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  1. #1
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    Default Seeking information on single and tandem axle ladders

    I am doing some research in to the various aspects of a single axle ladder versus a tandem axle. I have searched all of the internet and all of the publications and have the pros and cons for both. I am looking for some more information relating to these two subjects, especially comparing wheel bases and maneuverability. I would also like to know some history on what apparatus out there on single axle chassis relating to maintenance and reliability over the long haul. I have contacted the City of St Louis to find out about the reliability and out of service time for their quints they run with the TQC concept, but have not had any response. Any articles or information you can get me about this subject would be fantastic and I would really appreciate it. I have not had a lot of luck and am really trying to compile somoe good information and need everyone's help. Thanks.


  2. #2
    Forum Member MemphisE34a's Avatar
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    Maneuverbility of the apparatus should be determined by the steerings cramp angle and the distance from the front tires and the foward most rear tire. Single or tandom axles should not be a factor.

    The best sale for tandoms is weight distrubution and an extra set of brakes.

    We have tandom axle 100' straight sticks that have driven that are only hampered when compared to our pumpers because of the ladder overhang over the cab.
    RK
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    Management is making sure things are done right. Leadership is doing the right thing. The fire service needs alot more leaders and a lot less managers.

    "Everyone goes home" is the mantra for the pussification of the modern, American fire service.


    Comments made are my own. They do not represent the official position or opinion of the Fire Department or the City for which I am employed. In fact, they are normally exactly the opposite.

  3. #3
    55 Years & Still Rolling hwoods's Avatar
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    Thumbs up And............

    Bob covered a few Positive things on Tandems already, such as Better Braking and Weight Distribution, and I agree with his findings. I would add that if you get a Tandem, Get a Differential lock on the rears. This is a device that locks all rear wheels together so you have Eight Tires pulling in Mud, Snow, Etc. This device has saved my butt more than once. We've operated Two Trucks over the Last 30 some years, A Sutphen 95' Tower Ladder from 1971 to 1991 and a Seagrave 105' Tower Ladder from 1992 to 2005. Both were Tandems. During the 1980s, until I retired, I was a Driver on a Seagrave 100' rearmount on a Single Axle. Personally, I had no Problems with the Manuverability of any of them, They would fit into tight places with a little work. One difference that you need to consider is the Ladder Overhang. The Sutphen we had was a Midmount, with the Bucket off the rear. When you start having stuff hanging beyond the rear of the Vehicle, you really need to be aware of where it is at all times, since a turn that allows the Front end to squeeze by may result in the Bucket smacking something as the rear swings past. The opposite is true for Rearmounts, with the Ladder Tip/Bucket hanging in front of the Cab, although being able to see what it's doing is easier than with the rearmount.

    I can't address Quints, since they are not a big deal here, with only one in the County. Anne Arundel County, Maryland, Next to us on our East Side, has several, and they are continuing to add them to the Fleet. I'll see if I can find a Contact for you over there, and PM it to you. Good Luck with this.....
    Never use Force! Get a Bigger Hammer.
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    Forum Member Rescue101's Avatar
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    I agree Harve,except you can't. At least on the HEAVY spec axles. Believe me I tried on our new one. I had to settle for 1 locker,4 On-spots and ATC(Automatic traction control)Meritor WOULD NOT put double lockers on. T.C.

  5. #5
    55 Years & Still Rolling hwoods's Avatar
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    Thumbs up Hmmm..........

    Quote Originally Posted by Rescue101 View Post
    I agree Harve,except you can't. At least on the HEAVY spec axles. Believe me I tried on our new one. I had to settle for 1 locker,4 On-spots and ATC(Automatic traction control)Meritor WOULD NOT put double lockers on. T.C.

