Curt Axles

[familytruckster4]

We had a bunch of trucks at work in the early 2000's that used a rudimentary WABCO system with magnetic sensors. They required a lot of attention since the friction material that the pads shed would cover them and caused them to cease signaling. It didnt help that the pads wore down so quick from the abuse they were subjected to.

[Guest]

Rob knows we used optical speed sensors as well as mechanical ones in development. They are expensive and can easily be fouled up. But the ABS system only needs the latest vehicle speed as reported from the wheel sensors and driver input to operate properly through software and calibration.

We also used satellite systems from Race Logic.

https://www.racelogic.co.uk/index.php/en/

Jim

[Yoda]

Jlawles2

Ground speed radar on an RV trailer . . . Joseph, you do have a sense of humour .

Rob

I don't know Rob - next will be the Flux Capacitor - problem is getting to 88 MPH. Hint - I think I can get there, but can I afford it

But to be honest based on my reading (and I could be wrong) it is probably just simple wheel speed sensors . IH had the first ABS on on the IH Travelall before anyone else and it was simple wheel speed (magnets) and an electric solenoid that pumped the brakes. I was a curious kid and always snuck back to the guys working on the truck. Back then they were friendly and explained how things worked.

Dad had it on the truck I learned to drive with ( 69 IH Travelall https://www.google.com/search?client...9+IH+travelall ) was also our tow vehicle (390 gas 3 speed on the tree) . Was just on the rears and a pain to maintain. I think Dad had them deactivate it in the end.

But it sure would be great to get in, punch in your destination, and just warp there.....baring any Imperial interference,

YEP - The force has left the building Good Night Folks

Keith

[Cate&Rob]

Jlawles2

Ground speed radar on an RV trailer . . . Joseph, you do have a sense of humour .

Rob

[Jlawles2]

With the new technology it's possible that they have a ground speed radar. With that radar, they compare the wheel speed to the ground speed to see if the hub is moving slower than than the ground.

[ncitro]

My understanding from Grand Design is it is still a leaf spring based suspension, with the ABS axles. It was new stuff when I was at the factory last, and there was not a lot of information about how it worked or controllers yet. Hopefully they will release more information on it soon.

[Guest]

When I was at the Tampa show this past spring, a few other manufacturers were touting Curt suspensions which are not spring axles but independent suspension. I wonder if this is what the GD option is?



https://lci-support-doc.s3.amazonaws...cd-0004440.pdf

Vivian,

This would be good since front axle rise on heavy braking with an equalizer system could mess with ABS under some conditions.

Jim

[Beachcamper]

When I was at the Tampa show this past spring, a few other manufacturers were touting Curt suspensions which are not spring axles but independent suspension. I wonder if this is what the GD option is?



https://lci-support-doc.s3.amazonaws...cd-0004440.pdf

[Guest]

For our electric brakes, this can be done much cheaper than auto and still be effective. For instance, individual wheel speed is monitored where the surface condition could be approximated by measuring driver applied voltage, individual wheel speed and the rate of change of deceleration of each of four wheels under braking. While braking for instance on a frozen lake or plastic sheets, as the wheel(s) quickly approach zero speed, the controller modulates voltage to maintain wheel speed slightly above zero. There are other factors such as thresholds from any one wheel as compared to the other three. This is a simplified description where it takes ABS calibrators months to have this operating smoothly on a variety of surfaces.

Stability control in autos uses a complex hydraulic system to Robs point along with yaw measurement and steering angle (driver input) to use the vehicle braking system to return the vehicle in the direction to where the steering wheel is pointed. So for those in autos or trucks, remember to point the steering wheel where you want the truck to go while sliding. If you freeze on the steering wheel toward a forest, the vehicle will put you there.

Jim

[familytruckster4]

When towing our previous travel trailers on snow and ice covered roads I would also drop one link down on the weight distributing bars to aid in rear wheel traction. (although I also ran in 4WD on a lot of occasions)

[Yoda]

Particularly those that may not re-adjust their brake controller for wet or slippery conditions.

Frozen lake, Plastic Sheeting.... LOL! Like the humor.

And Welcome to the forum!

Jim

Jim
Excellent point on adjusting gain for the weather conditions.

Very few folks know that. Also few know how to get the trailer out of a slide when it happens. Step one is get off the brakes and steer. You need the trailer wheels turning to recover. I have driven over Vail pass under chain law conditions (got caught in one of our wait 5 minutes and it will change) with my old trailer and on dicey icy roads to Mississippi and back at Christmas through Colorado, Texas, etc. In hind site I should have parked and waited for the roads to improve, but time did not permit. I have learned the hard way to slow down and reduce the trailer braking. I still have the trailer brakes come on before the truck, but with less force.

Just my thought However if the ABS system works I would get that option. My guess it is a simple wheel speed sensor the keeps the wheels turning at all times - no lockup possible.

Keith

[Cate&Rob]

I would expect that "Trailer ABS" is simply comparing trailer wheel speeds and reducing brake apply voltage to a wheel that is slowing (approaching lockup) more quickly than the other wheels. There is no "information" connection to the truck. Note that ABS is only available with electric drum brakes and not with EoH hydraulically applied disc brakes where reducing an individual line pressure would require more complex plumbing and a more sophisticated controller.

Balancing ABS and ultimately vehicle braking is much more complex on a truck or car because the brakes have to be able to stop the vehicle under all conditions (even wet ice). Trailers are a little different . . . where there is a requirement for trailers to "have brakes" there is no performance criteria for these brakes. On the other hand, your truck must be able to stop its GCWR (truck and trailer) within a specified distance with trailer brakes disconnected per SAE J2807 procedure.

Rob

[familytruckster4]

My biggest geek question would be how the system determines its reference point for speed ? Vehicles use an input from a speed sensor on the trans or another source. The system then determines through the wheel sensors if any wheel is rotating slower and assumes its locking up and reduces brake force on that wheel (or multiples if the signal warrants it)
With a trailer I dont see how they could find a vehicle speed for reference ? It may just determine any discrepancy between wheel speeds and then adjusts based on that ?

BTW, having driven many times on a frozen lake (minus my RV) I find that amusing.

[Guest]

I'm wondering if they are using this system with something better than what we have for our suspension? Its easy to over gain and lock up the front axle alone with the use of an equalizer type suspension. So if they reduce braking on the entire system on near lockup of the front axle alone, this would be a concern. If each individual wheel or axle is separately controlled, this would help folks in low traction situations. Particularly those that may not re-adjust their brake controller for wet or slippery conditions.

Frozen lake, Plastic Sheeting.... LOL! Like the humor.

And Welcome to the forum!

Jim

[tlovell]

Yes apparently they work really well when you are towing on a frozen lake, or a road that is covered in plastic sheeting to decrease available friction. OK so I am a cynic. I have never in 28 years of RVing with four diff trailers locked up my trailer brakes. I guess I have never had them be too efficient.: https://www.lci1.com/products/rv-supplier/abs