Well, we did it.

[guy99]

Tim,
The consensus of the group on the Forum seems to be that the reason for the low towing rating of the classic motorhomes is the frame extension which moves the hitch far behind the wheels and the resulting long moment arm. The frame extension on my 310 isn't very long. Do you know if your coach has the same wheel base as a 345?, if it does I imagine your hitch is a long way behind your rear wheels.

It's not clear to me whether the concern about the moment arm has to do whith breaking the frame or stability while driving.

[Minnie's Mate]

Originally Posted by guy99

Tim,
The consensus of the group on the Forum seems to be that the reason for the low towing rating of the classic motorhomes is the frame extension which moves the hitch far behind the wheels and the resulting long moment arm. The frame extension on my 310 isn't very long. Do you know if your coach has the same wheel base as a 345?, if it does I imagine your hitch is a long way behind your rear wheels.

It's not clear to me whether the concern about the moment arm has to do whith breaking the frame or stability while driving.

My understanding is that the concern is the moment arm in turns. The extension isn't strong enough to handle a lot of weight pulling at an angle and can rack the frame behind the axles. I would be concerned about towing a 3000# vehicle. That is 50% above the limit set by Airstream.

[noiva]

guy99 and Minnie's Mate,

The frame extension on the 370 is less than 12", and only 3" to the receiver. In addition, this model was built on a Gillig chassis instead of the C-30 used by most of the other models. The frame is almost 8" tall, and the height of the coach is a little over 1 and 1/2 feet taller than the other models in 1989 - mostly due to the Gillig chassis and the way the coach body is mounted on that chassis. I don't think frame extension should be an issue.
However, it is a LONG vehicle The wheelbase is 218" vs 204" for the 345, so it's RELATIVELY less 'percentage' overhang than the 345. Not to say it's not a lot of overhang - it definitely is. I'm not clear what a "moment arm" is, but the Gillig manual shows a "Transverse Road Assembly" that is bolted on pivots from the top of the drive axle to the frame. It's designed to lower twist of the drive axle during hard torque situations. Is that what a moment are is? Anyway, just a few other things - I have a 5.29 rear axle, which is terrible for interstate speeds, but great for in-town and mountains. The extremely low gearing is very helpful with low end torque. I plan to add a Gear Vendors under/over drive to help me run interstate speeds at rpms that don't race the whole drive system. Currently, I keep things below 3,000 rpms, which limits me to 60 mph - a good speed anytime, but not practical when one has to travel interstates once in a while.

Finally, I have gotten private emails from a number of members of the forum who have towed up to 4,000 lb vehicles for many years without problems. That doesn't mean the 370 will do as well, but I have paid attention to their advice, just as I do with everyone who contributes. I greatly appreciate all advice and information on this issue. Thanks so much for helping. I welcome any further comments or suggestions.

Tim

[Minnie's Mate]

Basically, the moment arm of a hammer is the force applied to the handle multiplied times the length of the handle. The longer the handle, the greater the force exerted on the nail by the force applied to the tip of the handle. In the case of the motorhome, the length of the overhang multplied by the lateral or sideways force in the turn caused by the toad. The greater the overhang, the greater the force applied to the area of the frame directly behind the axel. This leverage is what would cause the frame to rack. In the motor home example, the center of the axel becomes the piviot point for the moment arm. In the hammer example, the head of the hammer is the pivot point for the hammer. This comparison may be too simplistic to be accurate for engineers and physicists. This is not to say your coach can't do it, just my understanding of why AS doesn't recommend more than 2,000#.

[noiva]

Originally Posted by Minnie's Mate

Basically, the moment arm of a hammer is the force applied to the handle multiplied times the length of the handle. The longer the handle, the greater the force exerted on the nail by the force applied to the tip of the handle. In the case of the motorhome, the length of the overhang multplied by the lateral or sideways force in the turn caused by the toad. The greater the overhang, the greater the force applied to the area of the frame directly behind the axel. This leverage is what would cause the frame to rack. In the motor home example, the center of the axel becomes the piviot point for the moment arm. In the hammer example, the head of the hammer is the pivot point for the hammer. This comparison may be too simplistic to be accurate for engineers and physicists. This is not to say your coach can't do it, just my understanding of why AS doesn't recommend more than 2,000#.

