72 replies to this topic

[stemmy]

Nice-looking gears, but I think Rick Davis has a point.
 
If these gears are going to be legal, then why not allow the same modifications to Parma gears?
 
I'm not talking about the Matt Bruce/Bryan Warmack style mods, just those that anyone can do with a Dremel or a file.

What exactly is the Bruce/Warmack mod?

[Cheater]

I sense a bit of sarcasm?

No, not really.

To the best of my recollection, I've never once used a 64 pitch crown gear, so no experience thus no recommendation.

All I could realy have offered was that I know of no one preferring to use 64 pitch crown gears.

My main point was that the rules don't prohibit their use.

[JohnnySlotcar]

Just spent 3 hours prepping sleeved gears for the season. My race budget is spent for the season. Run what ya brung now! LOL

[The Number of]

What exactly is the Bruce/Warmack mod?

The pics show better than a description:http://www.flickr.co...157623624722510

 

http://www.flickr.co...157623624722510

 

Notice the missing hub and the set screw now on the other side.

[gascarnut]

The JK 64DP crown gears do not last in Retro cars, as there is not enough stiffnes in the motor brackets to avoid the occasional chatter, at which point the whole gear strips.

 

If you run non-hypoid, then the old 64DP Sonic bronze crown gears wrok well if you can find them. In a hypoid situation they are not too good as they are very small diameter, but I have run hypoid brackets using the aluminum drag gears from Sonic in large tooth sizes (39 or 40), meshing with a 72DP pinion of the desired tooth count, and that works pretty well. It's just more effort and more expensive than using the Parma gears and tapered pinions.

 

I hate to say it for Parma's sake, but I don't think they will need to make gears for Retro any more unless they up their game to match these. So modifying them will be a moot point who will use them.

 

I would add that until we see how straight the RF gears are, whether their toothform will accommodate hypoiding and whether the teeth will survive crashes, the Parma gears remain a known and reliable item. The lack of ribs on the rear of the RF gear says to me that the material itself is very stiff, which may cause its own unique issues.

[MantaRay]

Notice the hub is lightened; how will this mesh (pun intended) with the rule that disallowed lightened Parma gears??

 

Looks like the hub from his regular spur gears.

[Greg VanPeenen]

The JK 64DP crown gears do not last in Retro cars, as there is not enough stiffnes in the motor brackets to avoid the occasional chatter, at which point the whole gear strips.
 
If you run non-hypoid, then the old 64DP Sonic bronze crown gears wrok well if you can find them. In a hypoid situation they are not too good as they are very small diameter, but I have run hypoid brackets using the aluminum drag gears from Sonic in large tooth sizes (39 or 40), meshing with a 72DP pinion of the desired tooth count, and that works pretty well. It's just more effort and more expensive than using the Parma gears and tapered pinions.
 
I would add that until we see how straight the RF gears are, whether their toothform will accommodate hypoiding and whether the teeth will survive crashes. The Parma gears remain a known and reliable item. The lack of ribs on the rear of the RF gear says to me that the material itself is very stiff, which my cause its own unique issues.

Did you not read Matt's post? If the information comes from Matt you can bet the farm on it.

[gascarnut]

Of course I read Matt's post.

But I know manufacturing, and I know how much difference there can be between prototypes and production quantities.

So let's wait and see shall we?

[Gator Bob]

  Nice gear, Matt. 

[Duffy]

As a guy who worked in plastics for a few decades, I agree with Dennis' comments. Peer review is a vital part of any development program, and a question ain't a slap.

 

The grainy finish on the samples in the pic suggests that this is a glass-fill compound. The surface finish of an injection-molded part decreases with the percentage of glass, and this doesn't look real smooth.

 

So if it is glassfill, it means several things:

 

The shrink factor - the amount the part will pull in as it cools and settles - also decreases with more glass; but the potential for checking and stress fracture increases. It's a balancing act, made more complex by molding around an insert.

 

Now the good part is, with the lesser shrink and increased rigidity you can control flatness and concentricity better than the plain polymer will allow. BUT you might get a part that'll shatter under extreme loads, where Ol' Pinkie will just flex. Just like the panic around glassfill guides a couple years back, we'll just have to put 'em into general use and see what happens.

