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Old 01-06-2015, 10:06 PM   #43
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On the subject of Propride/Hensley hitches, although they weigh more than the other hitches, the added weight in a perfect world would be distributed to all the wheels of the TV and TT. That means in general about 20-25 pounds per wheel. A fairly insignificant amount really. Now if you are at the hitch receiver limit on the TV, you may already be over the max gross limit. In either case, it is always safer to go to a higher rated vehicle.
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Old 01-06-2015, 10:07 PM   #44
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lewster -

Very interesting heads up on the new lithium batteries soon to be introduced, more lower and lighter weight loves two problems for us trying to reduce hitch weight. Lighter hitch weight and more storage capacity for our solar panels possibly eliminating need for a third battery. Very good, thanks !
I used to fly RC electric powered model airplanes. When I started in 2002 nicads and NMIH batteries were the norm. You were lucky to get 4 or 5 minute flights then it took an hour or more to charge the batteries. Then Lipos appeared in 2003. More AH and lighter weight. Now all RC electric model airplanes use Lipos and Lipos have gotten cheaper. New battery chargers were developed and at first were expensive and the price came down. Early LIPOs could only be charged at 1C but now they are being charged at at much higher C rates shortening charging time. Large electric powered models and electric ducted fan jets can pull over 100amps.

Each cell has to be monitored and balanced with the other cells. If one cell failed in a flight pack you would have to discard the pack. You can't fully discharge a LIPO cell risking permanent damage. If a cell was overcharged there was a risk of fire. There were incidents of hobby benches burning up when a cell failed during charging and lit up. I've seen photos of cars on fire when someone was charging the batteries from a charger connected to a car battery. Nowadays, it is mainstream and very safe. All the drones you hear about taking aerial photos use LIPOs. Most is developed and made in China.

I think it will be a while for LIPOs to come to mainstream RVs. By then maybe new technology will be on the scene. Probably whatever is used in electric cars will migrate to RVs. But with oil prices plummeting who wants to buy an electric car.

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Old 01-06-2015, 10:19 PM   #45
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The frame of Airstreams must have a good chassis ground. If not, how would the electric jack work with only a positive lead? That is why, during jack replacement, star washer(s) are recommended to bite into the "A" frame coupler metal through the paint. Check it out with a lighted circuit tester from battery positive to bare metal on the chassis. Now, you are going to make me go to the trailer and confirm that is how I shorted my nut driver across the metal cover of one of the battery circuit breakers while hooking up two extra Optimas. The circuit breaker was mounted to the interior skin through the mouse hair covering on the wall under the couch with sheet metal screws.
The negative terminal of the batteries is connected to the chassis at some point so the metal in the Airstream can act as the negative return path. However, sometime about 1970 Airstream started to use two wires to each item (other than the post jack), one + 12 volts the other - 12 volts. The minus wire is usually white in Airstreams. The positive wires can be red, black or other colors. This gives the 12 volt equipment a solid return path for the power rather than depending on rivets, grounding screws and so on all over the place. I remember so many times trying to isolate an electrical problem in old Airstreams and finding it was a bad negative path due to using a screw to the metal wall someplace.

BTW Argosy's up until at least 1975, and maybe later used the old system, no white negative wire but local screw grounding. The water pump on my '74 never ran well until I finally ran a negative white wire from it back to the battery. It had been built using a screw into the sheet metal wall for the return path.
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Old 01-07-2015, 05:46 AM   #46
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OK you two! I guess I can retire now!!! Good info in both of your posts.

The new lithium formula has added the element Yttrium. Prior to this new development, any LiFePO-4 batteries were susceptible to extreme damage when charging below 32F, but with Yttrium (now: LiFeYPO-4) this no longer a concern and will eliminate the need for heated battery boxes.

Cell balancing electronics will still be required and LiPos still can't be placed outside like our beloved LLA (liquid lead acid) batteries. From the early testing reports that I'm getting, the draw capacity is 80% and since there is no memory, full re-charge is not necessary either.

Special charging IS required, as these batteries want a CC/CV (constant current/constant voltage) charging regimen rather than the 3-stage Bulk/Absorption/Float that the LLA batteries require.

I'm hoping to get a pair of 100 amp/hour LiFeYPO-4 batteries for testing before the end of this month. The only problem is shipping, as they are considered hazardous (interesting, as Lifeline regularly ships their smaller AGM sizes to me via UPS ) but I'm sure that detail is under consideration.

I'll let you know when I get these new beauties? I'm sure that they ain't gonna be cheap!!!

And BTW, as idobra said, I have NEVER been a fan of frame/chassis grounding since the return path for DC should always be equal to the positive side. I have always been an advocate of 2-wire DC use with positive fuse blocks and negative bus bars, running every device's 2 wires directly to the positive and negative sources, unless accessible hubs are used.
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Old 01-07-2015, 06:57 AM   #47
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Lead in rear Bumper

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Might be some merit to this idea. Might be slightly less expensive alternatives to the lead, albeit a little less dense.

Seems counterproductive to put more weight into the equation to lighten the tongue, but if you did it, I would suggest you consider dipping those lead bricks in liquid plastic to coat them so that you don't get lead powder in the air that you could breathe in...
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Old 01-07-2015, 07:38 AM   #48
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Maybe the best solution is to rethink the tow vehicle choice or go with a smaller Airstream or if you still want to pursue present choice to take it to CanAm.

The published hitch weights AS uses are too low. A 25fb or 27fb from users posts are between 1000 and 1200lbs. My Classic 25fb is between 1100 and 1200lbs.

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Old 01-07-2015, 09:54 AM   #49
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The usual solution for too heavy hitch weight is a heavier duty tow vehicle, or a smaller Airstream. Both very expensive choices if you already have an Airstream and tow vehicle, such O.P. and me. And Kelvin and a thousand others who tow with half-ton pickups.

