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original class 8 fifth wheel wth air pinbox


73pete

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New to site . We are using an antique 1973 Peterbilt 359 with it's original Holland ffth wheel and are going to install a Trail-air pinbox. Does or has anybody used this setup ? Our trailer is a 2003 Newmar Mountain Aire 38.5 feet and weighs about 21,000 GVW. It has two 12K Dexter axles with dual wheels . Is the Trail-Air air pinbox a good choice? I pull regular semi trailers is the reason I haven't changed the fifth wheel.

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His Holland hitch is the single jaw style, with much more room for side to side "tilt."  I ran that way for two years. No issues, other than some items taking an unplanned trip to the rv floor.

Ever watch a commercial rig round a turn going over an elevated railroad crossing? There may be 3 inches of daylight showing at the edge of the hitch.  That's why commercial hitches are single jaw. The pin itself is the same as RV pins.

KW T-680, POPEMOBILE
Newmar X-Aire, VATICAN
Lots of old motorcycles, Moto Guzzi Griso and Spyder F3 currently in the front row
Young enough to play in the dirt as a retired farmer.
contact me at rickeieio1@comcast.net

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Trail Air might not have enough "oomph" for a fifth as heavy as Newmar. Pinbox air hitches are a great invention for lighter trailers, but because of the size limitation there is only so much room in there for a single air bag and its physical size.

With heavy pin weight if you have to inflate it beyond 80 psi (to bring it "up to the line") that airbag is pretty much useless, it's hard as a rock.

There was one manufacturer of heavy trailers (who shall remain nameless), who was "doing customers a favor" and shipping their rigs with a pinbox hitches, "to make live easier for customers" and no doubt making profit on those installs.

They shall remain nameless because they stopped doing this, after customers complained about blowing up the single airbags in those pinboxes.

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 I run a air pin on our 43' Teton. The original airbag had problems with temperature fluctuations affecting the ride height. If it was 20 degrees out it needed air. But when the temps warmed up it needed to adjusted to the proper pressure. For a better travel in its travel space.

 So I found the largest bag that fit into the space . Installed it and it now operates like it should.

 I also manufactured nylon blocks and installed them so the towards the front of the hitch so it does not move sideways. 

 Now the Binkly head rides on 2 1/4" of rubber that is in the sliding hitch on the truck. That will slide rearward about 2'. If needed.

 

 If you do pulled with the commercial hitch I would suggest to put appropriate blocking under the truck tires on the downward side to hitch or unhitch. This will help with less stress on the RV . And disconnecting much easier.

 Also if you run a nylon wear plate on the hitch it may restrict the movement between the two components.

 Another thing you may do is adjust your tire air pressure on tear axles.

 

  Safe Travels,    Vern

 

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10 hours ago, phoenix2013 said:

<snip>

With heavy pin weight if you have to inflate it beyond 80 psi (to bring it "up to the line") that airbag is pretty much useless, it's hard as a rock.

<snip>

 

 

Just some probably useless information:  If you buy a TrailAir hitch "off the shelf" it will have a one-size-fits-all air bag.  I am aware of at least three different size air bags that LCI can install on their hitch.  The diameter of each bag is different.  For example, a 7" diameter air bag is 38.48 square inches.  Multiply that by 80 psi and we can see that it is a good size for a pin weight of 3,040 lbs, a 2,640 lb pin weight should have a 6.5" air bag and a 3,500 lb pound pin weight would need a 7.5" air bag (in theory).  Since Goodyear uses hour glass shaped bags rather than straight sided the actual computation for size/psi/weight is a little different, but they do provide the weight ratings for a given pressure and size in their data sheets.  The standard for a TrailAir pin box is one shock absorber, if needed a second shock can be added to provide additional dampening.

300.JPG.c2a50e50210ede7534c4c440c7f9aa80.JPG

Randy, Nancy and Oscar

"The Great White" - 2004 Volvo VNL670, D12, 10-speed, converted to single axle pulling a Keystone Cambridge 5th wheel, 40', 4 slides and about 19,000# with empty tanks.

