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Old 10-02-2003, 07:06 PM   #1
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Axle upgrade

Need some advice from the axle gurus.
I'm adding some weight to my '59 Tradewind. Like A/C, greywater tank, some big batteries, and other stuff.
Figure the added weight will be about 500#. Original dry weight was 3180.
Can I do this:
1. Switch the old 3500# axle up to 5200#
2. Rebuild the springs and add a leaf. Change the spring rate from 1030# to 1180# per inch.
3. Upgrade the tires from original 7.00X14.5 (1870#) to ST225/75R15 D with rating of 2500#. (the extra height of the tire compensates for the added leaf in this underslung 4" drop knuckle dragger)
4. If necessary, I can open up the wheel wells for the bigger tires. I don't want to change the "look", but even the original tires were a tight fit.
By spreadsheeting the spring rate, it looks like the added dry weight at the same axle/frame clearance will be about 460 lbs, and a bonus of about 100lbs added to the wet weight.
Does this sound about right? Are there any problems I have overlooked? Is this a good idea?
Thanks in advance. I will karma anyone who answers (little bribe offered)
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Old 10-03-2003, 09:27 AM   #2
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Axle modification

Your suggested axle change should work just fine.

However, the necessity to keep the running gear (all of it) properly balanced, becomes more critical as you increase the spring rate.

I would also suggest that you install adequate shocks.

Or, you could also install a Henschen axle, if you wished.


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Old 10-03-2003, 10:06 AM   #3
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Axle upgrade

Thanks Andy,
Yeah, but I think the Henchen technology is still not quite fully developed. I don't fly either because I think jets are still a little bit too new-fangled.
Just kidding
Actually, I kind of like the old fashioned idea of riding around on 300# of leaf steel, that almost drags on the ground.
I do plan to keep the unit well balanced. I'm putting a new water tank and the 6V batteries across the from each other and just a few inches forward of the axle.
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Old 10-03-2003, 10:17 AM   #4
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Why six volt batteries?

If two sixes are in series and one gets weak, the party is over.

If two 12's are in parallel and one gets weak, you disconnect the bad one, and continue the party.

Two sixes in series have far less benefits than two 12's in parallel.

For equal size batteries, the wattage is exactly the same.

Different size 12's can be put in parallel. Different size sixes, must never be put in series.

Andy
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Old 10-03-2003, 12:50 PM   #5
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2 sixes

My guess is the "party" will last longer using 2 sixes. As long as the batteries are good, usuable battery life will be longer then a 12V set up. I think it's cause the 6V can go further discharged and still be useable. Or maybe it's cause the plates are bigger?

I have seen this set up in Mexico many times in homes that did not have A/C electric power. Just solar and wind generation to run the home and recharge batteries

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Old 10-03-2003, 01:22 PM   #6
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Axle batteries

Just about everyting I've seen, from off-shore trawlers to deep-in-the-woods solar junkies recommend 6V golf cart (or lift truck) batteries.
They're cheap for the amp-hours they provide, and like Action says, and they are designed for deep discharge and fast recharge. Normal size is the same as regular 12V (although you do need two, or four) Weigh about 35#ea., you do need to know what your doing, use good charging practices, and equalize once in a while.
Like anything else, if you take care and check them, they'll last a LOT longer and provide more power.
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Old 10-03-2003, 06:49 PM   #7
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see
http://sierranevadaairstreams.org/ow...ry-config.html
for a bit on the parallel vs series debate.

When you run parallel you will reduce the draw on the batteries. This tends to increase their usable capacity. (re Peukert)

When you run serial you get a bit more room for the cells which can also increase capacity.

But, using Trojan's deep cycle 6 volt series as a comparison, you can get more difference out of the battery design that you are likely to get out of any series vs parallel arrangement. The tradeoffs in battery design are in expected life, money, and capacity.

As far as failures. A bad cell in a series configuration drops supply voltage about 2 volts and that is about the only effect. In a parallel situation, a bad cell can cause circulating currents which can result in excess heat and overcharging of other cells.

For small banks, it really doesn't make much difference. For larger banks you are going to get into some interesting protections and load balancing considerations.
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Old 10-04-2003, 09:49 AM   #8
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The higher the battery voltage, the more efficient it becomes.

Surely, the auto industry didn't change from 6 volts to 12 volts, for the fun of it.

There is talk in some circles that the auto industry may change to 24 volts, in years to come.

The higher the voltage, the less current a given circuit will consume. That permits smaller wiring for starters.

The real problem with two sixes in series is that when one becomes even weak, the total output in volts will drop below a useable value.

Taking the same problem of two 12's in parallel, when one becomes weak, simply discoonect it from the circuit, and your still in business. Granted, perhaps to a limited degree, but any continuance of service fars exceeds none.

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Old 10-04-2003, 10:11 AM   #9
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New axle

While the battery discussion is very good, I want to get back to the axle topic.
Here are two pictures showing the differences between the original '59 axle and the new Dexter.
Axle dimensions:
Old axle 55.5" spring centers, 72" hub face, capacity 3500#. Total weight 153#.
Drum dia. 14.25"
New axle -same centers. Capacity 5200#.
Total weight151#. Drum diam. 13.125"
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Old 10-04-2003, 10:14 AM   #10
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New axle

The spindles are quite a bit larger:
Old spindles-inner 1.500", outer 0.9375"
New spindles-inner 1.750", outer 1.250"
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Old 10-04-2003, 10:19 AM   #11
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The _battery side_ of higher voltages is less efficient because more cells are needed which means more interconnections and stuff.

As you noted, though, higher voltages are more efficient in terms of delivery and transport of energy.

The automotive world is heading towards 42 volt systems (not 24). That gets into some of the interesting things they are doing for intra vehicle networks and power device control, too. There are standards and things nearing acceptance and chip makers have switching and control devices available now. Some of this stuff is already in current models. The IEEE Spectrum has run a number of good articles on this topic recently.

The problem with batteries in parallel is being able to detect when one becomes weak. Its weakness will be 'hidden' by the others as they compensate by feeding the weakness.

Continuance of service makes a good comparison. In series, you lose one cell worth of capacity at reduced voltage. In series you lose one battery's worth of capacity but keep the voltage.

And now, back to topic. Thanks guys - and for the good pics!
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Old 04-14-2004, 07:20 PM   #12
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Were the hubs on the old and new axels 6 on 5inch center? Is that a standard of sorts. Did the 75R15 tires fit the 14.5 wheels?

Thanks for the pointer.
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Old 04-14-2004, 07:42 PM   #13
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Quote:
Originally Posted by psychpw
Were the hubs on the old and new axels 6 on 5inch center? Is that a standard of sorts. Did the 75R15 tires fit the 14.5 wheels?

Thanks for the pointer.
15 inch tires must go on 15 inch wheels. If you put 15's on 14.5 inch wheels, it will almost certainly cause a catastrophic failure of the tire/wheel assembly, if you can even get them to hold on the rim long enough to inflate.
Terry
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