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I'm spinning crown gears


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#1 9lives

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Posted 23 November 2021 - 09:20 PM

Gentlemen,my name is John Hegedus. I race retro pro f1 and can am here in So Cal, SCRRA Piranha Raceway. Last race I spun crown gears 3 times. Twice in f1, once in can am. All crown gears ⚙ were kobold. It appears the the set screws cracked. I did come off and went a little wall to wall. I also had set screws fail Crack in rear tires. I've never had set screw issues like this before. Apparently Parma is out of business in terms of crown gears. Notwithstanding my minor wall to wall issues is anybody else experiencing this type of failures? Set screw issues in crown 👑 gears and rear tire hubs,more importantly what are some solutions I get the crashing g issue, but the offs were not significant hits. Any solutions would be appreciated 🙏 curt criticisms about my driving capabilities will not be appreciated by way of driving background check my a main results at buena park from January 2015 through October 2016 in both classes
John Hegedus




#2 swodem

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Posted 23 November 2021 - 09:22 PM

It’s impossible for a set screw to ‘crack’ when being done up in an aluminium hub
The aluminium thread will strip long before you could damage a steel set screw
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#3 Jay Guard

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Posted 23 November 2021 - 09:38 PM

Steve, I wouldn't say impossible.  Depending upon the base material and it's processing it's possible that there is something like hydrogen embrittlement happening.  I wonder if John was using the Koford "gold" set screws which some seem to have issues with and often replace before using.  The gold colored finishing process combined with possible stress risers on the inside corners of the set screws may allow the set screws to easily crack.  While this is all possible, and conjecture on my part, for this to happen on (apparently) a good number of set screws, especially if they are of different manufacture, seems unlikely but possible.


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#4 JerseyJohn

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Posted 23 November 2021 - 10:10 PM

John are these hollow screws? Any event I would use flat faced 4-40 set screws from McMaster-Carr.
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#5 MSwiss

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Posted 23 November 2021 - 10:28 PM

Not a fan of gold billet screws. Impossible to depend on, without flatted axles.

I never heard of them cracking, but still, replace them with traditional ones.


Mike Swiss
 
Inventor of the Low CG guide flag 4/20/18
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#6 9lives

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Posted 23 November 2021 - 10:46 PM

Gentlemen thank you, should I buy "better", higher quality set screws? What kind? My builder spun twice at Fall Brawl after contact with other cars. What's the deal with Parma ?
John Hegedus

#7 9lives

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Posted 23 November 2021 - 10:49 PM

Thanks, Jersey John. I did not see your post. Who or what is McMaster-Carr?
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John Hegedus

#8 W. J. Dougherty

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Posted 24 November 2021 - 12:34 AM

Aren't people using flatted axles?
Yortuk & Georg Festrunk

#9 MSwiss

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Posted 24 November 2021 - 12:52 AM

Racers come up with all kinds of interesting excuses not to use flatted axles. LOL.

Mike Swiss
 
Inventor of the Low CG guide flag 4/20/18
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Two-time G7 World Champion (1988, 1990), eight G7 main appearances
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#10 9lives

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Posted 24 November 2021 - 02:36 AM

Mr. Swiss, thank you for your replies. I was under the impression that all rear axle have a flat "notch" for crown gear installation. I'll inspect my cars asap. And thanks again.
John Hegedus

#11 swodem

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Posted 24 November 2021 - 02:39 AM

I’d be interested, if you have the capability to photograph clearly, a pic of one of your ‘cracked’ grub screws.


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#12 Shooter7mustang

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Posted 24 November 2021 - 08:01 AM

I had the same problem for for an extended period of time.

Turns out I was cranking them down, too much torque, as soon as I adjusted, haven't spun one since. That's my
story and I'm sticking to it.

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#13 Eddie Fleming

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Posted 24 November 2021 - 08:14 AM

John

 

https://www.mcmaster.com/

 

I have never had a problem with set screws cracking, but some years back when I started using Koford crowns I had several that were not drilled and or tapped well. the Koford screw would not go through into the axle bore. Replacing the screw with a regular screw would work fine because of the shape of the end of the screw. I have not had this problem in newer gears. With the old gears and the Koford screws I could strip the threads out of the gear hub and it would still not lock down. It would get snug but not stay put. 

 

To be on the safe side I still replace all the Koford screws.


Eddie Fleming

#14 boxerdog

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Posted 24 November 2021 - 10:30 AM

There is a huge difference in the quality of the threads on these set screws; another option is the knurled tip which seems to work very well. Most of the gears

 are supplied with  pretty cheap screws. The US brands are usually good:

 

https://www.mcmaster...read-size~4-40/

 

And...I have also seen many cases where the spurs are not tapped completely into the axle hole. Then they strip or spin. I usually try to remember to gently run a tap through to check. 


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#15 MSwiss

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Posted 24 November 2021 - 11:09 AM

Mr. Swiss,thank you for your replies. I was under the impression that all rear axel have a flat "notch" for crown gear installation. I'll inspect my cars asap. And thanks again.

I do.

CR055.

The flat is .500" wide, wider than any hub out there, so you can clearly see it with the gear in place.

That's important so you can get your set screw properly aligned to it.

If you miss it, you might catch the edge, which would be worse than using no flat at all.

A small side benefit of the flat is if you use a longer set screw that sticks out of the hub a little bit, it will now go in a little bit deeper , and provide you with more clearance between it and the end of the armature shaft.


