48 replies to this topic

[Duffy]

Replace one of the bushings with a ball bearing and I BELIEVE the drag/friction will be reduced, resulting in better performance in the form of higher RPM. I could be wrong, obviously, but it's a very simple common-sense kind of assumption I'm making. Frankly, I'm flabbergasted that no one else seems to think this plausible... that less friction would yield higher RPM.

I feel the same way, Tex; while Pablo trumpets the modern Slick 7 bushing and it can be great, and while modern synthetic lubricants like Mobil 1 are indeed actually little ball bearings on a molecular level, I can't get clear of the idea of two bits of metal rubbing past each other - however aided by oily little molecular balls - as being equal to good ol' steel rolling on steel. Can't see it, won't accept it.

Like I said before, maybe the advantage hasn't been measured by the clock. Okay.

There's a very important, very comforting aspect of all this that we shouldn't forget: what we think is happening - well, it has immense worth. Like Dumbo's feather. What we put into our builds may be right, may be wrong, but if we really think we're on the right track with it, it's one less thing to worry about as we narrow our focus down to driving that race.

Just to underscore that statement (and to run a da capo back up to Tex' bold-type), I totally stand by the sentiment so eloquently set forth by "Elder Price"in THIS pertinent clip from The Book of Mormon.

Duffy

[Tex]

All you guys who dismiss the simple premise that IN MOST CASES (yes, Pablo, there's always exceptions) BBs will have less friction and thus increase rpm ARE BARKING MAD! I'm not saying that BBs alone are the reason for the better lap times and race lap totals (tires, glue, practice, clean heats, etc.), but to not even acknowledge that using BBs COULD yield more rpm (much less PROBABLY) is ignoring the 800-pound gorilla in the room. I dare say that the F7 has been righteously obsoleted in the highest levels of IRRA{tm] competition.

Now, having said all that, can you guess what motors I'll run at the next IRRA[tm] race I attend? PRO SLOT, BABY!!! I have nothing against the PS motors, only turning a blind eye to the obvious.

[Mike Patterson]

I think there's waaaay more friction between the brushes and comm than there is between the shaft and bearings, regardless of material.

[Duffy]

Yup, brushes and comm get fricky. And that's over a larger diameter than the shaft/bushing, so the SFPM & therefore the induced drag goes up with the radius increase.

Now, consider, what happens when you add a side-load to the motor shaft in a bushing? Same thing as happens when you press a brush into a comm, only smaller.
I question: are we saying there's no difference in RPM with bushings over BBs, based on what? Amp draw? Dyno?
Does any test measure RPM under the kind of side-load situation we get with a pinion trying to turn an axle?

Because, if it's miniscule well okay it's miniscule - but it's there. I'm with Tex, even if it's still way down there in the Drag Soup and we won't see it on the clock.

BBs still last longer, and I'm lazy.

Duffy

[Tex]

Oh, I'm just gettin' started! Remember Galileo? The whole sun-centered universe thing? And how the Vatican took a dim view of this?

Am I to believe that ALL slot racers for decades have used BBs in their motors and rear axles merely so they wouldn't have to change out bushings so often? Would you have me believe that these PS motors with their ball-bearings are immune to the normal physics we've grown to love?

Good GOD, man, was I abducted by aliens years ago and taken to some Bizarro world where I was spoon fed this conspiratorial ball-bearing drivel by said aliens with a sick sense of humor and then dropped back on Earth so they could giggle at my plight from their inter-dimensional existence?!?!

[Pablo]

I had a talk with the IRRA™ Board of Directors.
They have hereby granted permission for Tex to use BBs.
Yer welcome

[Duffy]

Good GOD, man, was I abducted by aliens years ago and taken to some Bizarro world where I was spoon fed this conspiratorial ball-bearing drivel by said aliens with a sick sense of humor and then dropped back on Earth so they could giggle at my plight from their inter-dimensional existence?!?!

Sussed it out at last, huh, human?

