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Would some amazing person be able to help with some Physics I need help with??


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Now before you think, Why am I doing this kids homework?

Well your not :D 

I am a Engineer and am struggling to work out the golden number for the Thermal Expansion, TWR and Thermal Irradiation (More Chemistry) of my Jet engine! 

I am making a Drone, with a Jet engine, a RAMJET in specific, I have made four versions of the DIY engine and all of them melted or gave massive TWR that it bent a steel frame, I worked it out and the engine on the frame has a TWR of about 23.67, but my maths crap, and yes that's alot for a drone made from a DIY engine. 

I need help.

Any takers? :D 

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I dont think Ive got the maths to help you - but a ramjet powered drone? Interesting!

How are you going to get the drone up to ramjet speeds? How are you testing a stationary ramjet? You built a ramjet that can bend a steel frame?! Impressive!

How are you going to maintain remote control over a drone that will be going, like, SUPER fast?

Is this thing even going to be legal?

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Sounds impressive for sure!

If someone should help you with the numbers, you need to provide a lot more details though. For instance, to get the thermal expansion one needs all the expansion coefficients of all the materials used, as well as their shapes and masses, exact temps and delta temps etc. And to calculate how much heat is generated and lost to the exhaust must be very hard too. I think you'd need a very good test article equipped with sensors to get approximations of some numbers at best.

 

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38 minutes ago, KenjiKrafts said:

I am making a Drone, with a Jet engine, a RAMJET in specific, I have made four versions of the DIY engine and all of them melted or gave massive TWR that it bent a steel frame, I worked it out and the engine on the frame has a TWR of about 23.67, but my maths crap, and yes that's alot for a drone made from a DIY engine. 

I need help.

No, you need a smaller engine or a bigger drone :P

May sound flippant, but this is clearly a case of grossly mismatching parts to a vehicle. What you're doing, in KSP terms, is mounting a Mainsail on a Minmus lander. If your engine was 1/10th as powerful as it is now, it would still be too strong.

How are you testing your ramjet, by the way? Catapult? Airdrop? Electric turbine?

 

Edited by Streetwind
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15 minutes ago, Streetwind said:

No, you need a smaller engine or a bigger drone :P

Well the drone is 10th of the scale of a real UAV, I could always go with a heavier material :D 

17 minutes ago, Streetwind said:

How are you testing your ramjet, by the way? Catapult? Airdrop? Electric turbine?

Well, its currently mounted on a static steel frame that's been used to test my other engines, we are not ready for the "Kinetic Tests" yet as this issue comes up, the main concern at this time is that during a moving test we can't control it to well*, however we will be doing standard take offs as the tests, although that sounds silly, we need to know the basic reactions of a drone, if it can't take off on its own then we have failed. *The pilot is still learning as we are making a new interface designed to function with the critical systems in the drone. Examples are camera, thermometer, mach counter, and speedometer as well as a idea called sector sensing, this idea is that we can detect data influxes and anomalies, so for instance the nozzle has reached a critical temp state, we are able to tell during flight what damage has and exactly where. 

24 minutes ago, Streetwind said:

May sound flippant, but this is clearly a case of grossly mismatching parts to a vehicle.

Don't be silly, if I didn't expect negative feedback I wouldn't have asked the internet :D 

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25 minutes ago, Streetwind said:

No, you need a smaller engine or a bigger drone :P

May sound flippant, but this is clearly a case of grossly mismatching parts to a vehicle. What you're doing, in KSP terms, is mounting a Mainsail on a Minmus lander. If your engine was 1/10th as powerful as it is now, it would still be too strong.

How are you testing your ramjet, by the way? Catapult? Airdrop? Electric turbine?

 

Yes, but on the contrary, MOAR BOOSTERS!

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56 minutes ago, p1t1o said:

I dont think Ive got the maths to help you - but a ramjet powered drone? Interesting!

How are you going to get the drone up to ramjet speeds? How are you testing a stationary ramjet? You built a ramjet that can bend a steel frame?! Impressive!

How are you going to maintain remote control over a drone that will be going, like, SUPER fast?

Is this thing even going to be legal?

First and foremost, Yes its legal. (As far as I know in the UK)

Second, Super fast is a indeed a issue, To put this simple, we are making a custom control interface that allows it to be controlled by a PC, you will need a flight stick, but this is far away yet and for the now we plan to use a standard RC Controller :P 

The fact it bends steel is horrible yet fun to watch :D 

44 minutes ago, Dafni said:

Sounds impressive for sure!

If someone should help you with the numbers, you need to provide a lot more details though. For instance, to get the thermal expansion one needs all the expansion coefficients of all the materials used, as well as their shapes and masses, exact temps and delta temps etc. And to calculate how much heat is generated and lost to the exhaust must be very hard too. I think you'd need a very good test article equipped with sensors to get approximations of some numbers at best.

 

It is quite cool but not yet impressive as I wish :wink: 

Well the engine has been treated to a nice coat of heat paint, and to be honest it's not the best paint but hey-ho.

If you refer to my response of Streetwind's comment, you'll see the method we've devised :D 

 

11 minutes ago, peadar1987 said:

Yes, but on the contrary, MOAR BOOSTERS!

