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Screenshots & Videos / Re: Marvins Creations
« Last post by z26 on September 28, 2018, 06:18:33 pm »
just checked, and not always. a line of 5 continuums tied by long voltaic arcs, with one end fixed with a hook and the other end bent, then fixed with another hook keeps its tension if its hypercubed or if the game is saved.

I tried the same setup, but while also connecting the two extremities with a second line of continuums.  hypercubing or loading displaced the position of the second line.  the assembly was still under tension overall, but there no stress BETWEEN line one and line two.


I guess that the internal stress of a stucture is relieved, but not the stress that comes from external forces bending the structure.
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Screenshots & Videos / Re: Marvins Creations
« Last post by MarvinMan on September 28, 2018, 07:51:46 am »
Interesting idea. I've not come across any obvious mechanical integrity problems with the props I've been testing, but I assume offsetting the fins is beneficial because it counters some of the stretch in the arcs, letting them effectively move to their optimal position under load/at speed.

Can hypercubes be used for de-stressing any structure? For example a string of continuums bent into a loop being turned into a stable structure that won't spring back when broken.
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Screenshots & Videos / Re: Marvins Creations
« Last post by z26 on September 28, 2018, 02:21:33 am »
Thanks, its much clearer now.  I'll still need a bit of time to process the data, but I really like your test rigs :D

about the piston thing... I just did a reconfiguring continuum to test a concept and it seems to work (but only for anchored application because of phantom forces :( ).  Have two continuum each attached to to a solid attach point.  Then, attach both of these to a third part (can be a fin if you hack map files, must have at least two attach points otherwise) but do so in a way that the two arcs conflict with each other on what the position of the third part should be.  Now, by setting one of the continuums's mass to 0, you can weaken one of the connection and give near complete authority to another, thus changing the position of the third part.  This seems more rigid than pistons, but again phantom forces...

This might not be useful for prop planes, but there might be some applications nonetheless.


UPDATE: the technique itself seems useful, but a big problem is that when saving, any stress in the voltaic arcs is relieved, which stops anything from functioning.  My bigger worry is about how map files works: I'm not sure its possible to create a feature like that even using manual file editing.  Even just being swallowed by an hypercube then spit back cancels the effect
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Screenshots & Videos / Re: Marvins Creations
« Last post by MarvinMan on September 27, 2018, 09:24:16 pm »
I had noticed the graphs were broken when I uploaded them. I had hoped that google docs would make the spreadsheets more accessible than uploading them to dropbox.

When I started I wasn't particularly planning on publishing the data, so the labelling reflects my aversion to unnecessary typing. On the static results W is rotational speed of the prop, T is torque, and F is forward thrust (because T was already taken by torque). F/T gives a sort of measure of efficiency. On the second sheet, V is airspeed.

As torque and rotational speed are pretty constant at all airspeeds using variable pitch to control speed is probably better, but would need more work to characterise the pitch needed for peak thrust and zero thrust across the full speed range, especially if you did want to increase prop speed once in the air to take advantage of the improved airflow over the wings.

It appears that most of the energy input goes into just rotating the fins for no gain, so larger props allow more thrust/speed from a given rotational speed. The large props I tested using a cross piece as the hub were the best of the non-offset designs tested. Assuming it had enough thrust to get off the ground when retracted, a prop with pistons to increase its diameter might work well for efficient cruising or maximising top speed. I imagine such a design would make the handling of the plane awful, but it would be very fast.

Airspeed test rig.


Static thrust rig.
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Screenshots & Videos / Re: Marvins Creations
« Last post by z26 on September 27, 2018, 05:16:46 pm »
Nice analysis, a screenshot or two of your testing rig could be a nice addition.  Your graphs don't show anything on my end however.  I'm not quite sure on what the single letters mean, I assume v is velocity of plane, w is veloctiy of prop and t is thrust? what is f?

If I understand correctly, changing fin angle might be a better way to regulate speed than changing the rpm?  Also, what about prop diameter? is increasing that equivalent to increasing the prop speed while decreasing rigidity of the rotor?

Edit: about the graphs, they do show when I open with google sheets instead of looking at the previeew, every 0 cell show a divided by 0 error which is kinda ugly.  Not a major issue of course
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Screenshots & Videos / Re: Marvins Creations
« Last post by MarvinMan on September 26, 2018, 10:55:05 pm »
Propeller infodump

Propellers in Rawbots are weird. The high torque they require and their dependence on airspeed make them ideal for quadrotors, but very tricky for planes. I was looking for a better design to power my planes, so I've characterised several different configurations to try to find out what works best. I've put the results in a couple of spreadsheets.

Static results

The first set of tests were for static thrust against torque, measured by balancing the thrust against a jet. The offset elbow type is the one seen fitted to my propeller plane above, and turns out to be the best fixed-pitch design over much of the range tested. Logically, a faster spinning, lower pitch prop should require less torque to provide the same thrust, however this only appears to be accurate at the lowest power levels. In general, a 45 degree pitch works pretty well. For best performance, use the largest diameter prop you can, and offset the fins slightly, like the offset elbow design.

Airspeed


Optimising the pitch over a range of airspeeds is where things get really weird. With a fixed 45 degree pitch and constant torque, the rotational speed only changes by 12% from stationary to a forward speed of 70 while the trust decreases linearly. This suggests that most of the torque requirement goes into just spinning the prop. When the pitch is optimised at each speed, the thrust shows more of a 1/x decay with airspeed, enabling much higher aircraft speeds to be attained (to the point where the wheeled test platform used for these tests reached escape velocity). Interestingly, the rotational speed of the prop stays largely constant throughout the test. For most sensible speeds, the pitch can be mapped linearly to forward speed.

Overall, it's probably better to just use a lightweight fixed-pitch prop optimised for lower speeds, but higher pitches will be needed to go fast.
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General Discussion / Re: Is the development still being rebooted?
« Last post by z26 on July 09, 2018, 06:49:43 am »
Seems like Neil isn't joinable on facebook anymore
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General Discussion / Re: Is the development still being rebooted?
« Last post by cupid_the_conqueror on July 04, 2018, 07:51:22 am »
Don't trust anything any of the "devs" say. I've talked to them both too, and its clear they don't want to give us the truth. They offer lies and false hopes. Its unrealistic to expect anything to happen after a failed kickstarter, poor marketing, dev disappearance, website removal, investor vs studio lawsuit and not to mention a abused and mishandled fan base.

Hate to say it, but he's dead jim.
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Introductions / Re: Im back too!
« Last post by cupid_the_conqueror on July 04, 2018, 07:45:40 am »
Annoying that they didnt list this forum in the community section. But I guess there is nothing but bad publicity here due to  proof of dev incompetence
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General Discussion / Re: Is the development still being rebooted?
« Last post by MarvinMan on July 02, 2018, 08:46:36 am »
Welcome.

The only thing I've seen is this: https://rawbots.github.io/, although it doesn't exactly seem official. I think there was meant to be some sort of announcement months ago, but obviously nothing appeared.
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