Community Forums

Paul "Sully" Sullivan · 12-15-2008, 08:06 PM

Mark thinks it the changes were made in '02 when
the steering box was changed and in '04 when the pedals were changed.

sdcyclist · 12-19-2008, 02:32 PM

Hi Dale,

Thank you for the great pics of your fix. I took my 2006 36FDDS to RV Specialists here in San Diego where they examined the steering box mount and decided my coach was an accident waiting to happen. They employed your fix with the weld and angle brace as well as bolting a reenforcing plate on the back side of the frame rail. It had looked like the huck bolts were trying to pull through the frame rail--there was noticable movement on the back side.

My coach is now fine and my pocket book a bit more empty!

sdcyclist
(Milo)

dgerstel · 12-19-2008, 02:44 PM

Milo,

I am glad that the photo of the fix helped. I really didn't want to show the fix until I cleaned up the area and painted the new brace, but thought it couldn't wait for me to get home and do the work.

Do you know if you had the missing welds on the interior brace, like mine?

sdcyclist · 12-22-2008, 07:12 AM

Dale,
I checked with the tech at RV Specialists who did the bracing. He said WRV had a complete set of welds on the interior of the brace. The existing mount just appears to be a poor design.

Milo
2006 36FDDS
Plus My Bicycles

EngineerMike · 12-31-2008, 03:01 PM

On my coach, I affixed a 36" bar clamp to the front lower left corner of the steering bracket, with the bar 4.75" below the lower Huck bolt and the bar extending back thru the steering bar cutout in the bulkhead ahead of FL tire. Measuring up to the bottom of the bulkhead from top of bar at various steering positions, I get:
Full Hard Left.2.27" (to the stop)
Full Left........2.54" (but not to the stop)
Centered.......2.57"
Full Right.......2.62" (but not to the stop)
Full Hrd Right.3.06" (to the stop)

The measuring point is 27.5" back from steering mount bracket, and 4.75" below the Huck bolt. So movement in the bar is magnified ~27.5/4.75 times or 5.8x times the plate deflection. That means within the usual steering range (full left to full right) of in town driving (but before deducting for rolling and before adding for dynamics of pavement which could be significant IMO), twist in the bracket only induces 0.06/5.8 = .010" movement. This is not a deflection I feel I need to worry about even after dynamics. For the usual on-highway steering range (much narrower than in town), I'd say no problem at all.

Between a mere full turn & a hard-turn-to-the-stop the deflection is a different story. There is about 3/8" movement in the bar, for ~.060" added deflection in the rear bracket face, and I can hear the strain in the steering box. This happens in the final 1/2 or so turn of the steering wheel to the stop, either left or right. I haven't decided if this is a new problem, or part of the solution of the strain problem. The strain has to go somewhere, and if it doesn't get taken up in the bracket it will all go to the wheel pivots or steering linkage.

As a working hypothesis, I'm inclined to accept the bracket deflection on my coach. This is definitely not what we saw in Dale's bracket documentaries, so I know I don't have to panic. I'll be interested to see how various rigs compare @ DRR in a coupla weeks. I'll bring some 3/4" plywood for under front wheels, so we are not measuring on sand. See y'all in Quartzite.

Renipladlo · 12-31-2008, 04:57 PM

Thank you EM for taking the time to measure this out. I am hopeful it does not apply to my coach, but we are now just getting out of the snow so I have not crawled under it to check. In thinking about it, I remember having the coach undercoated when we purchased, so I am not to sure I will be able to see the bracket clearly anyway. I will post my results once I have taken pictures.

OldForester · 01-02-2009, 07:29 PM

One thing E-Mike's comments caused me to think about was coach size, weight, and tire pressure. Dale's coach is a 40' and probably fairly heavily loaded. E-Mike's and ours are both 2-slide 36's, ours being a mid-door, and I think Mike's a front door. IIRC, the total loaded GVW in a 36 is about 3000 lbs less than a 40'.

Yesterday I took our coach out of storage for its monthly drive to get the transmission fluid to full operating temperature and 2 hour generator exercise. I checked the steering gear bracket in full lock-to-lock on asphalt, and while I didn't measure it like E-Mike did, I couldn't see any movement in the bracket. It looked very solid, no paint cracking, or any other evidence of twist.

Now our coach is winterized with no water in any of the tanks or water heater, nothing in the refer, about 1/2 tank of propane, and probably only about 1/2 the normal load in the tank when we're usually gone for our snowbird winter trip to Palm Springs.

Additionally, we have 120 psi of air in the front Toyo tires, per WRV and Toyo's recommendation.

So I'm wondering if this lighter loaded weight, potentially higher tire pressure, and shorter coach is at play in reducing or eliminating (to the naked eye) any movement in the steering gear bracket. I also wonder if it may be a reason WRV didn't observe a lot of play in this bracket when they were building and testing new motorhomes, especially since they are not loaded with weight at the factory.

Thoughts?

Renipladlo · 01-02-2009, 09:02 PM

Old Forrester,
If I understand your comments correctly, you think the less weight of the coach would allow less flex in the bracket and it's associated attach points.

If the figure of 3000 lbs is good, that additional weight would be spread over a 40 food long area, which works out to about 75 lbs per foot of length spread over the 102" of width. I don't believe that weight spread out in that manner would cause any considerable difference at the steering bracket. If all the 3000 lbs were in the front end, that then would be another story altogther.