[Noose]

I have motors with both and no speed difference whatsoever. Have them where they were changed over to BBs during the refurb process, and again no difference. The benefit is definitely less wear on the shaft and the bearing itself vs the bushing.

[Cheater]

And, while my relative lack of success compared to theirs is a matter of record, I can watch my BB'd rear axle spin and spin and spin, finally coming to that little back and forth rocking motion before coming to a stop... I've not seen bushings do this.

Ask Manta Ray or Pablo if they've seen this behavior from the proper bushings aligned properly. And I can show it to you the next time we're in near proximity.

Maybe the lesser friction from using BBs doesn't offer a GREAT increase in performance, but you'll never convince me that there's NO increase in performance from using BBs as opposed to bushings.

Sounds like an experiment is in order, Tex. Baseline a car with good quality rear axle bushings that are properly aligned and then replace the bushings with bearings and put it back on the track. Let us know if you see any difference in lap times.

[Ron Hershman]

While BBs may spin nice sitting there spinning them on the work bench... that does not always equate to speed or going "faster" on the track.

If we were racing cars Pinewood Derby style where less friction means everything, then yes, they do go faster in "gravity" type racing. If we were to push cars around the track... BB cars would require less effort to do so.

In a slot car BBs can reduce friction and oilites can as well, as long as all are properly aligned.

In the slot car once the motor/car is up to speed... BBs don't make them run any faster. They may get to up to speed a tiny bit quicker but once top speed is achieved... BBs doesn't add to that speed.

We get our brakes from the motors... a car under braking will not "coast" any further when you compare BBs to oilites. But if we ran with NO brakes then a car with BBs may coast a tad further than one with oilites, but that again is it yet to be proven. In theory BBs should, but maybe not in the actual application.

I have won races with Can-Am cars with both BBs and oilites... I can tell NO difference in a car on the track that has BBs versus oilites.

With BB fronts I have noticed no increase in overall speed, but the car may handle a bit better due to less front wheel wobble between the axles and wheels.

[John Streisguth]

In Retro East, we have had some races where new track records are set, and some races where we didn't. IMO, track condition has a lot more to do with the lower times and higher lap totals that the tiny amount of difefrence a ball bearing in the motor may make, considering how much else is on play while a slot car is going around the track.

And as Ron mentioned, the BB front wheels probably would make a bigger difference, keeping in mind you are going from aluminum on steel to a BB, and a fairly wide contact area at that.

[Tex]

Sounds like an experiment is in order, Tex. Baseline a car with good quality rear axle bushings that are properly aligned and then replace the bushings with bearings and put it back on the track. Let us know if you see any difference in lap times.

I'm not consistent enough at driving OR setting up to be the right person for such a test.

How 'bout just puttin' a tach on the motors before and after installing the BBs? Anybody got a tach and a couple motors that need BBs installed? The before and after readings should take place immediately before and after the BB installation... no other refurbing done that might affect the results.

And, again, I'm still flabbergasted that only a couple people here think it plausible that BBs = less friction = more rpm. Absolutely dumbfounded.

[Cheater]

Tex,

Tests with meters kinda bore me. Only thing I am interested in is the on the track testing. And, if you or anyone else wants to A/B a motor with bushings and then a bearing, be my guest.

We're really discussing three different bearing applications here. Bearings in motor cans, bearings in front wheels, and bearings on rear axles.

If the rules allow for the can bearing, it is misguided not to use it, simply for the prevention of shaft wear resulting from the side-loading generated by the crown gear. It's a no brainer and that's why the IRRA™ eventually approved it.

I think for most racers, BB front wheels primarily address a wear issue. There may be some handling advantage, but most are happy the BB fronts outlast a whole bunch of quick-wearing aluminum fronts. They're costly though.

The only place where it is a toss-up in on the rear axle. I happen to think a well-aligned set of S7 bronze bushings will outlast a set of BBs, is more durable to boot, and the frictional difference isn't very much at all. I don't diss the bushings if my poorly-braced bracket bends...

