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Old 04-22-2010, 10:42 AM   #1441
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well, I HAVE read much literature on bearing design and engineering and disagree with you re: side vs. radial forces on a ball bearing - if ball bearing were designed to have the same side forces as the "normal" forces, then there would be no thrust bearings, conical bearings, etc.

Think about it - in simple terms, instead of having the force riding along a large portion of the ball (as it is "normally") you're taking the force and having it ride along the edge of the race as it contacts the ball - so all the force is riding on two very narrow channels.

On the other hand, a conical bearing spreads that force out by moving the races' force structure. A thrust bearing goes even farther in that direction.

Here are a couple of illustrations where you can see how the design of the conical (tapered) bearing has been designed specifically FOR a thrust force, as has a thrust bearing.

Note that ball bearings we use are rated ONLY for radial forces (forces that are perpendicular to the shaft) and NOT for thrust forces (forces that are parallel to the shaft)

Now, that being said, I've tried conical, thrust, and "normal" bearings and the conical just doesn't work. You can't apply force to it and get the same friction response that you get with a normal bearing. I've also tried thrust bearings and, when they work, they work amazingly well - but that was ONLY on 1/12. I could NEVER get the danged thing to work on 1/10th - could not get a consistent force set on it and it would not behave consistently.

So my only conclusion was that our abuse of a normal bearing is the only way to do what we're doing with them.
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Old 04-22-2010, 01:11 PM   #1442
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Well I have to disagree with you.

Quote from Boca Bearings in the Engineering data section.
Load:Single row radial ball bearings with ball separated by a cage can support radial loads, axial loads and tilting movements. All full complement V-type ball bearing can support only radial loads and some low axial loads.

Let me explain this engineering data note from Boca. If you have a full compliment ball bearing which means as many balls as will fit, then there has to be a hole or divot in the side of the race at least on one side to slip the balls in between the races. This type will not carry a side load. We do not use this type.
Somewhere on Boca there are radial and axial loads that a caged ball bearing can handle. They are not too different.

A caged ball bearing has no opening. The balls are inserted with the center moved to one side, the balls are then separated and a cage put on.
The contact of a radial ball bearing is a line contact. Whether this line is on the radius or slightly moved to the side is of little import. Naturally when the load is increased the line contact broadens and the wear increases.

There is no doubt that a tapered roller bearing will carry more thrust than a radial ball bearing. Now we have a much bigger contact area of the rollers to the races. We are not discussing these as they will not fit and there is too much friction for RC use.

We are discussing thrust bearings that used ball bearings. There is one type that uses a v groove. Here there are two line contacts but now there is some slipage as the ball rolls around the races. This is probably what created the roughness I felt on that first battle axe I tested in this thread.

To eliminate roughness eliminate this extra thrust bearing. The CAGED radial ball bearing will handle the side load just fine. It lasts just about as long as the right side axle bearing which only carries radial loads but larger ones from the thrust backward of the spur gear as it makes contact with the pinion.


From Shawns link below

Ball Bearings
Ball bearings, as shown below, are probably the most common type of bearing. They are found in everything from inline skates to hard drives. These bearings can handle both radial and thrust loads, and are usually found in applications where the load is relatively small.

Photo courtesy The Timken Company
Cutaway view of a ball bearing In a ball bearing, the load is transmitted from the outer race to the ball, and from the ball to the inner race. Since the ball is a sphere, it only contacts the inner and outer race at a very small point, which helps it spin very smoothly. But it also means that there is not very much contact area holding that load, so if the bearing is overloaded, the balls can deform or squish, ruining the bearing.
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Last edited by John Stranahan; 04-22-2010 at 09:41 PM.
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Old 04-22-2010, 03:12 PM   #1443
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John, thanks for the great service. Looking forward to getting my new JS pro10 on track!