Thanks to the O.P. what is being asked here is for a third choice, medium-sized Airstreams need for lighter hitch weight. Looking at the "numbers" most 25' Airstreams need no more than 800 lbs hitch weight to maintain the 10% usually recommended weight weight for sway resistance. And 800 lbs is close to the limit for European diesel SUVs, depending on whose chart you look at, or which sticker they place on the receiver.

In the case of our Ram 1500 and Kelvin's Tundra as well as O.P.'s Porsche diesel, reducing our Airstreams' hitch weight is the alternative to trading for a larger tow vehicle to effectively deal with receiver and payload limits. Hitch reinforcement will still be needed in some cases, I can see a slight receiver movement on our Ram when we tighten the weight distribution bars.

Just another way of looking at the hitch weight and tow vehicle payload issue.
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Old 01-07-2015, 10:21 AM   #50
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Originally Posted by dkottum View Post
The usual solution for too heavy hitch weight is a heavier duty tow vehicle, or a smaller Airstream. Both very expensive choices if you already have an Airstream and tow vehicle, such O.P. and me. And Kelvin and a thousand others who tow with half-ton pickups.

Thanks to the O.P. what is being asked here is for a third choice, medium-sized Airstreams need for lighter hitch weight. Looking at the "numbers" most 25' Airstreams need no more than 800 lbs hitch weight to maintain the 10% usually recommended weight weight for sway resistance. And 800 lbs is close to the limit for European diesel SUVs, depending on whose chart you look at, or which sticker they place on the receiver.

In the case of our Ram 1500 and Kelvin's Tundra as well as O.P.'s Porsche diesel, reducing our Airstreams' hitch weight is the alternative to trading for a larger tow vehicle to effectively deal with receiver and payload limits. Hitch reinforcement will still be needed in some cases, I can see a slight receiver movement on our Ram when we tighten the weight distribution bars.

Just another way of looking at the hitch weight and tow vehicle payload issue.

dkottum - perfectly put, this is where my head is at. I actually drove a 2500 truck prior to buying the Porsche but just could not accept that vehicle as my daily driver. Very capable tow vehicle no doubt but not for me.

Back to my question on cable rating, maybe another way to ask this question is what is the breaker rating on the 12V circuit for a recent 25 or 27FB? The breaker may be close to the battery, maybe under the bed?

The cable should be rated to at least that value with some consideration for volt drop also. Anyone close by their TT to take a look?
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Old 01-07-2015, 11:00 AM   #51
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Tongue Weight

Though a grand exercise in customization, I would really recommend rethinking the trailer size, or be serious about another tow vehicle. I own a 2014 27FB, we started out with a 2011 1500 Silverado 5.4L that was great in Florida (flat land) but was found lacking out west (up-hill). No tongue weight issues and you would think 9600lb tow capacity would handle a 7200lb trailer, just not without operator anxiety. Best solution 2015 2500HD DuraMax Allison. Tow all day long, up /down hills, in comfort.
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Old 01-07-2015, 11:37 AM   #52
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There's a huge difference between placing 150 lbs inside the confines of the frame/shell structure and cantilevering about 75-100 lbs FROM the rear of the frame and solely depending on it's integrity. The moment arm of a cantilevered load will greatly increase the actual weight seen by the frame while the load inside makes full use of the Airstream's monocoque frame/shell/floor structure.


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Lew, not trying to be belligerent
just sayin' there's a lot of discussion on putting weight out back the axles.

I may be talking out my arse but, whether it's inside or out, it's basically an issue of moment, which is weight x distance.

So, using some rough numbers for my 30' and the Airstream/Fiamma bike rack, we'd have 75lbs, 14' from center of axle to rack centroid. Giving us 1050 lb-ft.

Whereas, a couple of deep cycles in the rear at 110lbs, conservatively 11' from center axles, would give us 1210 lb-ft.

Personally, I think all the consternation is unwarranted, and all this talk about road vibration, cantilevered weight, and "over hitching" is hooey. My Airstream is built like a tank and I could hang a couple of bikes off the back to Timbuktu and back... but, since we're all about fostering an arena of ideas, I thought I'd run it up the flagpole and see if anyone salutes
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Old 01-07-2015, 12:16 PM   #53
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We've got bikes on the Airstream rack on the back as well and I'm comfortable with it. I see frame flex at the entrance door when tightening the stabilizers unevenly, so I'm pretty careful about loading too much behind the trailer axles.

That doesn't mean there is no way to lighten the hitch weight though.

Yes we all understand the bigger truck solution, lots of 1/2 tons and SUV's out there towing Airstream who do not choose that route for their own reasons. This thread is about hitch weight, it's effect on receiver and payload limits, and what may be done to lighten it.
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Old 01-07-2015, 12:21 PM   #54
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I guess I assumed from post 25 the OP had not yet purchased the Cayenne. Since he already has it and lives in Ohio I would contact CanAm in Ontario to get Andrew's advice. The hitch would probably need to be reinforced like the VW Touareg.

Removing propane tanks seems a drastic method that reduces the capability of the Airstream. If moving the batteries back to the front bed doesn't take much weight off the hitch, (maybe its only good if you are adding two extra batteries), there is not much else to do other than removing the spare tire on a 25fb or 27fb. That leaves the 23fb which has the lightest published hitch weight other than a Bambi 16.

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Old 01-07-2015, 12:26 PM   #55
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I think we need something outside the box:

- dual wing mounted directly to tongue provides 'lift'

- helium filled buoys attached to hitch
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Old 01-07-2015, 12:34 PM   #56
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Thanks Boon' for your contribution. Bye.
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