Axle Temperature Monitoring System
So why would I want one of these? What is one of these?.....
The Mog's strength is also it's weakness - each axle has a gearbox on the end which transfers the power downwards through a pair of gears. These gears are known as the "portals" and run in a small casing which has a small amount of oil for lubrication. These effectively "lift" the axles above where they would normally be on standard vehicles (ie the centre of the wheels), giving massive ground clearance.
BUT - the portals take all the power and weight of the truck and due to their design are pretty heavily loaded. As a result they do sometimes fail.
During the trip so far (to Windhoek), I've been checking on the oil levels in the front axles every day that we have travelled as the front portals have a nasty tendency to pump their oil out into the main axle. I've devised and tested a "fix" for this as described in the blog.
I've also been keeping an eye on the rear portals (they don't pump as they have a slightly different system), but it's a good idea to know what's happening back there in case an oil seal starts to leak. So far we've replaced one oil seal (front right) in Swakop as it started to seep and the rear left was replaced just before leaving UK.
I've picked up that a rear oil seal leak can be a harbinger of the bearing on that wheel starting to wear.....
Whilst at Elisenheim I heard of a German Unimog owner that we had met in Oppi-Koppi having been towed back in from Botswana in reverse due to one of his rear bearings packing up disastrously and of Merv from Ireland who is currently in South America having noticed a massive oil leak on one rear portal to find (just in time it seems) that one of his rear bearings was shot and had taken a gear with it.
As a result I drained the oil out of both rear portals and looked very closely at the magnetic drain plugs. What I found on the right hand side was no surprise - a black paste forming a mushroom on the magnet - gear wear particles, nothing to be worried about. However, the left side had the same particles plus two or three tiny shiny flakes - these I reckon are the first signs of bearing wear, so it'll need to be replaced.
OK, so it seems that I've caught the problem before it bites, but it's always in my mind while driving, so how to keep an eye on it?
Solution (at least one possible solution): to monitor the temperature of the portals as if a bearing starts to fail, it should generate more and more heat as things get worse. It's highly unlikely that both sides would go at the same time, so if I monitor both sides and watch for discrepancies, it should (could) give me some warning, allowing us to slow down, stop, or limp to somewhere safe.
I've given a lot of thought to how to do this and have decided to install a temperature sensor on each portal with some form of gauge in the cab allowing me to monitor not only the actual temperatures of each side, but also the difference.
Initially I thought of using thermocouples linked to a microlight aircraft Cylinder Head Temperature gauge as seen below.
So why would I want one of these? What is one of these?.....
The Mog's strength is also it's weakness - each axle has a gearbox on the end which transfers the power downwards through a pair of gears. These gears are known as the "portals" and run in a small casing which has a small amount of oil for lubrication. These effectively "lift" the axles above where they would normally be on standard vehicles (ie the centre of the wheels), giving massive ground clearance.
BUT - the portals take all the power and weight of the truck and due to their design are pretty heavily loaded. As a result they do sometimes fail.
During the trip so far (to Windhoek), I've been checking on the oil levels in the front axles every day that we have travelled as the front portals have a nasty tendency to pump their oil out into the main axle. I've devised and tested a "fix" for this as described in the blog.
I've also been keeping an eye on the rear portals (they don't pump as they have a slightly different system), but it's a good idea to know what's happening back there in case an oil seal starts to leak. So far we've replaced one oil seal (front right) in Swakop as it started to seep and the rear left was replaced just before leaving UK.
I've picked up that a rear oil seal leak can be a harbinger of the bearing on that wheel starting to wear.....
Whilst at Elisenheim I heard of a German Unimog owner that we had met in Oppi-Koppi having been towed back in from Botswana in reverse due to one of his rear bearings packing up disastrously and of Merv from Ireland who is currently in South America having noticed a massive oil leak on one rear portal to find (just in time it seems) that one of his rear bearings was shot and had taken a gear with it.
As a result I drained the oil out of both rear portals and looked very closely at the magnetic drain plugs. What I found on the right hand side was no surprise - a black paste forming a mushroom on the magnet - gear wear particles, nothing to be worried about. However, the left side had the same particles plus two or three tiny shiny flakes - these I reckon are the first signs of bearing wear, so it'll need to be replaced.
OK, so it seems that I've caught the problem before it bites, but it's always in my mind while driving, so how to keep an eye on it?
Solution (at least one possible solution): to monitor the temperature of the portals as if a bearing starts to fail, it should generate more and more heat as things get worse. It's highly unlikely that both sides would go at the same time, so if I monitor both sides and watch for discrepancies, it should (could) give me some warning, allowing us to slow down, stop, or limp to somewhere safe.
I've given a lot of thought to how to do this and have decided to install a temperature sensor on each portal with some form of gauge in the cab allowing me to monitor not only the actual temperatures of each side, but also the difference.
Initially I thought of using thermocouples linked to a microlight aircraft Cylinder Head Temperature gauge as seen below.
