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Software Tools / Re: Playing with Blender For Artists (Bforartists) - Easier way to learn Blender?
« Last post by vtsteam on Today at 09:00:09 PM »That bones concept is interesting. 
Recent Posts
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Project Logs / Re: Making a Prony Brake to Measure the Power of My Hot Air Engines
« Last post by vtsteam on Today at 06:56:14 PM »Further thoughts today:
I was thinking about drilling a new hole in the arm for the stylus to correct for the fact that 10 cm along the wooden arm is not the same thing as 10 cm along the moment arm to the point of contact on the scale.
But then I started thinking, as long as I'm drilling a new hole, can I also put it somewhere to eliominate some of the other math requirements, and simplify things that way?
Well, yes probably. So In the case of say 1000 RPM, 10 centimeters arm, and a reading of 3 grams, if I multiply speed times weight I get 3000 "pretend watts". But in reality if I do the proper math (RPM * Pi /30 * grams * arm length * .00009807 ) I get .3081 real watts.
Ignoring the decimal points for a moment that's 3081 real watts vs 3000 pretend watts, or a correction value of 3081/3000 = 1.027.
Or inverted, .974. So if I move the stylus location inboard to (10cm * .974) 9.74 cm that should apply just enough additional pressure on the scale to do the math for me.
Except I gotta remember to move the decimal point over to the left four places.
Oh yeah, I forgot also..... that 9.74 cm has to be the length of the diagonal from the center of rotation to the contact point on the scale.
Well we can figure that out also. The height of the stylus to the horizontal centerline of the brake drum is 4.1 cm.
The diagonal will be 9.74 cm. That's the hypotenuse of a right triangle. Therefore, its length squared equals the sum of the lengths of the other two sides squared. So 9.74 squared is 94.9, and 4.1 squared is 16.8. Subtracting: 94.9 - 16.8 is 78.1. Taking the square root of 78.1 we arrive at 8.84 cm. Or 88.4 mm. That should be the length along the brake arm to drill our new hole.
If we do that, and I have my figures right above, I can take a reading of RPM, and reading of the scale, multiply them together, and move the decimal point 4 places to the left, to yield an answer in proper watts.
Nice thing about that also... the closer distance now than my original 10 cm will put less braking force on the engine, and make it easier to start. All good: less math, bigger number, less stress!
Check me if I'm wrong guys, etc.......
Thanks!
I was thinking about drilling a new hole in the arm for the stylus to correct for the fact that 10 cm along the wooden arm is not the same thing as 10 cm along the moment arm to the point of contact on the scale.
But then I started thinking, as long as I'm drilling a new hole, can I also put it somewhere to eliominate some of the other math requirements, and simplify things that way?
Well, yes probably. So In the case of say 1000 RPM, 10 centimeters arm, and a reading of 3 grams, if I multiply speed times weight I get 3000 "pretend watts". But in reality if I do the proper math (RPM * Pi /30 * grams * arm length * .00009807 ) I get .3081 real watts.
Ignoring the decimal points for a moment that's 3081 real watts vs 3000 pretend watts, or a correction value of 3081/3000 = 1.027.
Or inverted, .974. So if I move the stylus location inboard to (10cm * .974) 9.74 cm that should apply just enough additional pressure on the scale to do the math for me.
Except I gotta remember to move the decimal point over to the left four places.
Oh yeah, I forgot also..... that 9.74 cm has to be the length of the diagonal from the center of rotation to the contact point on the scale.
Well we can figure that out also. The height of the stylus to the horizontal centerline of the brake drum is 4.1 cm.
The diagonal will be 9.74 cm. That's the hypotenuse of a right triangle. Therefore, its length squared equals the sum of the lengths of the other two sides squared. So 9.74 squared is 94.9, and 4.1 squared is 16.8. Subtracting: 94.9 - 16.8 is 78.1. Taking the square root of 78.1 we arrive at 8.84 cm. Or 88.4 mm. That should be the length along the brake arm to drill our new hole.
If we do that, and I have my figures right above, I can take a reading of RPM, and reading of the scale, multiply them together, and move the decimal point 4 places to the left, to yield an answer in proper watts.
Nice thing about that also... the closer distance now than my original 10 cm will put less braking force on the engine, and make it easier to start. All good: less math, bigger number, less stress!
Check me if I'm wrong guys, etc.......
Thanks!
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Software Tools / Re: Playing with Blender For Artists (Bforartists) - Easier way to learn Blender?
« Last post by sorveltaja on Today at 03:05:04 PM »I tried to install Nvidia drivers for Puppy, but no luck yet, so I'll leave it aside for now.
To get back to the topic, I thought to mention some of the keyboard shortcuts I use most.
To move an object, shortcut is (G) (for grab I guess). If that object needs to be moved along certain axis, key sequence G + X, Y or Z is used. Also, amount of transform can be added: G Z 100.
Same applies for scaling (S) S X 100 and rotation (R) R Y 90.
