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View Full Version : 2mm or 3/32 rear axles



RomanK
02-17-2011, 10:28 AM
could some of you guys that have been doing this a while chime in? besides the weight savings what other advantages to making this switch/

tks

wjdougherty
02-17-2011, 10:58 AM
http://www.slotcartalk.com/slotcartalk/showthread.php?25127-The-Father-Of-The-2mm-Axle&highlight=2mm+Axles

oldweirdherald
02-17-2011, 01:26 PM
could some of you guys that have been doing this a while chime in? besides the weight savings what other advantages to making this switch/

tks

Hi Roman,

As the link in the post above will demonstrate, many innovations in this competitive hobby of slot car racing enable us to reminisce and debate about just who it was who gets credit for doing it first.

Regardless of the possible actual performance enhancing advantages of such advancements, or the advancements in technology that may result in the steady progress from these kind of innovations... I believe that the main benefit, in spite of what any one else may think, is that it gives us another topic to debate over online.

I am rather shocked that the fundamental merits of the 2mm axle have not been argued, let alone the potential hazards of premature breakage. We could haggle over what materials and chemical compounds are best, as well as heat treating, chemical processing, and one of my favorites; cryogenic freezing.

I was a bit relieved, however, that the debate over who gets the actual credit for "pioneering" or at least popularizing the use of the 2mm axle seemed to actually subside without any name calling, insults, or unresolved issues.

There were also no conspiracy theorists who attributed the introduction of the 2mm axle to yet another ploy to boost sales by rendering 3/32 axles, wheels & tires, gears, & bearings into obsolescence.

I'm rather surprised that so many regular OWH posters missed that one - it must have slipped past the usual conspiracy theorists here.

I suppose we'll have to wait until 2mm axles are employed in any USRA restricted racing classes before the debates about legality, manufacturer submissions, and approval crop up - as well as all the related accusations of conspiracy, politics, boycotts, hidden agendas, etc...

And here you are... thinking it was all about saving a little weight! Ha! :p

That's what you get for thinking like a "Wing Car" racer! LOL :lol:

;) :p :rolleyes:

Zippity
02-17-2011, 01:40 PM
Propensity to snap is higher the small the diameter :( :(

oldweirdherald
02-17-2011, 01:44 PM
Propensity to snap is higher the small the diameter :( :(

Then how come my propensity to snap has increased steadily as my belly's diameter has grown larger??? Hmmm? :p


Besides... Roman asked about the possible ADVANTAGES. The potential for snappage is a fairly obvious possible disadvantage. :normal:

Zippity
02-17-2011, 02:01 PM
Oh, so I should have gone on about the angle of the dangle being greater than the ..............................?? :D :D

Jeff714
02-17-2011, 02:10 PM
Quite a diatribe Paul... Are you back to using that evil caffeine again? :)

oldweirdherald
02-17-2011, 02:16 PM
Quite a diatribe Paul... Are you back to using that evil caffeine again? :)

Naturally induced insomnia fueled by a bit of boredom. I'm happy, but I do miss my toys. :)

pilmat
02-17-2011, 02:39 PM
The only advantage beyond the weight that I can think of would be the ability to put the motor closer to the axle without notching mags... I think this would be important in the already fragile cobalts.

Zippity
02-17-2011, 03:10 PM
Phil is correct :)

wbugenis
02-17-2011, 03:14 PM
Zoom in on the yellow car here:

http://www.lslots.co.uk/worlds2010.html

I was told they went back to 3/32 for 1/24 euro but contunue to use 2mm in the 1/32 classes.

MentalKase
02-17-2011, 03:27 PM
Weight is not as important as the following:

If you use some basic Engineering equations for:

1) Bending of a cantileverd beam - To model wheel/wall impact, bending the axle
Ymax = (FL^3)/3EI, where F, force , L, Length and E, Modulus (material property) are the same for each instance leaving deflection inversely proportional to I where I = (Pi*d^4)/64, hence d^4 is the critical factor. So ratio 2mm to 3/32 = (0.078/0.094)^4 = 0.474
or a 2MM axle will bend 2.109 X as a 3/32 axle.
Is this good or bad? Depends on the Force of bending whether you pass the threshold of plastic deformation (ie bent it).