However, these gauges are only available in "high temperature" varieties and wouldn't be of much use for our purposes and thermocouples aren't too good with long cable lengths. So the hunt continued, with me looking at various possibilities until I came across the "Arduino" - basically a credit card sized computer onto which all sorts of sensors and outputs can be attached - including some "one-wire" digital temperature sensors (that are effective over 100m from the computer) and LCD displays. When I looked at the price of these I was amazed - £13 for the computer - £3 for the sensors, £4 for an LCD. So bought some and started playing.
There's lots of resources on the internet for these things, with lessons suggetsing that you start by making an LED blink, then go through a whole host of other exercises before being "proficient2 in programming them.
I did the LED-thing, then decided to just crack on - using code published by other people who have done something "similar", I manged last night to get something working - it shows the right and left temperatures on the lower line of the screen along with the difference between the temperatures on the upper line. It monitors this difference and when it is greater than a set amount it switches on an output which will operate a flashing LED and/or a buzzer to attract attention.
At the moment it's all "breadboarded" together (connected up on the bench with bits of wire), but it works well and has been working now for 24 hours. I'm now sourcing some more sensors that are encapsulated in stainless steel so they can be fitted to the portals and am looking at a larger screen so that I could monitor the front portals too if I wish.
If anyone is interested in how this goes together and/or the code that I've used to programme it, let me know and I'll be pleased to help.
I'll update this page with more information as the project progresses and as I get photos that are worth posting.
21 Dec 2012 update:
OK, so I've now got some pictures.
In the 1st photo you can see all the hardware used except the voltage dropper which hasn't arrived yet - there's the Arduino, the LCD and on the right hand side of the breadboard you can just make out the sensors I'm currently using (looking like 2 transistors).
The screen shows what can be done simply - there will be an external flashing LED as an alarm for either over temp or a large difference in temps. I may also be able to get the text to flash during an alarm.
There's also a photo of the new large screen showing the increased size - I reckon it should be possible to get all 4 portal temps on this clearly and still have room for another 2 if I can figure out how to measure 6 temps at the sams time.
Then the new sensors are in the last photo - they're neatly packaged in a closed stainless tube - all I've got to do is to work out how to mount them - I've got some 14mm ring terminals on their way to me now so I can play around with them.
There's lots of resources on the internet for these things, with lessons suggetsing that you start by making an LED blink, then go through a whole host of other exercises before being "proficient2 in programming them.
I did the LED-thing, then decided to just crack on - using code published by other people who have done something "similar", I manged last night to get something working - it shows the right and left temperatures on the lower line of the screen along with the difference between the temperatures on the upper line. It monitors this difference and when it is greater than a set amount it switches on an output which will operate a flashing LED and/or a buzzer to attract attention.
At the moment it's all "breadboarded" together (connected up on the bench with bits of wire), but it works well and has been working now for 24 hours. I'm now sourcing some more sensors that are encapsulated in stainless steel so they can be fitted to the portals and am looking at a larger screen so that I could monitor the front portals too if I wish.
If anyone is interested in how this goes together and/or the code that I've used to programme it, let me know and I'll be pleased to help.
I'll update this page with more information as the project progresses and as I get photos that are worth posting.
21 Dec 2012 update:
OK, so I've now got some pictures.
In the 1st photo you can see all the hardware used except the voltage dropper which hasn't arrived yet - there's the Arduino, the LCD and on the right hand side of the breadboard you can just make out the sensors I'm currently using (looking like 2 transistors).
The screen shows what can be done simply - there will be an external flashing LED as an alarm for either over temp or a large difference in temps. I may also be able to get the text to flash during an alarm.
There's also a photo of the new large screen showing the increased size - I reckon it should be possible to get all 4 portal temps on this clearly and still have room for another 2 if I can figure out how to measure 6 temps at the sams time.
Then the new sensors are in the last photo - they're neatly packaged in a closed stainless tube - all I've got to do is to work out how to mount them - I've got some 14mm ring terminals on their way to me now so I can play around with them.
Note that the 2-off DS18X20 will be on flying leads in the final version
I've moved the code to a separate page - there is now the "original code" that I used to measure 2 sensors and display the results on a 16x2 LCD and the latest code that I'm using to monitor 4 sensors, display them on a 20x4 LCD and incorporate alarms for high temperature differentials and high absolute temperatures. Click here for the page.
24 Dec 2012 update:
The code is now updated to make all alarms functional (ie either axle has a temp difference between each side greater than X OR any axle has a temp greater than Y results in an alarm. X & Y are easily programmable) plus all 6 thermometers are now functional (ie readings from all 4 portals plus cab & outside temps). This code is on the page liked to above. Note that all thermometers (DS18X20s) are connected to the same points on the circuit (+5v, ground, data) - this will make the final wiring much easier as there will effectively only be 5 wires exiting the system:
+24v
vehicle ground
sensor +5v
sensor ground
sensor data
The last 3 wires will split to each sensor.
I've been asked what screens I've been using here - the small one is a QC1602A, the large one is a 20x4 LCD Module 9mm Character Height (HD44780 Controller)
1 Jan 2013 update:
I've been looking at some small(ish) colour LCD screens that might make the display better still (and smaller). I might buy one just to play around with it for a while.......