 

The technique of "melting in" a mesh with a Bic lighter will probably need tweaking. You also may see increased wear in your pinions from what's now really a two-ingredient composite (which also figures into the melting thing!) - the fibers will become exposed and will abrade the pinion. Watch for that.

 

There may be other things. That's just what I see right off.

 

Duf

[TSR]

Between negative shrinkage and this game changer, our lives may shift from pink to black. Now I am depressed...

[Gator Bob]

 No politics a-loud. Back to the glass-half-filled.

Edited by Gator Bob, 19 February 2014 - 01:17 AM.

[S.O. Watt]

OK, gotta ask after PdL's comment....

(in my Cris Economaki voice)

Matt, is it true what they say about once you try black, you'll never go back?

[gascarnut]

As a guy who worked in plastics for a few decades, I agree with Dennis' comments.

 

Uh-oh, now you've done it!

 

You do know that agreeing with me about anything posted on Slotblog is in contravention of the Terms of Use, don't you?

 

[Noose]

Well, I have some of these and I did burn one on just to see what happens. Did not get any little tooth gremlins and it was smooth.

[HarV Wallbanger III]

I agree also, Dennis... we will see after the Retro dudes get hold of them and subject them to untold abuse... Time will tell but I hope they work as Parma has been asked for years to do 3/32" hubs...

[Half Fast]

If Gugu wants to torture test them, give them to us C, D, E , and F main racers, not the A main guys. We'll put them through their paces.

 

We will find issues that even Debby Downer Duffy didn't think of!!!

 

Cheers,

[TSR]

Glass-filled nylon is one of the finest anti-friction plastics out there, but its strength all depends on the amount of glass powder in the mix...

 

Cox used 18% in their famous Nylatron gears that were a bit too flexible. Over 35% and it becomes too brittle and can easily break.

 

Hence, a happy medium is 25 to 28%, that worked very well in many applications. It is used for many automotive suspension bushings...

[Duffy]

Yup to all, Philippe, but as Matt, you, I know, there're "polymers" and "polymers", and we haven't heard just which was used in these gears, nor the percentage of fill.

 

Nylatron originated as a sturdy wear surface, not necessarily a structural engineering plastic, which the trade name eventually became associated with about ten years after Cox did its thing with it - so that doesn't count here some 40 years hence; and we also haven't yet been told that we're looking at a nylon compound or one of the possible applicable copolymers.

 

None of which is gonna matter much to the racers, anyway! What we want here is to provide these bits of data to the racers that'll use these, so they can understand what they're looking at when they see something in their cars. Right, guys?

 

Take it to the track, and give us some more hard data to parse.

[Gator Bob]

 It is used for many automotive suspension bushings...

 

... and leaf springs.

 

Duffy, depending on the 'chemical compound' they might be a 'use no oil' component.... right?

 

Wait... support your local bottling plant.

[gjc2]

Good news, long overdue.

[Cheater]

I agree, George, long overdue.

But I must note that the pricing for the new Red Fox gears has not yet been announced. Will you still be as pleased if they cost twice as much as the existing sleeved Parma gears?

[SlowBeas]

First of all, I will admit to knowing nothing about the engineering and science of gear production. I'll defer to Dennis, Duffy, and anyone else with an inclination toward the achievement of a Mensa membership. I'll put it in plain language, as a buyer and user.
 
I bought some of the gears mentioned in a previous post because I thought it much smarter to avoid a sleeve and mount the gear directly to the axle of my Retro chassis. But I found that the teeth on 64-pitch crown gears are too fine and not strong enough to withstand lengthy interaction with a pinion. Despite a fine mesh in my setup, the pinion would eventually grind on the teeth and leave them a withering mess by the end of a race. I think it must have something to do with the amount of force being thrust upon such a small bit of plastic. Lost efficiency, lost speed, lost race.
 
I, too, am pleased to see Gugu taking the lead on this issue. Marketing 101 would tell you that you identify a need in the marketplace and you satisfy it.
 
It's about time.

[W. J. Dougherty]

Usually to use those 64p crown gears you must use a 72p pinion.  For some reason they seem to work better that way. 
 
They must work because that is all they use in ISRA 1/32 F1 Eurosport. That is a lot more HP than you Retro guys ever thought about...

[gotboostedvr6]

They use a tube that extends from the crown gear to the bushing or bearing which helps reduce side loads on the gear.