I haven't posted on the net in a very long time, though I do love to catch up on all of you now and then. I see from this thread that there are some questions regarding stopping distances with various configurations of control arms and brakes. Maybe I can clarify at least a little bit. Back in 2011 I wrote a small summary of our brake testing that occurred over a 3 month period. Please forgive me if these are too many words for the net as I am link challenged.
May 26, 2010
By: RICK FLANAGAN
THE CHUCK AULGUR REACTION ARM BRAKING SYSTEM
It’s been brought to my attention that not enough testing performed & data presented to justify spending big $$$$ on this system. TRUST ME, THE RUBBER HIT THE ROAD. The following is a summary of the testing performed over a 3-month period. A little project history first.
Chuck Aulgur, who I’m sure you all know, had the idea that by floating the brakes on the rear bogie arms and tying them back to the frame, you could eliminate the lifting energy created by the forward bogie arms when the brakes are applied. This would drastically reduce nosedive and backend lifting, which causes the rear tires to skid & diminished braking. Chuck spent several years designing and making prototypes of his idea, some of which he presented at various rallies. (See accompanying CAD model drawing) Chuck showed his design at the GMC International Rally in Santa Rosa, California. It was at that rally that both Jim K. and Chuck tag-teamed me and I finally acquiesced to help with the design.
DEVELOPMENT STAGES:
1. Model Chuck’s current design into CAD
2. Evaluate strengths and deficiencies in the current design
3. Make new design as safe & rugged as economically allowable
4. Perform stress analysis on the reaction arms in COSMOS WORKS
5. Minimize part count
6. Perform braking tests on GMC coach
By end of August 2008 Rev 1 of the system was complete and stop testing performed. (See accompanying CAD model drawing)
NOTE:
It should be noted that SUPER-8mm video was used for evaluation & analysis and was never intended for outside viewing. One of two tapes was converted to digital and I will turn it over to Jim K. for customer viewing. CAUTION, don’t try to make sense of what you see on the video, because without all the written notes to accompany each scene, you’ll go mad. Some day I might convert the other tape to digital & edit them both down to the pertinent shots only, but that’s a lot of work.
PRINCIPAL BRAKE CONFIGUERATIONS TESTED:
70mm DISK BRAKES ON FRONT & DRUM BRAKES ON BOGIES
A total of FIVE 35-MPH PANIC STOPS were performed & videotaped. Every stop resulted in either one or both of the rear bogie tires skidding. The AVERAGE STOPPING DISTANCE was about 95 FEET. ALMOST NOT ENOUGH STOPPING ROOM.
NOTE:
For this test, we threw a nylon flower sock out the passenger window. Those measurements were relative. For the remainder of the testing we used a brake light activated, solenoid held & spring loaded arm with chock attached to the end and mounted under the rear bumper. When the brakes were applied, the taillights came on and disengaged the solenoid. The arm is slammed to the ground leaving a chalk mark. This was a much more accurate measuring system and easy to erase. (Strange dragging noise heard in videos)
80mm DISK BRAKES WITH YELLOW PADS ALL AROUND & REV 1 REACTION ARMS INSTALLED (Going for max braking)
ELEVEN 35-MPH & TWO 60-MPH PANIC STOPS were performed, some of which were videotaped.
NOTE:
The first few 35-MPH stops with this configuration had negative results, in that either one or both rear tires skidded. In one case all 4-bogie tires skidded. We found that the ride height was way too high and close to bottoming the shocks.
Once the ride height was adjusted correctly, the remaining seven 35-MPH stops resulted in NO REAR BOGIE TIRE SKID.
One 35-MPH stop caused one of the forward bogie tires to skid some. Not sure why.
The AVERAGE 35-MPH STOPPING DISTANCE was about 59 FEET.
The two 60-MPH PANIC STOPS with the above configuration caused all 4-bogie tires to skid, thus causing the rear of the coach to start to come around. NOT GOOD! NO ANTI-LOCK BRAKES HERE. (See video)
Upon evaluation, we concluded that the dangerous skid was caused by too much braking power of the rear bogie brakes. With too much grip the rear brakes locked up too soon. When the rear tires started to skid, they lost most of their drag and thus forced the forward bogie tires to work harder. They in turn lost their grip and also skidded.
We didn’t measure the distance of these stops.
80mm DISK BRAKES ON FRONT & FORWARD BOGIE WITH YELLOW PADS & 70mm ON REAR BOGIE WITH SEMI-METALLIC PADS & REV 1 REACTION ARMS INSTALLED
A total of ten 35-MPH & two 60-MPH PANIC STOPS were performed, some of which were video taped.
