Floating axles

[Dr Goggles]

 Is there a maximum speed for non-floating axles?

What have people run with stockers?

We are getting our rear set up with 28 spline Ford axles and are wondering whether we should go to floating axles?

Hit me.

[maguromic]

Don't forget with a floater you  have two extra bearings which will add to drag.  There are things that can be done to minimize the drag like running oil in the hubs instead of grease and running a spacer between the bearings to keep them from ridding up on the snout and other oil control tricks.  Tony

[Dr Goggles]

Thanks Tony I've watched your hub/axle/brake developments with interest but detected a certain point where it got a little out of our range dollar wise. We'll be going to ball races either way, if we could get the kind of low drag you've managed we'd be pretty happy.... My question was more specifically about the rules. The Colonel and I had different opinions and no rule book at hand.

[Interested Observer]

In the same sense that a driveshaft (propeller shaft) has a “critical speed,” when its lateral natural frequency of vibration resonates with the operating rpm, any rotating slender elastic member would exhibit similar behavior.  While shafts can operate above the critical speed, passing through the critical zone can be dicey.  The speed depends on geometry/materials etc.

Since a floater does not have the added mass of flanges, brakes, wheel and tire, its critical speed would likely be well in excess of a non-floater.  But that is not to say a non-floater would be inadequate.

[Peter Jack]

IO, I see you've just reached a nice even 100 posts. Congratulations! 

Pete

[grumm441]

It was rule 2E
and it was just something I had in the back of my mind
and it looks like we could probably not really worry till we get past 300 mph

What with the SCTA rule book. The DLRA rule book. the Victorian road safety (vehicles) Regulations act (1999)
Australian Vehicle Standards and 3rd edition Australian Design Rules floating round in my head, it's a wonder I have room in there for anything much else sometimes.

I'm doing a Ducati 998 cam timing and valve clearances tomorrow, so I get to give my mind a rest!!!

G

[Rex Schimmer]

If you so a quick calculation of the natural frequency of let's say a 1.5 in. dia shaft x 20 inches long that is in bending (simply supported at both ends, which is the case with an axle that has a bearing at one end and a flange with the wheel mounted to it) the first critical frequency is around 17,875 cycles/min. If you looked at the cycles to be revolutions then that would be 17,875 rpm and with a 28 inch tire that would be about 1500 mph so I don't think your lakester has that level of speed potential so the flanged, single bearing axle should be fine.

Rex

[SPARKY]

Big Ford 9" ball brg housing ends with related stuff = what most of us over here use for c-clip eliminators

[floydjer]

IO lost me at " Propeller"

[Captthundarr]

IO lost me at " Propeller"

Propeller = make her go fast as to "propel her on down the road.  oop wrong thread

[wobblywalrus]

Rex, how do you do those calculations?   

[Rex Schimmer]

Wobbly,
I still have a number of machine design books that I kept from college days that  I found to be very helpful when I was working and I find that I can still pretty much grind through the calculations to come up with numbers that are at least close enough to give some good indication of what is happening. I will bet if you do a search for something like " natural frequency of rotating shaft" you can find plenty of info to come up with some numbers. The trick is to be able to recognize what set of parameters are important in the specific case that you are looking at.

Rex

[Dr Goggles]

If you looked at the cycles to be revolutions then that would be 17,875 rpm and with a 28 inch tire that would be about 1500 mph so I don't think your lakester has that level of speed potential so the flanged, single bearing axle should be fine.
Rex

What are you saying Rex?

just because we haven't run 200 yet that we won't run 1500?

Sheesh, a guy's just trying  here

[wobblywalrus]

Thanks, Rex.  There are no long rotating shafts on anything I race. I was just curious.

[Rex Schimmer]

James,
I am sorry if I implied that your lakester would not do 1500 mph, the mere application of an additional 125,000 horse power should get you to that number. So maybe a turbo next year???

Rex