skp51443 Posted March 25, 2015 Report Share Posted March 25, 2015 Just keep an eye on your front axle weight with a big mid-mounted tank, aside from not wanting to overload it your ride will be a bit better if the load on it is lighter. First rule of computer consulting: Sell a customer a Linux computer and you'll eat for a day. Sell a customer a Windows computer and you'll eat for a lifetime. Link to comment Share on other sites More sharing options...
trimster Posted March 25, 2015 Author Report Share Posted March 25, 2015 Thanks Stan. I guess I'm not to concerned as similar trucks (working) have 2 - 50 gal tanks (one on each side) a bit further forward. I could downscale the tank to a 50 to be on the safe side. It would also do less damage to the credit card when filling up...doh. Fortunately the truck already has a dash switch and switch-over valve for the second tank. I'll need to get an in-tank fuel gauge float sending unit thing for the tank, as the dash fuel gauge does switch over to monitor the Aux tank. Robert & Lisa '14 Keystone Fuzion 315 38' 5er 2015 Volvo VNL 670, D13, iShift 'The Tartis' (ours) 2013 Smart Fortwo Passion 'K-9' 2011 CanAm Spyder RT Limited (Ours) We are both USAF vets. Link to comment Share on other sites More sharing options...
bstark Posted April 5, 2015 Report Share Posted April 5, 2015 Oh boy, does this thread ever bring back memories. I ordered my 4400 new in 04 as a cab chassis and the lightest arrangement available then through Diamond Spec was a 17,600lb rear axle with 15,500lb bags...a rough riding little beast with a 215" WB. I patterned my set up with hitch-pin placement 14" behind axle center line. My trailer had approx. 3500 pinweight. My understanding and knowledge of pneumatics lead me to believe that the only way to change the ride characteristics via the air bags was to increase the overall volume of the system from the levelling/supply back. To accomplish either through much larger 'volume only' capacity bags or the addition of a large "ping" tank added to the circuit as near to the bags as possible. I commenced with a 7 gallon ping tank added with a large capacity 12v solenoid valve installed right on the top of the tank and reasoned that this would of course require a higher "flow rate" of air between the bags and from bags to tank to realize any ride improvement effect, so.... installed larger fittings to tops of bags, got rid of the 5/16" feed to bags and installed the 5/8" inside dia. lines like those that feed your brake canisters from bags to the tee fitting from the tank with 1" brass piping from tank to that tee. All of that premised upon allowing for more rapid transfer of air from bags under shock loads from bumps to utilize the larger overall volume "compressibility" factor to soften ride. It helped but not as much so as to make the effort repeated on any other truck worthwhile, as it is my belief you would need volumetric increase far greater (even larger tank and piping) to effect a marked ride improvement. I think one iteration of Peterbilt had a ride enhancement from factory with 1" crossover piping between the rear bags and perhaps scavenging that hardware would reap benefits for the back of these MDT's Additonal weight still remains the singular most effective way to enhance ride characteristics. Tampering with spring rates through leaf removal or substituting lighter rating etc., simply transfers ride levelling requirements to an even greater extent to those air bags which in turn harshens ride slightly by requiring additional air pressure to achieve same ride height, which in turn decreases compressibility of air within when it's already at a higher static pressure. It's a veritable catch 22. Today is just the tomorrow you worried about yesterday! Bruce, Sandra & Scampi cat SKP#86370 Link to comment Share on other sites More sharing options...
skp51443 Posted April 6, 2015 Report Share Posted April 6, 2015 IH used to offer 12K air bags, if they fit your rig it might be worth swapping to them to help the ride. Brian at Stalick had to fuss at the factory a good bit to get them as OEM installs but they helped the ride enough he thought it worth the effort. First rule of computer consulting: Sell a customer a Linux computer and you'll eat for a day. Sell a customer a Windows computer and you'll eat for a lifetime. Link to comment Share on other sites More sharing options...
bstark Posted April 7, 2015 Report Share Posted April 7, 2015 Yessir Stanley; that would definitely be the way to go. Coming up with a bag that achieves a lifting capacity to level a set-up but still retain the resiliency with compressibility of air within is the challenge that they haven't had to face in the commercial industry. Some of the trailer or suspension/axle outfits have experimented and spent development money of coming up with axles that will give expensive race horses a smoother ride to the track or breeding appointment such as Dexter's trailing axle air suspension but very few of these MDT providers give a rip if your fillings are jarred as long as the goods arrive in a timely fashion. Today is just the tomorrow you worried about yesterday! Bruce, Sandra & Scampi cat SKP#86370 Link to comment Share on other sites More sharing options...
trimster Posted April 19, 2015 Author Report Share Posted April 19, 2015 Update the lead-in-the-butt process. Did the whole build the mold (sled and drag) sand casting thing for a test. My problem is that my forge isn't big enough to melt the required amount of lead to fill the mold. So...after having bars welded between the bed sub-frame to hold the cast lead weights on, I'm cutting those out and going for plan B. Always need a plan B. I'm getting several metal ammo boxes and welding those into the back, between the frames. 30cal boxes are just the right size to fit 8 boxes in the open spaces. Then I'll just dump the lead tire weights in, pour epoxy over the lead bits, to hold in place. I'll start on that in a week or so. Question about the 12k air bags. Are there third party air bag providers that would offer 12k bags instead of IH? Robert & Lisa '14 Keystone Fuzion 315 38' 5er 2015 Volvo VNL 670, D13, iShift 'The Tartis' (ours) 2013 Smart Fortwo Passion 'K-9' 2011 CanAm Spyder RT Limited (Ours) We are both USAF vets. Link to comment Share on other sites More sharing options...
skp51443 Posted April 19, 2015 Report Share Posted April 19, 2015 I'm sure you could source the 12K bags elsewhere, IH buys their bags from outside sources. Just look for a 12K bag that matches the mounting and ride height of your current bags. Plan B sounds good, I've never been happy around large quantities of molten metal. Did enough damage with my 10 pound bullet casting pot! First rule of computer consulting: Sell a customer a Linux computer and you'll eat for a day. Sell a customer a Windows computer and you'll eat for a lifetime. Link to comment Share on other sites More sharing options...
phoenix2013 Posted May 10, 2015 Report Share Posted May 10, 2015 Stan, thanks. My air pressure valve seems to be working just fine actually. It brings the butt up when low. Hook the trailer, and you hear it adjust. Unhook the trailer and it re-adjusts. Guess I am just trying to soften the ride with less air pressure in those bags. Maybe that's not possible with just air pressure alone. Adding weight might be the best way. Less air pressure makes it worse. The reason it's worse because your air volume remains the same. Less air pressure would improve things if it was driven by increasing the air volume (larger air bags or adding a ping tank), but that requires significant re-engineering effort to make it work. Link to comment Share on other sites More sharing options...
sclord2002 Posted May 16, 2015 Report Share Posted May 16, 2015 Trimsters, your leveling valve is supposed to do exactly what you describe in post #18 above. If you are really running 110 psi in your bags, something is really wrong. You won't be able to add enough weight to get a good ride at that pressure. Your leveling valve should only allow enough air to the bags to raise the suspension to the proper ride height....no load=low pressure, heavy load=higher pressure. In less than overload conditions you should never see that kind of pressure in your bags...never. That kind of pressure would probably blow out most of the bags on our older RV toting trucks. Your leveling valve is bad or badly out of adjustment or your pressure is not really at 110 psi. Keep us informed as to what your outcome is. Be safe, Charlie Don't ever tell a soldier that he doesn't understand the cost of war. Link to comment Share on other sites More sharing options...
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