1441 replies to this topic

[Phil Smith]

But--sorry--your point's wrong: that's not stress relieving, not by a long shot, and it won't stay stress-relieved.

Well it does lessen the stress, but you're right. It doesn't completely remove it.

What it does do, is induce an equal amount of stress in the opposite direction, and they cancel each other out.

So I'm not saying it completely relieves the stress. I'm saying it counter balances the stress, and it will stay straight.

[Duffy]

I'm not saying it completely relieves the stress. I'm saying it counter balances the stress, and it will stay straight.

I'm feeling kinda bad about this, but--I gotta address this from a machinist's POV:

That isn't stress relief, that's induced dynamic balance. I'm sorry, but there're more forces at play here than just bending back and it can't be expressed in short terms. --Not by me, anyhow. Sorry, again.
The thing we're not looking at here is what happens to a long piece of metal when we take material away on one side. Whether by milling, filing or grinding or even EDM, we disturb a varying amount of the neighboring material on each side of the cut, on a molecular level. With endmill, saw or abrasive, part of the material is forced away from the cutting element and has to shove into the surrounding space--and it will expand that suface, imparting a stress on that edge of the cut. That's why the long workpiece warps away from its cut.
There're two good ways of dealing with this:
One is going thru a stress-relief heat cycle, literally relaxing the molecular structure of the workpiece, and then re-hardening and drawing back (and sometimes going through the same process again). I've done all this, with 20"-long reamer blades; beyond our capability, or at least our desire, I'd think.
OR, we can peen the opposite side--systematically tapping with a hammer and locally compressing the surface of the workpiece so it's similarly stressed and in balance. Works on long gib wedges in milling machine slides and the like.

--Trouble is, the minute we hit either with sufficient heat--and a soldering iron represents sufficient heat--we're back to all-bets-are-off.
Just exactly like if you bend a warped piece past flat and then re-bend, to "counterbalance" it: it'll be conditionally flat, until you do anything with it.
And "anything" includes a season of racing. It won't STAY.
That's the cold facts of steel.

Now, we can ignore any of these facts, and I and you and all of us routinely DO!
We build what we've got in mind to the best of our ability on this night...and by darn, most of those chassis do well, and are successful, and win when all is right...
...So, why argue these details, past the point of Informed Choice?

Maybe that's the point where we agree to go with what we're comfortable with.

Duf

[Greg VanPeenen]

Here is a real short and to the point post for ya. If stress is a concern, get off a couple of grand and buy your self a Metal-Lax table.

Look it up.

Be well,
Greg V.

[Bryan Warmack]

Bryan,
Is the above process how you made the flat wire that John Gorski has used on some of his beautiful chassis?

Mike,
Yes, except I removed more than 20%...from both sides I believe. I think it was .093 and ended up about .050, exactly the stuff the IRRA is trying to avoid and I understand your reasoning. About the same time I made some stuff for John, I also posted something on Slotblog with pictures showing exactly how I was doing it. I had no idea until recently that removing even small amounts was taboo. I thought the issues with my cars were the main rails being higher than the rest of the chassis and I know that has been sorted out. The little amount I removed was probably just overlooked as it was hidden by the pan tubes. I wasn't trying to cheat and it wasn't intentional. I just had no idea about the rule. Here is a pic of the basic set up I use. I am not trying to advocate anything or change anyone's mind here, just add little information racers may use.
,


Keeping the piano wire (or any small round stock) from rolling around is 90% of the problem. The "U" bend prevents rolling and adds a leg you can hold while grinding the other leg. I use a $9 Harbor Freight air angle grinder here. If you only want to remove a small amount a good file also works as the piano wire is really not that hard. The other 10% is a good eye and a steady hand!!
Out here in La La land any specific limitations on main rail construction were never an issue as D3 and now the SCRRA have just chose to overlook it as long as the basic chassis restrictions are met. No flat rail monster has shown up yet in 6 years out here and if it does we will just address it then. Different rules philosophies but as long as they work for their respective organizations and racers that's all that matters. Didn't Duffy imply somewhere here that there is more than one way to skin a cat?? I think?

[MSwiss]

No one thought you were cheating.

Being on top, Noose might of missed it.

