The aim was to make an accurate and cheap coolant temperature gauge for my elite class liquid cooled mini moto. These are very handy items as they can help you assess whether certain modifications are causing the bike to run too hot or if that giant $200 billet water pump actually made a difference amongst other things. 2 strokes are very sensitive to coolant temperature as well and run best around 65 degrees so its handy for getting maximum power.
The device i originally wanted was an awesome device called a mychron 4, but at nearly $600 that was way out of the question. I got to thinking about using an aquarium digital thermometer but most only advertised a maximum temperature of about 80 degrees at best and with an update time of 50 seconds or more which is not very useful for what i wanted to do.
I got onto an online store a while later called http://www.dealextreme.com/ and while buying other things saw they had a few thermometers for $3.29. so i grabbed a handful of them with the intention of hacking them into a working coolant temp gauge.
These are the ones i used - http://www.dealextreme.com/details.dx/sku.15553
Here they are! the temperature probe is just a thermistor epoxied into the metal tube you see in the top left of the picture.
After some experimenting it was found that despite the claims of the manufacturer they actually read all the way up to 120 degrees before reading error on the LCD as well as being only 1 to 2 degrees off an expensive brand name thermometer. Unfortunately the update time of the screen was indeed about 50 seconds apart.
On closer inspection there are blank solder pads with no components on them labelled SW1 SW2 etc.. with a bit of experimentation it was found you could change the display from degrees F to C and if you joined the two pads labelled SW3 together the update time was reduced to only 7 seconds. That was good enough for me!
So now i had a digital thermometer that read up to 120 degrees C and updated every 7 seconds. perfect for the bike. Next an adaptor had to be made to position the sensor in the coolant stream to read accurately.
In the picture below is the semi complete item. its a 2024 aluminium rod turned down to have 10mm ends for the hose with a large center section and a bolt tapped in sideways. there is a hole drilled straight through the center of the bolt (i ended up using a different bolt ill explain why later). The sensor has to be placed in between the cylinder head and the radiator as that is where coolant is hottest!
The sensor from the thermometer was placed into the hollow bolt and some metal epoxy was used to fill in the back of the hole and make it water tight. i used a socket head bolt instead of the hex one in the above picture so the epoxy could flow into the middle and seal better. The sensor is flush with the outer diameter of the adaptor so that the coolant flow isn't inhibited in any way.
some permanent loctite kept things water tight and reduced the risk of it every vibrating loose.
and here is the complete project! excuse the state of the bike in the picture. had a few other projects going on that ill post up soon ;)
The unit got its first test last weekend at Wollongong city race way and worked absolutely flawlessly. No leaks and accurate reading all day. The hottest i managed to get the bike too was 74 degrees in the hottest part of the day and 68 degrees in the night time race. So the coolant setup is pretty well ideal. ill look at ways to get another 5 degrees off and that is one job done.
If there is enough interest i will make a few of these including the adaptors and all the mods to the thermometer for $50 each. so drop me an email at Glen.M.R@gmail.com
No comments:
Post a Comment