24 replies to this topic

[CDavis7]

What axle do most prefer for ball bearings? Lately, the axles Ive bought (slick 7 and koford) seem so tight that they stress my ball bearings while old stock axles slide through and spin better.

What axles are retro racers using these days?

[Bill from NH]

Chris, have you tried polishing the Slick 7 & Koford axles down with ultra-fine grit sandpaper, such as 1500 or 2000 grit, so they fit in your existing bearings?  We did that to arm shafts in the '70s &  '80s so they'd fit in German GRW bearings. Drill blanks come in all sorts of 'plus' & 'minus' sizes. 

[MSwiss]

The Koford axles typically fit great.

 

What brand axle BB's are you using.

[Highnoon]

I started rebuilding a 1986 perimeter car today and I could not get any of the modern axles to fit. They fit fine in my modern ball bearings. I found the original axle in a box with the tires and fast gear, slipped right in but the bearings were seized. So I used acid flux and squirted a bunch in and worked them free, flushed with lighter fluid and the spun pretty good, not like new but good enough.

I’m pretty sure these were GRW.

[JerseyJohn]

#42 drill blanks are .0935 compared to 3/32 blanks which are  .0938. if the BB are slightly under and the axle slightly over than size really does matter.

[CDavis7]

I mostly have been using Bartos bearings. Great product with the right axle but lately new axles have been too tight. Im not new to the game and usually axles will slide through when the chassis is tilted on its side. This is a new problem. Sadly, cheap $2 bearings dont have the same issue.

Ill try polishing these new axles and see what happens. Thanks for listening, reading, and suggestions. JJ, I like your suggestions on using blanks

[Pablo]

-Koford axles are the best and if you are using Bartos BB's you are on the right track

-Keep in mind an axle typically fits more snug in a BB than a bushing or an oilite (in reference to your "slides through" test)

-Make sure there are no Qtip or pipe cleaner fibers making the axle seem tight

-If you are sure the axles need to be shaved to fit, like Bill said, polish them with sandpapers up to 2,000 until you get the snugness you desire. I use a drill and do half the axle at a time.

[Dominator]

CD, I use a piece 3/32 plated piano wire. It is slightly thicker than a standard axle and helps keep the bearings positioned during install. I dont have a lot left but if you want a piece I'll give you one next weekend.

[CDavis7]

So, I now think that my jig axle is the culprit as it spins easily in chassis where race axles seem too tight.

I suspect that the jig axle is slightly under sized after lots of use and some repeated aggressive cleaning. Thus, current work might be allowing the bearings to be slightly misaligned and then creating the tight fit with a race axle installed

[CDavis7]

So, I now think that my jig axle is the culprit as it spins easily in chassis where race axles seem too tight.

I suspect that the jig axle is slightly under sized after lots of use and some repeated aggressive cleaning. Thus, current work might be allowing the bearings to be slightly misaligned and then creating the tight fit with a race axle installed

[Pablo]

Maybe. May I suggest thinking of it like this:

-Checking for axle fit as far as too tight or too loose is something you check one side at a time

-Checking for alignment is done with axle through both sides

 

Back to your OP, do you mean the axles are tight when installed through both bearings,

or the axle is tight in both BB's?

[JerseyJohn]

Some more advice. after selecting the ball bearings and axle, take each bearing and slide it from end to end. It should move freely across the entire length if at some point it gets tight, get another axle. You now know that if there is resistance running the axle threw the installed bearings ,you have an alignment issue.. Proformance has a alignment tool for BB. its a spring and colors. What it does is push the bearings out towards you wheels keeping the bearings square to the axle.You can also make your own using 2 dubro 3/32 collars and an 1.2 to 1.5 spring that fits in a axle tube...

[MSwiss]

The problem with reducing your axle size, to fit particular ball bearings, is that your tires now won't run as true as they can be.

So you should buy BB's, to fit the axle, that is the proper fit, for the tires you use.

[CDavis7]

Pablo and JJ- Ive determined it was an alignment issue on my two most recent builds. The BBs slide on the axle fine if done one at a time. Its only in the chassis that was an issue.

[Pablo]

Glad you found the problem

[JerseyJohn]

The problem with reducing your axle size, to fit particular ball bearings, is that your tires now won't run as true as they can be.

So you should buy BB's, to fit the axle, that is the proper fit, for the tires you use.

Real like situation. How do you componsate for manufacturing variations. For instance I now have an axle that fits perfectly in my tires I go to your counter and buy a set of koford bearings. I check them on my axle and they are tight. What's the next step. Will you let them go thru your bearings till the find a pair that fits?