Thanks so much for the explanation. I understand fully what you are saying now. I'm glad you kept it simplistic. I agree with you completely that the 2,000 lb recommendation is a real concern. I've been working on asking questions about the rating since I first got involved with my 370 a year and a half ago. In my 30 years of trailer towing, I could only afford a correctly rated tow vehicle in the last 12 years. Before that I was always over the manufacturer's limits. I'm not advising that, but I had no choice. Of course, I always beefed up my tow vehicles the best I could with larger radiators, more frequent oil changes, air shocks, and even a rear axle gear set change. I never broke down on a trip. Now, I know the situation with the MH is not the same issue. The overhang is a real concern of mine. I've heard from a number of 345 and even a 370 owner who have all towed loads above 2,000 lbs with no problems. I would like to know if anyone has experienced this frame twisting with a load of, say, 3,000 lbs. Again, I'm not saying it's the best idea, but I can't afford a lighter vehicle, and my camping habits tend toward staying in one place for weeks at a time. Towing a car is the only logical way to get around once I get to a campground. It's the old "benefit/risk" issue, I suppose. I need the car, but I don't want to ruin my rig or get someone killed in the process. Thanks for your help.

[cooperhawk]

I have for ten years towed a full sized vehicle behind my 345 diesel. I towed my wife's Taurus accross the country, my own Explorer as well, and now we tow a 05 VW Jedda Diesel. I have encountered no problems at all. I use a tow dolly made in Iowa with a long tongue which gives a lot of swing up and down. (Demco).
The only trouble I have had is going through a swale, sometimes the hitch will bottom out and scrape the ground. But that happens whether I am towing or not.
I at first understood that Airstream was worried about the strength of the hitch, but it is solidly attached (welded) to several frame members.
My feeling is that if one is careful, you can tow whatever you want. Just don't put a lot of stress on it. Like jerk it around.

[noiva]

Originally Posted by cooperhawk

I have for ten years towed a full sized vehicle behind my 345 diesel. I towed my wife's Taurus accross the country, my own Explorer as well, and now we tow a 05 VW Jedda Diesel. I have encountered no problems at all. I use a tow dolly made in Iowa with a long tongue which gives a lot of swing up and down. (Demco).
The only trouble I have had is going through a swale, sometimes the hitch will bottom out and scrape the ground. But that happens whether I am towing or not.
I at first understood that Airstream was worried about the strength of the hitch, but it is solidly attached (welded) to several frame members.
My feeling is that if one is careful, you can tow whatever you want. Just don't put a lot of stress on it. Like jerk it around.

Copperhawk,

Your comments reflect what I've heard most often from people who have towed with these MoHos. I appreciate your sharing your experiences. No one has related experiences towing that would lead me to believe there's a major issue, if one takes proper precautions as with towing anything. My "master plan" is to put a Gear Vendors under/over drive unit on my tranny since my rear Gillig axle is so low (5.29). That will effectively give me a 6-speed transmission with an overdrive. That should allow me to cruise interstates at the speed limit without revving my engine so much, and at the same time retain the torque from the Ford 460 and very low rear axle for in town and mountain climbing. Thanks again for the advice.

Tim

[outofcontrol]

So I'm trying to figure out where the weakness is in the AS and why the tow limit is 2,000 lbs.

From what I gather it's the long length from the rear duals to the ball (moment arm).

I can imagine turning in a tight circle too fast where the trailer is almost jack knifed. if you slammed on the brakes with a 3,000 trailer, it would bend the frame behind the rear axle. Maybe even kink the body?

Besides re-inforcing the reciever to the frame, is there a way to beef up the frame behind the rear axle?

If you made the RV stronger would you still be illegal by going over the limits set by the manufacturer?

I am totally comfortable overloading a vehicle, but with 11 years of truck driving experience I've learned there's more to it than just smashing down your suspension. If you get into a wreck when you are overloaded, you're toast.

BTW, I'm considering the purchase of a classic MoHo, and i have to pull a 2800-3200lb 6x12 wells cargo MC trailer.

