~Since 2004~
A site about memories, thoughts, photos, and unrepentant opinions about motorcycles and motorcycling after four decades of twisting the throttle.

Monday, August 14, 2006

More Hot Shots


2005 ST1300 thermocamera image
How hot does your bike get while merely sitting in the sun? Why does the gas tank burn your thighs when you hop on the bike after work? Men have pondered it, talked about it, argued about, even as they found valuable electronics be roasted in the storage compartments of their touring or sporty bike. A question for the Ages, to be sure.

Last year I did some observations on my Aprilia Caponord so we'll just call this an annual 40on2 blog entry to be made when it's too hot to ride much and I can't think of any good stories at the moment.

The weird looking picture above was made with the FLIR P40 thermocamera ($40,000 if you want your own). The measurements are not completely conclusive since there are a variety of factors involved in measuring the heat of surfaces (emissivity of each different material, reflected heat, blah, blah, blah) but are close enough for our humble purposes here.

Having access to some heat measurement goodies like thermocouples and a FLIR P40 I decided to explore the fun world of infrard and motorcycles a little more before we move on to other, more important topics like "What bike should Doug buy next?"

From the thermal image above (since the image is a bit grainy):

Side of fuel tank = 151°
Side of seat = 181°
Fairing "tip over wing" = 161°
Saddlebag side = 151°
Hondaline Top box = 151°
Note here that the ST was only sitting in the sun, not running nor had it been since 8:00 in the morning.
The FLIR P40 measures 75,000 data points at once and then translates that into pretty pictures for our eyes. Color equals temperature. Think thermally, not photographically. Note the temperature scale on the side of the image. Dark colors mean a cooler temp but it's cool relative to the scale, not your refrigerator. In these images, cool = about 100°F. Also, really shiny metal stuff like mufflers, control levers, etc. reflect the heat around them so the camera is seeing mostly the reflection, not the temp of the part. It gets complicated sometimes so that's why the temps you see in these images should not by any means be considered exact but they do match pretty well with more rigorous measurements I've done on lesser vehicles such as cars. The camera accuracy is +-2% >30°C so there's that to consider too.

The external surface temps I measured on the ST would be typical for most any modern bike (or car for that matter). Plastic and paint don't vary all that much these days. Some of the bikes done in flat colors on the bodywork or gas tanks (Aprilia "ash black", Honda 599 a couple of years ago, etc, etc.) might get a good bit hotter. It is possible under "just right" conditions to get transient spot temps of over 230F on some surfaces like the corners of leather covered seats when the sun is at just the right angle for a few minutes. Covering a bike is best but even tossing a towel over the seat or instruments cuts heat substantially and reduces long term negative effects on the materials. If you value your bike, cover it when it's parked outside.

How hot does it get inside the fairing storage compartments of the Honda ST1300? If you have one you'd be curious. Topics of heat and the Honda ST series go together like Harley and vibration or BMW and over-priced.

Below are some fairing storage compartment temperature observations taken from my trusty ST1300.

Note: I did all this "quick and dirty" by any normal test standards. The equipment was borrowed from work and frankly, no one was paying me so I wasn't going to get too carried away.

The test plan was this:

Add two Type K thermocouples to the right fairing compartment of my ST. One would measure air temp in the compartment and one would be affixed to the floor of the compartment.

The bike would sit in the sun all day facing north. This is the least damaging position for the bike here in Arizona. I could have set the bike up for "worst case" temperatures but hey, it's MY bike.

At the end of the day I went out and connected the temp. measurement unit (Fluke 52 K/J digital thermometer for the geeks) to the T/C's and read the temps. My apologies to the true geeks / European readers for doing this in Farenheit but we must sometimes defer to cultural norms.

Test conditions:

Ambient = 106°F
RH = 25% (humid for AZ)

In the compartment:

Air temp = 116°F
Floor temp = 120°F

Not too surprising. Cars can get to 175° air temp inside under the right conditions.

So I attach the Fluke with highly scientific black tape to the storage compartment cover and start the bike.

…I head for the front gate and home…guess what…the temperature drops slightly. Must be some airflow in and around the compartment. Interesting.

The road home is mostly country 2 lane. Speeds vary from 45 mph to 50 mph posted. As this was all for science I road a bit faster, about 60 - 65 mph. Only three stop signs and one stop light for the 17 miles home.

Cruising at 60 - 65 the temps in the storage box start to climb slightly and max out at about 125°F on the floor. Air temp is slightly less.

Here's where it gets more interesting.

As I get into town and drop to 45 mph the bike is now properly warmed up and with the lower speeds the compartment temps start to climb. After two stops signs we're at 130° inside the compartment. Roll through my little neighborhood at 25 mph and we're at 140°. I park the bike in the driveway and let it idle. The radiator cooling fan kicks on and off and the temp inside the box starts to climb. After about 3 minutes the floor temp in the box is about 73.3°C…oops…163.9°F. Is your cell phone dead yet? Your PDA gasping it's last? Maybe. I was certainly hot standing there in the sun and having done enough for science that day, I shut off the bike. The temp inside the box climbed to 162° and then after a couple of minutes began to slide back as the engine cooled.

I rolled the bike in the garage and the Mrs. came out so see what I was up to. Happily, she brought some cold water with her. My next immediate project was to clean tape glue gook off the fairing. The heat had made a mess of the tape hold the instrumentation in place. Yuk.


high tech mounting system
So how hot COULD it get in the storage compartments? Can't say for absolutely sure and I'm not devoted enough to do a whole test regimen on the bike but I'd guess that stuck in traffic on a hot day the temp might climb to 180°, maybe a little more. If one is given to continous high speed riding (perish the thought!) it could get hotter.

No doubt Honda has done all this themselves but they will never tell us the facts. "Engineering secrets not fit for the unwashed masses" and all that. Given that the inside of a parked car can reach 175°F air temp and surface temps on dashboards can reach 240° I suppose the temp inside the fairing storage compartments isn't all that out of line but I still wouldn't put anything in there that was electronic. That sort of continuous heating can't be real good for consumer electronic components, never mind the tuna sandwhich in my lunch sack.

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