    Tim, Thank You. I may a bit outdated on this. Our Sutphen (Eaton Tandem Rears) had a Air Operated Switch, Single Throw, that locked the Pots together. The Seagrave had Electric Switches, one to lock the Differential/axle interface (Positrack??) and a separate one to lock the Pots together. Or so it seemed. Power was by an 8V92 thru an Allison HT70 on the Sutphen, 62,500 Lbs. The Seagrave was powered by an 8Vsomething thru an Allison that lacked the HT70's guts. That boy weighed in at 70,000...... I'll look over the setup on our new Pierce Tandem Heavy Rescue and get back here with the info on that.....
    Last edited by hwoods; 11-25-2009 at 09:44 AM.
    Never use Force! Get a Bigger Hammer.
    In memory of
    Chief Earle W. Woods, 1912 - 1997
    Asst. Chief John R. Woods Sr. 1937 - 2006

    IACOJ Budget Analyst

    I Refuse to be a Spectator. If I come to the Game, I'm Playing.

    www.gdvfd18.com

  6. #6
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    What you will probably be able to do is ask for an Inter-Axle Differential lock. Since the power to wheels going down the road floats back and forth between the front and rear axle of the tandem, this Inter-Axle Differential lock, sometimes known as a "power splitter," assures that both axles get power. On our Meritor axles, this is an air acutated device. This is also what keeps you from getting stuck should you get one axle on some uneven terrain and take weight off the other axle, allowing it to spin.
    Then, you can ask to have a differential lock on one axle. As the truck goes down the road, the power floats side to side depending on which wheel has the least traction. The differential lock on an axle makes that one axle a positive traction rear end, with power going to both wheels. On our truck, this is an electric switch. You have to be careful about driving too fast, cornering, etc. because there is no give in the axles. Just like when a 4x4 vehicle is put in "low lock", this is not used on dry surfaces. Otherwise, you might snap off an axle in turning a corner.
    We have this set up on a tandem quint, and put the On-Spot chains on the axle with the differential lock. Figure if we have both axles pulling, and one of them is posi=trac with chains and we are still stuck, we need the big wrecker anyway.
    I have also seen the electric differential lock on a single axle pumper, which I thought that would be a good idea to get you out of a slick spot. You would not be able to use to travel over a crawling speed, but at least it would get you moving.
    Our tandem axle quint has been great. It has the tightest turning radius (with a straight axle under the front) of all our apparatus, including single axle/TAC4configuration on our pumpers and heavy rescue. Add the extra set of brakes,4more tires to spread the weight, eliminating the ladder overhang, and it really makes good sense to me.

  7. #7
    Forum Member CaptOldTimer's Avatar
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    Ok this it for Quints, but if you don't and have a RML then the single vs. tandem still applies......



    Single or Tandem Axles on 75 Foot Quints??


    Tandem of course!!

    A 75’/500 gallon Quint with a heavy duty ladder (500 lb tip load) and a full complement of ground ladders places an unacceptably heavy load on a rear axle.

    The weight of the apparatus itself, along with the weight added by water, personnel, equipment and hose all must be considered.

    With a 31,000 pound single rear axle, most 75’/500 gallon Quints are over rear axle capacity when actually in service.

    Contrary to what some apparatus manufactures would lead one to believe, there is not a significant weight savings associated with an aluminum ladder. In fact, there is less than 200 pounds of weight difference in the actual aerial device between a 75’ heavy duty aerial and the aluminum aerial. Both weight about 7,000 pounds!!

    In attempts to “loose weight” in a 75’/500 gallon single axle Quint, several other areas of the overall apparatus design may be compromised, some examples include the following:

    • Size and strength of aerial lift, extension and stabilizer cylinders may be minimized.

    • The aerial hydraulic pump may be run off the engine’s power steering pump rather than a dedicated PTO.

    • Body materials and structural support of the body may be lightened.

    • Frame liners and reinforcements that improve chassis ride/handling may not be used.

    In short, in attempting to stay under 31,000 pounds on the rear axle, other elements of the overall apparatus design must be compromised.

