Daveinet
il
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Ok, was thinking about the fact that my new motor has virtually no engine drag, and I mean nada, zip, nothin. I haven't done any long steep hills, so it hasn't mattered yet, but I was wonder what will I do when I hit real mountians. Seems I could easily get into real big trouble.
So a crazy idea pops into my head. Has anyone tried to set up a monitor to watch the caliper temp? I'm assuming that the critical issue is to keep the fluid from boiling. It seems if we monitor the caliper temp, we should be able to predict a safe temp, as the caliper would have to heat up some if the fluid was going to boil. So why can't I just go buy one of those cheapo meat thermometers and permanently attach it to the calipers? For 12 to 15 bucks, it seems like that could be money well spent. Meat thermometers also have a alarm setting too. Could be useful to let you know if you ever had a caliper hang up, if you weren't specifically paying attention to it. Any thoughts?
Dave
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oemtech
Elgin, Texas
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Yep.... Brake Monitor
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adondo
Pasco, Washington
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Nice job on the monitor setup, Dale. Not that any money would be saved, but you could also get off the shelf hi-temp panel mount displays and T-couples from W.W. Grainger.
If you're handy with electronics, you could build a timer/cycler with a 555 timer chip. Also, use a 740 series comparator chip to just have a go no-go over temp alarm, although actually seeing the temps would be the best.
If you can find cheap meat thermometers with an alarm, you could build a power adaptor for each one (to avoid constant button battery swap-outs) and feed each alarm output out and up to the dashboard. You’ll have the biggest problem weather sealing the things since they’ll be mounted underneath. That idea could have a panel made with a graphic of the coach, and LED’s on each alarm output so you can see which wheel position is frying.
One thing about Dale’s setup, you can’t easily kill a thermocouple unless it seriously overheats. Not an issue since you’ll be running for your life from a burning RV by then anyway.
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50pascals
rochester, ny
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For those who are running a PC, you can do this with USB datalogging hardware and free software. You can do LOTS of cool stuff with it.
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Big Katuna
Deland, FL
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KEWL!! I can't really tell in the PIX what the thermocouple is fastened to. What is the lag time? Can you watch the temp rise on a long down hill and let up at a certain temp and watch the temp go back down? How long does it take for brakes to cool off?
Good job!
I was a bench tech in a switching power supply dept. decades ago and we made our own temp measuring stuff from thermocouple wire (which we bought by the roll) and simply used Fluke meters set to millivolts, run it through rotary switches so we could monitor 20 or so points.
I like yours better.
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hwybnb
Southern California
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Monitoring temperature is a great idea but I suggest measuring at the brake pads as shown in the preceding post rather than at the caliper.
What I am really interested in is rotor or brake pad temperature because those are the hottest points. I have tried measuring the calipers and found that they were much lower in temperature and that they heated and cooled much more slowly because of their larger mass.
The question that I cannot get an answer to is "how hot is too hot"? I have measured 550 degrees F on the rear brake pad backing plates going down a steep grade with heavy engine braking and moderate foot braking but have no idea where that number lies on the badness scale. I have been told that brake fade occurs at about 700 degrees and that race car brakes can each 900 degrees, which is the point that they glow red, but can't get any meaningful numbers otherwise. If anyone reading this can shed some light please do so.
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othertonka
Stockton, CA
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I don't understand the "No engine drag" part. Can't you down shift the transmission to use the engine compression to hold you back and then just use the brakes once in a while to keep the speed/RPM's in check? Any clarification on that?
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hwybnb
Southern California
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Big Katuna wrote:KEWL!! I can't really tell in the PIX what the thermocouple is fastened to. What is the lag time? Can you watch the temp rise on a long down hill and let up at a certain temp and watch the temp go back down? How long does it take for brakes to cool off? I am the builder of the system shown in oemtech's post.
The thermocouples are mounted to the brake pad backing plates. They are bolted on using holes drilled and tapped in the plates. The TCs are commercial types that came assembled with pigtail wires attached. Regulation Type K thermocouple wire connects them to the monitor.
The lag time is very short and yes, you can watch the temps climb as the brakes are used and cool off afterward. They take alot longer to cool than to heat.
The maximum temperature I have observed so far is about 550 degrees on the rear brakes going down a 7% grade with engine braking assist. They would likely have gone much higher if I hadn't been watching and down-shifted another gear.
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Jim@HiTek
Gresham, OR, USA
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It would seem that you could just place a nice simple IR detecting LED close to the area, calibrate it to a hand held both in positioning and temperature, and then design a display circuit as simple as a comparator (or 4 comparators) that would sound an alarm.
Here's a nice IR detector, don't know the range though...part of the design process to find out. I'd think you'd need an industrial part too.
IR detector...
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JohnnyT
Goshen New York
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Moved from class A forum
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