pictures speak volume..
Pictures of a Spartan K3 passive steer chassis plunger(L or Top) v freightliner passive steer chassis plunger(R/ bottom). this picture is some how turned sideways!! you can see the disk brake on the bottom of the picture. rotate (ccw) and then compare the two.
The plungers lock the steer tags at speed and in reverse. they retract to free the tag wheel to steer at slow speeds.
Spartan plungers retract from 0-45mph and lock in at 45.
under deceleration, the spartan unlocks at 15 mph.
Freightlliner retract from 0-20 mph, lock at 20 mph. and unlock at 20 mph in deceleration .
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I'm not an engineer, and the differences from a quality perspective are not apparent to my eye. Also, it seems like the bottom one has a disc (spartan) and not the other way around. Care to expand on your observations?
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Phil and Laura (and Sam too!)
2017 DSDP 4369 on Spartan K2
2017 Unltd Rhino Rubi Recon Toad
I'm not an engineer, and the differences from a quality perspective are not apparent to my eye. Also, it seems like the bottom one has a disc (spartan) and not the other way around. Care to expand on your observations?
I am an ME and not sure what his point is. I can't really tell scale nor can I see moment arm length. Also I am not sure exactly how some of the parts work since not entirely in the picture. Like are wheels tied together so both turn same amount at same time?
Hope op replies on what he was trying to point out. Biggest thing I actually notice is top photo has more expensive parts with weldment construction and lower one has cheaper construction with casting or forging construction. I will note sometimes the loser tolerance construction will work better as too close of tolerances can cause problems with dirt and things locking up from bending.
Tom
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2016 American Coach Tradition 45A
2022 Ford Expedition
The fccc is a 2017. K3 is for a 2018 unit and does have the disk brake (see pic), this k3 is for a cornerstone.
It is worth looking at the bear bone chassis and compare.
Tom, on fccc you can see the arm length as it is.
The two tag wheels are connected via toe link. they steer together. no independent steering, otherwise it would be problematic. The plungers operate via an air valve. air valve is similar to those operating brakes or the air bags.
These are "general" descriptions/observations. would be nice if the engineers from both fccc and spartan would help and provide information on their product.
I "believe" there is only one air valve operating both plungers for fccc. spartan has one for each plunger. When slowing down, the air valve dumps the air, then the plungers under spring load (?) retract. hence freeing the tag wheel to steer.
Attached is a short video of the fccc plunger in action. one of the items you may observe, is the tardiness of the plungers.
Note on the video.
That plunger only restricts movement one way.
Plunger motion and speed are about what I would expect. I would expect some slop to be required and thus possible to be too fast. With plungers on both sides if stroke is not limited it would be possible to lock with wheels turned. Hence slower movement helps to avoid this and makes timing less critical.
Plunger is such that it will need adjusted at some point in the future for wear.
It would be possible to lock wheels at slight angle or with some shutter if this is only type of lock should either side not extend proper amount.
NOW while I am a ME I spent my career in transmissions, transfer case, and air conditioner manufacture. So I have a decent idea on design of those items but chassis is a different ball game. So I am making some educated guesses that may well be wrong.
Tom
Edited because I missed part of your information first time. pps:
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2016 American Coach Tradition 45A
2022 Ford Expedition
"if stroke is not limited it would be possible to lock with wheels turned."
the stroke is limited, the video shows that.
"...and makes timing less critical."
timing is critical.. for one, it is a reflection of a cheap design. one concern would be during the backup after turning while going forward. Only one plunger operating (the second one on a delay), the one plunger can no way straighten up a 12k tag wheel. The air valve dumping air on the tag during back up takes way too long to of load the weight on the tag. If anyone saw the tag wheel jammed during the back up, they may have second thoughts about this passive steer, at least in its current configuration.
"Plunger is such that it will need adjusted at some point in the future for wear."
Good observation. that seems to be one of the problems. from the video (at about 7-8k mi) the steel plates on mine had already developed a grove! so what happens over tiime as the grove potentially deepens? who pays for its adjustment and potential tire wear?
"It would be possible to lock wheels at slight angle or with some shutter if this is only type of lock should either side not extend proper amount."
I don't think they'd lock at speed. however, they would be unstable, tire wear and tire roll out. see the other discussion with LTL.
and speaking of shutter (ironic you had to use that term). all of this started when I repeatedly raised concerns over a shuttering sensation from the back end while slowing down ( around 20 mph). fccc claimed it is normal engine trans!!! ask the chassisguy who knows a thing or two about chassis. I asked them to put in writing and they did! the original video recording from under the coach and behind the tags showed the tag wheels consistently turn left, when plungers retract (at 20 mph), under deceleration.
