Integral Power Steering conversion on a 4106

Darkspeed · July 05, 2015, 07:44:45 AM

Has anyone done this?

It is something I am considering because the 4106 has large number of components that can lead to lash in the steering and the conventional upgrades seem to have their own set of problems in the form of not being able to remove the lash from a Sheppard unit.

This would be a pretty simple system consisting of a modern tilt steering column directly connected to a TRW/ROSS HFB70 (MC-9) connected to a fabricated 90deg steering arm by a drag link.

The frame mounted HFB70 would mount ( with reinforcement ) in the location of the original miter box.

The only serious fab would be the steering arm. The 4106 has a cut off steering arm that acts as a mount for the drivers side brake can and could easily be replaced with a 90deg fabricated steering arm. The only obstacle is the driver side shock would limit the length of this new arm but this could be easily solved by relocating the drivers side shock either to the backside of the axel or to the inboard of the air spring mounts.

The end result would be a modern self centering power steering system with very few potential slop points that should drive like magic.

TomC · July 05, 2015, 09:41:37 AM

Don't try to reinvent the wheel. Use what works and is proven. Sheppard is a little wondering-but most don't realize you just have to drive it with little steering wheel movements. Increasing caster helps. I converted my AMGeneral from air assist to Sheppard. Changed the mitre box from 1.5:1 to 1:1, and had to increase the pump pressure to 2,000psi. I use 15w-40 engine oil in the power steering. It went from 8 turns lock to lock to 3.5 turns. Granted the power steering has a bit less wheel cut, but the fact that it is finger tip fast steering more than makes up for it. Good Luck, TomC

Darkspeed · July 05, 2015, 09:59:02 AM

Tom there seems to be a lack of 1:1 and Sheppard axel mount gears that are not pre worn out.
Seems like there have been a lot of people spend a lot of money sorting out a Shepphard's only to see no improvement.
On my bus ALL of the components in the steering are worn out so its going to be work either way.

OneLapper · July 05, 2015, 07:47:37 PM

Several years ago I purchased a Sheppard box for my 4106 direct from Sheppard. They had them in stock, $1200 with exchange, $1500 without. It's worth giving them a call. It has a warranty too.

Mark

luvrbus · July 06, 2015, 06:17:49 AM

Go for it Kirby did the integral steering on his 4104 and never regretted it

Darkspeed · July 06, 2015, 06:32:45 AM

Quote from: luvrbus on July 06, 2015, 06:17:49 AM
Go for it Kirby did the integral steering on his 4104 and never regretted it

Links? Photos? Info?

Thank you luvrbus!

luvrbus · July 06, 2015, 06:35:33 AM

He is kirby4104 here on the board he used a MCI 9 box I recall

Darkspeed · July 06, 2015, 06:39:38 AM

Ok thanks - found this so far:

http://www.busconversions.com/bbs/index.php?topic=21329.20

"the key is getting the Ross integral steering box, from an MCI 96A2 which is axle-mount. Because I could only find one from an MCI-9 (not a 96A2) I had to fabricate a half-inch steel plate and attach it to the axle, and then mounted the steering box on the plate."

Sounds like he fabricated an axle mount for a frame mount gear.

I was thinking of going with a straight frame mount system but still very interesting!

Darkspeed · July 06, 2015, 07:00:03 AM

Everything I have drawn up so far looks very doable.
The only issue is clearing the tire when the bus is in a full right turn.
I need to put the wheel / tire back on to measure the available space for a drag link between the frame mounted gear and the fabricated steering arm.

RJ · July 06, 2015, 05:50:53 PM

Todd -

I understand what you're thinking of doing, my MC-5C has the steering gearbox mounted like your idea. Turning radius is a city block, worse than the OEM 4106 setup.

I think you're aware that the "frame" inside that exterior compartment underneath the driver is really just the side wall to the spare tire compartment. I doubt if GM Engineering designed it sufficiently strong enough to withstand the forces a steering box would impose on it.

OTOH, you're also in the process of dropping the floor rather than raising the roof, so what's some additional welding?

FWIW & HTH. . .

Darkspeed · July 07, 2015, 08:19:59 AM

Hi RJ, yes that area would need to be significantly reinforced for a frame mounted gear.

Are you saying it has bad turning after the frame mounted gear? Because of clearing the tire with the draglink? wrong pitman arm length?

RJ · July 08, 2015, 06:39:30 AM

Quote from: Darkspeed on July 07, 2015, 08:19:59 AM
Are you saying it has bad turning after the frame mounted gear?

Yes, that's what I'm saying. LH turns aren't too bad, but RH turns are terrible - it's almost like driving a 4905 with the huge 318" wheelbase. And IBME that we make far more RH turns than we do left. MC-8s and -9s of that vintage are all known for the large turning radius.

The GM transits (Fishbowl & RTS) have the best "cut" of the front wheels, it's like 52^o or so. Designed for working city streets, not highway use. Where the 35' 4106 has a normal 40' turning radius, IIRC, the 40' Fishbowl's is 35' - much tighter. Yes, a Sheppard gear mounted on the axle.

Another possibility would be to study the Setra's set-up. Their SD215, a 40' coach, also has a 35' turning radius. I don't know if they use an axle-mounted gearbox or a frame mounted, you'd have to research it. Their steerable rear axle also contributes to the tight circle.

FWIW & HTH. . .

B_K · July 08, 2015, 06:48:54 AM

FWIW Setra uses a frame mounted gear box and has independent front suspension as well!

BK

Darkspeed · July 08, 2015, 08:01:31 AM

RJ - that has to be because someone limited the right turn stop so as to not hit the drag link with the drivers side tire during a full right turn.
This could probably be fixed by bending up a new drag link with a clearance for the tire.
Just guessing because that is the current flaw in my plan..

Unless.. they installed a very short steering arm so as to not have to relocate the drivers side shock, but im guessing it is the drag link.

If I cant find an acceptable solution to a frame mounted design I will fall back to making a mounting plate to convert the TRW/ROSS HFB70 from frame mount to axel mount and rebuild the steering linkage to get the lash out.

uncle ned · July 08, 2015, 09:04:16 AM

I do not know what box is under Huggy but I had to put special stops to keep from rubbing holes in my air bags.

Blew the left front one and had to replace it.

Hard-headed Ken probably knows what rig was put under her. but she drives great, very little play .

A couple months ago a tree blew across the Inter-state 85 in SC and blew the right front tire. I was running about 60 to
65 mph. She did not waver just jumped the tree.

Had to pick parts of the tree out from under her for days.

uncle ned