Another way is to use transform gizmo:
Show add new object menu . . ..Shift A
Select all objects in the scene .. .A
Zoom to selected object(s) ....Numpad , (Del)
Toggle shaded/wireframe .... ...Shift Z
Switch between object and edit mode ...Tab
Duplicate object(s) ...........Shift D
Move duplicated objects along axis .. .....Shift D + X, Y or Z
In edit mode:
Vertices .......... ..1
Edges ............... 2
Faces ............ 3
Select vertex/edge/face loop. ......Alt click
Select vertex/edge/face ring ....Alt Ctrl click
Select more........................................Ctrl +
Select less..........................................Ctrl -
Shortcuts are customizable, and in Blender there can be different keys for similar actions in several editors it has, so it has a lot of options available.
What comes to simulating objects, so far I've been using rigid bodies; some mechanisms seem to be easier than others. Seemingly simple one is centrifugal governor. It gives wild results where parts fly around.
There is another way to link objects to form a mechanism, though. It uses bones, which are widely used in character animation. It may give more predictable results, once I learn how to use it.
To get back to the topic, I thought to mention some of the keyboard shortcuts I use most.
To move an object, shortcut is (G) (for grab I guess). If that object needs to be moved along certain axis, key sequence G + X, Y or Z is used. Also, amount of transform can be added: G Z 100.
Same applies for scaling (S) S X 100 and rotation (R) R Y 90.
Another way is to use transform gizmo:
Show add new object menu . . ..Shift A
Select all objects in the scene .. .A
Zoom to selected object(s) ....Numpad , (Del)
Toggle shaded/wireframe .... ...Shift Z
Switch between object and edit mode ...Tab
Duplicate object(s) ...........Shift D
Move duplicated objects along axis .. .....Shift D + X, Y or Z
In edit mode:
Vertices .......... ..1
Edges ............... 2
Faces ............ 3
Select vertex/edge/face loop. ......Alt click
Select vertex/edge/face ring ....Alt Ctrl click
Select more........................................Ctrl +
Select less..........................................Ctrl -
Shortcuts are customizable, and in Blender there can be different keys for similar actions in several editors it has, so it has a lot of options available.
What comes to simulating objects, so far I've been using rigid bodies; some mechanisms seem to be easier than others. Seemingly simple one is centrifugal governor. It gives wild results where parts fly around.
There is another way to link objects to form a mechanism, though. It uses bones, which are widely used in character animation. It may give more predictable results, once I learn how to use it.
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Project Logs / Re: Making a Prony Brake to Measure the Power of My Hot Air Engines
« Last post by vtsteam on Today at 09:31:17 AM »Hi CB thanks! I suspect fractional watt in its present form, without pressurization, snifter, etc. But we'll see once I have it working properly and a good procedure.
Problems off the bat:
The moment arm is wrong. It's not 10 cm. I thought of this this morning. It's really the length of the diagonal from the center of the drum to the point of contact on the scale. My bad!
Too much friction to start the engine. This can be reduced, and will also reduce naturally by breaking in. Also need lighter springs.
The scale shuts itself off after a period automatically save batteries. Then if you hit ON again while the engine is running it tares itself at whatever the pressure plus stylus weight is. If you turn on while stylus is lifted, you can't tare the stylus weight.
I think the solution here is to weigh while the engine is stationary, and make up an indexing weight to equal that amount. Then if the scale turns off during a run, lift the stylus, add the indexing weight, and turn on the scale. Once it tares, remove the weight and lower the stylus.
Finally the math: I thought that by going w/ metric grams, 10 cm, watts etc. it would be simple multiplication and possibly moving decimal points, but it's not. Newtons isn't grams by a conversion factor and RPM needs to be converted to radians per second to get watts, so math is just about as complicated as good old imperial to figure.
No problem however for a spreadsheet formula, which I've made up this morning, so on with the show!
Problems off the bat:
The moment arm is wrong. It's not 10 cm. I thought of this this morning. It's really the length of the diagonal from the center of the drum to the point of contact on the scale. My bad!
Too much friction to start the engine. This can be reduced, and will also reduce naturally by breaking in. Also need lighter springs.
The scale shuts itself off after a period automatically save batteries. Then if you hit ON again while the engine is running it tares itself at whatever the pressure plus stylus weight is. If you turn on while stylus is lifted, you can't tare the stylus weight.
I think the solution here is to weigh while the engine is stationary, and make up an indexing weight to equal that amount. Then if the scale turns off during a run, lift the stylus, add the indexing weight, and turn on the scale. Once it tares, remove the weight and lower the stylus.
Finally the math: I thought that by going w/ metric grams, 10 cm, watts etc. it would be simple multiplication and possibly moving decimal points, but it's not. Newtons isn't grams by a conversion factor and RPM needs to be converted to radians per second to get watts, so math is just about as complicated as good old imperial to figure.
No problem however for a spreadsheet formula, which I've made up this morning, so on with the show!