I use a thrust bearing in my diff but only because so many people do. Most improvment came when I switched to carbide balls and ceramic bearings. I also strip my diff and lube my bearings after every track day. Also have to clean my damper tubes as they are like dust buckets.
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Old 04-22-2010, 08:42 PM   #1444
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An interesting read on ball bearings.

http://science.howstuffworks.com/bearing3.htm

Shawn.
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Old 04-24-2010, 04:51 PM   #1445
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What traction additives are people using? Are there any cheap household chemicals that are a good or better alternative?
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Old 04-24-2010, 05:31 PM   #1446
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I like Corally "Jack the Gripper" Stormer carries it. I also like Kingford Charcoal Lighter fluid that you use to light your BBQ charcoal grill. I am told they are the same. Both work well on foams.
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Old 04-26-2010, 11:20 PM   #1447
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Shawn- thanks for the link



JS pro 10 Wide Pan at 42.6 ounces

Can-Am/GTP/WSC 2010 ROAR rules for the wide pan regulate the minimum weight to 42.3 ounce minimum. I usualy run my race cars a few tenths over the minimum. Here is the JS Pro 10 at 42.6 ounces. So you can have your cake and eat it too. You can have a dual A-arm front end, 3 link rear end, Nylon bumper and Nerfwings and still meet weight. Lightening efforts were not extreme, but typical. Lightened battery top strap and some Aluminum Screws in places where I am confident they will survive. This is actually a very good weight outdoors as the car is heavy enough to penetrate the dust. At 39 ounces you will loose a lot of forward traction if it is dusty. (There may be other parts of the world with a lighter minimums.)

Further steps could get rid of that extra .3 ounces. A lighter servo. Miniature receiver, Shorter battery leads, etc.
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Old 04-28-2010, 09:49 AM   #1448
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Hi guys -

As far as bearings go - I don't use howstuffworks for technical documentation as they are simplified down for general readers. I try to get as close to engineering specs as I can (without having to pay for an IEEE subscription since work no longer supplies it Oh well. )

Anyway - http://www.globalspec.com/Specificat...ings_All_Types has some fairly good technical discussions available (not just the general article, there are links to follow as well)

Note:
Quote:
Radial, or deep groove bearings, can take radial and axial loads to varying degrees but are used when the primary load is in the radial direction.
Once we load the bearings as thrust bearings (axial direction) the primary load is now axial and not radial (I'd love to get actual load measurements but I don't have them) especially as this bearing itself does not rotate much at all.

So yes, they can support axial loads but they're designed to be primarily radial.


That being said, they're the only thing that works in our application. (and I'm not trying to be argumentative - truly - just to shine light on a subject that I enjoy! )
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Old 04-29-2010, 10:27 PM   #1449
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Panhard Bar Prototype

The design team has been busy. Here is a new Panhard bar prototype that I plan to start testing. It requires a tab on the front of the pod plate off to the side. There is enough material in the CRC frame off to the side to accommodate it with some sanding. The advantage is that the Panhard bar ends upfarther forward on the car. You can really put on the huge gears now. The second picture shows the bar with a motor installed running a 93/13 gear ratio. (Note this gear is accommodated by the previous Panhard bar.) There is room to move the motor farther forward unlike the old bar. A second advantage is that it uses the larger Traxxas link with large rod ends for trouble free performance. The mounts at either end are both stronger than the previous bar. A fourth advantage is the pod can be pulled up tight to the frame now. This will effectively move weight back in the chassis which will help on outdoor asphalt. Simple parts are used like pyramid washers instead of custom drilled and tapped Standoffs.

I want to say that I ran the previous bar for about 4 months now with no problems once that screw that went into the motor plate was secured with red high temperature Loctite. A new Panhard bar is not a necessary change but a change that will improve the breed.

Other things in the works.
  • A factory cut side plate to mount the 3-link suspension's shocks. A no drill install will result.
  • A minimized lightweight battery top plate. These will fit any Gen X 10.
  • A new chassis with more meat around critical suspension and bumper holes front and back. This new chassis will be combined with the new pod bottom plate and new Panhard bar on JS Pro 10's only at first.
Don't expect lightning fast changes to occur. Let's say 2-3 months.

