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Re: Engineering Question Regarding Splined Shafts

To: shop-talk@autox.team.net
Subject: Re: Engineering Question Regarding Splined Shafts
From: Don Malling <dmallin@attglobal.net>
Date: Sun, 12 Oct 2003 14:32:14 -0400
Linden,

Is there any mention of the aspect ratio of the spline. Are they assumed 
to be square: height == width?

I have never owned/driven a car with wire wheels. My experience is 
limmited to two MGB parts cars with wire wheels and some spares in the 
trunk. Some of them have good splines and others are in sad shape.

The cones are covered in grease. I don't know if the PO greased the 
cones or the spline grease migrated (spun) out of the splines and up 
onto the cones. Looks like it would be difficult to keep the grease off 
the cones. Perhaps keeping them tight keeps the grease out. The spline 
grease on some of them has migrated onto the spokes, and I understand 
that is a common problem.

Do I understand you correctly that the Torque at the wheels is carried 
by these smooth cones and not by the splines  -- something like a taper 
joint?



Don Malling

Linden Thomson wrote:
> 
> Let's try to get this discussion back to engineering.  I am not an engineer
> but offer this quote from "Machinery's Handbook",  11th ed. (1942), p568:
> 
> "Torque Capacity of Spline Fittings:  The torque capacity of spline 
> fittings,
> per inch of bearing length at 1000 pounds pressure per square inch on the
> sides of the spline, may be determined by the following formula, in which
> T = torque capacity in inch-pounds per inch of length,  N = number of
> splines, R = mean radius or radial distance from center of ho;e to 
> center of
> spline,  h = depth of spline:
> 
>             T = 1000 N R h."
> 
> This is for conventional straight sided splines for which  standards exist.
> 
> The discussion I have seen on this thread thus far about wheel hub splines
> ignores the fact that the drive is meant to be via the cone on the axle hub
> and the inner cone of the wheel hub, and via the outer cone of the wheel 
> hub
> and the inner cone of the wheel retaining nut (neither of which should 
> be greased).
> Very little, if any, torque is meant to be applied to the hub splines.  
> Any that is,
> is the result of insufficient tightening (and checking of tightness) of 
> the retaining nut.
> In other words, on properly maintained knock-on hubs, the splines will 
> not wear.
> 
> Cheers,
> 
> Linden





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