[Mark Wampler]

Mark, please enlighten or correct me as needed: having chiseled out this little semantic niche, can you describe, sketch out, or photograph an application for what you're concluding this rule to mean in your specific interpretation here, and show how it might work to the advantage of the builder?
Aspiring minds want to know.

duf

Duf,..... Semantics, don't ya love them? Webster to the rescue, lol ! We get our connotations from how words and phrases are used. So main rails are a component that come in pairs. There may be more than one pair but the MAIN rails are the primary rails that are designated by the builder accordingly. The outer pair maybe the Main support rails and the inner two secondary or "stabilizer" rails.. Visa versa. The inner pair may main and outer be secondary. Get my drift? I like to call the secondaries 'stabilizers' if I feel they specifically serve that function. More often they're used for specific tuning purposes, of which is a guarded secret ! Since there are only ONE pair of main rails, the second or third pair are free to be shaved to builders specs. That's my take . Since I'm on the left coast, all of the above is purely academic.

I admit I'm no match for your posting word count.

[Noose]

And the point of this is none of the tools shown to grind these rails is a file or a Dremel. Look at all the fancy stuff. The average builder does not have this stuff and THAT is the point of the rule.

[Tex]

Main rails to remain untouched

Then secondary, not main rails will be ok to shave.
Secondary rails connecting the motor bracket to the front axle assembly are considered stabilizer bars.

I'm bettin' the IRRA won't make any such distinction. Their take will be ANY rail connecting the front to the back is a "main" rail. I understand your distinction, and it's a nice attempt at pleading your case with the judge, but it probably ain't gonna fly. While I may not agree with the actual rule about modifying the main rails, I personally have always considered any rail connecting the front to the back to be a "main" rail.

[S.O. Watt]

Joe, see post 842, a file one can buy at any Big Box Home Improvement Store works fine.

[MSwiss]

Mark,
If these "stabilizer" rails are soldered and connect the front of the car with the bracket area, they are still considered main rails and can not be flattened more than the 20% and only on the bottom.

In the future you'll have to provide pictures since you have your own unique terminology for the component of a slot car.

[Ron Hershman]

And the point of this is none of the tools shown to grind these rails is a file or a Dremel. Look at all the fancy stuff. The average builder does not have this stuff and THAT is the point of the rule.

Oh but Joe...... they have done it a 9 buck Harbor Freight Air grinder........ that's way cheaper than a 60 buck and up Dremel tool....well except one needs a decent air compressor to run their air grinders....... add another 2 hundred bucks of so for a decent air compressor. LOL

[TSR]

DECENT AIR COMPRESSORS

[Ron Hershman]

DECENT AIR COMPRESSORS

Which one would you suggest???

[TSR]

The cheapest at 64 bucks (97080) works great with the 5-dollar grinder. I have one at home and use it for all kinds of things from keeping tire pressure on my cars to power a power washer.
However I am not as sophisticated as using an air grinder to grind chassis rails, I use a battery powered Dremel and a thicker "brown" disk, works great. No need for a machine shop, mill or special talent.
I think I paid under 50 bucks for the Dremel tool with a ton of accessories, when my April 1970 Dremel at last, died of old age last year.
RIP.

[Guardrail]

I have the item # 97080 and highly recomend it.

[Phil Smith]

I'm feeling kinda bad about this, but--I gotta address this from a machinist's POV:

That isn't stress relief, that's induced dynamic balance. I'm sorry, but there're more forces at play here than just bending back and it can't be expressed in short terms. --Not by me, anyhow. Sorry, again.
The thing we're not looking at here is what happens to a long piece of metal when we take material away on one side. Whether by milling, filing or grinding or even EDM, we disturb a varying amount of the neighboring material on each side of the cut, on a molecular level. With endmill, saw or abrasive, part of the material is forced away from the cutting element and has to shove into the surrounding space--and it will expand that suface, imparting a stress on that edge of the cut. That's why the long workpiece warps away from its cut.

Well, assuming that you work slow and don't heat the metal, milling and grinding only effects the surface, a tiny, tiny percentage of the mass of the wire. So it doesn't seem likely that this very thin veneer of disturbed metal would have anywhere close to enough stress to induce warping--at all.

What seems more likely to me is that the metal already has surface stress from the manufacturing process, and when you grind or mill one side, you are removing stressed material, causing the metal to warp, induced by the opposite side, which is still stressed.

[Bryan Warmack]

And the point of this is none of the tools shown to grind these rails is a file or a Dremel. Look at all the fancy stuff. The average builder does not have this stuff and THAT is the point of the rule.

No one is questioning your rule and reasoning concerning the main rail. Some are questioning your knowledge of tools.