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Project Logs / Re: Making a Prony Brake to Measure the Power of My Hot Air Engines
« Last post by Country Bubba on Today at 08:18:29 AM »Nice job, and am looking forward to seeing just how much power one of these engines puts out. Have always wondered, but have never seen any results.
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Software Tools / Re: Playing with Blender For Artists (Bforartists) - Easier way to learn Blender?
« Last post by vtsteam on May 23, 2025, 10:17:22 PM »I forget how to do Nvidia drivers in Puppy, but the Puppy Linux forum is extremely helpful for that kind of thing. Just ask and somebody will almost certainly help. Specify that you are using BookwormPup64 and your hardware.
https://www.forum.puppylinux.com/
https://www.forum.puppylinux.com/
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Project Logs / Re: Making a Prony Brake to Measure the Power of My Hot Air Engines
« Last post by vtsteam on May 23, 2025, 08:41:48 PM »I drilled and tapped the brake arm to accept the stylus at a distance of 10 centimeters from the center of the brake drum, then secured it in place with two nuts. The height of the brake arm is therefore adjustable, and should be set level. A 10 cm moment arm means that every gram registered on the digital scale will be approximately ten times the newton-meters of torque absorbed by the brake. So grams divided by 10 is ~ Newton-meters. From that, and RPM, Watts can be easily calculated.
With this work done, the Prony brake was operable, though I'm not finished. But I couldn't resist setting it up temporarily and trying it out!
I was disappointyed when at first the engine wouldn't start at all with the brake just sitting, applying no pressure to the drum. And for the first 15 minutes the engine ran I could hardly even touch the drum without nearly stopping the motor. But eventually the engine seemed to loosen up and gradually increase speed to the point where I could attach the brake arm...but without the adjustment springs... just letting the parts run together.
This brake definitely needs to be run in -- it needs more of that. But eventually this evening I was able to adjust the thumbscrews (without springs) for very slight pressure, and get the engine to run at reduced speed, registering a torque reading on the digital scale. I was gratified to see it was a reasonable stable digital reading, probably helped by the inertia of the brass stylus, which, unlike the other parts does not weigh on the drum.
Here's a picture of the first run. I do need to do a little more work to get easier and more consistent readings, to work out a measurement procedure, and to finish it off, but I'm very happy that it works quite well already!
With this work done, the Prony brake was operable, though I'm not finished. But I couldn't resist setting it up temporarily and trying it out!
I was disappointyed when at first the engine wouldn't start at all with the brake just sitting, applying no pressure to the drum. And for the first 15 minutes the engine ran I could hardly even touch the drum without nearly stopping the motor. But eventually the engine seemed to loosen up and gradually increase speed to the point where I could attach the brake arm...but without the adjustment springs... just letting the parts run together.
This brake definitely needs to be run in -- it needs more of that. But eventually this evening I was able to adjust the thumbscrews (without springs) for very slight pressure, and get the engine to run at reduced speed, registering a torque reading on the digital scale. I was gratified to see it was a reasonable stable digital reading, probably helped by the inertia of the brass stylus, which, unlike the other parts does not weigh on the drum.
Here's a picture of the first run. I do need to do a little more work to get easier and more consistent readings, to work out a measurement procedure, and to finish it off, but I'm very happy that it works quite well already!
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Project Logs / Re: Making a Prony Brake to Measure the Power of My Hot Air Engines
« Last post by vtsteam on May 23, 2025, 08:20:21 PM »I cut the stylus to length, and rounded the end. Here it is finished:
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Project Logs / Re: Making a Prony Brake to Measure the Power of My Hot Air Engines
« Last post by vtsteam on May 23, 2025, 07:53:59 PM »And thinking I'd break out my never before used tailstock die holder, ran into problem number two. Despite the fact that it had many different die holder recesses and attachments, it wouldn't accept a plain 1" hex sided die -- which was what I had for cutting a 6-32 thread. Rats! I should have made one myself instead of buying one to... ahem, save time.
Well, the ER collet holder to the rescue again, I started the threads in the lathe by holding a die handle and then transferred the collet holder block to the bench vise and turned the threads the rest of the way.
Well, the ER collet holder to the rescue again, I started the threads in the lathe by holding a die handle and then transferred the collet holder block to the bench vise and turned the threads the rest of the way.
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Project Logs / Re: Making a Prony Brake to Measure the Power of My Hot Air Engines
« Last post by vtsteam on May 23, 2025, 07:48:24 PM »Today I started on the stylus that will transmit the force of the brake arm to the digital scale I'll be using. I started with a piece of brass 3/16" and immediately ran into the problem that my 4 jaw chuck won't hold anything that small. That's a feature among others that bothers me about that chuck. Nevertheless I worked around it by taking my square ER collet holder, and clamping that in the 4 jaw. Kind of overkill for a piece this small, but it beats having to change chucks. Funny to see an ER chuck, in a 4 jaw chuck, mounted on a faceplate, but that's what got the job done today. I thinned the brass down to .134" for threading 6-32.
