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Vertical climbing tank/rover

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Old 06-16-2003, 02:44 PM
  #1  
Ralph E Boy
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Default Vertical climbing tank/rover

As an arborist, I have a need for a vertical climbing vehicle to pull a fine line up to a desired height in a tree (over a particular limb), then descend back down. Naturally, I would then tie my climb line on the fine line and pull it through. My prospective vehicle is a small tank weighing .37 lbs (before I lighten it). My prospective engine & prop is a cox black widow .049 coupled to a 5"x 3.5 pitch 3-blade prop. If known, will this combo produce suffient thrust to press my tank onto the tree, or will the little .049 have the power to adequately turn the prop? I've not figured in the engine weight or fuel since I've not acquired any of this equipment yet. I am not an avid RC'er and would appreciate any advice on whether this is indeed a feasible endeavor. Torque twist is another consideration which I do not forsee being much of a problem since the tank tracks shuld by all rights maintain sufficient traction, IF the thrust is appropriate. Again, any advice would be most appreciated... I like doing things the right way the first time... especially since time IS money...

Cordially, Ralph E Boy (treemendous1@webtv.net)
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Old 06-16-2003, 02:52 PM
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Default Vertical climbing tank/rover

This is one of the most interesting questions I've seen here! First of all, how do you expect a tank to climb vertically? And tell us how the propeller is supposed to help. Do you have some kind of helicopter in mind?

It sure seems to me that climbing is the easier way to go.

Tom
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Old 06-16-2003, 04:04 PM
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Default Vertical climbing tank/rover

Tom:
First of all, climbing smaller trees (1'-2' in diameter) is indeed the more efficient means of getting to a nice "tie-in" point. BUT when trees get considerably larger, just getting to your intended destination can certainly get a person fatigued, as well as waste unnecessary time. As far as how the tank is supposed to climb vertically, please excuse me for not elaborating. The engine would be mounted on top of the tank/rover and would incorporate a pusher prop, thereby pressing the vehicle onto whatever surface and at whatever angle it may encounter. Technically, with enough thrust it should be able to climb walls and ceilings. The determining factors are of course thrust vs. weight vs. traction when climbing vertically. When inverted, I'm not sure how much traction would be a factor. If you can give me a ballpark on how much thrust the little .049 coupled with the 5" x 3.5 pitch tri-prop might produce (if in fact it will turn it at all) I would appreciate it. Something tells me I'll probaby have to go with a much larger/expensive engine, but I hope not (wishful thinking, eh?). Thanks for your reply, Tom. Any future advice, positive or negative, would be most appreciated. Basic rationale tells me this concept should by all rights work, unless there's some type of physics I'm overlooking.
Cordially, Ralph Ivey
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Old 06-16-2003, 04:36 PM
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Default Vertical climbing tank/rover

Ain't gonna work

First, an .049 won't have enough power.

Second, there IS a type of physics you're overlooking.

You are assuming that this thig is going to go whichever way you point it.

What about prop torque?

ok, forget the torque, have you ever been driving down the freeway and let go of the steering wheel? Did the car keep going exactly straight?

When going vertical this is amplified, once it goes SLIGHTLY to either side, gravity will keep pulling it to that side until it is coming straight down (at you with a spinning propeller!).

And I won't even MENTION what an uneven surface Tree Bark is!
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Old 06-16-2003, 04:38 PM
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Default Vertical climbing tank/rover

Ralph, This sounds like it would be really cool when you get it working. Unfortunately, I don't know how much thrust you'd get from one of them small motors. I'm sure it would be something less than one pound.

Have you thought about training a small monkey to run up the tree for you? They don't eat much and you could play with him while you work!

