Rear Axle Spline Compression Springs

E

Ed Price

Guest
While measuring the spring rate for my front springs, I also checked the rate
for the much smaller springs that fit across the rear drive axle spline joint
(keeping pressure on the differential oil seals). I'm just putting this info on
the record should anyone ever need to find a commercial replacement.

Here's the results:

For 1 inch of compression:
Original Amphi Spring #1: 70 pounds
Original Amphi Spring #2: 40 pounds

For 2 inches of compression:
Original Amphi Spring #1: 140 pounds
Original Amphi Spring #2: 80 pounds

Averaged out, the spring rates for each are:
Original Amphi Spring #1: 70 pounds per inch
Original Amphi Spring #2: 40 pounds per inch

I conclude that one of my axle springs is weaker than the other. I don't know if
this is significant or not. Both springs are identical in size, and the weaker
one doesn't show any visible damage.


Ed
El Cajon
67 Rust Guppy


[Non-text portions of this message have been removed]
 
W

WB6WSN

Guest
Roger:

I don't mind tough questions, although subjective ones (like "Are you an
idiot?") always give me a problem.

Anyway, the data was obtained using a large, hydraulic press with an electronic
load cell placed between the ram and the top of the spring. A large 5/8" thick
aluminum plate was used to support the spring, and a pair of 5/8" plates were
used to maintain an "on-axis" force on the load cell. The springs were clean,
and there was no indication of friction or binding. The springs were measured
from their totally relaxed (extended) condition (11" long in the case of the
front suspension springs). I loaded them with only a couple of pounds pre-load,
just enough to get an indication of the load cell digital meter, then I pressed
the "Tare" function, zeroing out the initial couple of pound load.

A record of the fun can be seen at:

http://members.cox.net/edprice/Springrate/Setup.JPG
http://members.cox.net/edprice/Springrate/Cell.JPG
http://members.cox.net/edprice/Springrate/1.JPG
http://members.cox.net/edprice/Springrate/2.JPG
http://members.cox.net/edprice/Springrate/3.JPG

The axle springs both "looked" identical, but, when I get ready to test the rear
springs, I'll retest the axle springs once more. Yeah, the data looks
suspicious. BTW, notice the lack of a safety cable to catch the spring should
any part of this stack "slip"? Fast & loose engineering!

Ed
El Cajon
67 Rust Guppy

----- Original Message -----
From: Rogtwo@aol.com
To: wb6wsn@cox.net
Sent: Wednesday, November 05, 2003 10:24 AM
Subject: Re: [amphicar-lovers] Rear Axle Spline Compression Springs


Hi Ed,

Let me first apologize for being critical, but I have a hard time believing
that two springs that are the same size have rates that are so different.

First, are all the dimensions of the two springs approximately the same?

Spring diameter

Wire diameter

Number of coils

How did you measure the forces? Were the springs still on the drive shaft?
Is there a possibility that there was friction in the system somewhere that gave
you erroneous results?

I believe you were the one that used a spring calculator earlier. While these
calculators don't give exact results (mainly do to estimates of the number of
active coils), the results can usually be expected to be within 10% of the true
values. The large differences you found just don't seem possible for two
springs that are of the same size and material.

Roger St. John
White '63
Seattle


In a message dated 11/5/03 2:43:14 AM Pacific Standard Time, wb6wsn@cox.net
writes:
While measuring the spring rate for my front springs, I also checked the
rate for the much smaller springs that fit across the rear drive axle spline
joint (keeping pressure on the differential oil seals). I'm just putting this
info on the record should anyone ever need to find a commercial replacement.

Here's the results:

For 1 inch of compression:
Original Amphi Spring #1: 70 pounds
Original Amphi Spring #2: 40 pounds

For 2 inches of compression:
Original Amphi Spring #1: 140 pounds
Original Amphi Spring #2: 80 pounds

Averaged out, the spring rates for each are:
Original Amphi Spring #1: 70 pounds per inch
Original Amphi Spring #2: 40 pounds per inch

I conclude that one of my axle springs is weaker than the other. I don't
know if this is significant or not. Both springs are identical in size, and the
weaker one doesn't show any visible damage.


Ed
El Cajon
67 Rust Guppy

[Non-text portions of this message have been removed]
 
R

rogtwo@aol.com

Guest
Ed,

Great job. Your spring measuring method looks great. I'm still confused by
the differences you found between the two drive shaft springs, but with
quality setup like that your numbers must be right.

Roger

In a message dated 11/6/03 4:04:15 AM Pacific Standard Time, wb6wsn@cox.net
writes:
Roger:

I don't mind tough questions, although subjective ones (like "Are you an
idiot?") always give me a problem.

Anyway, the data was obtained using a large, hydraulic press with an
electronic load cell placed between the ram and the top of the spring. A large
5/8"
thick aluminum plate was used to support the spring, and a pair of 5/8" plates
were used to maintain an "on-axis" force on the load cell. The springs were
clean, and there was no indication of friction or binding. The springs were
measured from their totally relaxed (extended) condition (11" long in the case
of
the front suspension springs). I loaded them with only a couple of pounds
pre-load, just enough to get an indication of the load cell digital meter, then
I
pressed the "Tare" function, zeroing out the initial couple of pound load.

A record of the fun can be seen at:

http://members.cox.net/edprice/Springrate/Setup.JPG
http://members.cox.net/edprice/Springrate/Cell.JPG
http://members.cox.net/edprice/Springrate/1.JPG
http://members.cox.net/edprice/Springrate/2.JPG
http://members.cox.net/edprice/Springrate/3.JPG

The axle springs both "looked" identical, but, when I get ready to test the
rear springs, I'll retest the axle springs once more. Yeah, the data looks
suspicious. BTW, notice the lack of a safety cable to catch the spring should
any
part of this stack "slip"? Fast & loose engineering!

Ed
El Cajon
67 Rust Guppy


[Non-text portions of this message have been removed]
 
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