DIY Hardness testing. Part 1 of 2

Everybody with a home workshop needs a hardness tester. My motivation was to measure the hardness of motorcycle cylinder heads. This video series shows how to make and use two such testers. Both very simple but accurate. One is mechanical only and the other uses some simple electronics and an Arduino. This part 1 shows the mechanical aspects of this very simple device and part 2 deals with the electronics and part 2 deals with the electronics. Here is part 2: • Hardness Testing part ...
Video is not the best format in which to present some information so I wrote a companion PDF file which can be viewed and/or downloaded from here: s3-us-west-1.amazonaws.com/hm... this also gives a permanent record to keep.

[@MotoChassisByTonyFoale]

Video is not the best format in which to present some information so I wrote a companion PDF file which can be viewed and/or downloaded from here: s3-us-west-1.amazonaws.com/hmt-forum/tony_foale_hardness_tester.pdf this also gives a permanent record to keep. Also there is additional information available here: www.homemadetools.net/forum/everyone-needs-hardness-tester-83780#post175021

[@noforkGTS]

Fantastic work, Tony. Thank you for sharing with the rest of us mere mortals!

[@TheKnacklersWorkshop]

Hi Tony, This is really interesting and I think it would be a great addition to any workshop as so many don't actually know that level of hardness they are working with... I am off to watch part two now.... Take care. Paul,,

[@KravchenkoAudioPerth]

Very clearly presented Tony. Thank you for sharing.

[@maxlemesurier]

Excellent! Thank You!

[@AutoBeta2T]

Very interesting - many thanks for sharing :)

[@compassprecision]

Very informative. Thanks for sharing and I’ve subscribed! :)

[@vladi_g]

It was possible to use only one optocoupler. Calculate the shading time of the ball of this optocoupler. The first time during the fall, the second time during the rebound.

[@MotoChassisByTonyFoale]

It is possible but it would be less precise. Optocoupler are so cheap that saving one is not a consideration.

[@pinklightfever]

Thanks for the upload. Do you have any data on what a suitable hardness for a used (but not overheated) aluminium cylinder head might be?

[@NicolaSartoriVomiero]

So, making the ratio from incidence and rebound speed is a ratio bitween cinetic energies (taking the measurement really closed to the impact point makes drag losses irrelevants) . It's like if you are calculating the efficiency of the material in not absorbing energy. If I understand it right perfectly rigid material will have a ratio=1...and a jelly material a ratio=0. Is it correct?

[@MotoChassisByTonyFoale]

I have already answered this same question for you on LinkedIn. The energy ratio is not the same as the velocity ratio, it is the square of the velocity ratio. A ratio of 1 is infinitely hard material, a ratio of 0 means very little but could be considered to signify zero hardness or "dead" material like sand. What does zero hardness mean? Zero hardness will not stop the ball, which will continue accelerating and go straight through. So the concept of zero hardness is a nonsense.

[@NicolaSartoriVomiero]

Another solution could be using an ultrasound (car parking) sensor on the top of the tube. There are sensors with 0.5m of range really cheap and easy to use.

[@MotoChassisByTonyFoale]

Yes the price is right, the range is plenty but you have not mentioned resolution nor accuracy. I suggest that you think about the wavelength of the ultrasound.

[@NicolaSartoriVomiero]

@@MotoChassisByTonyFoale Yes, true.

[@markrainford1219]

Or a microphone to start timing on first impact, and stop on second impact. Which on your opening scene I thought you had done.

[@MotoChassisByTonyFoale]

There is only one impact of interest.

[@NicolaSartoriVomiero]

Thinking again in what I wrote, I think a ratio = 1 is impossible to obtain because of the "softness" of the ball. For materials harder than the testing ball the results will be not trustable.

[@MotoChassisByTonyFoale]

Yes a ratio of one is infinite hardness and such material has yet to be found. As long as measurements are repeatable and consistent they can be trusted. The ball characteristics are part of the whole system response but that is no reason not to trust the results. Consider a tennis ball, very soft. Drop it on concrete and it bounces high, drop it on dirt and it bounces less. Then you have a tennis ball hardness scale. As I pointed out hardness is a number dependent on your testing machine.

[@4623620]

👌 BMW 👍

[@MotoChassisByTonyFoale]

Some years ago I gave the after dinner speech at the airheads annual convention and the coat was my punishment.

[@4623620]

@@MotoChassisByTonyFoale I have ridden an R60/6 motorcycle for over thirty years (never had an other motorcycle).

[@MotoChassisByTonyFoale]

@@4623620 I got my first, an R60, around 60 years ago. Here is a link to the last special one that I built motochassis.com/wp-content/uploads/2018/06/Milan2.jpg More here motochassis.com/photos/My%20QL/