High Pressure Tube Plugs
- pyronaught
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Re: High Pressure Tube Plugs
Here's a video showing the RC blimp in it's current state. I'm going to modify this same blimp to use the pressurized tubes for the next version.
https://www.youtube.com/watch?v=zIQ9Crb ... oXccpORKLA
https://www.youtube.com/watch?v=zIQ9Crb ... oXccpORKLA
Experience is what you get when you didn't get what you wanted.
Re: High Pressure Tube Plugs
Well, that was sort of my point. The drones (that is, the quad copter type) aren't violating FAA rules, either, but the FAA is getting freaked out by them, or at least is being pressured by people who are getting freaked out by them.if they ever rammed through some of those draconian "drone" rules being proposed
Re: High Pressure Tube Plugs
Cool video. How much lift does that thing generate?
Re: High Pressure Tube Plugs
yeah that is cool. i does really look like its tricky to fly. looks like it cools down real quick and wants to come down. seems like you have to start heating way before it begins coming down. something i guess you just gotta get a feel for.
- pyronaught
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Re: High Pressure Tube Plugs
Lift is a variable that depends on the outside temperature, the temperature inside the blimp, altitude and air density. I designed it using a relatively conservative value of 13 pounds lift per 1000 cubic feet of volume at 200F inside the blimp and 80F outside at sea level. Since it is a 4000 cubic foot blimp, that makes it around 52 pounds of gross lift under those conditions. The total weight on the fully fueled blimp is 52.6 pounds though, so you have to fly it hotter than 200F to get it off the ground on a hot morning. The max temp before damaging the fabric is 250F.Tim wrote:Cool video. How much lift does that thing generate?
Experience is what you get when you didn't get what you wanted.
Re: High Pressure Tube Plugs
wow yeah your right there then close to max temp. i assume you would have some type of temp feedback to the remote or a temp cut off so you dont get it too hot. so where do the tubes comes into play on this thing? its part of the structure or just an air chamber?
- pyronaught
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Re: High Pressure Tube Plugs
jimc wrote:yeah that is cool. i does really look like its tricky to fly. looks like it cools down real quick and wants to come down. seems like you have to start heating way before it begins coming down. something i guess you just gotta get a feel for.
It is indeed tricky to fly because it does cool fast. It cools even faster than a normal hot air balloon due to its small size ( higher surface area to volume ratio) and the fact that air from the outside must be continually pumped in via ducted fans in order to both replenish the oxygen that is being consumed by the burners and also maintain envelope pressure. This means internal air is being forced out and thus losing heat that way. The air being forced out is at the bottom and contains a bunch of CO2 from the combustion of propane, so it needs to be drained out anyway or the burners would cease to operate. In a hot air balloon the CO2 just drops out the open hole at the mouth since they are not fully enclosed the way a blimp is.
I didn't really build this to fly it for fun, so I never fly it. The purpose was to trial and error my way through the problems of building hot air blimps at a much smaller scale where the cost of failure is much less. I actually had to build three different blimps before finally getting the design nailed down. But yeah, buoyancy control is tricky due to the slow response time and you do in fact have to burn before it starts coming down. What makes it even trickier is that if you are flying forward then you get "false lift" from the nose being pitched up, then when you stop the false lift goes away and you are left with much less lift and it drops out of the sky. I never really got the hang of it, even though I've flown real balloons and they have similar slow response times. I think the low altitude and faster cool-off times makes the blimp more challenging than a real balloon. If I were going to fly these all the time I would have to add a sort of "cruise control" for buoyancy that measured the internal temp and burned when necessary automatically to keep it there. I don't know that I would ever fly it enough to be worth the development time for something like that though. You can only launch it on absolutely zero ground wind mornings or evenings, which is a pretty limiting thing. If it ever got away from you due to wind then you'd have about $2000 in materials and a big fire hazard flying off to God knows where.
Last edited by pyronaught on Sat Dec 27, 2014 6:42 am, edited 1 time in total.
Experience is what you get when you didn't get what you wanted.
- pyronaught
- Posts: 684
- Joined: Mon Dec 01, 2014 8:24 pm
Re: High Pressure Tube Plugs
The aluminum tubing in the perimeter of the fin will be replaced with a network of air tubes to keep it rigid. The aluminum tubing works fine for a small model like this but does not scale to full size, whereas the pressure tubes scale very well. The full size fins are giant too so they must be able to deflate and pack away, whereas my current aluminum tube fins just stay assembled and detach via zippers when the blimp is packed away. So they are a pain to store even at this small size.jimc wrote:wow yeah your right there then close to max temp. i assume you would have some type of temp feedback to the remote or a temp cut off so you dont get it too hot. so where do the tubes comes into play on this thing? its part of the structure or just an air chamber?
There will also be a pressure tube running from nose to tail at each seam, making 12 altogether. This stiffens the nose and reduces envelope sag, making up for the inherently low pressure inside thermal blimps. Full size thermal blimps can't take a head wind much more than 12MPH before the nose caves in.
It actually takes 720 feet total of tubing to do the RC model. Full size is over 2000 feet of tubing! So the next problem is how to fill and deflate all these tubes as fast as possible.
Experience is what you get when you didn't get what you wanted.
- pyronaught
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- Joined: Mon Dec 01, 2014 8:24 pm
Re: High Pressure Tube Plugs
My 3D printed Turbo Inflator fills that tube seen in the top picture in just 9 seconds. Ooooh Yeeeeah!
Experience is what you get when you didn't get what you wanted.
Re: High Pressure Tube Plugs
thats pretty quick for a little hand held unit. i have 2 of those here for filling stuff like air mattresses and kids stuff. its nowhere near that fast.