Thanks,
Kevin

[Chaplain Kent]

This subject has been discussed here quite a few times. I think if you do search you will find all of the threads. I believe you are correct that the frame is the problem in Airstream's eyes. Many of the late 70's and early 80's trailers were subject to frame droop and our coaches are really no more than a trailer put on a truck chassis. There are quite a few members who tow heavy cars, trailers, and even trucks with their classics. I do not know if anyone has ever encountered a problem or had the frame separate due to excessive weight. I do know that when I look at my receiver and how it is welded to the frame I would be a little concerned at pulling too much weight. I might consider having the receiver placed and welded better than it is. In fact mine is bent up from having been bumped by the PO. There is no other noticeable damage just the bent receiver. I use it with my utility trailer but that is all.
Good luck to you, and keep searching. Don't let this discourage you as you will find from the threads others before you have found a way.

[Poprivet]

I'm Really Intersted. I Am In The Process Of Purchasing A 250 And I Alread Have A Xb (that I Really Like). I Am Attacted To The 250 So , Like You, On Long Trips I Won't Need To Tow - But I Can Vision Wanting The Option.

Can You Tell Me What Was Involved In Modifications To The Xb?

[guy99]

If your xB is a 5 speed, then all you need is a base plate (and a braking system if you decide to have one like I did). You then need a tow bar which works with the base plate and wiring for lights (and brakes if you have them).

If your xB is an automatic, you will need a trailer or tow dolly since the automatic can not be flat towed. (I called remco the expert on after market products for towing and they said you can not equip an automatic xB for flat towing)

[jking]

Hi, Guy -
We tow a 2002 Saturn SL2 with some stuff in the trunk (est. total about 2600-2650) all four down, and use a M&G air-over-hydraulic auxiliary braking system. We get about 11-12 mpg with our '84 turbo diesel 310, driving conservatively. That will improve when we get an overdrive installed this winter.

[gunner]

I was one of the unfortunate ones that had the hitch seperate from the frame. I was towing a 14 ft. fiberglass boat at the time. I was lucky, since I was going through a town at 35 miles per hour when one side of the hitch broke loose at the weld and came down. I was able to pull over to the side of the road before more damage was done. My wife was following me with the pickup and we were able to transfer the boat to the pickup and continue our vacation. I was able to jack the hitch back up and secured it with chains to the frame. I have since replaced the hitch with a class 3, rated at 5,000 lbs., that fastens by heavy bolts in four locations approximately a foot apart on each channel and is also welded. The previous hitch was just a 6" C channel which was welded but the flexing of the C channel finally broke the welds. I would not feel comfortable towing anything close to the 2,000 lbs. with the original hitch after I saw how easily the welds broke.

[livexl]

Thanks to guy99 I went with the same set up as his. I just got home with it yesterday after towing the xB more than 60 miles in High Winds and Rain. The 350 LE and the xB handled great! Guy, thanks for your help.

Here's a link:


AIRSTREAM

Dan

[guy99]

Cool, why don't you bring it to Cassini and we can fly in formation or something

[livexl]

Cassini is going to be big fun I'm sure, but I'm booked with old car events for a while. I hope to get to an Airstream event in the near future. A formation of Motorhomes would be a good photo op.

[str8strm]

Originally Posted by livexl

Thanks to guy99 I went with the same set up as his. I just got home with it yesterday after towing the xB more than 60 miles in High Winds and Rain. The 350 LE and the xB handled great! Guy, thanks for your help.

Here's a link:


AIRSTREAM

Dan

If you were out yesterday, you definitly experienced high winds. That storm cell was really something. I agree with Guy, come on up to Casini with us. We need more moho's.

[livexl]

I can't make it to Casini ... are there any SoCal gatherings any time soon?

[guy99]

I just remembered something. Our Scion manual says that after towing you should start the car and let it idle for a couple of minutes before driving.

When we first started towing I had overlooked this and wasn't following this direction. A friend mentioned this, I verified it in the manual, and since then we do as the manual suggests.

[livexl]

Thanks Guy, I did read that in the manual 3 minutes is the recomended amount of time .. We're looking forward to getting out this weekend ...