36 replies to this topic

[Ross Fox]

How much added friction might there be if the pinion gear is worn? Spur gear is worn? Spur and pinion worn? The mesh is still proper, not too tight and not too loose, as agreed upon by quite a few checking it out. I know that friction in this area exists between pinion and spur, but don't know if it even to be considered. I am talking mostly straight pinion and straight spur now. Looking for any place that might slow the car down friction wise. This is for a box stock class, no ball bearings allowed on either chassis or motor  Just wondering at where else to look.

[Richie]

Ross,

I remember reading somewhere going from the press on pinions we have to run to a new good steel angled pinion and spur gear was maybe .1 gain. My pinion has been showing wear for a few races now lol

[Zippity]

Noise will tell you if your mesh is bad.

[Dave Crevie]

To answer your question, Ross, gear tooth profiles are developed so that as the gears run together, each tooth "rolls" against the tooth it bears apon. In the drawing below, imagine that as the gears turn, the angle between the two teeth changes, and the curved sides of each tooth roll against each other rather than slide. As the teeth wear out, the radii of the curved sides change, and the teeth no longer roll smoothly against each other. That adds friction between the gears. I wish I had an animation of this, but I don't.

 

 

[John Luongo]

ideally, both drive and driven gear are changed at the same time for matched wear and longer life. but, as a practical manner, i will re-use either gear probably longer than i should. in a 1/1 vehicle they would disintegrate. as the gears shown in daves response above, have a contact area similar a clearance ramp on a cam profile. designed to roll, lift and accelerate the follower in a gradual manner to improve idle quality, wear, and to reseat the valve "gently" . during the 70s, the clearance ramp in the profile was eliminated, made more abrupt for emission control purposes so roller lifters were used for wear issues. are the OPs gears an in-line or angle drive set up? on some newer crown gears, i have had to apply a very small dab of water mix valve grinding compound on the thrust side of the gear to help improve the mesh and quiet the gear noise. easy clean up with water, followed by a low friction lube oil. i use a blend of transynd and mystery oil. best regards

[Pappy]

Looking for any place that might slow the car down friction wise. 

Some guys wax the sides of the guide flag.

[Pablo]

Generally the pinion is going to wear quicker. If the mesh is still good and not noisy, and teeth are OK, why mess with it?

 

If you are wearing teeth out prematurely, it can be caused by worn axle bushings.

[Bill Seitz]

The JK narrow "Falcon" spurs have noticeably less friction than a full width spur. However, with only half the width, they're not as robust and may be damaged in a rear end collision.

 

I've found pinion gears are not all the same quality, and the press-on ones I've had were the worst.

 

Freshly routed tracks wear down guides rapidly, the plastic depositing on the walls of the slot. Once the slot is plastic coated, friction is pretty low, but in a new slot or to be very fiddly about friction reduction, waxing or some silicone spray on the guide can't hurt.

[Eddie Fleming]

Ross

 For me the sound is the telling thing with a gear mesh. If it sounds good run it. Someone mentioned the axle bushings. If there is any play between the axle and the bushing try a new axle and if that does not tighten it up replace the bushings, Bushings do wear and cause handling problems. If the bushings are lined up well the axle should fall through both bushings with just it's weight.

 

In Box stock motors are put in with screws. the screws can cause the bushing in the motor to bind. With the screws loose or out check the amp draw of the motor. When you tighten the screws does the amp drew go up? You can also have a motor that is warped from crashes or by screws pulling it against a chassis that is not straight.

 

Good luck.

[Richie]

Well said, exactly the reason my motor screws are loose and motor is soldered in...

[snolde]

Ross,

Also make sure the rear axle is NOT touching the motor can after the gear mesh is set.

73

[Dave Crevie]

Equal wear on the mating gears does not increase gear life. A worn gear is just that, worn out. Any change to the gear tooth profile will change the dynamics of the gear mesh and reduce the efficiency of the gears. Typically, gears wear more at the pitch diameter, which changes the profile of the curved contact areas. They no longer roll against each other as designed, and that adds friction. 

 

The biggest contributor to gear wear is alignment. Spur gears and pinions work best when the shafts are perfectly parallel. So what do we slot racers do? We angle the motor so we can use a smaller rear tire. But that upsets the gear mesh, and we see premature wear of the gears. There is less contact between gear teeth. Using angled spurs and pinions helps, but the angles of the gears must be matched, determined by a formula that divides the angle between the motor and rear axle into the proper angle for each gear.  

 

Right angle drives like we use in our retro cars have a bunch more issues that I won't try to explain here. Until some manufacture gives us matched sets of bevel gears, we will just have to use what we have.

[dalek]

Regarding an anglewinder, how important is it that the centerline's of the motor shaft and rear axle be in the same plane?

[mreibman]

I hear a lot of things in this thread, so read it twice before throwing in 2 cents.

