From: Peter Scott <motormcraft@...>
Subject: [Jumbuck] Re: Collapsed Rear King Springs
To: Jumbuck@...
Received: Saturday, 18 April, 2009, 4:26 PM

G'day All,
I was out unloading my Jumby just before and I thought that now is the ideal time to do some spring rate calculations.
So off I went armed with the trusty bathroom scales and weighed everything that was in the back of the beast.
I have been working on a building site over the other side of Melbourne for the last 10 weeks doing structural steel fabrication so I have been carrying around oxy cutting gear, welding equipment, grinders, safety gear, drills, hand tools etc. Before unloading, I crawled underneath with a measuring stick and measured the gap between the bump stop and the spring. Yes, I said gap. With all my gear, I have an 11mm gap between spring and bump stop. I then weighed everything and the total came to 237.5kg. The beast was reloaded with the weight evenly distributed in the tray and measured again. Still 11mm. The front height was checked to make sure that no weight was transferred to the front wheels, and the front moved less than 1mm.
For the purpose of this exercise I am assuming no front bias.
When empty, the gap between bump stop and spring is 28mm, giving a deflection of 17mm. The springs are the originals as fitted to vehicle and my driveway is flat and level.
So now I have arrived at this: 237.5kg/1.7cm = 139.7kg/cm, divide by 2 springs gives a rate of 69.85kg/cm.
Or in imperial, 523.7lb/0.67" = 781.6lb/", divide by 2 springs gives 390.8lb/".
Neil, while I realise that my method here isn't perfect, it is a far cry from the 110lb/" that Mr King Springs is claiming as stock and I'm afraid that your 130's are not even worth making a crossbow out of. Feel free to check this for yourselves and also pass on to King Springs if you see fit. BTW, if the stocks were 110lb/", then the load I've been carting around would have moved the wheels up 4 3/4"!
Hope this helps someone out there.
Cheers,
Pete.

--- In Jumbuck@yahoogroups .com.au, neil jeffries <vk2kyg@...> wrote:
>
> Hi Pete
> Yeah that pretty much says it all,I couldn't believe what I was reading either.I'm going to have go on a diet now as my lunch box and work boots in the back now exceed my load capability,so I guess I can forget about carrying my spare tire now.Let me know.
> Regards neil
>
>
> --- On Tue, 24/3/09, Peter Scott <motormcraft@ ...> wrote:
>
> From: Peter Scott <motormcraft@ ...>
> Subject: Re: [Jumbuck] Collapsed Rear King Springs
> To: Jumbuck@yahoogroups .com.au
> Received: Tuesday, 24 March, 2009, 10:35 PM
>
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> Hi Neil,
> I'm interested in what you've found so far from
> King's.
> Unfortunately it sent my Bullshitometer into
> overdrive with their last response.
> If the stock springs are only 110lb/" rated then
> the car would be almost undrivable. Now, with me standing on my tow ball on an
> empty ute, stock springs, and my weight being 95kg, the deflection measured at
> the end of the tow bar was approx 5mm.
> Bear in mind that I'm not standing over the rear
> axle, but on the tow bar (extra leverage).
> If the stock spring is 110lb/", then the back
> should have dropped by about 30mm.
> Yesterday I went to an on-site welding job in Loch
> Sport (Vic), a round trip of 560km with approx 340kg of tools, equipment, oxy
> bottles, etc, and full fuel. When loaded, I still had suspension travel,
> and at no time was there any clunking or banging indicating that I was doing any
> damage. BTW, I did the trip on less than one tank of fuel!
> The statement that "a leaf spring cannot lose its
> spring rate over time" is BS in it's purest form. I've had spring makers claim
> that any spring cannot lose rate, only height. Well, rate = load x
> height!
> "There is no manufacturer in Australia who can
> remanufacture parabolic leaf springs". Maybe not but we've got two in Melbourne
> who can, and my brother is the workshop manager at one of them, so I'll make a
> call tomorrow for you and see what he says.
> Sadly, if the guy is IT manager, he may know about
> computers, but not much about springs.
>  
> Cheers,
> Pete.
>  
> PS. As a rough guess, I would expect the stock
> springs to be around 240-250 lb/", but I'll find out.
>  
>  
>
> ----- Original Message -----
> From:
> vk2kyg
>
> To: Jumbuck@yahoogroups .com.au
> Sent: Tuesday, March 24, 2009 8:52
> PM
> Subject: [Jumbuck] Collapsed Rear King
> Springs
>
>
>
> Hi Guys
> Well after many emails to king springs an inspection at bowers
> suspension I'm informed by king springs that they are normal and at the
> correct height and the fact the car bottoms out now is normal because of the
> reduced travel after they have settled. They did offer to replace the
> destroyed bump stops and have sent new ones to bowers suspension for
> fitting.
