Ross power assist steering gear.

[artvonne]

  There have been a few threads about these gears, the older MCI's have this type steering. Many, myself included, have/have had a lot of play in the wheel. While replacement of the gear is certainly an option, as well as converting to an integral gear, I thought I would ask to see how best to adjust these gears as well as where else to look to reduce slop and play. Looking at my MC5, my first observations seem to think most of the play is above the gear, and I will be pulling the column shroud off to investigate further.

  Obviously a gear could be worn so far beyond limits there is no reasonable adjustment left, and, if its heavily worn on center and you take out all the freeplay you could bust the gear housing when you swing it right or left, causing it to bind. Knowing how to determine this could also prove helpful in at least protecting the gear as a core.

 

[bevans6]

My MC-5C manual has several pages on how to adjust the Ross steering gear.  Basically there is a cam, with a groove in it, that you and I would call a worm gear.  That is connected to the steering column.  There is a lever assembly with two studs in it that ride inside the groove in the cam.  That lever is connected to the pitman arm.  When the steering wheel turns, the cam rotates, the studs follow the groove along and the pitman arm turns (notice how I am totally ignoring the whole power assist bit, because I haven't figured that out.  I figured out this part when I first got my bus and went under to adjust or at least inspect the steering box, which is when I figured out that I had upgraded-to-Sheppard integral steering) which moves the drag link, which turns the wheels on the bus which go round and round.  (sorry, long morning.  I play on Bus Conversions to reduce stress from my day job, which also involves sitting typing long messages on a computer).

There are both internal and external adjustments you can make and check.  The very first thing you want to check is that the steering box is centered when the front wheels are exactly straight ahead.  You check this by visually centering the front wheels so that they are in line with the rear wheels.  I do this by sighting down the sidewall of the front tire, getting a virtual line to the rear tire and making the virtual line intersect the rear tire at the same point on each side.  This negates any effect of toe in.  Race car alignment trick, I have no idea if anyone else does this on buses.  Point is to get the front tires in the exact balanced straight ahead position.  Then you look at the pitman arm which is hanging down more or less vertically from the steering box.  There is a witness line on the shaft that the pitman arm is mounted on.  The witness line must be at 90 degrees to the cam shaft that the steering column is attached to.  There is a machined edge on the box that is the handy reference plane to check against.  This puts the steering box at it's exact center when the wheels are straight ahead.  You adjust by changing the length of the drag link.

The reason you need to have the steering box exactly centered is two-fold.  First is that the hydraulic assist is engaged by the steering box coming off-center.  It sucks to have power assist trying to help you when you are trying to just steer straight, believe me (my professionally installed new drag link was installed an inch too long and I had steering wander like you would not believe.  Yet another reason why I don't like to go to professional bus mechanics).  The second reason is that the groove in the cam that the studs ride in is cut shallower at the center and deeper at the ends, so that you get tighter steering in the center where you need it, and you have capacity to adjust for wear without binding at the ends (to your adjustment point).  Wear adjustment ability is built in.  You adjust the position of the lever arm that the studs are attached to relative to the position of the cam shaft using a big bolt with a adjuster inside it.  You basically move the studs in until they drag when the gear is centered, then out a scotch, and then check for binding and lock it down.  I have never done that so I can't tell you exactly how it works, but you adjust the plug that is inside of the nut in some way.  Best to get the manual, it has pictures and everything.

Anyway, that is Brian's Ross steering gear 101 precis.  I hope it gets you started.

Brian

[gus]

The manual instructions tell you to jack the front and move the wheels full lock both directions with the engine off after adjusting to check for binding.

This prevents the power assist from damaging the gear box in case you get it too tight.

Since I'm too lazy to do all this I just adjusted it a tiny bit at a time(about 1/8 of a turn of the screw) until it was reasonably tight (about 1" at the steering wheel rim) and stopped at that.