 

Things that might be areas of concern:

- Alignment of any bushings - check, test, make sure stuff spins free.

- a big sign of worn out axle bushings is chatter

- Worn out gears and pinions alert you to their demise with noise.

- Noise is bad.

- I don't hear a word about lubrication, and when I think of friction, this is my first thought to address.

- Are you oiling your bushings? When? How often? with WHAT oil?

- Do you oil your gear/pinion mesh? I know this sounds silly, but way back when we would put some tire traction on this section and use that as a lube. Lately I've also used red grease for this purpose. It's going to lower your friction. Not sure if it's going to cause you any other grief.

- Tires. Make sure they're trued and matched size. Make sure your rims aren't bent. Bent rims are a lot of fun.

- Axle - make sure it's clean, rust free, and STRAIGHT. Bent axles are a lot of fun.

 

 

Waxing the guide? I like it, just not sure what it's going to do.

[Ron Sullo]

ProTek RC "Premier White" Friction & Noise Reducing Gear Grease Lubricant (10ml) (from AMain Hobbies) 

 

For R/C applications, Premier White is best used with plastic spur gears, 1/10 scale transmission gears and 1/8 differential ring, pinion gears and axle joints. Testing has found the Premier White helps increase roll-out speed, higher RPM's and increased parts life.

To use, simply apply a small amount of Premier White across the width of one gear. As the gears spin, Premier White will spread across all gears and teeth providing a thin layer of lubrication. This also helps reduce gear mesh noise, as well as seat brand new 1/8 ring and pinion gears.

Premier White also works great as a general R/C assembly grease; use it with bearings, servo gears, axle joints or even the threads of a turnbuckle when installing new ball cups.

=========

My thoughts were if it works for the R/C world then why not go for it with our 1/24 scale

a little dab will do ya ...

applied it during 'break-in' on a DYNO (not track time) ... just saying

Plus I burnt up too many spurs using the lighter ... 

[Dave Crevie]

Any misalignment of the gears is detrimental. Looking at the rear of the chassis, you should be able to find a viewing angle where the motor shaft and axle are perfectly level with each other. You won't get this with an anglewinder with the motor mounted below the axle centerline, which is how most of us set up a flexi. So we end up building a misalignment into the car. 

[dalek]

FWIW, this is how I determine if the motor and axle centerlines are on the same plane in an aglewinder.  Being on the same plane should give maximum gear life and probably performance benefits as well.

 

The height of the can of a Retro Eagle is .602".

 

I install it flush with the bottom of the chassis.  The result is that the motor shaft centerline is .301 above the bottom of the chassis.

 

If I put tires on the car, say for example .702 in diameter and have exactly .050 under the chassis (directly beneath the axle) that means the axle centerline is, just like the motor shaft centerline, .301 above the bottom of the chassis.  So they are on the same plane.

 

[Ross Fox]

All great answers guys and I will check with each of those points. One thing I had never thought about was waxing the guide flag - hmm!  Another thing I have never done was put any type of oil or grease on the pinion or spur. I came from flying RC Helicopters where we had a steel drive gear against a phenolic spur gear. Rule of thumb was not to put oil or grease there. However, running nitro engines in these helis, there was always oil on the pinion and spur gear from the exhaust. I need every molecule of efficiency, as I am not that good a driver.

[Bill from NH]

I've been slot car racing since 1963. Not once in that time have I ever waxed a guide flag. I have greased gears. In the 70s we ran steel pinions against bronze spurs. I don't believe I've seen phenolic slot car gears in any pitch.

[Zippity]

Teflon coated guide flags?

 

 

[mreibman]

Teflon coated guide flags?

 

Why don't we just mold them out of PTFE (aka teflon)?

[Ross Fox]

Dave Crevie, I liked your drawing and explanation. Any recommendations for steel pinion brands. I haven't used press on's or solder on's, as I have found that I can use Locktite 680 and they never come loose, even after only curing for 5 minutes.

[Dave Crevie]

Of what is currently available, I like ARP pinions. A good compromise of quality and price. They are fine for either solder on or glue on. 

 

I realize that there is a lot of mystery about gears, so I whipped up a quick drawing to try to un-fog the subject. This would be a 12 tooth, 48 pitch pinion. The terminology remains the same for all pinion and spur gears. Only the dimensions would change.

 

[Dave Crevie]

Of what is currently available, I like ARP pinions. A good compromise of quality and price. They are fine for either solder on or glue on. 

 

I realize that there is a lot of mystery about gears, so I whipped up a quick drawing to try to un-fog the subject. This would be a 12 tooth, 48 pitch pinion. The terminology remains the same for all pinion and spur gears. Only the dimensions would change.

 

 

(click on the drawing to enlarge)

[Eddie Fleming]

I was under the impression that a JK pinion was required in the JK Box Stock class?