I like it :P 

But i guess it doesn't need more TWR :P 

Edited by KenjiKrafts
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7 minutes ago, KenjiKrafts said:

Well, its currently mounted on a static steel frame that's been used to test my other engines (...)

Ummm... please forgive my confusion, but how does that work? o_O A ramjet doesn't develop any thrust at standstill. It needs air to be moving through it at at least a significant fraction of the speed of sound for anything to happen at all. That's why I asked in the first place, because it struck me as such an unusual engine type for a hobby project, even for an enthusiast. I wondered what kind of rig you have to make it ignite. At bare minimum you must be using an ancillary turbine to force air into it, right?

By the way, if you have pictures of a burn, I'd love to see them. :)

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11 minutes ago, Streetwind said:

Ummm... please forgive my confusion, but how does that work? o_O A ramjet doesn't develop any thrust at standstill

Sorry, mb, we do use a airflow at 200+ PSI. Should have explained huh? :blush: 

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1 hour ago, KenjiKrafts said:

... and for the now we plan to use a standard RC Controller :P 

Um. Eeek?

The range on those things is not too large, and with that engine it could go out of range in seconds - far too quickly for a pilot still learning the ropes to be able to turn it round and keep it in range. You will need a high-end RC controller to improve range, and be sure there is a safety cutout so the damn thing shuts off quickly in the event of signal loss. I assume you thought about this, but still, I felt the need to express my concern!

Another point is that the relevant laws tend to use phrasing like "recklessly endanger persons or property". In the event of somebody not liking what you are doing, it could be argued in a court of law that flying an RC vehicle with that sort of engine is reckless endangerment, wherever you fly it and no matter how good your control. Beating a rap like that would be time consuming and expensive, and not in any way certain. Frankly, there are no places in the UK where you are sufficiently far from "property" (which includes livestock, crops, etc) that somebody won't consider flying that thing to be "reckless endangerment".

How are you planning to land it? Normal RC aircraft engines don't get hot enough to start fires, but this one will. It's going to be pretty limiting waiting until you actually get a soaking-wet weekend, the way the weather has been the last few years!

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2 hours ago, KenjiKrafts said:

First and foremost, Yes its legal. (As far as I know in the UK)

If you are below 20kg max tow and your rc controller stays within the limits of frequencies (list is publicly available) and transmission power (depending on frequency between 10 and 100mW me thinks) then you are legal. If you stick your nose over 500 feet above the ground you are about to make step towards jail if endangering other traffic. Interfering with air traffic or abusing frequencies are no legal peanuts as you might not know whom you disturb in the vicinity.

So, if you didn't know before, now you do.

Nothing personal :-), I only post this to avoid further legal limitations to all the serious rc model makers, which is the case after the incidents we had and still have.

Edti: as you ask the internet, may i suggest to ask people from an rc model makers clubs who have an own little airfield and fly models with jet engines ? They might have solutions for your questions, including the technical ones, though most model engines are real turbines.

Edited by Green Baron
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40 minutes ago, softweir said:

*snip*

Normal RC aircraft engines don't get hot enough to start fires, but this one will. It's going to be pretty limiting waiting until you actually get a soaking-wet weekend, the way the weather has been the last few years!

Piston engines don't, jet engines are likely to do. It's advisable to fly them on e registered model airfield and since many them are above 20kg they need some registration and maybe even a clearance anyway.

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1 hour ago, softweir said:

How are you planning to land it? Normal RC aircraft engines don't get hot enough to start fires, but this one will. It's going to be pretty limiting waiting until you actually get a soaking-wet weekend, the way the weather has been the last few years!

Yes the weather in the UK is horrible all year round :P 

The engine has two coolant systems, a "Passive" coolant system that cases the engine in coolant, bringing the temp down, failing that we have made a solution, "Active Flooding" this floods the engine with coolant, snuffing out the engine, and rapidly cooling the engine, with this method we have cooled the engine from 700 degrees to roughly 80-100 degrees Celsius.

1 hour ago, softweir said:

You will need a high-end RC controller to improve range, and be sure there is a safety cutout so the damn thing shuts off quickly in the event of signal loss. I assume you thought about this, but still, I felt the need to express my concern!

 We have both of those, actually ones just been explained! The Controller is custom Gold Certificate Jet controller, I say custom as we had it upgraded in nearly every way! Even a custom name! :D 

3 hours ago, TheKorbinger said:

Have you tried adjusting the thrust levels of your vehicle? That could help if you reduced the engines thrust a bit.

Yes. To plainly put it we can adjust the fuel to air ratio for "Cleaner" combustion, the thing is that unclean combustion can/does give nasty fumes.  

1 hour ago, Green Baron said:

If you are below 20kg max tow and your rc controller stays within the limits of frequencies (list is publicly available) and transmission power (depending on frequency between 10 and 100mW me thinks) then you are legal. If you stick your nose over 500 feet above the ground you are about to make step towards jail if endangering other traffic. Interfering with air traffic or abusing frequencies are no legal peanuts as you might not know whom you disturb in the vicinity.

