Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by FritzW, Apr 16, 2015.
I was referring to moving the wing aft.
Oops. BTW, on further thought, I suspect you'd only have to enlarge the tail with a large prop when moving the engine forward by itself, not along with the wing. Or when moving the wing back, of course. That's playing with fire unless you know the tail surfaces are overly large to start with. And the nose would still look longer.
G-BUCO is supposed to have a C-90 in it, which I suspect is comparable in weight to a geared VW. Looks pretty good, IMHO.
By Arpingstone - Own work, Public Domain, https://commons.wikimedia.org/w/index.php?curid=547944
I’d prefer more legroom!
It would change the looks of a Pietenpol, but not of a Highwing Volksplane.
Other then the Parasol and wood as building material concept, it doesn’t have much in common with a Pietenpol SkyScout.
But of course, it might be stretched to become a VolksCamper, as the base is the Volksplane with a Highwing, and enlightable by some construction details.
It's about 3 feet from the front seatback to the firewall already. How much legroom do you need, and won't you be flying from the back anyway? I suppose you could move both people forward a bit to make up for the light engine. How does one see where you're going when turning a Pietenpol? Doesn't the wing really get in the way?
If my legs are flat on the ground with my back on a wall, I would require 4‘ 3“, but as the legs are bent a bit I spoke that 3‘ 10“ would be about fine.
It’s not really a problem. You can still see plenty under the wing and beyond that it’s just important to pay attention during the times when you aren’t turning.
This is an interesting CNC machine (only $350) that might work for this project...
Ah, the dreaded Maslow scheme again.
I hate to use the word 'impossible' but cutting out something like a VP21-HWC with a Maslow would be impossible.
The slop in a Maslow creates an error that's easily 2 orders of magnitude too big to be able to cut something like this. You need to be within a few thousandths, with the Maslow your lucky to get within a few tenths.
The Maslow is a neat theory but completely impractical for this kind of work.
Even if this one goes with its precision into the world of a child, I’d like to build a cnc router out of wood.
The size I’d like to build my self is 8x4, so big enough to work on standard size sheets.
So far I haven’t found a gantry cnc router made out of wood, that is firm and sturdy enough, that looks like it could withstand solid wood working.
there is at least one professional built series of wooden cnc routers:
it doesn’t have to look this good, but the direction, as it looks really solid to me.
such a beast would for sure enhance the precision to build any kind of wooden airplanes even a Volksplane :gig:
I looked up the Maslow router. Very clever, but unless they've tightened it up since the other video I saw, not super accurate. Not enough for joinerwork, I think. Maybe someone really clever will figure out how to make it accurate. Maybe some kind of optical feedback?
This concept would allow the following seat configurations;
- sit on top
- sit in single seater
- sit in sbs two seater
- sit in tandem two seater
I could be a fan for either one!!!
The tandem and the sit on top are my favorites, if feasable.
The figuring out isn't so hard but the hardware to make it ridged will make it more expensive. Feedback servo rather than stepper would help.
I'm kind of surprised that no one has built a single arm router with software to convert G-code to polar coordinates. Such a hobby CNC would still have rigidity problems but would be super simple to build and compact to store.
No matter what you build you will want more accuracy in harder/stiffer materials. Wood routers can work for wood and light cuts in aluminum. 4x8' requires something other than ball screws for the 8' direction so it gets a little more tricky. Belts can work. There is nothing magic about building a CNC router out of wood. It is just limited by its stiffness. All of the bearings and linear rails are pretty cheap and available on ebay.
I think part of the point of feedback would be to reduce the required rigidity.
About the software, it might be too simple to bother using someone else's function library, but if not, perhaps this would help:
I don't know what people are doing about toolpaths, but this software might be good for that as well. Just do me a favor and don't pester him unless you're a little bit serious.
The problem with the Maslow isn't the rigidity of the frame, it's the flexibility of the cables the router is hanging on. The router can twist on the cables due to torque (no matter how many bricks you weigh it down with) also any deflection in those cables translates to error in the cut. "...you can't shoot pool with a piece of rope"
Optical Feedback!?!? C'mon fellas, you know better than that. The motors already know where they're at, they don't need, and wouldn't benefit from, a feedback loop.
Even if you had some sort of magic feedback system between the cutter and the stepper (or servo) it wouldn't help as long as there's a length of flexible cable between the feedback sender and feedback receiver. You can't send corrections back to the stepper/servo fast enough to make up for how incredibility slowly and unpredictably the flexible cable can handle those correction. You'd be trying to measure a fart with a micrometer.
You CAN make a CNC machine out of wood, PVC pipe and skateboard wheels that would be accurate enough for this kind of work but you CAN'T do it by hanging a router on two flexible cables. You can't do brain surgery with a marionette
...okay, I'm out of metaphors, I'll stop :gig:
But for the graphically minded among us:
Probably correct. :cry:
Add a third cable or compound CNC by putting one of these at the end of the cables.
Better off with one of those Shaper Origin handheld routers than a Maslow. At least it's portable and flexible.
Meanwhile an extrusion and v-wheel router is plenty good enough for wood and alum sheet, and those kits are relatively cheap. In fact you don't even really need a kit nowadays there's enough off-the-shelf parts and easy-to-emulate plans and designs out there that you just need to sketch out a few dimensions, guess at a few quantities, and put a few things into an online shopping cart. OpenBuilds has a lot of ready-fit assemblies and railings that could probably make the foundation for a serious little unit for cheap.
Trying to go super cheap with a machine that can cover a whole sheet of material is tough. I would say there's nothing out there worth the time that you could put together for less than $1000, and chances are the budget should look more like $2k.
To build one, figure $3-700 for the linear motion components, $1-200 for drive means (either ballscrews or belts or rack/pinion or some other system) $1-300 for random materials, $4-800 for electronics (assuming basic steppers and such, not bothering with servos here), and then routers/spindles cost anywhere from $50 to $400 once you add it all up. And then I didn't include the table/base which could be anywhere from some scrap wood to some nice LVL to a bunch of 80/20 or even a welded tube steel frame. (I've seen people make tables from granite and epoxy leveling compounds, so there's that.)
There's room for some clever guy to make it work but we've been playing with these things for years and nobody has come up with a reasonable way (so far) to handle the necessary forces with flexible cables. Using a polargraph to control a router dates back to, at least, the day after the first Ardiuno hit the market and probably goes back a century or two before that. ...you can make a hammer drive a screw but you'd just be making a f@^%ed up screw driver.
..remember when these were all the rage?
That's the "Magic Feedback System" I mentioned in post #157
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