Tom
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Old 06-16-2003, 05:23 PM
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Ralph E Boy
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Mike:
Mucho thanx for your reply. As I say, did NOT think the .049 would produce enough thrust. But as far as prop torque goes, was hoping with aggressively spiked tracks and ample thrust to keep that sucker PASTED to the tree, perhaps I could continuously counter the prop torque with steering input. Naturally, it would be a bit of a chore to keep going in the right direction, but with a lttle practice & maybe a tail rotor or some other means of vectoring a counter thrust, I believe I may be aqble to pull it off. Are you telling me this concept is impossible? It may difficult to counter the prop torque, but other than that, with somewhere around 1.5 - 2 lbs of thrust my little 5"x2.5" 3/4 lb tank should stick like glue to any tree (I hope!) Incidentally, there will be a shroud around the prop with lightweight screen mesh on the intake & probably the exhaust. Also I was thinking that little training wheels mounted to the very outside of the shroud might be useful in deep grooved bark. The question is... how big of an engine will be required to be used in conjunction with the prop I'd like to use to develop my desired thrust? Is there a formula?
Cordially, Ralph Ivey
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Old 06-16-2003, 07:11 PM
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Default Vertical climbing tank/rover

This is a very interesting concept to say the least. Another problem that may come into play on this project though might be engine cooling. Typically a pusher set-up on an airplane relies on airspeed to cool the engine as prop wash is going the other way.
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Old 06-16-2003, 07:37 PM
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Default Vertical climbing tank/rover

Just so I understand the concept...

The little tank is going to 'walk' up the tree past a certain level, then walk past the next sizable branch and then back down. Effectivley allowing you to hoist your climbing rope over the same branch and then asscend to that level... does that sound about right? Actually as soon as the little tank is above the said branch the engine could be shut down and it could be lowered back to the ground by its tether. right?

You might think about a slightly larger CL engine... just let it go full throttle the whole way... lighter/simpler carb

I think this would be doable... given a light enough 'tank' ... I would think that four driven wheels made from 4.5" circular saw blades would walk relatively well up the bark and be big enough to navigate the rough bark...

How long a climbing durration are we talking about? (will affect batter pack size, fuel tank size, etc.

Ok... juices are flowing now...
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Old 06-16-2003, 07:52 PM
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EXACTLY what crossed my mind! However, since there will indeed be air moving past the engine (albeit the opposite direction), there will be a bit of a cooling effect, tho probably/certainly not as much. BUT since the extent of operation should never exceed 5 minutes (depending on height/structure of the tree, etc), hopefully overheating will not be an issue. Mucho thanx for your input. Before I go ordering anything at all, I've gotta find out roughly (exactly?) what engine should be used in conjunction w/my 5" x 3.5 pitch tri-prop
to deliver maximum thrust. Not being an avid RC'er, I'm fairly ignorant on engines/power & rpm. But being fairly educated in airboat specs concerning prop length, pitch & rpm, I DO know that after a certain rpm, the efficiency/thrust decreases. If anyone out there can tell me what the perfect engine for this specified prop might be and what it's approximate thrust might be, I WILL begin rolling the dice soon. (Only one way to find out, eh?... or is there already someone out there who's tried this?)
Cordially, Ralph Ivey
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Old 06-16-2003, 08:26 PM
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Default Vertical climbing tank rover

Daver...
... you got it! Only prob w/going to four wheel/blade drive vs. tracks is how to steer? With tracks I could, if necessary, silicone tacks of some sort for additional clearance & traction. Naturally, Dave, there are a variety of devices which will shoot a tiny lead filled "shot bag" thru the desired area. BUT overshooting/undershooting, getting thru dense foliage has always been a problem wth these type of devises. Having been a climber since 18 (now 44), I've always dreamed/fantasized of being able to simply "drive" my line to my desired destination and back down. As far as cutting power and simply lowering the vehicle via it's own weight, yes, this would work in many but not all trees. Some are so densly congested you can't even see thru them unless you're right next to the base - even then sometimes NOT! This unit would only apply to certain trees, but the majority of them, yes. Any further input would be most appreciated.
Mucho thanx to all... Cordially, Ralph Ivey
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Old 06-17-2003, 01:47 AM
  #11  
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Default Vertical climbing tank/rover

Hate to throw cold water on this, but I too doubt you'll ever get it to work. I really don't like being the guy that says, "It'll never work", because I also believe there's a solution to every problem but....

A 5X3.5 prop is about the right size for an .049 engine, but the .049 will NOT provide sufficient thrust to hold the tank against the tree and give it the necessary traction. In order to get that type of thrust, I'd guess you'd need more like a bearing type .40 or .46 at least. Then you're looking at props in the 9" to 11" diameter range. (Maybe an 8X7", 3 blade prop.) But now you'll never get something this size up a tree, "so densly congested you can't see through them."