A JS Pro 10 is off to Spain-Good luck Oliver!

Pics: left view from rear of the car motor out.
middle, from the front, pic of the right side Panhard bar mount showing pyramid washers above and below link.
Right, A view with motor in, showing generous clearance on motor and battery running a 93/13 gear ratio.
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CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-panhard-bar-prototype-005.jpg   CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-panhard-bar-prototype-001.jpg   CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-panhard-bar-prototype-003.jpg  
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Last edited by John Stranahan; 04-30-2010 at 11:03 AM.
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Old 04-30-2010, 07:50 AM   #1450
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What motor pod plate are you using?
My one does not have enough on it to make that tab
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Old 04-30-2010, 11:00 AM   #1451
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Nimo-It is a prototype pod plate that I made yesterday with a Dremel. If it works out, I will have some CNC machine made in a month or so. In my experience so far, It may take several months before I will have one for sale. It will work with a standard Gen X 10 chassis with a little sanding.
John

Alternate Side Mount Plate Assembly on JS Pro kits

I thought I would show this picture of an alternate way to setup the side mount plates which support the shock towers on JS Pro kits. One of the side plates had been drilled through requiring a nut underneath which interferes with link up travel. I put the 5/16 aluminum colored Standoffs under the side mount plates instead of above. This freed up a lot of room for the links to travel upward.

As a side note you can make fine adjustments to droop at the rear by putting washers under the side plates. I have been using spacers inside the shock below the shock piston.

Pic this view shows the raised position of the side mount plates required by a stripped hole. Also the standard Panhard bar can be seen.
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Last edited by John Stranahan; 04-30-2010 at 11:54 AM.
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Old 05-03-2010, 10:31 PM   #1452
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I have just bought a CRC Gen 10 for playing with as touring cars are so yesterday....
I will be mucking around at the track on race days when i'm not in my touring classes, but want to get it well tuned so I can hopefully entice a few others to get into it and get a class going!
We race on a large (1/8 nitro) outdoor asphalt track. I'll be using a 13.5 with 2S lipo for now, as it's already gear I have for touring. I'm sure it will be plenty of speed to start with.
Anyway, to my point. What parts do I need to add proper dampers to the sids instead of the ali tubes it comes with? I haven't raced it yet, but can already see the extra maintenance and imited tuning being a pain.
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Old 05-03-2010, 11:02 PM   #1453
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What I like to use for rear side shocks are Associated RC18T rear shocks. The ends are so much stronger than Pan car type shocks. Here is a pic with only one shock like the Associated RC10R5. This setup worked very well and is what I ended up using on my car. You need a set of RC18T shocks and ballstuds. The 2 x 56 ballstud on the top plate will work with the shock. Good luck!
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Old 05-04-2010, 04:20 AM   #1454
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Thanks John, that's exactly what I was after.
I was curious about the single shock idea, as I had seen it on 1/12's, but wasn't sure if it would be right for the larger car.
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Old 05-04-2010, 09:54 AM   #1455
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Not much damping is required in the rear. Using the one shock lets you use normal shock weight oils of around 30-35 weight. It reduces weight and the car handles well.

When you build the shock you can build it to be very neutral in the range where it is used. If you are getting a lot of spring back when you push the shaft in, push it in half way, open the top just a little and bleed out a tiny bit of oil. From mid stroke to full extended the shock can be very neutral (it will stay put when moved). Associated accomplishes this with a shaft that goes all the way through both ends. That is another suitable shock that was not available when I built up the car in the pic. Shocks to avoid are ones with an Aluminum #4-40 threaded shaft on one end. These bend almost immediatley outdoors on first contact. The RC18T shock does not. I believe the Associated shock has two good ends.
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