I've moved the code to a separate page - there is now the "original code" that I used to measure 2 sensors and display the results on a 16x2 LCD and the latest code that I'm using to monitor 4 sensors, display them on a 20x4 LCD and incorporate alarms for high temperature differentials and high absolute temperatures. Click here for the page.
24 Dec 2012 update:
The code is now updated to make all alarms functional (ie either axle has a temp difference between each side greater than X OR any axle has a temp greater than Y results in an alarm. X & Y are easily programmable) plus all 6 thermometers are now functional (ie readings from all 4 portals plus cab & outside temps). This code is on the page liked to above. Note that all thermometers (DS18X20s) are connected to the same points on the circuit (+5v, ground, data) - this will make the final wiring much easier as there will effectively only be 5 wires exiting the system:
+24v
vehicle ground
sensor +5v
sensor ground
sensor data
The last 3 wires will split to each sensor.
I've been asked what screens I've been using here - the small one is a QC1602A, the large one is a 20x4 LCD Module 9mm Character Height (HD44780 Controller)
1 Jan 2013 update:
I've been looking at some small(ish) colour LCD screens that might make the display better still (and smaller). I might buy one just to play around with it for a while.......
Dec 2013 update:
I built a colour screen version that gives the temp not only of all 4 portals, but also the outside and inside air temps, the differences between each portal on an axle and changes colour from blue to red when either a temp is exceeded on a portal or one portal gets much hotter than the other on the same axle.
This has been tested on this years trip from Namibia to Tanzania and proved itself invaluable in that a quick glance at the colours on the screen tell you everything you need to know!
The hardware used is as follows:
Arduino Mega 2560
Screen : 3.2" SSD1289 TFT LCD Display Touch Screen With MicroSD : http://www.sainsmart.com/arduino/arduino-shields/lcd-shields/sainsmart-3-2-tft-lcd-display-touch-panel-pcb-adapter-sd-slot-for-arduino-2560.html
"Shield" : TFT LCD Adjustable Shield for Arduino Mega 2560 R3 1280 A082 Plug : http://www.sainsmart.com/arduino/arduino-shields/lcd-shields/sainsmart-tft-lcd-adjustable-shield-for-arduino-mega-2560-r3-1280-a082-plug.html
6-off DS18B20 sensors (waterproof)
It's quite simple: connect the Arduino to the shield, then the screen to the shield (they form a stack).
Wire from GND on the Arduino to black on the sensors (they are all in parallel)
Pin 8 on the Arduino to yellow on the sensors
5v on the shield to red on the sensors
A 4.7k resistor is placed between red and yellow on the sensors (just the one as they're all in parallel) - I used a small chocolate block to achieve this without more soldering onto boards.
You'll need to apply power to the Arduino - either via the input jack or as I did by soldering onto the 2 solder pads beneath the jack and putting about 9v on them via a small voltage dropper.
All of the above is easily (and cheaply) sourced on ebay....
Each of the sensors needs it's address verified (instructions for this are on the "Code for the Arduino" page as will be the code for this new colour gauge (shortly as I don't have too much time at the moment....)
I built a colour screen version that gives the temp not only of all 4 portals, but also the outside and inside air temps, the differences between each portal on an axle and changes colour from blue to red when either a temp is exceeded on a portal or one portal gets much hotter than the other on the same axle.
This has been tested on this years trip from Namibia to Tanzania and proved itself invaluable in that a quick glance at the colours on the screen tell you everything you need to know!
The hardware used is as follows:
Arduino Mega 2560
Screen : 3.2" SSD1289 TFT LCD Display Touch Screen With MicroSD : http://www.sainsmart.com/arduino/arduino-shields/lcd-shields/sainsmart-3-2-tft-lcd-display-touch-panel-pcb-adapter-sd-slot-for-arduino-2560.html
"Shield" : TFT LCD Adjustable Shield for Arduino Mega 2560 R3 1280 A082 Plug : http://www.sainsmart.com/arduino/arduino-shields/lcd-shields/sainsmart-tft-lcd-adjustable-shield-for-arduino-mega-2560-r3-1280-a082-plug.html
6-off DS18B20 sensors (waterproof)
It's quite simple: connect the Arduino to the shield, then the screen to the shield (they form a stack).
Wire from GND on the Arduino to black on the sensors (they are all in parallel)
Pin 8 on the Arduino to yellow on the sensors
5v on the shield to red on the sensors
A 4.7k resistor is placed between red and yellow on the sensors (just the one as they're all in parallel) - I used a small chocolate block to achieve this without more soldering onto boards.
You'll need to apply power to the Arduino - either via the input jack or as I did by soldering onto the 2 solder pads beneath the jack and putting about 9v on them via a small voltage dropper.
All of the above is easily (and cheaply) sourced on ebay....
Each of the sensors needs it's address verified (instructions for this are on the "Code for the Arduino" page as will be the code for this new colour gauge (shortly as I don't have too much time at the moment....)