I actually doubt this would climb a smooth concrete wall very well (if at all). You're relying on prop thrust to push something horizontally with enough force to overcome gravity AND provide traction. You'll also need to consider the prop trying to "suck" air from around the vehicle.

At the very least, the engine would have to have some degree of "down thrust" to overcome gravity.

Wish I was a physicist. I'm sure there's mathmatical theory that would give a better indication of the possiblity.
Dennis-
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Old 06-17-2003, 05:43 AM
  #12  
Ralph E Boy
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DBCherry...
I sincerely appreciate your time in responding to my rather unusual endeavor. Being the rookie RC'er that I am, I was wonderng if by chance I'd have to go the next step of utilizing a 4-prop, 9" x 6 pitch pusher. If by chance you can tell me what size engine I might require and what thrust I can expect (roughly), it would be most appreciated. Price (within reason) is really no object. Naturally, I'll have to go with a larger tank/rover unit to accommodate the larger prop/engine, & possibly a gyro to boot (?). But if it can be done, I CAN DO IT!!! (with you pro's help, of course). OOPS!!!... just looked at the Tower Hobbies APC 9x6P 4-blade prop (stock# LX1634) and find it is a tractor rather than a pusher prop. Any help in finding what I'm looking for would certainly be appreciated (wearing out that word, eh?) I am NOT a "giver-upper" and will overcome this obstacle (I hope!). Incidentally, tho some trees are indeed grossly congested, my prospective unit can simply NOT be used on such. But then there are the grand old wide-open oaks (5'-10'+ at the base) which my little concept could earn its weight in diamonds/platinum (almost). As I say, I've fantasized about such a unit over the years, and uh, as we speak... well, I'm getting a bit turned on and gotta go (yukyuk)... ANY input from ANYONE on overcoming my obvious physics problems will be appreciated!!!!!... & rewarded!!!

Cordially, Ralph E Boy in need of knowledge!
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Old 06-17-2003, 06:07 AM
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To all concerned...

Unbeknownst to me what the overall weight of my prospective vehicle/crawler might be, since "more is better" (tho increased prop thrust vs. prop torque is a factor with "more"), can someone give me a figure (engine & prop specs) to produce 4-5 lbs of thrust. To counter the prop torque, I WILL deal with it! All I want is engine size/make & prop specs (must be pusher type!) There WILL be a $10.00 (big deal, eh?) reward for accurate info...

... I need help before I waste too much $
... Cordially, Ralph E Boy
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Old 06-17-2003, 09:09 AM
  #14  
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Default Vertical climbing tank/rover

A 30 size with a 9x4 will give you 5lb of thrust.
Vibration might impact on traction, another thing to think about.

I think a crossbow will save you a lot of time, money and brain drain.
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Old 06-17-2003, 01:52 PM
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Default Vertical climbing tank/rover

Don't forget that you will be needing (I'm no physicist either, but I'll venture a guess) 3 of your 5lbs of thrust to hold it against the tree. And the extra friction involved will undoubtedly increase its weight in the form of drag.
If it weighs 5lbs, I'm thinking you'll need at least 8lbs of thrust just to keep it glued to the tree without rising. so 10 -15lbs to make it advance. (and don't forget to add the weight of the engine at 10 - 15- lbs of thrust, you're talking about a big engine!)
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Old 06-17-2003, 02:16 PM
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Sounds like an atomic fly swatter to me. There has GOT to be a better way.
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Old 06-17-2003, 02:39 PM
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Ditto
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Old 06-18-2003, 01:42 AM
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If it weighs 5lbs, I'm thinking you'll need at least 8lbs of thrust just to keep it glued to the tree without rising. so 10 -15lbs to make it advance. (and don't forget to add the weight of the engine at 10 - 15- lbs of thrust, you're talking about a big engine!)
Thanks Minnflyer.
This is where I was headed when I said .40 to .46 intsead of .049 for a .37 pound vehicle.

We've all heard, and used the "TLAR" principle (That Looks About Right) with RC planes. Well, my mind just won't come up with anything TLAR for this project.