> Below is the email response from KING
> SPRINGS
>
> Neil,
>
> We do not see an issue with the spring and the
> issue with the bump stops are a bi-product of the car sitting at the height it
> is. We can certainly send 2 new bump stops to Bowers to have them replaced, if
> you wish. The shackle angle is more than adequate and would certainly not get
> any closer to the chassis as the leaf spring is very close to being flat
> cambered, which they all are as they need to be basically flat to have the
> spring rate and height required. These springs, nor any for that matter,
> should not have a shackle that points straight 90 degrees and should always be
> "broken" i.e. kicked back, which these are.
>
> The amount of suspension
> travel and HTG measurements are basically where the car should sit, once the
> leafs have settled.
>
> All King Springs leaf springs have a 12 months
> warranty.I am more than happy to have the pack "modified", since the car has a
> slightly higher horse powered motor, etc, and possibly add an extra leaf to
> the pack, which we can do for you if you wish to do so at a discounted rate.
>
> Regards ,
> Kris Tarrant
> Sales and Technical Services
> IT
> Manager
> KING SPRINGWORKS PTY LTD
>
> My Response to this
> email...
>
> Hi Kris
> Thanks for your reply,but I am still a little
> bemussed by this as I have been driving utes for 35 years and have never had
> an unladen ute bottom out metal to metal so hard like this one does now.
> Perhaps as a layman I am using the wrong terminoligy but as an end user they
> seem to offer little to no
> resistance in an up/down motion.Is it possiable
> for the spring to have lost it's tensile strength,while maintaining it's
> camber and hight.?? Bowers are sourcing me some new performance replacment
> shocks that may be more suitable for the low springs hoping to stop the sudden
> bottom out with such a small bump in the road like it's doing now.
> I would
> apprecate some new bump stops sent to bowers ,they can fit them when they do
> the shocks.
> As for the extra leaf,that might be interesting, as if I
> ever did want to carry anything in the back,it would be impossable with the
> springs the way they are, One adult standing in the back and they drop onto
> the half a bump stop left..
> Can you tell me a price,and if the extra leaf
> would be a long one similar to 2nd leaf down in this pack or some other
> size,and would bowers be able to do this work.Also what load rating are these
> springs,since the jumbuck is rated at 560kg load carrying capasity, it may be
> nessasery to have my ute re enginennered and down rated to be legal on the
> road.
> Also if an extra leaf was fitted wouldn't that leave even less down
> travel and make the problem worse??
> Regards Neil
> vk2kyg@optusnet. com.au
>
> There
> Reply to this email
>
> Neil,
>
> The major issue with the Jumbuck rear
> suspension is that it is an "over slung" system, where the leaf spring is on
> top of the diff. The OE spring is a single leaf parabolic (hence less pack
> thickness, i.e. more travel) but they tend to break, which is dangerous as
> they are the only leaf locating the diff, and there is no spring manufacture
> in Australia who can remanufacture parabolic leaf springs.
>
> Once a
> multi leaf pack is made for the Jumbuck there is very little suspension travel
> left and the spring is very flat cambered (to achieve the best spring rate and
> height drop), so you can be left between a rock and a hard place as you can
> not add more spring rate to the pack as it will raise the car and you can not
> lower the car any further due to the lack of travel and camber in the springs.
> Also when you add more material to the pack to help with increasing spring
> rate (and reduce the amount of deflection due to the added rate) you then
> decrease the suspension travel you had due to the added pack
> thickness.
>
> The Leaf springs you have fitted are sitting at the correct
> height and are the correct spring rate and have not sagged. A leaf spring can
> not loose its spring rate overtime.
>
> The leaf springs you have fitted
> are a 130lb/" spring (OE is approx 110lb/"), i.e. it will only take 130lb of
> load (59kg) to deflect the spring 25mm and if you only have 25-30mm bump
> travel then it will go onto them.
>
> I have sent Craig new bump stops
> which he will receive later this week..
>
> Regards ,
> Kris
> Tarrant
> Sales and Technical Services
> IT Manager
> KING SPRINGWORKS PTY
> LTD
>
> So there you have it end of story. If you use king springs on the
> jumbuck you will reduce your carrying capacity from 560kg to 59kg and it will
> be sitting on the bump stops(if there is any left) so guys you be the
> judge.
> Regards Neil
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