Date: Wed, 1 Apr 1998 10:03:35 -0500 (EST)
From: Allan Duncan
Subject: Re: "Transaxles"
> The Sport, Husky and some Mk 2 Export had 1" instead of 7/8" shafts. The
> length is same for both: the only exception is very early Mk 1 (up to
> B.411 000340) which were different length, with corresponding change in
> hub spindle. Change to pressed-on drive flanges also no influence on
> shaft length. (All this from about 1967 copy of Rootes manual.) The
> manual states that the 1"shafts 'must' be used if the engine is tuned
> for sporting purposes.
I was following a Honda 4x4 the other day and was astounded to see the drive shafts - they must have only been 5/8" !
Date: Wed, 1 Apr 1998 17:06:45 +0200 (MET DST)
From: Allan Duncan
Subject: Re: "Transaxles
I was following a Honda 4x4 the other day and was astounded to see the drive shafts - they must have only been 5/8" !
Date: Wed, 1 Apr 1998 15:18:20 -0500 (EST)
From: Nickcleak
Subject: Re: Transaxles
Yes , but they only take a small amount of torque , I assume it was a small engine ... 850cc or similar ? Being Japaneese they don't put any more material than the bare minimum to just do the job ! Remember the torque is split 4 ways instead of 2 ways ... and due to the laws of mechanics , a 5/8 shaft will probably take say 80% of the torque of a 7/8 shaft !
Another thought ,maybe the Honda shafts were a special steel , or shorter ???
Did you know a standard Imp will produce a maximum of about 800 lb/ft of torque in the driveshaft !!
I have used the standard driveshafts on a tuned Imp with 'small' driveshafts with no problem ...
You will find they are under the most strain when for example a wheel spins on a wet manhole cover then digs in when it grips the road again , that is the worrying time !
Nick ...
Date: Wed, 1 Apr 1998 20:54:22 -0500 (EST)
From: Gary Henderson
Subject: Re: Transaxles
>I was following a Honda 4x4 the other day and was astounded to see the
>drive shafts - they must have only been 5/8" !
That's 'cos the rear wheels are hardly ever driven with their 'unreal time' 4WD system!
GaryH
Mk 1 Imp
L300 4WD
Date: Wed, 1 Apr 1998 20:52:04 -0500 (EST)
From: Gary Henderson
Subject: Re: Transaxles
No, sounds like a CR-V - about 2000 cc. The rear transaxle is 'interesting'; would be more interesting if the user had the choice to lock it up when required...
GaryH
Date: Wed, 1 Apr 1998 20:54:12 -0500 (EST)
From: Gary Henderson
Subject: Re: Transaxles
Hi Nick
I think it's a square-law situation, so a 7/8" shaft will handle almost twice what a 5/8" one can. 49/25 to be exact; the 1" Imp ones are therefore approx 30% stronger than the 7/8". (This is because the outside circumference of the shaft is both "longer" and acting at a greater radius.
By the way, a hollow shaft would lose very little torsional or bending strength.) Actually, I doubt the figure of 5/8" because the CR-V is quite a large vehicle, so even 7/8" would look tiny... I'll check the size of the front shafts on the L300 sometime; this is a part-time 4WD only so situation is similar to CR-V rear end.
The Imp shafts are also well cushioned from shocks by the Rotoflexes, but I guess that standard shafts probably should not be fitted with stiffer competition Rotoflexes?
Cheers
GaryH
Date: Wed, 1 Apr 1998 19:05:45 -0500 (EST)
From: Allan Duncan
Subject: Re: Transaxles
Not so. Without going back to my mechanics notes from a long time ago, the torque at yield point (which starts at the outer surface) will be between r^2 and r^3, ie for r^2 51%, r^2.5 43% and r^3 36%. At r^3 (I think this is the right one, but tensor analysis is beyond me sitting at the terminal miles from my books) the 1" shaft has 50% more strength than the 7/8" one.
Remember, torque is the tangential force times the radius it is acting on, so as you get larger the radius goes up proportionally, the force goes up quicker (because the circumference goes up AND the effective depth goes up).
If the difference was as small as you suggest, then consider the size that would be needed for a ship's prop. shaft. A tube has nearly as good a limiting torque, but isn't normally used because the savings in metal used doesn't outweigh the extra cost of ensuring no flaws in the construction. When weight _is_ important, tubes are used - eg the prop. shaft of a normal car.
Date: Fri, 17 Apr 1998 03:24:09 +0100 (WET DST)
From: Gary Henderson
Subject: Re: Transaxles
Hi again Nick
I finally remembered to admire the L300 driveaxles. They are 30 mm dia and have to take a share possibly peaking at 50% of - wait for it - 5049 lb-ft of torque! Engine gives 192 N-m (about 260 lb-ft if my conversion is right) and in low-drive bottom gear the overall ratio is a tad over 35:1.
Cheers
GaryH