Coach/suspension Damage From Torquing While Off-Roading

Topic: Coach/suspension Damage From Torquing While Off-Roading (Read 10493 times) previous topic - next topic

Re: Coach/suspension Damage From Torquing While Off-Roading

Reply #200 – July 22, 2021, 01:22:07 pm

I believe that the route cause of the air bags and tire clearance is this. Foretravel build motor homes they are Not engineers. Example, the discussion of monocoque or semi monocoque or inverted truss, the people who built them don't know what they are, Mr Fore said it's a semi monocoque.
Similarly the bulkhead problem, from the top of the chassis up they are great but it seems that things below are ? ?
Now that I've got that off my chest, I enjoy my ORED every chance I get and I will drive the wheels off it.
IMHO

Re: Coach/suspension Damage From Torquing While Off-Roading

Reply #201 – July 22, 2021, 01:37:48 pm

Quote from: Olde English – July 22, 2021, 01:22:07 pm

I believe that the route cause of the air bags and tire clearance is this. Foretravel build motor homes they are Not engineers. Example, the discussion of monocoque or semi monocoque or inverted truss, the people who built them don't know what they are, Mr Fore said it's a semi monocoque.
Similarly the bulkhead problem, from the top of the chassis up they are great but it seems that things below are ? ?
Now that I've got that off my chest, I enjoy my ORED every chance I get and I will drive the wheels off it.
IMHO

Foretravel had some great minds, and some were very good engineers. It's just the scale they did it on. It wasn't a big corporate thing.With big corporate dollars behind them, to do whatever they wanted to do.

BTW, 3208 Cats, just like 3126's, are not throw away motors. That is a nickname, because they don't have sleeves like many diesel engines. So to call them "throw away" say's all gas engines , SB chevy, BB chevy, Fords and Chryslers, are all throw away, because you have to bore them, to rebuild them.

Removable sleeves can create issues, I have a bored and permanent sleeve, no issues.

Anyway, to stay on track, any Monocoque chassis foretravel built, that hasn't had any other major issues, is still rolling down the road. I love mine, wouldn't trade it for any kind of sprung truck chassis with a house box on it, it is one of the main reasons I bought a U coach.It is the reason they demanded big bucks in their day.

Cheers
Chris

Re: Coach/suspension Damage From Torquing While Off-Roading

Reply #202 – July 22, 2021, 02:22:06 pm

Chris,
It's a shame nobody had a tape measure to get the airbag mounts in the same place on both sides.
It's an inverted bridge truss.
Mick

Re: Coach/suspension Damage From Torquing While Off-Roading

Reply #203 – July 22, 2021, 02:53:13 pm

Quote from: Olde English – July 22, 2021, 02:22:06 pm

Chris,
It's a shame nobody had a tape measure to get the airbag mounts in the same place on both sides.
It's an inverted bridge truss.
Mick

I fixed a bunch OR TVR cars ( still have one). Got done bonding a left to a right half of the tip foreward hood. Ready for the paint shop.. The paint guy says that the right fender is 1/2 in longer than the left fender. Measured the other 2 on site and they all measured the same . 1/2 in longer.

Re: Coach/suspension Damage From Torquing While Off-Roading

Reply #204 – July 22, 2021, 02:59:57 pm

Yes, British Leyland managed to put out tens of thousands of one model that was 3/4" shorter/longer on one side. Must be what we refer to as Not Bespoke engineering. My mind goes to Lotus as an advanced operation case in point, noise canceling headphones, big deal, Lotus offered a noise canceling system over 30 years ago.

Re: Coach/suspension Damage From Torquing While Off-Roading

Reply #205 – July 22, 2021, 03:00:03 pm

Quote from: gracerace – July 22, 2021, 01:37:48 pm

Anyway, to stay on track, any Monocoque chassis foretravel built, that hasn't had any other major issues, is still rolling down the road. I love mine, wouldn't trade it for any kind of sprung truck chassis with a house box on it, it is one of the main reasons I bought a U coach.It is the reason they demanded big bucks in their day

A Foretravel chassis is no where near being a monocoque chassis. Only the mid section. The long front and rear are add-on conventional frame chassis. That's one of the reasons there was no room for a side to side radiator and simple fan drive.

To break it down, we have 12.5 feet of conventional frame at the back, 14 feet of monocoque construction or really truss construction and 9 feet of conventional frame construction at the front. In other words, 39% of the total frame is truss construction and none of it has to do with the suspension.

For a monocoque chassis you have to look at all the old GM buses and others. It's a lot harder and more expensive to go monocoque all the way.