[Bryan Warmack]

Oh but Joe...... they have done it a 9 buck Harbor Freight Air grinder........ that's way cheaper than a 60 buck and up Dremel tool....well except one needs a decent air compressor to run their air grinders....... add another 2 hundred bucks of so for a decent air compressor. LOL

Which one would you suggest???

You can get a little pancake air compressor at Harbor Freight at times on sale for $40.

[Noose]

Bryan it's not just the tools or my knowledge. This was BOD decision and in fact suggested by Tony P whom I am sure you know can use tools.

It's the ability of the average guy to do it. Why is this such a big problem? There are hundreds of frames out there built without grinding down the rails. They were built within the confines of the rules and thee have been plenty of racers within IRRA^TM using them.

If everyone had access to the tolls and the skillset then fine. They don't. You are special as are some other some other guys. We don't cater to special though.

You cars are fine for SCRRA though so they can be used there.

[Duffy]

This has turned into a geeky hijack within a rules-comment thread & it may not be appropriately placed, but I'm likin' it.

Well, assuming that you work slow and don't heat the metal, milling and grinding only effects the surface, a tiny, tiny percentage of the mass of the wire. So it doesn't seem likely that this very thin veneer of disturbed metal would have anywhere close to enough stress to induce warping--at all.
What seems more likely to me is that the metal already has surface stress from the manufacturing process, and when you grind or mill one side, you are removing stressed material, causing the metal to warp, induced by the opposite side, which is still stressed.

These are well-thought-out points, but unfortunately that turns out to be the case in real life: machinists routinely wrestle with the flatness issue, coming down if necessary to air passes on the grinder & multiple flip-flops to equalize the warps; and even at that we know it won't stay straight. Ultimately, you just design around the problem wherever possible.

Your observation about stresses in the original stock is true to an extent, but it doesn't explain why a piece cut from the middle of a bar would still warp away from the side just machined. The real cause just sounds counterintuitive: we don't wanna buy it. But it's there, like it or not.

And the more we're aware of it, the better we deal with it!

See, this sort of argument is a very typical day's talk around old-school toolmakers & such. I say "argument" because that's what it sounds like on the outside, but it's the crunching of ideas and concepts important enough to get loud about; it's job-related, it's vital, and it's not about the personalities, it's about the steel. It informs our work in more ways than just doing it right, it also gives some ideas for why something's going wrong. We may never need the information - or it might save a workpiece.
The same applies here, and for all the same reasons. I like that.
We may be talking in tolerances we don't need to look at; we might get a flat-enough piece of wire, or we might bend it flat or whatever, and that chassis might be perfect for its whole career. OR, it might need regular re-jigging, or it might have one irritating habit you can never tune out, or, or...and you might have a cause.
What you do then, you think of a way on the next chassis to try to get around what happened there. Or not!
Informed choice.

Duffy

[Mark Wampler]

Mark,
If these "stabilizer" rails are soldered and connect the front of the car with the bracket area, they are still considered main rails and can not be flattened more than the 20% and only on the bottom.

In the future you'll have to provide pictures since you have your own unique terminology for the component of a slot car.

See here's an example of arbitration without documentation. There isn't an official definition of what a main rail is. How many "mains" exist in common uses of the term? ONLY ONE. Semantics, yes, but since there are some Retro organizations that are so dead set about being absolutely anal about their rules, EVERY word, term and expression should have its own glossary and thesaurus attached.

[Noose]

Main rails are all the rails that connect the front to the rear. That's how I look at them in tech. Id they were side rails, front rails, rear rails, or anal rails then they would not be main rails.

When you come race with us I will show.

[Mark Wampler]

Is that the "official" definition? Then it must be written alongside the section in your rules encyclopedia dealing with chassis construction, so there won't be any confusion.

[Noose]

Mark, if you read the rules it is what it says.

A rail is defined as that which connects the motor bracket to the front of the chassis.

But since you don't race IRRA™ how would you know, right?

[Duffy]

Thee's also a convention in society we can think of as "The Common Usage" - there are words and phrases that a given population - Brooklynites, for instance, or Slot Racers - understand in their context. We don't need to constantly reinforce them: if we are to live in the community, we will abide by the community's structure and just go along. Common Usage.
--Well, in Brooklyn, now and then you get some guy on a street corner shouting his take on something: he's right & that's all dammit, the rest of you don't get it. Well, three things usually happen around this scenario: the wagon comes and scoops him up, or some local guys'll put him on the sidewalk and/or chase him off, or people just walk by.
That's Brooklyn.

Duffy