[luvrbus]

Check out http://www.dot.gov/rules  393.209 tells you the allowable lash for what size steering wheel example a 21 in wheel can be 5 1/2 inches you guys worry to much, BW put me on to this fwiw a years ago when I was worried about 3 inches on a 21 inch wheel 

good luck

[artvonne]

  Clifford, Id kill for 5 1/2, I think ive got about twice that now.

  Copy on centering Brian, I do all my own wheel alignments with eyeball, string, tramel gauge....I know their ground to be tighter on center, some even have different ratios between center and the ends, making it all the more important to be on center.

  Dont know what your saying about a cam though. Are you talking about the big screw and locknut that face toward the passenger side?? The one that takes out backlash??

I washed the front bay yesterday so I can climb in there without getting filthy, yuck, lot of black greasy grime. But not a speck of rust anywhere, except some surface stuff along the bottom main beams running back to the bulkhead. I didnt know the gear was battleship grey, lol.

[bevans6]

They call the main "gear" inside the steering box the "cam".  It's the part that the steering column actually is connected to.  Like I said, you and I probably think of it as the  worm gear.  It is not cut with gear teeth that mesh into a gear on the pitman arm shaft like you would imagine, but instead is a cylinder probably about 2" in diameter, with a tapered groove cut into it in a spiral that the studs mesh in to.  The cam rotates when the steering column is turned, the studs slide along the spiral groove and turn the pitman arm.

The adjustment is basically moving the thrust bearing on the pitman arm shaft so the whole shaft moves closer to the cam, hence a little bit deeper into engagement.  The big nut that locks it all down it on the opposite side of the steering box from the pitman arm itself, on the other end of the shaft from the pitman arm.

Brian

[artvonne]

  So loosening that big jam nut, I then back the adjustment screw "out" (left hand) to draw the pitman arm into the cam?

[bevans6]

Other way around, you are pushing the studs on the lever arm into the cam.  They are on the opposite side from the actual pitman arm.

Brian

[bevans6]

I sent these to Paul in an  email, but thought that someone might find them useful sometime...

Brian

[bevans6]

three more pages

[artvonne]

 Thanks a lot Brian, that'll keep me busy a while.

[rgrauto]

On the Ross steering gear, I have a 1967 MCI 5a and the  steering wheel shaft moves up and down when turned. Should it move up and down and if so,how much? Also how do you stop this? I also would like to know how the valving in this sector works,may help me understand how to fix the excess play in steering. I do have all the manuals,coach,Detroit 71 series,etc. but the adj. is a little vague , Thanks Glen

[luvrbus]

You guys are never going to get the lash out of those antique gear boxes they were manufactured with a yard stick,update is the only way

good luck

[bevans6]

"Measure with a yard stick, cut with an axe, file to fit"

[artvonne]

  While im sure Clifford is more or less right, its also probably safe to say few of the steering gear adjusments were ever tended to when these old rigs were in service. As most of these are the refuse of the Bus industry, and many of us are now dealing with a lot of deffered maintenance issues. As these adjustments are hard to find knowledge on, and harder yet to get anyone in there to tackle them, the upgrade to a new style gear takes center stage, and of course youll see great improvement over an old sloppy gear. One thing ive noted, is I can crank the wheel around fairly easy without the engine running. I doubt the same can be said for an integral gear. Something to think about if you lose your pump.

  Myself, I have a lot better things to spend $1000+/- on right now than a steering gear. If I can get most of the slop out she'll work for now.

  From reading the pages Brian so graciously provided, it appears you adjust the cam end play first (read "Centering Steering on High Points"). That will stop your wheel shaft going up and down. According to the instructions it shouldnt have more than .050" end play. Once you correct that, then you proceed with Cam Groove adustment.

  Brian, if im seeing this right, there is what appears a plastic plug in the center of the retainer (D in the figure 11-4). I assume this is plug "C"??  It says to break it, are we just supposed to bash it out of there with that axe? And once broke out, does anyone replace it?? Bet its never been out.