ARS - WB4BZX, Electrical Engineer, Master Electrician, D.Ed., Professor Emeritus - Happily Retired!

 

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Thanks for replying.Some more information I forgot to tell, truck has a Peterbilt air leaf rear suspension and also has the Don-Vel air bag system on the front springs.

Randy A I measured the air bag on the Trail-Air and the best I can tell it's 7.5 inches, it also has two shocks and a tag that says GVW 21,000.I think the part number is 155948.

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 Brain said one thing....?.. tear axle     ?...... .?

 I mean adjust tire air pressure when pulling the RV .

 

 Now I was at Kaman bearings and seen a air bag similar to what was in the pin box . So I asked them and they supply then for sawmills and other industrial situations.

 I did some research and measuring. Bought one about 8 3/4" diameter. It is the same design shape, just larger in diameter.

 Unfortunately I sand blaster the hitch when it was apart . So no stickers for info. It does have two shocks.

 After adding the nylon guide blocks I painted it with an epoxy paint.

 

 Safe Travels,.   Vern

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Vern - do you have a photo of the nylon guide blocks?  I would really appreciate seeing exactly what you have done.

 

300.JPG.c2a50e50210ede7534c4c440c7f9aa80.JPG

Randy, Nancy and Oscar

"The Great White" - 2004 Volvo VNL670, D12, 10-speed, converted to single axle pulling a Keystone Cambridge 5th wheel, 40', 4 slides and about 19,000# with empty tanks.

ARS - WB4BZX, Electrical Engineer, Master Electrician, D.Ed., Professor Emeritus - Happily Retired!

 

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23 hours ago, 73pete said:

Thanks for replying.Some more information I forgot to tell, truck has a Peterbilt air leaf rear suspension and also has the Don-Vel air bag system on the front springs.

Randy A I measured the air bag on the Trail-Air and the best I can tell it's 7.5 inches, it also has two shocks and a tag that says GVW 21,000.I think the part number is 155948.

I'm interested in feedback on your Donvel system on the front axle. Have the motion controls installed on the cab, seats, and drive axle already.

1999 Peterbilt 385 C12 430/1650 13spd

2006 Dodge 3500 DRW 4x4

2010 Hitchhiker Champagne 36 LKRSB

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On May 18, 2017 at 9:18 AM, CrazyCooter said:

I'm interested in feedback on your Donvel system on the front axle. Have the motion controls installed on the cab, seats, and drive axle already.

X2

2016 Western Star 5700xe (Pathfinder) DD15 555hp

w/12 speed automatic 3:05 diffs

2005 Newmar Mountain Aire 38RLPK

2 Great Danes

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  RandyA,. I use a iPad mini and cannot post pictures on this forum with it.

 If you send me a email link I can send you pictures.

 

 When this iPad was new I could take a picture and immediately post a picture.

Then the DW updated it and it lost the ability to post pictures..

  

 

Now for what have been working lately is installing a Aquqhot heating system in our Teton .

 I have been taking photo's. The heating unit is installed and the 4 heat exchangers are in stalled.

 Two heat exchangers are operating with there own thermostats.

 The other two are larger heat exchangers with speed controllers on the fan motors. These two units are not finished as I need to wire the remote thermostats and some other lose ends.

 We were hiding in Utah,Idaho and Montana for about 4 weeks on vacation. So it may be a few weeks till it is finished.

 

 So at that point I will find a way to post pictures. And post the ones on the nylon blocks also.

 

 Safe Travels to all,.   Vern

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Performance of air bags is strictly governed by size and air volume. Whether they are Goodyear, or Firestone, or others they are rated at maximum pressure of 100 psi. They are constructed as single, double convoluted, triple convoluted, or others, Dividing the air bag (double convoluted, etc.) increases it's capacity at 100 psi in the similar volume and size.

mGyllwGl.jpg

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7-8 inch airbags are rated at 2,200-2,500 pounds at 100 psi depending on construction. That does not mean that they should be working at 100 psi, at that pressure they are pretty much useless and hard as rock. The other rating on the airbags is the jounce pressure which is 200 psi, beyond that pressure they will burst.