ALL TEN 35-MPH STOPS RESULTED IN NO BOGIE TIRE SKIDDING. One front tire chirped a couple times, but didn’t skid.
AVERAGE STOPPING DISTANCE was 59 FEET
THIS WAS OUR BEST PERFORMING CONFIGURATION & WHAT WE INTENDED TO RELEASE.
From testing, it’s possible that, even with this system, sometime you will lay down some rubber. There are too many variables such as road, tire, brake conditions & the fact that these are not anti-lock brakes.
Jim, Chuck & I had this setup on our coaches for at least 1 year with many thousands of miles on them, most while towing with no tow brake assist. Over that time I’ve gotten so used to these brakes that I don’t really think about braking any more. At the Auburn rally, when I saw that even with video no one was getting it, I made the scary decision to have people drive my coach HARD with the confidence that, then they will understand. I think they did.
We also performed five 35-MPH panic stops with the same setup above, but with the reaction arms removed. The system is designed so that, if the reaction arms fell off, the coach will still have brakes. (See video)
ALL FIVE 35-MPH STOPS RESULTED IN BOTH REAR TIRES SKIDDING. It’s easier to skid the rear bogie tires when you have good brakes & no reaction arm on them.
AVERAGE STOPPING DISTANCE WAS, I think 68 FEET.
OTHER CONFIGURATIONS TESTED:
80mm BRAKES ALL AROUND WITH YELLOW PADS & WITH REV 1 REACTION ARMS ON FORWARD BOGIES ONLY.
THIS RESULTED IN BOTH REAR TIRES SKIDDING ON ALL STOPS.
80mm BRAKES ALL AROUND WITH SEMI-METALLIC (NOT YELLOW) PADS.
BRAKING DIDN’T SEEM QUITE AS POSITIVE AS WITH YELLOW PADS, BUT WAS STILL VERY GOOD. I would have no problem using these pads.
With the camera installed on the frame, we also tested backing, tight turning and rough road driving. The reaction arms worked flawlessly. Video of one 60 MPH test on very rough road shows this.
REV 2 REACTION ARM (See accompanying CAD model drawing)
In December 2009 Jim Kanomata told me that he had a customer who wanted the reaction arm braking system, but also wanted sway bars. Oh boy, that’ll be big $$$. As it turned out, it was cheaper. I remembered that Chuck had, at one time used one of his sway bars as an arm. He wasn’t real pleased with it and later replaced it. His complaint was that the mounting brackets were too light, it bent his torque box and the 1-1/4” diameter sway bar was too stiff.
We knew we would need a custom designed sway bar for this application. We contacted some sway bar manufacturers, one of whom we selected. We gave them the motorhome’s weight, height, width and physical limitations of bar size. They calculated that, in the design I requested, we would need a total of 250 pounds per inch of deflection. Two 1” diameter sway bars with 12” long arms were specified. I believe they hit the nail on the head as my coach rides great, though I’m sure you all feel the same about yours.
Any way, the floating part of the reaction arm braking system didn’t have to change. We knew the sway bar would work as a reaction arm once we got the mounting squared away.
The sway bars are mounted to the underside of the frame using a 1-1/4” thick steel mounting block that has a large urethane bushing in the center. The slit bushing is held in by its large flange on one end, a plastic spacer and a steel shaft collar.
I have now had this configuration on my coach for 3,600 miles, many of which, while towing our Honda Fit across the Rocky Mountain States without tow brake assistance. I AM NOT ADVOCATIONG TOWING WITHOUT TOW BARKE ASISTANCE.
THIS IS THE CONFIGURATION THAT PARTICIPANTS AT THE AUBURN WESTERN STATES RALLY TEST-DROVE.
I can’t address the specifics of the brake booster, master cylinder, etc, because that is not my thing. I’ll let Jim K. address those questions.
Jim Kanomata will be posting the before mentioned videos on APPLIED GMC’s web site.
When first approached by Jim Kanomata from APPLIED GMC, I was very reluctant to take on a brake design project. Once I started looking into how it works though, my interest was sparked. It wasn’t really until we installed REV 1 on my coach and started field-testing that I became convinced that this was truly a leap in the evolution of GMC brakes. First time I hit the brakes, WOW THAT’S UNBELIEVABLE! No matter what anyone else decides, there’s no going back for me.
Thank you,
Rick Flanagan