Hi all,
My name is Relja Novovic, I'm from Serbia (Europe/former Yugoslavia). This is my first post, though I've found this forum (and the bobistheoilguy.com site) a great source of good information. That's why I'm posting here, hoping to get more opinions, ideas and corrections. Apologies in advance for my Tarzan English and probably incorrect English technical terms. All suggestions and corrections are more than welcome.
If all goes well, before the end of this month, I'll get access to a lab testing machine of a local mechanics faculty. My goal is to test how various types of lubricants (greases, might do a test with oil, just for comparison) fare when used in bicycle bearings.
The presumptions, based on my previous experience and knowledge, but haven't found any tests (in books or on line) to scientifically confirm it, is that bicycle bearings don't take much load (compared to motorcycles, cars, not to mention heavier machinery) and that paying for any premium grease is not justified. That is what I want to test and compare if more expensive, higher quality greases make any measurable difference. With and without EP and other special additives. I also plan to test if filling the bearings 100% with grease, not leaving any gaps as is generally recommended, prolongs the life of bearings exposed to water and dirt, or harms them - or makes no measurable difference.
What I'll have at my disposal is a machine with controlled number of revolutions per minute and static load on the bearings. The machine has an axle, onto which a bearing can be screwed on. I will also be able to perform controlled impacts on the bearings (Charpy pendulum in English?).
My plan so far:
1. Using cartridge bearings, for easier mounting and lower price than cup and cone hubs. 6903 model.
2. Assuming an average wheel circumference is 2.1 meters (26" are smaller, even with wide tyres, 28" are a bit larger, but that's about middle ground).
3. Simulating 30 km/h speed for 90% of the test, with 10% at 100 km/h. With 2.1 meter wheel circumference, that's about 240 to 800 revolutions per minute.
4. Assuming one wheel carries 60 kg of weight, 30 kg per bearing. That load will be simulated, as constant.
5. Since rolling bearings that roll while loaded don't suffer measurable damage from road buzz, only impacts, I will disregard road buzz simulation. This will make the test less useful for the headset bearings, but good for all the others.
6. For impacts, simulating drop off a 20cm high kerb, with 50 kg load, 25 kg per bearing, without any damping from rim and tyre deflection, I'd test with 5 kilopond-meter impacts after every 12 hours of testing (about 50 Joules). My estimate is that's reasonably high impact, since off road bikes have wider tyres and suspension, and riders will usually use hands and elbows to absorb the shock. While road bikes don't get those impacts often (and they still have tyres, rims and riders to dampen the impact). 10 impacts after roughly every 12 hours of testing.
7. Assuming bearings are never submerged into water, but often sprayed with rain and dirt. A mixture of 1dl water, 1 spoon of sand and 1 spoon of soil will be poured over bearings after every 12 hours of testing.
8. Will degrease bearings in diesel, then "medical petrol" (is that the correct English term), then add tested lubricants.
9. Will do a test with 30% less lubricant than 100% full bearings, and compare that with 100% grease packed bearing. See which option fares better for this purpose, since bike bearings roll rather slowly.
10. Will use a fan to simulate air cooling, if there's measurable heat build up over 50 degrees Celsius. Will also use more stops for cooling down if required. Reduced speed as well (to 20 km/h average speed).
11. Wear measurement will be done by completely cleaning/degreasing a bearing and measuring it on a precise scale. Also, visual inspection for ball and race wear will be done at the end of testing.
12. I will do a first test on a 3000 km service interval. Then 5000 km. Then 8000 km. With 30 km/h estimated average speed, 5000 km will take about a week. If there's not much heat build up, I'm considering increasing the test speed to 60 km/h, and max speed to 120 km/h.
13. Assuming side loads are not relevant for lubricant performance comparison and the application, so will not bother with them (would have to improvise to achieve lateral loads).
Questions:
a) Are the estimates of loads and shocks realistic (strict) enough? Any better ideas on rain/dust/mud simulation?
b) Did I miss something?
Thanks in advance for any help.