2 ) Torque similiarly - power applied via acceleration and braking. :sleeping: This causes a twist or Theta as it is called is governed by (TL)/(GJ) where T is torque, L is length, G is Torsional Modulus (material property) and J is polar area moment of inertia. J= (Pid^4)/32, hence d^4 is the critical factor
or a 2 mm axle will twist 2.109 X degrees as a 3/32 axle. More twist, more lag, less instantaneous power applied to wheel hub.
Is this good or bad? Depends on the Torque applied.

3 ) Basic Friction - If you use basic sliding friction for bushings, equal length axially, ignoring unit loading due to different radii, then a given the OD determines the swept area of contact (imagine unrolling a carpet) so 0.78/0.094= 0.83
or a 2 mm axle will incur roughly 83% of the parasitic loss of a 3/32 axle.

4 ) Mass moment - this is the parasitic loss associated with accelerating a round bar about it axis and IGNORES translational inertia for this discussion. I=(md^2)/8, where m=(Pid^2tp)/4g throw out all the common factors and..... :confused:... I is proportional to d^4 (will we ever get away from this???)
Hence a 2 mm axle will require 0.484 or 48.4% of the power to accelerate in rotation compared to a 3/32 axle.
IE less parasitic loss.

There is a small secondary benefit for ball brgs, the ball race (same ball dia.) rotates about a slightly smaller radius and it takes less power to accelerate them around in a circle.

So 2 mm axle vs 3/32: less parasitic losses, less strength. No free lunch.
Is it worth it? F1 seems to think so.

I can go on further

fxgeorge
02-17-2011, 04:32 PM
could some of you guys that have been doing this a while chime in? besides the weight savings what other advantages to making this switch/

tks

Hi Roman! I started using 2mm axles on all my eurosports maybe four years ago...1/32 F1, 32 Euro and 24 Euro...because Lee Gilbert was building my cars at that time. Lee is perhaps the first racer to use the 2mm axle on a regular basis. I think there was a thread on Lee's tech tips, something like "The Father of the 2mm Axle". Just to dispel some myths, we have used 2mm axles for at least four years...that is a number of eurosport racers....and we have not seen a single broken axle. I would call that an advantage! Vladimir Horky did break a 2mm axle in 1/32 F1 some time ago in the UK, but I understand it was a wreck of biblical dimensions....and ever since, Horky has used 3/32" for everything. Lee Gilbert started to use the 2mm axle mainly to get the motor moved as far back as possible. Yep, that's right, you might be thinking "but that must only be a few thousandths of difference!" Anybody who knows Lee well knows that he looks for every ONE thousandth of an inch if it gives an advantage. Lee is also the father of the notched rear side of the motor....another way to move the motor as far back as possible. Since the 2mm axle became widely used in eurosport racing, there have been a lot of gears made in both 72 pitch and 80 pitch. My favorite are the Cahoza 44T 80P spurs in 2mm available from Camen, and for F1 I like the Vitula hypoid gear in 2mm. Excellent magnesium wheels are also widely available, my favorite being the Hermanator line.

That being said, I understand that OWH user "Slotcar Racer" is about to build a new 24 Horky chassis with 3/32" rear axle so he can try out the Cahoza carbon fiber rear wheels. You may want to check the results of his testing perhaps as early as this weekend.

Zippity
02-17-2011, 04:54 PM
Just to dispel some myths, we have used 2mm axles for at least four years...that is a number of eurosport racers....and we have not seen a single broken axle.

Then I must have be one hell of an unlucky SOB :( :( :( ;)

Slidergreg
02-17-2011, 05:48 PM
I run them in all Euro classes and have never bent or broken one.

Woody-England
02-17-2011, 05:57 PM
Hi George,
hope you are keeping well.
Just a couple of points, Horky still uses 2mm in both F1 and 1/32nd Euro, I have a RTR F1 from him last year with a 2mm rear axle, and they still use them in 32 Euro for sure.
Sat around a table for a beer or two, either in Milton Keynes or Slovakia Josef Korec told us that they were not using 2mm in 1/24th due to strange tire wear paterns, which they believed was due to the axle's flexing.