    Another tactic that is sometimes suggested is to have a customer insert wording into their specifications stating that the apparatus “must not exceed the front or rear axle weight rating at delivery.” This, of course, presents a major problem because the customer then has the burden of limiting their equipment or hose load for the life of the vehicle.

    The supposed principle advantage of a single axle Quint is that it is more maneuverable. In this case, perception does not match up with reality. In any single axle Quint application, the rear axle is located further to the rear, in order to shift additional weight forward. With a tandem rear axle, this not necessary. As a result, the tandem has a shorter wheelbase and a better turning radius.

    Single Axle Tandem

    Wheelbase 219’ 213’

    Turning Radius 37.28 ft 36.43 ft
    (curb to curb)

    It is important to state that the overall length of the body is about 36” longer in the tandem axle application. This added length offers two (2) benefits:

    • A smaller front overhang for the aerial ladder

    • A longer, larger hose bed. This makes hose racking and packing easier.

    Maintenance with a single axle is more as there is more break wear and suspension wear as well. Better handling and breaking are another advantage of the tandem axle design. In the tandem, there is more tire surface in contact with the road and there are more brakes working. The tandem provides more stable handling and better breaking, making is a safer vehicle.

    Cost is another consideration. The cost difference between a 75’ single and a tandem is approximately $12,000. The cost of the tandem is greater, it is important to put this cost difference in perspective. Over the in service life of the Quint, the extra cost approximately $600.00 per year, is very little. Based on a twenty year life of the apparatus. It is entirely likely that this cost would be more than offset by reduced maintenance costs, making the tandem a better investment when view from this perspective.

    Bottom line is what the department can afford at the time of the bidding and the awarding of the bid vs. what they will be spending over the life of a single apparatus rig, against a tandem axle rig.
    Stay Safe and Well Out There....

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  8. #8
    Forum Member gunnyv's Avatar
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    CaptOldTimer has great advice.

    We bought a quint about 5 years ago. The guidance was that it would be used as an engine co. but the Chief wanted another aerial to meet ISO. He insisted on a single axle 75' w/450 gal water tank, the largest that could fit by weight. Any more water would have required waiving the loose equipment allowance. It has a 33500 split rim rear axle to make the weight. It carries only engine company ladders.

    The rig drives great but goes through brakes and tires quick. It is handicapped as an engine by a smaller hose bed, and as a ladder by lack of ladders and storage space. The chief who bought it retired and now we're stuck with a rig that is a minimally useful engine and useless as a truck company apparatus. Even though it is one of our newest rigs, it is in reserve service because of all the drawbacks.

  9. #9
    Forum Member Rescue101's Avatar
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    Can't agree on the maintenance.Ran a 100' single X for 15 years. Never put a spring in it and replaced rubber(tires)only for age not wear. Now our NEW 100' is already wearing tires and is harder on suspension that the single ever was.Matter of fact we never did brakes on the old Ladder either.Yes you'll have more brakes with a 'screw(tandem). T.C.

  10. #10
    Forum Member gunnyv's Avatar
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    Quote Originally Posted by Rescue101 View Post
    Can't agree on the maintenance.Ran a 100' single X for 15 years. Never put a spring in it and replaced rubber(tires)only for age not wear. Now our NEW 100' is already wearing tires and is harder on suspension that the single ever was.Matter of fact we never did brakes on the old Ladder either.Yes you'll have more brakes with a 'screw(tandem). T.C.
    When ours was in service as an engine co., it did 2000+ runs and over 15K miles a year. How much did yours run?
    Last edited by gunnyv; 11-25-2009 at 10:11 PM. Reason: grammar