"NOW while I am a ME I spent my career in transmissions, transfer case, and air conditioner manufacture. So I have a decent idea on design of those items but chassis is a different ball game. So I am making some educated guesses that may well be wrong."
the idea is to understand what is going on with this design. hopefully to benefit all. thank you.
Basicallly what I'm reading is an endorsement of one chassis over the other. In my opinion both chassis configurations have their "up" sides and each has their "down" sides.
So, which car is better, a Ford or a Chevy?
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[SIGPIC][/SIGPIC]2016 Newmar Dutch Star 4369
Newmar Owners Club
USAF 1966-1969,- Law Enforcement 1969 - 2003, Retired since March 2003
Basicallly what I'm reading is an endorsement of one chassis over the other. In my opinion both chassis configurations have their "up" sides and each has their "down" sides.
So, which car is better, a Ford or a Chevy?
I pretty much agree with what you say here. Personally I do like the basics of the Freightliner system. I don't really know on the Spartan system since I've not seen it action. (Also however note FL has a second passive tag and I don't know if it works the same or not. Only coach I saw it listed for was American Eagle but I only checked American and Newmar on the FL website.)
A couple of points for Rd1:
I have always been trying to go straight a bit before backing up. Never noticed a problem with taking too long to dump personally. Backing for me really only occurs parking and that takes a few min. esp since I prefer to walk around first and perhaps in middle of parking.
If you have a shimmy be sure to have tag inspected to see both pins are in contact when wheels are straight and locked. Looks to be an easy adjustment.
The slower motion helps with not having pins too far out of position when closing. Better than being faster IMHO. Also not sure it's really a bad design choice as looks pretty reasonable to me.
Tom
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2016 American Coach Tradition 45A
2022 Ford Expedition
"I have always been trying to go straight a bit before backing up. Never noticed a problem with taking too long to dump personally."
Tom, you have to watch the backup when someone else is driving! If the tags are jammed/locked during backup, you will not notice it. there is no feed back in the driver seat.
Some of the issues raised in regard to passive steer, is just the characteristic of passive steer. for instance, They lock the tags at speed because they coach will be unstable. The early passive steer tags did not lock at speed, only in reverse. changing lanes with passive steer unlocked would make the coach very unstable.
This is not a ford and chevy issue. If you had a chance to look at the bare bone chassis (I wish I had before purchase), you will notice a much more robust setup in a spartan. ultimately, yes it is a personal choice.
However, the broader issue is the fact that FCCC passive steers were produced with their tag axles mounted of center. This fact was known to FCCC from the beginning and for some two years they continued this production knowingly and intentionally. This is inexcusable, irresponsible, and even negligent to say the least.
At first, I assumed it was just mine and perhaps a few others. It turns out, most have this issue and many owners are simply not aware of this problem. How would any one expect Daimler/freightliner to produce such a defect in their product knowingly and then hide it!
Now it seems, more and more of these chassis have also had their drive axle not true to the chassis! These "seem" to indicate the tooling of assembly/production lines done in haste in order to rush a product without proper testing. I guess freightliner considers their customers to bare the R&D expense for them!!!
The ultimate question is, what happens to those owners who are not aware of their tag axle and potential alignment problem? what happens in their 3rd, 4th year or when tire wear becomes an obvious problem. Would frieghtliner stick it to them?
It was at the International Rally that we saw the stripped Spartan and Freightliner chassis...
After seeing both and comparing them we decided to order our DSDP on the Spartan. Heavier duty chassis and what appeared to be a more solid tag design. After reading the various comments in this and other threads on FCC we are positive we made the right choice. We even got there one with disc brakes on all axels!
I honestly believe that the German factories are using the customer for R&D....not a known fact just a gut feeling.
Bob
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2021 DSDP 4363 Spartan K2, NKK F21594
Bob, Loretta, & Paddy the Westy, No Pronouns, HOOTS
2021 Tesla MYP
I don't think Freightliner was trying to hide the alignment issue. During my first call to Freightliner for another issue, they asked me to measure the tag (left to right) My tag was about 2 inches to the left. They said have it fixed and I did. (warranty issue) So, they do know about the issue and are trying to take care of it Shortly after having the repair, I got a letter from Freightliner telling me to check the alignment.
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[SIGPIC][/SIGPIC]2016 Newmar Dutch Star 4369
Newmar Owners Club
USAF 1966-1969,- Law Enforcement 1969 - 2003, Retired since March 2003