The Cahoza carbon wheels are now availabe in 1/32nd sizes for 2mm axle's

Jeff714
02-17-2011, 05:58 PM
Naturally induced insomnia fueled by a bit of boredom. I'm happy, but I do miss my toys. :)

Lol! My insomnia is naturally induced by my kids!!!

wbugenis
02-17-2011, 06:04 PM
Hi Roman! I started using 2mm axles on all my eurosports maybe four years ago...1/32 F1, 32 Euro and 24 Euro...because Lee Gilbert was building my cars at that time. Lee is perhaps the first racer to use the 2mm axle on a regular basis. I think there was a thread on Lee's tech tips, something like "The Father of the 2mm Axle". Just to dispel some myths, we have used 2mm axles for at least four years...that is a number of eurosport racers....and we have not seen a single broken axle. I would call that an advantage! Vladimir Horky did break a 2mm axle in 1/32 F1 some time ago in the UK, but I understand it was a wreck of biblical dimensions....and ever since, Horky has used 3/32" for everything. Lee Gilbert started to use the 2mm axle mainly to get the motor moved as far back as possible. Yep, that's right, you might be thinking "but that must only be a few thousandths of difference!" Anybody who knows Lee well knows that he looks for every ONE thousandth of an inch if it gives an advantage. Lee is also the father of the notched rear side of the motor....another way to move the motor as far back as possible. Since the 2mm axle became widely used in eurosport racing, there have been a lot of gears made in both 72 pitch and 80 pitch. My favorite are the Cahoza 44T 80P spurs in 2mm available from Camen, and for F1 I like the Vitula hypoid gear in 2mm. Excellent magnesium wheels are also widely available, my favorite being the Hermanator line.

That being said, I understand that OWH user "Slotcar Racer" is about to build a new 24 Horky chassis with 3/32" rear axle so he can try out the Cahoza carbon fiber rear wheels. You may want to check the results of his testing perhaps as early as this weekend.

The New Horky and the Cahoza hubs are 3/32 because they feel the 2mm axel is not rigid enough for 1/24 eurosport.

SteveDee
02-17-2011, 06:11 PM
The only important advantage that I can see, is being able to set the motor back slightly and therefore one is able to get a straighter shot pinion to spur, which seems quite important with 80p gears, other than that I really don't see much else. But then.again I could be wrong. Again.

Woody-England
02-17-2011, 06:15 PM
Hi Bill,
exactly right.
The F1 and 32nd Euro come with optional pillow blocks.

Woody-England
02-17-2011, 06:17 PM
Steve,
I'm pretty sure thats all it is, better gear mesh. Lee Gilbert converted me to them three years ago, never done a gear or axle since.

Monty@B.O.W.
02-17-2011, 07:03 PM
One other (very slight) advantage does come to mind. With what is currently available in the slot car industry, its easier to source the highest quality bearings in 2mm. No doubt there is such an animal as a GRW 3/32 bearing, but unlike the 2mm, nobody has them, AFAIK.

Slapshot
02-18-2011, 07:49 AM
Roman:
There are a few main reasons for use of 2mm axle. Aside from the obvious minute angle that is availible there is other advantages. Monty brought up an excellent point about bearings.
One disavatage of a low angle is wall incursions. Most eurosport motor failures are cobalt magnet breakage. Aside from a motor bearing failure the next cause is that the axle slaps against the magnet momentarily. With a smaller axle this increases the distance that the axle clears the magnet and reduces the problem. It also allows not grinding into the magnet which can upset the magnet field or make a starter break where the ground out section is. Grinding for lower angle is good but there are dangers with cobalts.
When you can reduce the angle in the motor you gain traction and handling especially in eurosports.

2mm blanks have proven that they can handle high RPM as evidenced that they are common in armatures turning upwards of 150-250 K rpm.