  11. #11
    Forum Member Rescue101's Avatar
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    Nowhere near that much Gunny.Our issues stem from all the tight turns and weird azz roads we have. We run around 380 fire calls a year. Urban.surburban and rural. But 'screws are netoriously hard on rubber.Necessary for todays bigger aerial devices but hard on tires nonetheless.But We've NEVER had any suspension issues on our single X rigs and we've got some with some pretty big GVW's. Most of our rigs carry 11-1500 water and 13-1400' 5". If you're running a little quint and putting everything on it,you'll be at or over the 'balance" point. But if you use youe head and a heavy spec rig with a reasonable tool load,there's still a place for a single.And over long ownership in a moderate run dept,they'll last OK. In a high run,high use maybe not so well.But I've had this arguement before. what works for us won't work everywhere any more that what works for you is necessarily going to work for me.That's why we have CHOICES,hehe T.C.

  12. #12
    Forum Member MemphisE34a's Avatar
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    Quote Originally Posted by Rescue101 View Post
    Can't agree on the maintenance.Ran a 100' single X for 15 years. Never put a spring in it and replaced rubber(tires)only for age not wear. Now our NEW 100' is already wearing tires and is harder on suspension that the single ever was.Matter of fact we never did brakes on the old Ladder either.Yes you'll have more brakes with a 'screw(tandem). T.C.
    Quote Originally Posted by Rescue101 View Post
    We run around 380 fire calls a year.
    And there you have it.
    RK
    cell #901-494-9437

    Management is making sure things are done right. Leadership is doing the right thing. The fire service needs alot more leaders and a lot less managers.

    "Everyone goes home" is the mantra for the pussification of the modern, American fire service.


    Comments made are my own. They do not represent the official position or opinion of the Fire Department or the City for which I am employed. In fact, they are normally exactly the opposite.

  13. #13
    Forum Member FWDbuff's Avatar
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    Quote Originally Posted by Rescue101 View Post
    Can't agree on the maintenance.Ran a 100' single X for 15 years.
    Yeah but when all you are going to is the occasional "Assist the tipped cow" run in a 2.5 square mile first due......Of course you can run it for 15 years!
    "Loyalty Above all Else. Except Honor."

  14. #14
    Forum Member Rescue101's Avatar
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    Yup,and the new Ladder has been in service less than six months and has already worn the rear tires more than the single X did in 5 years so I'm not misrepresenting anything here. Do DUE research,while the tandem will PROBABLY be necessary,they aren't ALWAYS the best choice. And in another industry I've run a bunch of Single X trucks in extreme conditions and you can do more with them than you can a tandem(Towing/recovery). T.C.

  15. #15
    Forum Member Rescue101's Avatar
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    2,5 Sq mi? I wish! Better do a little more research and lay off the Lehigh squeezin's. Try about 64 Sq and a LOT more than that in the Auto aid agreement. And the ONLY cows we got around here are our freezer fillers.Cattle industry along with the chicken ranchers left here a LONG time ago. What you get out of a rig is quite dependant on what you put UNDER them. We've always had well specced chassis. Good thing because the last 15 yr rig we bought just went out for bid,thirty years after purchase.31 actually. T.C.

  16. #16
    Forum Member DeputyChiefGonzo's Avatar
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    Quote Originally Posted by Rescue101 View Post
    2,5 Sq mi? I wish! Better do a little more research and lay off the Lehigh squeezin's. Try about 64 Sq and a LOT more than that in the Auto aid agreement. And the ONLY cows we got around here are our freezer fillers.Cattle industry along with the chicken ranchers left here a LONG time ago. What you get out of a rig is quite dependant on what you put UNDER them. We've always had well specced chassis. Good thing because the last 15 yr rig we bought just went out for bid,thirty years after purchase.31 actually. T.C.
    However.. the fishing is great!
    ‎"The education of a firefighter and the continued education of a firefighter is what makes "real" firefighters. Continuous skill development is the core of progressive firefighting. We learn by doing and doing it again and again, both on the training ground and the fireground."
    Lt. Ray McCormack, FDNY

  17. #17
    Forum Member Rescue101's Avatar
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    Hey bambi, the water is stiff,hehe. T.C .

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