit too much, but it's not really a huge deal.

I tried the 26t first but switched back to the 27. The difference is minuscule, but the better acceleration from the 27t on my track is probably worth half a tenth or so. Can't argue with the results.

@Dan: I tried your mod, and it seems to have worked. There's not so much of a performance difference between a warm and cold motor now. Thanks.

[Pittman]

@Dan: I tried your mod, and it seems to have worked. There's not so much of a performance difference between a warm and cold motor now. Thanks.

Can you tell us how Dan reduces the difference between warm and cold motor performance?

[cydewaze]

Can you tell us how Dan reduces the difference between warm and cold motor performance?

You'll have to ask him. I accidentally deleted the PM with the instructions, and I don't want to forget a detail and have you screw up your motor.

[Pittman]

Dan, how do you get SCX motors to run the same warm as cold? Blueprinting?

[Danni_OLaisip]

I am liking these "Project" threads of yours. Keep it up.

Do you have a better picture of that two story garage? What a great idea!

[cydewaze]

I am liking these "Project" threads of yours. Keep it up.

Do you have a better picture of that two story garage? What a great idea!

lol, it's just some hobby plywood.







Problem is, I now need a second garage!!

[yellowdog6769]

Dan, how do you get SCX motors to run the same warm as cold? Blueprinting?

Sort of! Most of the series I race in don't allow the motors to be opened, but this little trick can be done without opening the motor.
First, the reason why SCX motors need to "warm up" before they run fast is the brush springs have too much pressure on the brushes. This causes drag on the com and heat starts building up in the endbell. Ever notice how cool the arm is but how hot the endbell gets during break in? Bingo! When the springs get hot, they weaken and the motor speeds up. This is not good for a couple of reasons.
1. Springs will weaken too much over time and cause poor performace and even more heat.
2. Too much spring pressure can and will cause damage to the com. It can cause groving and very high rate of wear to the brushes. This can cause enough brush material to clog up the space between com segments and short out the motor.
3.Too much heat build up on a new motor can get the solder joints on the com-disk to fail. That is a very bad thing! Some times it can be fixed, sometimes not.
First I tried putting a bend in the brush spring. Hard to get it just right and springs don't like being bent the second time, they have a nasty habbit of breaking. Then I tried cutting material off the brush. That has problems too. Sometimes the brush would crumble and be unuseable.
This works and it is easy to do. Remove the motor from the pod. then carefuly dissengage the spring end from the holder clip. Tap the brush out of the brush tube and inspect for roughness. Remove the other brush.
On the spring end of the brush you will find a small grove all the way across the brush. That is your cutting guide. Measure down from the edge of the brush 1mm. and carefuly make a line. Now take a fine tooth saw( I use my trusty X-Acto fine tooth thin blade saw) and VERY carefuly and slowly cut down to your 1mm. mark. Stop and check often to make sure your cut is good. Cut straight and without side pressure. Even a little side pressure can get your cut off course and ruin the brush. When you'r done cutting and have removed all the cut material, reassemble your brushes.
The first time I did this I was rewarded with a motor that started at a much lower voltage and didn't get hot. This works better on a brand new motor, but it will also help older ones too. I have a Audi R10 that was just a dog and stayed at home (stay on the porch if ya can't run with the big dogs) so it got the treatment and now I run it alot!
Now go forth and kick Scaly Butt!
Dan
Team Super Tires

[Pittman]

That is really interesting.

In model railroading, where we want a low starting voltage, and we want smooth low speed operation, we used to reduce the brush pressure on the old inline, open frame motors that had exposed brush springs. At the same time, where we wanted more RPM out of similar slot car motors, we would increase brush pressure. Extra pressure meant higher RPM, because the commutatiors were untrued, and the pressure reduced brush bounce and arcing.

On the test stand, I have found that SCX motors have about the right spring pressure at 18k or above, to ensure the highest RPM reading on the tach, no load at 12 v. I'll try your method and see what I come up with.

Thanks!

[LanciaB]

Good advices !!

Another - cheap - way you may try to increase your Peugeot's handling, is to lower the front axis.

The front tires of most of the SCX cars are a little too high, as they are the same as the rear ones.
So the front axis is a little to high on the track, and the guide blade is not going deep enough in the slot, and the car deslots on hard cornering.

You can solve it two ways :
- if the front axis is at the good height (ie front wheels not touching the track, you can pass a photo-paper sheet between the track and the tires : OK !! Don't touch anything !
- if that space if larger than a photo paper sheet : you have to reduce you braid to make it thinner. First make them single-pass instead of double pass, you'll gain half a millimeter at least. If not enough, change them for pro braids.
- if the tires are touching the track, lower them !! You can easily change the tires for "0-grip low profile" ones, Slot It and NSR are making some (17x8 an 17x10) working perfectly on SCX wheels ; on an other way, cheaper and "home made", you can just hardly sand your front tires until they don't touch the track.

The car will be really better balanced, will make less noise and will be more stable and better planted in the slot.

[DaVols]

fine-tuning the magnet height

Considering all the modifications you've done, you ought to give it a try without the magnet. My track is similar to yours with tight turns, short straights, and decreasing radius turns and because of the slower speed of that type of layout, going without isn't as difficult compared to a faster layout.


Da Vol - Bruce

[cydewaze]

I have a couple of SCX no-mag cars now, as I've pulled the mag from both my C6R and my Aston (figured the Aston can't handle much worse, so no harm in trying). The Aston isn't so bad without the mag, about even with the Vette. I'll try de-magging the Pug soon and seeing what happens.

[LanciaB]

Best car on my track, far before all NSR and Slot-it from my friends, is an Aston, fitted with a Cartrix TX6 motor (special SCX version with long arm and adaptors, 25krpm @ 12v and a lot of torque), SCX Pro braids, NSR zero Grip 17x8 front tires and Paul Gage's Urethane 20x12 rear tires.
The pod movement is limited by a strong tape.
All the rest, wheels, axles, etc...is genuine SCX .
We run without magnet, on a 2 lane 19.38 m Scalex Classic bumpy track, 12volts, 10 amp max, Parma "custom" controllers (3 avalaible sets : 20/40/60 ohms with a swith & 2 resistors)

.....and the car is amazing on the track, much more beautiful than all these NSR Mosler crap !