Adventures of Newbee - when a wheel stops doesn't stop

[JMH]

Yet an other newbie question about our Newbee. When you need to make a sharp turn does you steering wheel hit a hard stop or does it hit a stop and then will turn with additional force about 2-3 more inches.

I've noticed that when making a sharp turn and the steering wheel stops it can continued moving some with additional force. Seems like I get a little sharper of a turn after. Newmar tech said sounds normal and is just how power steering works. I've never had power steering work like this on any other vehicle.

So, next time you are in you coach make a sharp turn and see if you can move the wheel past the initial stop. Let me know what you find out. Thanks.

Mark and Louene Hetrick
Newbee the last VTDP 3725

[mel s]

Originally Posted by JMH

Yet an other newbie question about our Newbee. When you need to make a sharp turn does you steering wheel hit a hard stop or does it hit a stop and then will turn with additional force about 2-3 more inches.
I've noticed that when making a sharp turn and the steering wheel stops it can continued moving some with additional force. Seems like I get a little sharper of a turn after. Newmar tech said sounds normal and is just how power steering works. I've never had power steering work like this on any other vehicle.
So, next time you are in you coach make a sharp turn and see if you can move the wheel past the initial stop. Let me know what you find out. Thanks.
Mark and Louene Hetrick

JMH
When my steering wheel is turned all the way, (in either direction), it doesn't "stop" until it "stops".
Mel
'96 Safari

[Capt. Bill]

I tried mine & it only stops at full turn of the steering wheel in either direction. I'm on a Freightliner chassis with Comfort Steer.

[siggyd]

Your steering stop and then go a little more with force , IS NOT NORMAL,
Have it checked out by Freightliner.
Siggy

[mel s]

JMH
When you turn the steering wheel 2-3 more inches beyond the initial "stop point" do the front wheels turn?... or just the steering wheel?

[PanJH]

Ours does the same thing... at least while backing. Getting out of my space at the storage lot, I back up, crank the wheel when I clear the coach next to me-- it will stop, but then as I back up, I get some more movement and a sharper turn.

[KenSherwin]

What the OP is describing is the completely normal operation of the poppet valve in the steering gear. There is a hard mechanical stop on the axle that prevents the wheel from turning further but there is also a valve in the piston of the steering gear that starts to open just before the wheel hits that hard stop. The poppet allows some of the oil to get from the high-pressure side to the low-pressure side of the gear, increasing steering efforts. That increased efforts make you think you are at the end of travel but pulling harder can make it go farther, finally reaching the hard end of travel.



The valve is there for two purposes. The most important is to limit force that the steering gear is able to put into the axle stop and the steering linkage, thus preventing a lot of high-load fatigue damage. The other is to wash oil all the way through the gear, thus washing out any air bubbles that can accumulate in the high cavities of the gear in normal operation.

I designed several of these valves early in my TRW steering career.


Ken

[JMH]

Thanks Ken. My system works just as you described. The wheel hits kind in a "soft" hard stop then it feels like non-power steering for this short turn to the hard stop. I do get a slightly tighter turn.

My question now is; should I not be driving the linkage to its hard stop? Am I damaging anything by doing so? Thanks.

Mark and Louene Hetrick
Newbee the last VTDP 3725

[tizzyfit]

Originally Posted by KenSherwin

What the OP is describing is the completely normal operation of the poppet valve in the steering gear. There is a hard mechanical stop on the axle that prevents the wheel from turning further but there is also a valve in the piston of the steering gear that starts to open just before the wheel hits that hard stop. The poppet allows some of the oil to get from the high-pressure side to the low-pressure side of the gear, increasing steering efforts. That increased efforts make you think you are at the end of travel but pulling harder can make it go farther, finally reaching the hard end of travel.



The valve is there for two purposes. The most important is to limit force that the steering gear is able to put into the axle stop and the steering linkage, thus preventing a lot of high-load fatigue damage. The other is to wash oil all the way through the gear, thus washing out any air bubbles that can accumulate in the high cavities of the gear in normal operation.

I designed several of these valves early in my TRW steering career.


Ken

THANKS Ken for the excellent explanation.

[KenSherwin]

Originally Posted by JMH

My question now is; should I not be driving the linkage to its hard stop? Am I damaging anything by doing so?

You can't hurt it from the steering wheel for 2 reasons. The first is that the steering gear is designed to relieve the excess load at the stops. The second is the we put very few steering cycles on our coaches. Consider that a transit bus uses the same gear and linkage components as a motorhome but it has to make a 90 degree turn every few blocks for over a half a million miles reliably. Most coaches will never see a tenth of that mileage and certainly never see that many corners.

Does this help?

["007"]

Originally Posted by mel s

JMH
When my steering wheel is turned all the way, (in either direction), it doesn't "stop" until it "stops".
Mel
'96 Safari

When you try to compare the steering of a 96 coach with a Newmar 2008 and beyond and to coach's with the Comfort Drive system we, you and I, maybe love our coach's to much and may give disservice to a question like Mark has asked.
Thanks to our friend Ken on board we have the simplification of a non -problem.
I thank you Mel for your help on the board but even I have to watch what my answers might grow into if it was not for all the DP OWNERS on board that know what they are talking about.

[JMH]

Ken, you da man (or engineer if you prefer). Thanks for taking the time to provide such complete answers. I admit that I do "fuss" over my Newbee. So I appreciate you putting me at ease on this. Being an engineer myself, some of the answers from the tech services folks can make me crazy. Usually I get the "then the magic happens" answer, as I did on this one from Cummins.

007, you might want to put this one in the archives. Bet someone will ask this same question in the future.

Mel, I did take your answer as satire.

Mark and Louene Hetrick
Newbee the last VTDP 3725

["007"]

Will do Mark, thanks for the thread question.

[mel s]

Originally Posted by "007"

When you try to compare the steering of a 96 coach with a Newmar 2008 and beyond and to coach's with the Comfort Drive system we, you and I, maybe love our coach's to much and may give disservice to a question like Mark has asked.
Thanks to our friend Ken on board we have the simplification of a non -problem.
I thank you Mel for your help on the board but even I have to watch what my answers might grow into if it was not for all the DP OWNERS on board that know what they are talking about.

"007"
In JMH's original post he asked: "When you need to make a sharp turn does you steering wheel hit a hard stop or does it hit a stop and then will turn with additional force about 2-3 more inches".

In my reply, (message #2), I answered: "When my steering wheel is turned all the way, (in either direction), it doesn't "stop" until it "stops".

That simple answer is nothing more than a true/factual statement about the steering on my particular coach.

Mel
'96 Safari