Honestly Ralph, I'd like to see you suceed with this, beacause I've never seen nor heard of anything like it. But you mentioned wasting too much money, and I think everything you throw at this will be "wasted". EXCEPT, for the fun you'll have trying and learning!

My best for your success!
Dennis-

Oh, by the way, I've never seen a 4 blade pusher prop, not sure there is such a beast.
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Old 06-18-2003, 03:08 AM
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"$10 reward for accurate info?"

Here ya go: "Ain't gonna work!" A Cox .049 won't hardly get out of its own dust. I just can't imagine this concept working although I am no physicist. I think if you get enough power on it to get it running up the tree, sooner or later its gonna turn around and chase you out of the forest.

But good luck nevertheless, and let us know how it goes.

Clair
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Old 06-18-2003, 06:07 AM
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Default Vertical climbing tank/rover

Not an engineer, but a biologist - so here's my proof of concept for what its worth.

Take a flat wood plate. Put a motor mount on it, tank, throttle servo, engine, protective cage. Weigh this.

Put the pusher prop on it and figure out how to start it (can't finger flip with the cage on it). Put it against a wall and watch it fall off and break. It'll probably counter-rotate as it falls off.

Now, if you're a glutton for punishment, put some wheels on the plate and see if it sticks any better. I'm thinking extending the prop away from the wall will actually cause a longer angle moment and cause it to topple off backwards.

Simply put, there is no suction to hold it to the tree, pressure will cause it to drift off to one side or the other. As an example of this, try balancing a ruler on a can. If you can, then tap the table and watch it fall off to the side.

This isn't a Monster Garage project, but I've always been the kind to try something before I get deep into the dollars. Might even be able to take one of your boat engines and use it.
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Old 06-18-2003, 02:49 PM
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Simply put, there is no suction to hold it to the tree
Which is why I said you'd at least need some degree of down thrust Ralph.

Actually, it's easier for me to "see" Steve's "flat plate with engine" trying (and failing) to hold itself against the wall. To me "THAT looks about right." (The falling off the wall part. )
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Old 06-18-2003, 04:28 PM
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Alright, so newton's law will most likely prevail here. But before I throw in the towel, can anyone tell me how much thrust and at what rpm my 5" x 3.5 pitch tri-prop will deliver? Or will I have to contact the manufacturer for an accurate answer? Is there a larger pusher prop out there? (by the way, the quad prop 9 incher I spoke of earlier is NOT a pusher - my mistake)
Also, since I'm so uneducated in this field, how much does a .40 - .46 engine weigh with 5-7 minutes of fuel? I've not given up yet!!! I may have to resort to forking out the $1000 or so it costs for one of them airscoots. For those unfamiliar, go to airscooter.com to see the first counter rotating fixed blade helicopter that anyone with half a brain can fly. Pretty cool unit!!! Anyhow, as always, mucho thanx for everyone's input, and if any of my questions can be answered, I could use the help - & lots of it, eh?
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Old 06-18-2003, 10:38 PM
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A .40 - .46 engine w/muffler is around 16-17 oz.
5 to 7 mins. @ full throttle will probably need about 8 oz. of fuel.
I agree with the others that you most likely won't get the needed amount of thrust with a 5x3.5 three blade, you'll need more prop for a .40 - .46 engine.
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Old 06-19-2003, 01:21 AM
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you most likely won't get the needed amount of thrust with a 5x3.5 three blade
I would NOT use this small a prop on a .40 size engine. The engine will over - rev and most likely cook itself to an early demise.

5X3.5 IS the correct size for the .049 originally discussed, but NOT for these larger engines. (Therefore, I can't give you a thrust guess with this prop.)

Just so you know Ralph, "thrust" is not a number, or factor, that's used very often in RC flight. We usually talk in RPM, HP, and "torque" curves. Some folks have played around with these engines pulling against a scale of some type, but I'm not one of them. Sorry.
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Old 06-19-2003, 11:01 PM
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Originally posted by: DBCherry

I would NOT use this small a prop on a .40 size engine. The engine will over - rev and most likely cook itself to an early demise.
I don't believe anyone told him to use the 5x3.5 prop on a .40 nor did Ralph E Boy say he would.
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