[xj] Belt Tension

After devising a ridiculous looking tool consisting of fishing weights,
string, bamboo and duct tape. I carefully manipulated this gadget so as to
apply 6.4 lbs onto my fanbelt while measuring the resulting deflection with
my micro-calipers. After this exercise in futility, I realized that it will
be pretty much impossible to get any degree of accuracy in applying fan-belt
tension. I think I’ll just go with the recommended finger test…

snip <Here’s a suggestion – your pinky can deliver the 3.2lb with it just
starting
to be uncomfortable; likewise for your forefinger and 6.4libs – who needs a
gauge?! No other fingers please gang. > unsnip
Thanks Alex.
Dave Cooke '87 VDP (V12)

After reading the ROM - of course, after I had completed the job above
( I noticed that it is quite specific about fanbelt tension. ie: there
must be a deflection of 3.3mm when a load of 6.4 lbs is applied at the
mid

point of the belt. This brings two questions to mind: a. How does the
hobbyist mechanic achieve this accuracy in fanbelt tension (I’ve been
thinking of somehow using my wife’s kitchen scales or my sportfishing
scale)…and question b. does anyone on the list know what the tension
of
the other belts should be (I can’t find mention of these tensions in the
ROM
or the archives) and perhaps more importantly how do I achieve the
correct

tension??
Thanks
Dave Cooke
'87 VDP (Cdn spec) 196,000km

G’Day David,
According to my ROM (Edition 2 1985) The tension for the alternator
belt is 1.5 kg (3.2 lb) should give a deflection of 3.8mm (0.15 in) and
for
the air pump belt 2.9kgf (6.4lbf) should give a deflection of 5.6 mm or
0.22
in. Don’t know why it says lbf in this case. For the power steering pump
it’s 3kg (6.4lb) and 4mm(0.16in) , all the above for 12 cylinder engines.
I don’t see how you could do this and get results to the tenth of a
millimeter or how you’d measure the deflection to that degree of accuracy.
Tight belts put more strain on the bearings, so better to err on the side
of> looseness I think. The power steering on our '85 used to squeal like a
stuck pig on full lock, tightened the belt today as suggested in the
archives and no more noise!
Regards,
John Hudson,

===================================================
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be pretty much impossible to get any degree of accuracy in
applying fan-belt
tension. I think I’ll just go with the recommended finger test…

Something to keep in mind with any drive belts: you want them tight enough
to not slip, but not so tight that they put excessive lateral load on the
accessory bearings.

So, a simple test is to attempt to turn the accessory pulley the opposite
direction of normal rotation. If you can turn the pulley easily against the
resistance of the belt, it’s too loose. Tighten and repeat the test.===================================================
The archives and FAQ will answer many queries on the XJ series…
FAQs: http://www.jag-lovers.org/xjlovers/xjfaq/index.html
Archives: http://www.jag-lovers.org/lists/search.html

To remove yourself from this list, go to http://www.jag-lovers.org/cgi-bin/majordomo.