The ideal operating pressure for all air bags is between 40-60% of the maximum pressure of 100 psi which means that for these airbags they should carry a load between 1,000-1,500 pounds.

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Quote

7-8 inch airbags are rated at 2,200-2,500 pounds at 100 psi depending on construction. That does not mean that they should be working at 100 psi, at that pressure they are pretty much useless and hard as rock. 

I would argue that at 100 psi & 2500# load on the bag they are not hard as a rock, and in fact virtually identical to the same bag with 60psi & 1500# load although undersized for the 2500# load.

"There are No Experts, Do the Math!"

2014 Freightliner Cascadia DD16 600hp  1850ft-lb  18spd  3.31  260"wb
SpaceCraft S-470
SKP #131740

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There is lot more engineering that goes into air bag suspensions and utilization than maximum pressure.

These are are the engineering parameters that go with the single convoluted 2,200 air bag shown above

gv8hJJTl.jpg

It actually shows the disclaimer that if you design will run at 100 psi or above you better call the Goodyear engineer first.

It also shows the design range of only 1 inch with pressures between 40-60 psi. Goodyear and Firestone provide this data so that the design engineers study and consider these parameters in their products, rather than "argue" about it.

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I think if you read the graphs, you'll find my above statement to be true.  No arguing with science.

Or maybe my rocks are just softer than your rocks :huh:

"There are No Experts, Do the Math!"

2014 Freightliner Cascadia DD16 600hp  1850ft-lb  18spd  3.31  260"wb
SpaceCraft S-470
SKP #131740

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28 minutes ago, NoDirectionHome said:

Or maybe my rocks are just softer than your rocks :huh:

We're getting a little personal here.

KW T-680, POPEMOBILE
Newmar X-Aire, VATICAN
Lots of old motorcycles, Moto Guzzi Griso and Spyder F3 currently in the front row
Young enough to play in the dirt as a retired farmer.
contact me at rickeieio1@comcast.net

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If you can't poke fun at yourself, you have no right to take a poke at others. Glad you like it.

And Rocky and his darling wife are first class folks.  Glad we got to spend a little time with them recently, although it was too brief.

KW T-680, POPEMOBILE
Newmar X-Aire, VATICAN
Lots of old motorcycles, Moto Guzzi Griso and Spyder F3 currently in the front row
Young enough to play in the dirt as a retired farmer.
contact me at rickeieio1@comcast.net

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3 hours ago, rickeieio said:

 

And Rocky and his darling wife are first class folks.  Glad we got to spend a little time with them recently, although it was too brief.

I have to agree. I met them at the HDT Rally last year, along with many great people, including Jack Mayer!

Just need to watch out for that Georgia Hybrid guy...............:P

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 The c/l of airbag on my pin box is 24" from the rear pin. 

The c/l of pin for the hitch is 12" from the center of the airbag and 12" from the rear pivot pin.

 So Phoenix could calculate the pin weight that would be appropriate for this hitch.

 I do have a double convoluted air bag. 8 3/4" dia airbag.

 Safe Travels,.   Vern

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  • 2 weeks later...

Thanks for all the replies. Sorry for the delay but have been traveling. Randy A I can't seem to be able to send a picture of the Pete,so give me an e-mail also the Trail-Air would not hold air.

Wrknrvr, What did you mean about the nylon wear plate restricting movement I thank they work alot better than grease.Thanks for the information about Karman Bearing. I'm going to ckeck on a larger bag.

Crazy Cooter and Heavy Metal ask about the DonVel system. I only have the front axle kit that has two single air bags for each front spring. I think the system helps my Peterbilt. It takes the hard bump out of the truck when hitting the bridge joints and also concrete joints on concrete roads. I have been thinking about getting the ones for my four rear air bags.

Thanks again for all the great advice.                     73pete

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