Pierce

Re: Coach/suspension Damage From Torquing While Off-Roading

Reply #206 – July 22, 2021, 03:06:01 pm

This will be the last time that I try.
Not monocoque
Not semi monocoque
It's a space frame or to be precise an inverted bridge truss, if you were in the army think Bailey Bridge.
Instead of rockers and rollers at the ends of a bridge it has axels.

Re: Coach/suspension Damage From Torquing While Off-Roading

Reply #207 – July 22, 2021, 03:16:46 pm

The attachment below is an example of monocoque. Ours has zero steel up front except for the conventional frame down low. This is why our windshields crack, the body creaks and groans and the front has no protection from an accident or even a big bird.

Pierce

Re: Coach/suspension Damage From Torquing While Off-Roading

Reply #208 – July 22, 2021, 04:06:17 pm

Monocoque by definition is by example an aircraft fuselage where the all or most of the loading is in the skin, a semi monocoque uses a n internal frame to reinforce the outer skin.
That's a semi monocoque in the picture.
I simply googled, definition of monocoque, as the three American/English dictionaries that I referred to don't have the word monocoque.

Re: Coach/suspension Damage From Torquing While Off-Roading

Reply #209 – July 22, 2021, 05:03:47 pm

So the front drag links are exposed to opposing torsional loads when the axle is articulated. The bushing help in unloading some of this stress but this design is always twisting them. Not present in the rear because ride height valves prevent most differential articulation but is exposed to effects of torque damage or wear from normal driving. Neither seems to be a issue. But this design is wonderful on most groomed roads and at highway speeds.
Scott

Re: Coach/suspension Damage From Torquing While Off-Roading

Reply #210 – July 22, 2021, 07:11:06 pm

Quote from: dsd – July 22, 2021, 05:03:47 pm

So the front drag links are exposed to opposing torsional loads when the axle is articulated. The bushing help in unloading some of this stress but this design is always twisting them. Not present in the rear because ride height valves prevent most differential articulation but is exposed to effects of torque damage or wear from normal driving. Neither seems to be a issue. But this design is wonderful on most groomed roads and at highway speeds.
Scott

I've read the above but after all that, what's your take of Elliot's event? You are generalizing and not pointing a finger in any direction.

What are the shortcomings off the smooth pavement and what bends/flexes enough to cause the contact in your estimation? In other words, what part twisted enough to cause it? We go off the pavement onto really rough roads without any kind of event. Our driveway has enough twist in it on the downhill 120 degree turn to move the windshields around and make a lot of noise on each trip up and down it.

I checked all the bushings today for signs of wear and movement but there is none. At ride height, all the drag links are parallel and so is the Panhard bar designed to locate and stablize the side to side movement. As the body raises from increased air bag pressure, the entire front suspension will try to move to the curb side very slightly as the Panhard geometry changes. The drag links will also try and rotate the suspension very slightly as the bags inflate over their normal ride height. With one side deflated and the other side inflated, will that twist any part of the suspension? While the Panhard rod is not as efficient as a Watts Llnk, it's still should be adequate for the coach.

Pierce

Re: Coach/suspension Damage From Torquing While Off-Roading

Reply #211 – July 22, 2021, 08:17:49 pm

I love the ride/ feel of my upside down bridge, Foretravel, with my throw away Cat. I'm hard headed, and simple minded. LOL
Cheers

Re: Coach/suspension Damage From Torquing While Off-Roading

Reply #212 – July 22, 2021, 08:20:16 pm

Quote from: gracerace – July 22, 2021, 08:17:49 pm

I love the ride/ feel of my upside down bridge, Foretravel, with my throw away Cat. I'm hard headed, and simple minded. LOL
Cheers

Hey my throw away ISB is starting to get a hurt feeling.

Re: Coach/suspension Damage From Torquing While Off-Roading

Reply #213 – July 22, 2021, 08:27:52 pm

Quote from: dsd – July 22, 2021, 08:20:16 pm

Hey my throw away ISB is starting to get a hurt feeling.

LOL

Re: Coach/suspension Damage From Torquing While Off-Roading

Reply #214 – July 22, 2021, 09:26:00 pm

Reply 197
What happens to the parallel links when one side is articulated full down and weightless and the other is bottomed out on the frame rail stops and loaded beyond. I suspect this is what flexed the axle sub structure and then returned once leveled. My best guess
Scott

Re: Coach/suspension Damage From Torquing While Off-Roading

Reply #215 – July 22, 2021, 10:06:44 pm

The trailing arms bend when one side is higher than the other. The axle twist a very little also but the trailing arms act like a sway bar.