The part I believe you're missing is that the total of the "losses" in our little electromechanical device is the sum of a lot of little losses, of which friction is one. The level of loss imparted by friction in a slot car (the well-built ones we're racing, anyway) is a very small percentage of the total losses. Even if a bearing is 50% better than a bushing in terms of friction (nowhere near that, of course), the difference it will make in the total losses number is perhaps measurable, but almost certainly insignificant. And that's what I think most of us are trying to say: it our experience, the difference seems so minuscule as to be indiscernible.

The same situation exists in the IC engine, i.e. there's virtually no horsepower to be found by reducing bearing friction. Bearing durability and cost are now more important factors than any measurable frictional reduction for 99% of the industry. Years ago, it was not unknown for some sports car and racing engines (Bugatti, Porsche, etc.) to use roller element bearings for rod and main bearings. This is rarely done anymore, except in motorcycles where a roller element bearing can save of space as compared to a plain bushing.

[TSR]

The biggest friction loss on a slot car is that of... the braided contacts!

We need infrared laser contacts, worth 3 seconds per lap!

[Duffy]

One prominent whiner at Prof. Fate's local track once accused Rocky's cars of being faster because he'd figured out some means of "transmitting" more power to his motor. No kidding.
We had a great time with that in conversation, it's such a perfect Guy thing--

"Ah! I have discovered Broadcast Power--what should I do with it?
"Solve the world's energy problems?
" --Or win a slot car race?..."

Only recently we came across a paper in one journal describing a property of electromagnetic bleed-off from one motor to another nearby...
And we both went "Oooooo, Broadcast Power!!"

I'll get to work on that infrared thing. I'm sure there's a way to hook an Arduino up to that... I'll get back to you.

Other'n that, I think Greg's pretty much said all I've been ramblin' on about. Good on you, chee.

[Tex]

Well, convinced of my righteousness and everyone else's dumbassness, I went over to OWH and pitched my case.

The first post was by a local Ft. Worth guy whom I know personally and respect his knowledge and experience. He echoed what you guys have been saying. I made one last desperate attempt at finding vindication, calling up another local DFW guy who's been around so long he saw dirt get invented. He, too, echoed what you guys have been saying.

Mmmm... crow, the OTHER dark meat; it's not just for breakfast any more.

[Cheater]

Tex,

When we met at Sano I, it was immediately apparent to me that you were stubborn, opinionated cuss.

Today, like me, you are a stubborn, opinionated OLD cuss.

But I don't hold that agin' ya. Some of my best friends as jest the same. LOL!

[Duffy]

But NOBODY'S saying you're wrong, Tex! You're right - it's just so far down in the soup that these RACERS don't bother to look at it!

We fringe guys, we KNOW. Don't it make us feel all righteous n'all?

Even-OLDER-Duffy

[Cheater]

Gentlemen,

Please don't forget that it is differences of opinion that often result in good racing!

[Ron Hershman]

OK, Tex, I did the dyno test this morning... took a oilite PD motor and ran it on the dyno... got the readings then popped off the can and put a BB in it and put it back together... ran on dyno and there was no increase in RPM on the dyno.

To me... free revving and spinning are the same in a motor on the dyno... bushing or BB. I would like to think once the motor is in the car there could be a "slight" increase once the motor shaft is under load. But is it much of a difference?

[MantaRay]

Ron, great test...

And while you were at it, you got a refub done. LOL!

[Uke]

Curious... in IRRA™ Retro racing you can run bearings everywhere or just in motor can? And D3/SCRRA, just in the chassis or not at all? I know I could probably look it up but I'm lazy.

Thanks,

Ryan

[Cheater]

In IRRA™, ball bearings are allowed on both axles and in the can end of the Pro Slot motors.

I think D3 is rear axle only, but don't take my word for it.

Someone else will have to chime in regarding SCRRA.

[Ron Hershman]

In D3 they use FK motors that can't be opened or refurbed and the FK motors come with oilites... so no ball bearings in the D3 FK motors.