Using my weights as a guide we are about 1500 lbs under the GVWR of the coach, that is with full diesel and water tanks when I weighted the coach the last time. I leave that much empty to ensure we don't go over on a shopping trip. We need to however in the spring go through the unit and remove any thing we don't need in there, because we tend to put items in it we will need once we are using it months at a time. I think we could take out some cooking items which weight a lot. Because it's an APEX we also tend to always travel with close to a full tank of fresh water. 105 X 8.3 = 871.5 lbs of water.

I am not however any engineer, so my quick calculations should be taken with a grain of salt.

EngineerMike · 01-03-2009, 06:06 AM

Last time I weighed the coach: 32,000#, with about 500# shy of full load per axle, i.e. close to full design weight of 33,000.

The amount of flex thru most of the wheel turn on my rig was ~ a hundredth of an inch (very hard to see), then between where the steering wheel settles (either left or right) & full lock- about 6 hundredths. I didn't have a driver, so I had to turn the wheel hard over then tie it off then crawl under the coach. However I'm guessing that if'n I was under the rig while a suitable amigo turned the wheel that last 1/2 turn I'd see that movement.

That .06" on my coach is in resistance between coach parts winding up against the turn locks, not in tire resistance to pavement during maneuvering. That's leads me to speculate that the last 1/2 turn of steering wheel doesn't buy me much in turn angle, but that's yet to be proved. Tho I'd expect to see additional flex if I held against the lock while rolling in a tight turn on pavement (that's where I'm waiting anxiously for Dale's upcoming live-on-the-road video) (hope he doesn't hit any bumps while filming under there

). I guess the thing I learned was the amount of stress winding up against the lock is far greater than for almost all ordinary steering, and when I hear the steering fluid hissing from the strain I need to back off the steering wheel a bit.

OldForester · 01-03-2009, 09:42 AM

I'm also anxious to see Dale's over the road video.

Last time I weighed our coach it was right at 30,000 lbs with as full a load as we normally carry. So it weighs 2000 lbs less than Mike's newer 36'. Spread over the whole vehicle it probably doesn't matter that much, but it was just a thought.

Again, although I didn't measure it, I'm in agreement with E-Mike that there's not much flexing and it probably is the most at the last 1/2 turn of the wheel each way when it tries to build up more pressure. I am also careful not to turn the wheel to full lock when I hear the steering fluid hissing from the strain.

I would agree that I wouldn't notice .01 to .06 of an inch of movement with the naked eye, but I would notice the kind of movement Dale had. I had a trusty amigo turn the wheel, but I would like to do it again with some measurements at the same time.

I still have the question about tire pressure in the front -- if the 120 lbs in my Toyos is reducing the flexing, especially with less weight.

Mike and Dale, what tire pressure do you use in the front tires?

dgerstel · 01-03-2009, 10:13 AM

I like to carry anything that I think I might want while traveling, not the best way to travel in an RV. Since I am right near max weight, I carry 120 lbs in the front. From what has been posted about this, I think that the weight on the front axel is probably the determining factor. If I saw such small movement that it had to be measured or no movement in the frame rail, I wouldn't worry about it. I am not sure why anyone thinks that I am going to produce a on the road video, mine no longer does the interesting dance.

EngineerMike · 01-03-2009, 10:55 AM

Dale- so you can publish proof of concept, patent the design & start collecting royalties

I'm guessing the axle load isn't the central issue. Steel spring action is mostly proportional (and if not your junk is stretching or fatiguing the steel). So if you add 1,000# to the front axle, or 500/tire on a 10,000# base, its 10% and you should have ~10% more resistance telegraphed to the steering junk and ~10% more deflection in the usual swing of steering. Winding up to the steering lock, however, seems to be mostly internal resistance of the junk elements, so added weight in this portion of steering swing appears essentially unimportant, and even fairly significant weight increases wouldn't add much to this portion of the bending. These are guesses based on my junk. YJMV (your junk may vary).

OldForester · 01-04-2009, 07:16 PM

I don't disagree with the steering windup. I noticed a little difference at the end of the steering. So, Mike, once again, how much air do you have in your front tires? Do you think it has any impact if you're below max weight? Apparently it didn't in Dale's, since he carries 120 lbs but he's at max weight.

EngineerMike · 01-04-2009, 09:41 PM

Bill- Tire resistance (friction) will be a given percentage of weight, and therefore proportionately higher with more weight. My tentative conclusion is that tire resistance isn't a problem if the bracket is properly built (and that would account for the minimal deflection on my rig within the normal steering range while my front axle is near rated capacity). Tire pressure shouldn't be a factor either, as it wouldn't change the coefficient of friction of the rubber at all and would only modify the contact patch a minuscule amount. Dale's was way not right, bracket built wrong, and deflection cured to a comfort level using an alternate design. Some others may be not up to snuff which is why checking out multiple years & conditions @ DRR is a handy exercise. I'm guessing if Dale's was properly welded internally his alignment guy wouldn't have noticed anything; we'll see how comparable year coaches act.
FWIW my tires are G670's and carry between 115 & 120 for the fronts (IIRC); Goodyear suggests higher pressure per load ton than Toyo by 10-15#.