I've been one of those hold outs who thought there was no way my light weight hybrid would ever stop my motor home!

I looked at the Air Force One and I liked it. However, I'd rather pay someone for professional installation than spend 6 hours crawling around under my coach. I also want to know it's working correctly and that if there is a problem I have someone to go back to. The closest place to Vegas that has even done an installation was in Lake Havasu.

I'm now thinking about the Roadmaster which is similar and installed for about the same price as the purchase price of the SMI. http://www.roadmasterinc.com/products/braking/brakemaster/brake_m.html

Anyone have any experiece with this system?

Thanks for the information on the thread. It convinced me I should add a breaking system.

Michael

2005 Dutch Star 40' 4 slide
2005 BMW K1200LT motorcycle on lift
2006 Ford Escape Hybrid

I believe the Roadmaster will be applying pressure to a dead pedal, no power boost. The SMI charges the power booster with vacuum, therefore the in car cylinder doesn't have to apply high forces to brake the toad.

Our PT weighs in at about 3500 lbs which I don't consider a lightweight. The Ford Escape Hybrid weighs in at close to 4K.

I cannot imagine anyone towing a car without a supplemental braking system. At the worst, you probably have no breakaway system .

Michael,

In an effort to keep this thread devoted to generic information about tow braking, I am starting a new thread to specifically answer your question. Ford Escape Hybrid Braking

Brent Schuck
Research and Development
Graphic Design

This message has been edited. Last edited by: SMI Manufacturing, Inc.,

quote:

Simply stated, it comes down to this: When you are trying to stop in a panic, you are not only trying to stop faster, but you are also trying to stop more weight.

I am not happy having problems with the 'lecture' after so many positive reviews. But it does grate on my understanding of physics and my distaste for hyperbolic fear mongering.

The weight does not change no matter how fast you try to change the speed of the rig. Weight is defined as the force due to gravity, not any change in inertia.

The mass also does not change.

The whole argument is much simpler than presented. Stopping quicker means you need more force than stopping slower. Stopping more mass, which has a greater weight, requires more force than stopping less mass. That's all.

As far as I know, any towed vehicle over 1500 to 3000 lb, depending upon state of registration, is required to have braking. This makes me wonder about the scare story used in this presentation and whether it is really appropriate to an honest message.

The limiting factor on stopping force is almost always the tire friction on the road surface. If you slam on the brakes, both your towing vehicle and the towed vehicle should be laying down rubber.

Without the FUD, the lessons I see are these:

1) if you are towing any significant weight without proper brakes, you are probably towing illegally.

2) you must compensate in your driving for the size and weight of the rig you are driving.

3) your RV does not handle like a sports car and should not be expected to.

4) rig your RV and maintain it properly so that it is dependable and is safe if driven properly.

5) safe driving depends upon a confident attitude based on experience and training. Trepidation and fear are indications that this experience and training is insufficient for safe driving.

I note that RV's are generally the safest vehicles on the road and that the primary cause of accidents (after DUI) is not paying attention. Stay awake and alert, take care, and drive safe.

BryanL,

Thanks for your contribution to this thread. I realize that no one can ever make everyone happy, so I make it a point to try to cater to as many as possible. I agree with all five of your points, although number one has been a topic of heated debate on many occasions. I also agree with your summation as well. You need more stopping force to combat the additional force (F=ma) generated by the towed. Many people want to know more than just what is happening: they want to know why. If you wanted to dig a little deeper, you could find how many watts would be created with the addition of the towed by using the formula Kinetic Energy= 1/2 mv2 (the “2” after the “v” being exponential) and compare that to the coefficient of friction on the coach’s braking system. If the coach brakes try to dissipate this heat from the additional wattage, it will result in a lock-up; or, more likely, severe brake fade. This topic can be as simple or as complicated as you like. The statement regarding more weight to stop in a panic did not refer to the towed magically gaining weight (gravitational mass) as we all remember the Lomonosov-Lavoisier law from elementary school (conservation of mass), but the fact the there is more force (perceived as weight) on the back of the coach in a panic. To make it more simple (at least to me ), I referred to force in its perceived form of weight to help readers relate. I apologize if my post seemed to cast “Fear, Uncertainty, and Doubt.” My intention was to supply a “why” that was easy to understand rather than getting up on a soap box and beginning the mundane “You need a brake” speech while I shake my finger.

Brent Schuck
Research and Development
Graphic Design

I will .



Toads do need brakes!!

I suspect I'm from the old school which tries to use some common sense. We have a 2005 Georgie Boy Pursuit, 35 foot, double slide, F53, V10. We tow a 2001 Jeep Cherokee. We use our Brake Buddy every time we tow. Now here is the common sense part. The most precious items are my family; therefore, we make sure that the coach is as safe as it can possibly be by keeping up with all the essentials; we "drive" the coach by being aware of what is around us all the time; we do our best not to get too close to any other vehicle; If we're tired we pull over; We respect other vehicles on the road; we leave in more than enough time to get where we going; We try to always know our exact route before we leave; our speed is dependant on many things including but not limited to weather, traffic, time of day. We realize that any RV does NOT handle like a sports car. We have been know to communicate to a higher source and we hope that others on the road keep their minds on the road, instead of their phone or other distractons. It's taken 65 years to get this far, we want to be careful going down the road so we can continue to enjoy this Great Nation of Ours.....

I just love the ones that argue that the law specifically says trailers over XXXX# have to have a braking system. Therefore, the towed car is not a trailer and exempt from the braking requirement.

I guess that in the great wisdom of the chassis manufacturers, they have designed the chassis such it can determine if it has 3500# of rocks on a trailer or 3500# of dinghy trying to push the RV along.

I agree, the dinghy must have a braking system.

Ken

I would also like to reiterate that many people "overlook" the part in underneath their coach's towing guide that states:

"Any trailer over 1,xxx lbs loaded must be equipped with its own braking system of adequate capacity."

That's coming from a coach with a hitch rated at 10,000 lbs pulling weight. This limitation is not from a "Law" or lack of a "Law," this is a chassis limitation.

Brent Schuck
Research and Development
Graphic Design

yes it is 'interesting' that the basic requirements for towed vehicle braking are in such dispute as they are rather well defined.

As for "you could find how many watts ... and compare that to the coefficient of friction" -

this is confusing force and energy.

In a panic stop, you are not concerned with the problems of heat dissipation. You are concerned instead with the total force you can apply. The heat dissipation or energy problem is usually only a concern on downgrades without proper engine braking or other driver compensation.

The short term energy dissipation needs from a panic stop are well handled by the thermal mass of the components.

The short term force you can apply is limited by the tire on the road and that is highly dependent on conditions.

As for physics, this does get into the problem many have in distinguishing between momentum and energy conceptually. In the example provided, I think that distinction was a critical factor. Momentum has a direction that energy doesn't have. Momentum requires a force to change it while energy does not. Energy comes in flavors while momentum does not. Energy is conserved while momentum is not.

(ever try to get across the distinction between elastic and inelastic collisions in the physics context to someone?)

The natural inclination of those facing a crash is to try to evade or avoid it. In an RV, this can often be a bad idea. You can create more damage by trying to maneuver (as in the example provided) than by just putting the effort into straight line reduction of speed.

Managing momentum gets to be a lot of fun when you start to consider the moment arm between the center of gravity and the points where you can apply a force to the rig. That gets into why you slow down on curves but that is a different topic than braking.