My name is Relja Novovic, I'm from Serbia (Europe/former Yugoslavia). This is my first post, though I've found this forum (and the bobistheoilguy.com site) a great source of good information. That's why I'm posting here, hoping to get more opinions, ideas and corrections. Apologies in advance for my Tarzan English and probably incorrect English technical terms. All suggestions and corrections are more than welcome.
If all goes well, before the end of this month, I'll get access to a lab testing machine of a local mechanics faculty. My goal is to test how various types of lubricants (greases, might do a test with oil, just for comparison) fare when used in bicycle bearings.
The presumptions, based on my previous experience and knowledge, but haven't found any tests (in books or on line) to scientifically confirm it, is that bicycle bearings don't take much load (compared to motorcycles, cars, not to mention heavier machinery) and that paying for any premium grease is not justified. That is what I want to test and compare if more expensive, higher quality greases make any measurable difference. With and without EP and other special additives. I also plan to test if filling the bearings 100% with grease, not leaving any gaps as is generally recommended, prolongs the life of bearings exposed to water and dirt, or harms them - or makes no measurable difference.
What I'll have at my disposal is a machine with controlled number of revolutions per minute and static load on the bearings. The machine has an axle, onto which a bearing can be screwed on. I will also be able to perform controlled impacts on the bearings (Charpy pendulum in English?).
My plan so far:
1. Using cartridge bearings, for easier mounting and lower price than cup and cone hubs. 6903 model.
2. Assuming an average wheel circumference is 2.1 meters (26" are smaller, even with wide tyres, 28" are a bit larger, but that's about middle ground).
3. Simulating 30 km/h speed for 90% of the test, with 10% at 100 km/h. With 2.1 meter wheel circumference, that's about 240 to 800 revolutions per minute.
4. Assuming one wheel carries 60 kg of weight, 30 kg per bearing. That load will be simulated, as constant.
5. Since rolling bearings that roll while loaded don't suffer measurable damage from road buzz, only impacts, I will disregard road buzz simulation. This will make the test less useful for the headset bearings, but good for all the others.
6. For impacts, simulating drop off a 20cm high kerb, with 50 kg load, 25 kg per bearing, without any damping from rim and tyre deflection, I'd test with 5 kilopond-meter impacts after every 12 hours of testing (about 50 Joules). My estimate is that's reasonably high impact, since off road bikes have wider tyres and suspension, and riders will usually use hands and elbows to absorb the shock. While road bikes don't get those impacts often (and they still have tyres, rims and riders to dampen the impact). 10 impacts after roughly every 12 hours of testing.
7. Assuming bearings are never submerged into water, but often sprayed with rain and dirt. A mixture of 1dl water, 1 spoon of sand and 1 spoon of soil will be poured over bearings after every 12 hours of testing.
8. Will degrease bearings in diesel, then "medical petrol" (is that the correct English term), then add tested lubricants.
9. Will do a test with 30% less lubricant than 100% full bearings, and compare that with 100% grease packed bearing. See which option fares better for this purpose, since bike bearings roll rather slowly.
10. Will use a fan to simulate air cooling, if there's measurable heat build up over 50 degrees Celsius. Will also use more stops for cooling down if required. Reduced speed as well (to 20 km/h average speed).
11. Wear measurement will be done by completely cleaning/degreasing a bearing and measuring it on a precise scale. Also, visual inspection for ball and race wear will be done at the end of testing.
12. I will do a first test on a 3000 km service interval. Then 5000 km. Then 8000 km. With 30 km/h estimated average speed, 5000 km will take about a week. If there's not much heat build up, I'm considering increasing the test speed to 60 km/h, and max speed to 120 km/h.
13. Assuming side loads are not relevant for lubricant performance comparison and the application, so will not bother with them (would have to improvise to achieve lateral loads).
Questions:
a) Are the estimates of loads and shocks realistic (strict) enough? Any better ideas on rain/dust/mud simulation?
b) Did I miss something?
Thanks in advance for any help.
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