Re: Coach/suspension Damage From Torquing While Off-Roading

Reply #216 – July 23, 2021, 11:09:14 am

Thinking about this I starting to think the bushings in the trailing arms were fully loaded and distorted causing the tires to rub as they did then once unloaded relaxed returned back in there proper location. Just doing there job. Regardless I change the bushing before returning to service IMO
Scott

Re: Coach/suspension Damage From Torquing While Off-Roading

Reply #217 – July 23, 2021, 11:41:53 am

Quote from: dsd – July 23, 2021, 11:09:14 am

Thinking about this I starting to think the bushings in the trailing arms were fully loaded and distorted causing the tires to rub as they did then once unloaded relaxed returned back in there proper location. Just doing there job. Regardless I change the bushing before returning to service IMO
Scott

The end of the arms with the bushings is a tight fit into the location where the big bolt goes through it and any movement will leave a mark showing the extent of the movement as the lip of the bushing is flush with the sides. Just no movement at all with only one showing perhaps 1/32" maximum movement.

Think I will take my 7 inch disk and take off 1/8" of the possible contact area on the air bag mount.

Pierce

Re: Coach/suspension Damage From Torquing While Off-Roading

Reply #218 – July 23, 2021, 01:17:37 pm

It's hard to believe that coach's that are 20 year old and have hundreds of thousands of miles on them all put together that all of a sudden this problem comes up and have to start modifying bottom plates there has to be something that is different And I still think it's in the tires I've had my coach for about two years now I read about problems with the bulkhead, steering box , Cruise control, radiator windshield but nothing about steering and suspension and now start grinding on plates that been there for 20 years something does not add up drive a rig for 20 years with no problem To turn into my driveway from main road it is a very ,very steep incline in too my driveway. I have to raise the coach on air bags to it's maximum. I have to turn into a steep incline so I don't hit the back or scrape the back trailer hitch into the pavement I've pull the back mud flap off a few times So I'm turning and climbing with the air bags maxed out and on a hard turn everything is twisted and never once have I scraped the tires on the bottom part of the air bags . I don't think you can twist a coach any harder than this driveway . So cannot imagine why you would have to modify a coach that is 21 years old. With all the rigs out there there has to be a coach that went through the same driving conditions as Elliott something is Worn out or bent or been damaged there 20 years with no problem. What is on that coach that is not original from Foretravel if everything else is OK or in specs the tires on it are not the original size there is a different that why 275 are not 295 they are different just my way of thinking. I like to keep everything stock not looking for problems I believe Foretravel have done there home work we do have some problems like the bulkhead but there 20 years old and you can see the problem there rust out need to repair but taking a piece out of a good plate?

Re: Coach/suspension Damage From Torquing While Off-Roading

Reply #219 – July 23, 2021, 02:15:49 pm

Tire size charts all say the same thing about the diameter of the tire. Different manufacturers all have slightly different diameters and the one in the photo may be slightly larger. New tires will always be larger in diameter compared to a used tire. No such thing as a "good plate" if it touches the tire. Can you imagine anyone designing suspension geometry where the clearance is so incredibly close?

Other than a very occasional polishing of the front right plate, our 295's are perfect in our 28 year old coach.

Once again, here is the chart below. 39.8 vs 39.9 or .1 of an inch and the important radius is only .05 of an inch. The width is about 3/4" wider or about 3/8" on each side. Our comes close to touching from the edge to further in than 3/8" on the face of the tire. 295s work on a big percentage of Foretravels. Always has on ours.

Pierce

Re: Coach/suspension Damage From Torquing While Off-Roading

Reply #220 – July 23, 2021, 02:16:01 pm

I don't have a U320 handy to look at so I have to ask. That box tube to which the bag mount is welded? Does that go from side to side in one piece? If it does, is Elliot's box tube properly centered?

Re: Coach/suspension Damage From Torquing While Off-Roading

Reply #221 – July 23, 2021, 02:23:08 pm

Quote from: Old Toolmaker – July 23, 2021, 02:16:01 pm

I don't have a U320 handy to look at so I have to ask. That box tube to which the bag mount is welded? Does that go from side to side in one piece? If it does, is Elliot's box tube properly centered?

Yes and yes. Assuming it was done on a jig, it probably is centered but never hurts to check it along with the distance from the edge of the rear mounting plate to the edge of the front mounting plate. Tough to do with the tire in place.

Pierce

Re: Coach/suspension Damage From Torquing While Off-Roading

Reply #222 – July 23, 2021, 02:39:25 pm

So in rethinking the bushings. They can't effect distance from axle to bag mount because they are all on the same platform. So yes bushings will deflect but will not effect distance to lower bag pads