Re: Question re: Tapered Bearings

[Chip Old]

David, Your question came via private e-mail, but I'm replying to the list because it's a continuation of the current thread. Hope you don't mind. Besides, this way others can offer their input as well. I'm not an engineer, but experience in the years since I wrote the TSO article someone else referenced has taught me that the spindle (which is rather, um "spindly" compared to those on other cars) is less likely to break if the spacer is used. I agree with you that columnar strength probably isn't the issue, but that doesn't mean you should leave out the spacer. If you look at a cross-section of the assembly, you will see that with the spacer in place and clamped down, the inner race of the inner bearing in effect increases the diameter of the root. That helps to prevent the spindle from flexing at its root. I suspect that is what makes spindle breakage less likely with the spacers in place. As for the problem of spacer length, obviously that has to be adjusted to give the correct play at the new tapered roller bearings. See my message of earlier today to the MG-TABC list on that.

On Thu, 20 Dec 2001 Davidtasa@aol.com wrote: > Dear Chip, > > I don't remember if actually you joined the recent discussion in the tabc > list about whether or not to use the spacers with tapered bearings or not, > since I usually delete the emails quickly so they don't pile up on me. But I > most value your wisdom and opinions so I wanted to get it straight from you. > I'm not an engineer, but I have a hard time understanding just how the > presence of the spacer would strengthen the stub axle when used with tapered > roller bearing conversions. As far as I can understand it, the stub axles are > stressed and prone to cracks and breaks at the base of the stub, or in other > words, on the inward side of the larger inner bearing race. It would seem to > me that the spacer would add strength (rigidity) between the races, but I > don't see how that would strengthen the spot where the stub is prone to break. > Proper length of the spacer would be critical with tapered bearings because > if too long, it would prevent proper adjustment and too short, it would just > sit on the stub between the races doing virtually nothing. Isn't the spacer > exactly that - a spacer between the original ball bearing races to tighten > down on and hold the ball bearing races in place? I can see where in that > context, the spacer is essential and adds strength to the entire hub unit. > If you say "put them back in, it's better that way" - I will do it! But I > don't really understand how their presence, even when adjusted to exactly the > right length, would help strengthen the stub axel at the point where it is > most stressed (and likely to break) or relieve any stress someplace else > thereby strengthening the stub when used in conjunction with tapered roller > bearings. > The consensus appears to be to put them in. Any explanation you can give me, > and your opinion, I would greatly appreciate. > > Sincerely, > > David Tasa TC 3896 -- Chip Old 1948 M.G. TC TC6710 XPAG7430 NEMGTR #2271 Cub Hill, Maryland 1962 Triumph TR4 CT3154LO CT3479E fold@bcpl.net

[Ray]

break if the spacer is used. I agree with you that columnar strength

> probably isn't the issue

Only part of the equation....

> If you look at a cross-section of the assembly, you will see that with the > spacer in place and clamped down, the inner race of the inner bearing in > effect increases the diameter of the root. That helps to prevent the > spindle from flexing at its root.

And this is the part I forgot to add......it puts the bending moment on the kingpin via the two bushed points. This is also why the king pin hole has to be round without a lot of play..... Best, Ray