Another feature is that there is minute flex, Contrary to Horky's belief of flex creating adverse tire wear in this case creates a different harmoninc depending on the bearings involved. This flex is part of the reason that not as many break a axle as compaired to a 3/32 axle. While not set in stone the more ridged the axle the better chance it will break on impact. Not that a 2mm won't break but most will bend before breaking giving a racer a chance to drive longer or to pits instead of a marshal car tossing and replacing. It a valuble time issue.
As I mentioned earlier there are harmonics involved also. I call it the dog whistle theroy. While I would love to do sound and pitch comparison in theroy they would create a higher pitch vibration due to weight and revolving more or faster which filter out under racing conditions. I would hope to say that they are smoother in the higher frequency because of the time to reach peak. Thats an open debate. Again just a theroy a larger axle due to added wieght and size create a lower pitch vibration which can get into the range of effecting chassis handling. Of course I could be wrong, but I like to think otherwise.

Raymond

AndyHSr
02-21-2011, 05:18 PM
I have obtained a selection of 72p 2mm spur gears . At this time im not rebuilding from 3/32 if anyone is interested message me . Im interested in maybe some horse trading

GearBear
02-21-2011, 06:02 PM
Just as an FYI: I have actually had 2 break on me now. The first one in the first 24 Euro race last season, and the second when Lee launched my 32nd Euro off the bank of the Hillclimb into the wall at full punch (can you say "Senior Moment"? I knew you could! :)). Neither one would have survived even if they had been 3/32" IMHO as the crashes were violent enough to do some serious damage.

RomanK
02-21-2011, 06:24 PM
For those that were ever curious....Titanium isn't a good idea. tried one last Saturday figuring I would split the diff between weight of a 3/32 and 2mm.....so much for that idea. Took an otherwise great car (Mack & Camen Gulliver, shameless plug:)) and turned it to crap when the axle bent in a not so violent crash in the 6th heat. Oh well, live and learn.;)

GearBear
02-21-2011, 07:16 PM
So, can anyone tell me what type of Drill Rod you are using for your axles? I was looking at http://www.onlinemetals.com/toolsteelguide.cfm to figure out what I wanted to order for some motor slug shafts and started thinking about this thread. It seems to me that if we were to use the O-1 the axles would end up being too brittle, but would A-2 be better than say W-1? I'm wondering if W-1 might be better as an axle since it will bend rather than break. At least with a bent axle you might be able to limp it to the end of a heat before replacing it. <shrug>

O-1 -- Rockwell 62c - 64c
A-2 -- Rockwell 59c-62c
W-1 -- Rockwell 56c
M-2 no hardness listed

miluk
02-28-2011, 01:54 AM
Guys, what gears you are using for f1/32 with 2mm axle?

Woody-England
02-28-2011, 12:16 PM
Either Vitula or the green JK ones
Strangely, whilst you have to pick through a bunch of JK 3/32 to find a straight one, most of the 2mm ones are good.
Haven't seen any 2mm Valico yet.

wbugenis
02-28-2011, 02:05 PM
So, can anyone tell me what type of Drill Rod you are using for your axles? I was looking at http://www.onlinemetals.com/toolsteelguide.cfm to figure out what I wanted to order for some motor slug shafts and started thinking about this thread. It seems to me that if we were to use the O-1 the axles would end up being too brittle, but would A-2 be better than say W-1? I'm wondering if W-1 might be better as an axle since it will bend rather than break. At least with a bent axle you might be able to limp it to the end of a heat before replacing it. <shrug>

O-1 -- Rockwell 62c - 64c
A-2 -- Rockwell 59c-62c
W-1 -- Rockwell 56c
M-2 no hardness listed

Do not use drill rod for your axles. You need a brill blank. Drill rod is not heat treat treated. The rockwell numbers you have found gives the hardness that is POSSIBLE to achieve primarily due to the carbon content of the steel after heat treating. PM me if you need good drill blank 2mm axels.

Bill

Speedshop
02-28-2011, 06:47 PM
Speedshop has been using 2m axles since 2006. Herman James ran the first on at the Hershey Nats in PA. Finished 2nd without breaking one. In those days I had to solder on a brass shim to the 2m axke and lathe it to 3/32 because there were no 2m gears. I made 2m rims. Today all the parts you need to race 2m are out there. The reason we went to 2m was the Speedshop is a big believer in low motor angle. We use to cut the can and cobalt magnet to push the motor back as far as possible. With a 2m axle you can get the lowest motor angle without cutting into the magnets and only notching the can a hair reducing magnet breakage.