Sent from my Pixel 2 using Tapatalk

[MSwiss]

If you buy Koford BB's, or a pair of my CR016 Economy BB'd, a Koford axle will never be tight in them.

Racers get in trouble when they make the mistake of buying a drill blank, instead of using an axle especially made for slot racing.

[Ecurie Martini]

Out of curiosity - just looked at 3/32" drill blanks in McMaster - a range of specs:

 

-0.0003" + 0.00"

-0.0003"  + 0.0003"

-0.001"    + 0.0005"

-0.0         +0.0002"

-0.0002"  + 0.0

 

With prices ranging from $17.10/ 3 ft to $19.48/ft

 

How do the specs compare to purpose-made slot car axles?  Straightness spec, where given is 0.001"/2 1/4" or 0.005"/ft.

 

(I have used BB on 1/8" axles but routinely rely on drill blanks for 1/32 (3/32 axle) applications

 

EM

[Upfront slot cars]

Just use koford axles. Problem solved.

[MSwiss]

Out of curiosity - just looked at 3/32" drill blanks in McMaster - a range of specs:

 

-0.0003" + 0.00"

-0.0003"  + 0.0003"

-0.001"    + 0.0005"

-0.0         +0.0002"

-0.0002"  + 0.0

 

With prices ranging from $17.10/ 3 ft to $19.48/ft

 

How do the specs compare to purpose-made slot car axles?  Straightness spec, where given is 0.001"/2 1/4" or 0.005"/ft.

 

(I have used BB on 1/8" axles but routinely rely on drill blanks for 1/32 (3/32 axle) applications

 

EM

It doesn't matter what the straightness spec is on a drill blank, because they are the wrong temper for slot racing.

 

They're not designed to hit a 1/2" thick, hard wall, at 30-100mph. ( not saying the Koford will survive a 100 mph hit in the Bank)

 

Guys that were unwise enough, to run machine shop drill blanks, for front axles, (because it was straighter than piano wire) on cars as slow, as Retro F1 cars, got to walk to the pits, out of the race, with a tricycle in their hands.

 

I remember staying late at work, one night , at Koford, to go through 100 axles, on our optical comparitor, to compare straightness.

 

While a found a few that were dead nuts, after about 30-40, I quit, because it was pointless to spend time I could be using on other things,  to separate axles that varied by a few .0001's, that were going be spinning less than perfect spurs, and tires with rubber on the rims, that at G27 and G7 speeds, were going to quickly wear round.

[Pablo]

Guys that were unwise enough, to run machine shop drill blanks, for front axles, (because it was straighter than piano wire) on cars as slow, as Retro F1 cars, got to walk to the pits, out of the race, with a tricycle in their hands.

 My ears are burning LOL. I only made that mistake once

[JerseyJohn]

drill blanks are M2 hardness next up is m42 alot harder with lots of cobalt but with that hardness comes being more brittle.. what is the hardness of koford . parma etc. . i also get my blanks cut to length from Genco, the company that is used by several a main pros in retro east. m2 hardness, custom length for about 3.00. i can see using an abec7 or 9 bb for high-end performance cars..IMO its a bit overkill for the average racer.. there's something for everyone and price. out there that fit. ..

[Ecurie Martini]

"Guys that were unwise enough, to run machine shop drill blanks, for front axles, (because it was straighter than piano wire) on cars as slow, as Retro F1 cars, got to walk to the pits, out of the race, with a tricycle in their hands."

 

Of course, with 65-90 g  scale 1/32 cars, this is not an issue. Adding to that, with motors typically in the 20 to 30K RPM range and ~ 3:1 gearing, the axles are turning at most 10K RPM. I've run a few experiments comparing bushing and BB in this application with load simulated by running small paddles instead of wheels in a shallow pan of water (messy!) and recording current draw over time.  I did not find a repeatable difference but, of course, these experiments were at constant speed and did not examine side loading.

 

I do use ball bearings for certain front end applications where I want to model the front suspension of an open wheel car without an axle shaft intruding and the wheel insert design, i.e. photo etched wire wheels, precludes the use of an external retainer.  In this case, I machine out the back of the wheel to accept, with a light press fit, a shouldered BB which is then secured with Locktite.  The same "glue on" approach is used to fasten the wheel assembly to the stub axle.

 

Now back to deciding what to do with this Maserati shell which has only 32 rivets securing the fuel tank where there should be 38!

 

EM

[Bill from NH]

Al, it sounds like you have to scratchbuild six(6) rivets.

[mreibman]

I'm still shuddering about squirting acid flux into ball bearings. There's a lot of less aggressive chemicals out there that will do the job.