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Mike Swiss
 
Inventor of the Low CG guide flag 4/20/18
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Two-time G7 World Champion (1988, 1990), eight G7 main appearances
Eight-time G7 King track single lap world record holder

17B West Ogden Ave., Westmont, IL 60559, (708) 203-8003, mikeswiss86@hotmail.com (also my PayPal address)

Note: Send all USPS packages and mail to: 5858 Chase Ave., Downers Grove, IL 60516


#16 Matt Sheldon

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Posted 24 November 2021 - 12:24 PM

I ran these axles for a long time and they are are superb.
Matt Sheldon

#17 Bryan Warmack

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Posted 24 November 2021 - 12:42 PM

Like a few racers have mentioned here a good idea is to simply replace all the original sets screws with McMaster-Carr or similar alloy steel quality ones. The McMaster Carr number for the shorter 3/32" is  #91375A102 and for the regular 1/8" is #91375A103.

 

My experience is that probably 95% of gear related problems come from overtightening the set screws and shearing the small 4-40 threads in the hubs. I know with the old Parma gears I never had to worry about overtightening causing damage but with a lot of the new gears you need to be very careful about this and perhaps just replace them after 5-6 tightenings.


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#18 Eddie Fleming

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Posted 24 November 2021 - 01:43 PM

I was just looking at McMaster Carr and they have 18-8 stainless steel setscrews cheaper than the alloy steel ones.

 

I have not tried them. Is there any reason not to use the stainless?


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#19 Bill from NH

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Posted 24 November 2021 - 03:25 PM

I have some stainless from another source. They were soft, so I just use them in jig wheels.


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#20 S.O. Watt

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Posted 24 November 2021 - 07:41 PM

Stainless Steel is softer than hardened steel. Cup point is better than hollow especially on a non flatted axles. Keith Libby and I just had a hollow SS one split, crack, and cost a race finish at the Fall Brawl. That said, follow Bryans advise as its virtually the same thing I do. Flatted axles are not needed in retro even with the new CR motors. And chuck the Koford gear after 5 or 6 uses. Yes it costs more but at the top level of racn it takes more than luck to win. Set yourself up by minimizing equipment failures.

that is all.

I was just looking at McMaster Carr and they have 18-8 stainless steel setscrews cheaper than the alloy steel ones.
 
I have not tried them. Is there any reason not to use the stainless?


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#21 MSwiss

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Posted 24 November 2021 - 08:36 PM

Flatted axles are not needed in retro even with the new CR motors. And chuck the Koford gear after 5 or 6 uses. Yes it costs more but at the top level of racn it takes more than luck to win. Set yourself up by minimizing equipment failures.

Tom,
You contradicted yourself.

One minimizes equipment failures by doing simple things like spending $3 more for an axle with a flat.

So what if it takes you 2 minutes to get a perfect mesh, vs. 30 seconds.

You do it once a race.

And the CR motor has nothing to do with it.

At the same Sano, I saw 2 of the top 5 or 6(?) winningest Retro racers, have crown gears come loose.

And that was obviously pre CR102.

It cost Edsel 2-3 places in Can Am, and Willy, a new record lap total in the Coupe race.

Ed was lamenting about it over a few beers, at the house, that night.

"I never had one come loose before".

I told him it reminded me of my old G7 days when a top Pro had his axle bearing come loose, and started chewing up spur gears.

He admitted to me he had Loctited it in .

"I never had one come loose before", and added some mumbo jumbo about not wanting to heat up his ball bearings.

I replied "I solder mine in and have never had one come loose and never will. And if the heat shortens their life a little bit, I'll change them".

IMO, there is zero chance the car will perform any differently.

Mike Swiss
 
Inventor of the Low CG guide flag 4/20/18
IRRA® Components Committee Chairman
Five-time USRA National Champion (two G7, one G27, two G7 Senior)
Two-time G7 World Champion (1988, 1990), eight G7 main appearances
Eight-time G7 King track single lap world record holder

17B West Ogden Ave., Westmont, IL 60559, (708) 203-8003, mikeswiss86@hotmail.com (also my PayPal address)

Note: Send all USPS packages and mail to: 5858 Chase Ave., Downers Grove, IL 60516


#22 MattD

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Posted 24 November 2021 - 08:54 PM

Listen to Mike.


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#23 S.O. Watt

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Posted 24 November 2021 - 09:13 PM

No, I didn’t contradict myself. I have a different view than you and it has worked quite well for many.


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#24 MSwiss

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Posted 24 November 2021 - 10:21 PM

Are you saying a set screw will hold better on a round axle then one with a flat?

 

If you're not, than you are not minimizing equipment failures.

 

You are just trying to save $3 and a minute adjusting your crown gear.


Mike Swiss
 
Inventor of the Low CG guide flag 4/20/18
IRRA® Components Committee Chairman
Five-time USRA National Champion (two G7, one G27, two G7 Senior)
Two-time G7 World Champion (1988, 1990), eight G7 main appearances
Eight-time G7 King track single lap world record holder

17B West Ogden Ave., Westmont, IL 60559, (708) 203-8003, mikeswiss86@hotmail.com (also my PayPal address)

Note: Send all USPS packages and mail to: 5858 Chase Ave., Downers Grove, IL 60516


#25 S.O. Watt

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Posted 24 November 2021 - 10:32 PM

You are missing completely why i do it. 

 

I have won many enduros where good pit work saving precious seconds gets the advantage. In haste and missing getting the set screw perfectly aligned on the flat then having the wheel or gear come loose has been eliminated from my way. So you see, there is several ways of doing things, do what is comfortable for you.

 

Are you saying a set screw will hold better on a round axle then one with a flat?

 

If you're not, than you are not minimizing equipment failures.

 

You are just trying to save $3 and a minute adjusting your crown gear.


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