So, if you didn't know before, now you do.

Thanks!

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4 hours ago, KenjiKrafts said:

we plan to use a standard RC Controller

2 hours ago, softweir said:

Um. Eeek?

The range on those things is not too large

Using the FM band, you can get some pretty impressive range. One guy had an rc plane flying from Canada (IIRC), across the atlantic, towards England (or was it Ireland?) where a 2nd crew took over and landed the plane. Video to be found on the web.

 

Edited by LN400
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7 hours ago, Green Baron said:

If you stick your nose over 500 feet above the ground you are about to make step towards jail if endangering other traffic. Interfering with air traffic or abusing frequencies are no legal peanuts as you might not know whom you disturb in the vicinity.

I did a quick Google search because I was sceptical about the 500 ft value. Aviation regulations tend to be harmonized as much as possible across the developed world by international agreement, and the US and Canada recently reduced the ceiling for operating a drone to 400 feet (120 metres).

It turns out that the UK has also followed suit. They also restrict drones to operate below 400 feet, they must remain more than 500 feet away from built up areas and crowds (and may not overfly those areas), and they must remain within unaided visual sight (i.e. no FPV) of the pilot at all times.

I think, in general, the authorities will look the other way when it comes to enforcing these kinds of rules, unless you tick off the wrong person that is... And the likelihood of doing that probably increases with the speed/noise of your aircraft.

Edited by PakledHostage
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6 hours ago, PakledHostage said:

I think, in general, the authorities will look the other way when it comes to enforcing these kinds of rules, unless you tick off the wrong person that is... And the likelihood of doing that probably increases with the speed/noise of your aircraft.

If you combine altitude, long range or even ultra long range and restricted airspace you can hardly avoid entering restricted airspace unless your drone is professional grade with all the sensors and telemetry and the pilot has the necessary certifications and have all the aviation charts at hand. You can fully expect the gates of hell to open and all bad things coming after you if your drone causes an incident, like interfering with full size aircrafts or it crashes into something it REALLY shouldn't have crashed into.

Edited by LN400
tidying up
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19 minutes ago, LN400 said:

If you combine altitude, long range or even ultra long range and restricted airspace you can hardly avoid entering restricted airspace unless your drone is professional grade with all the sensors and telemetry, the pilot has the necessary certifications and have all the aviation charts at hand, and you can fully expect the gates of hell to open and all bad things coming after you if your drone causes an incident, like interfering with full size aircrafts or crahses into something it REALLY shouldn't have crashed into.

That much is obvious and wasn't my point.

Perhaps I should have been more clear, but I was referring to the type of transgression that your typical hobbyist might do with his/her quad rotor: Maybe flying a bit further away or higher than they should while looking at a video downlink, etc, while otherwise staying out of trouble.

Flying too close to an airport, having a near miss with an aircraft, crashing in a crowd of people, etc will certainly and quite rightly get you busted.

Edited by PakledHostage
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1 minute ago, PakledHostage said:

That much is obvious and wasn't my point.

Perhaps I should have been more clear, but I was referring to the type of transgression that your typical hobbyist might do with his/her quad rotor: Maybe flying a bit further away or higher than they should while looking at a video downlink, etc, while otherwise staying out of trouble.

Flying too close to an airport, having a near miss with an aircraft, crashing in a crowd of people, etc will certainly and quite rightly get you busted.

Just thought I'd mention it since the depressing fact is quite a few, worldwide, do fly their drones in restricted airspace, causing problems for air traffic. With long range the risk increases.

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Just now, LN400 said:

Just thought I'd mention it since the depressing fact is quite a few, worldwide, do fly their drones in restricted airspace, causing problems for air traffic. With long range the risk increases.

I agree that a few [change in acceleration with respect to time]s do act selfishly and irresponsibly. I am glad that there are tough new rules in place to give the authorities "teeth" when dealing  with those people. 

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50 minutes ago, PakledHostage said:

I agree that a few [change in acceleration with respect to time]s do act selfishly and irresponsibly. I am glad that there are tough new rules in place to give the authorities "teeth" when dealing  with those people. 

And that is why i hope that OP will join others who fly similar things, who have a a small airfield, know the regulations, can help with constructive things,  and surely can help him with his "stove pipe" :-))

And i admire people who build and fly things in real world :-)

Edited by Green Baron
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8 hours ago, PakledHostage said:

I think, in general, the authorities will look the other way when it comes to enforcing these kinds of rules, unless you tick off the wrong person that is... And the likelihood of doing that probably increases with the speed/noise of your aircraft

I do question that statement, as the British Police Force is not all the best, I think it's a joke, you hit the nail on the head, however the CAA would prosecute.

That's going to be about 100+ mph and 105Db+

1 hour ago, LN400 said:

Just thought I'd mention it since the depressing fact is quite a few, worldwide, do fly their drones in restricted airspace, causing problems for air traffic. With long range the risk increases.

Sadly yes. Lazers are another way of disrupting air-traffic :/ 

(I just know I haven't been cautioned or arrested for it) :P 

Edited by KenjiKrafts
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On 5/10/2017 at 1:49 AM, KenjiKrafts said:

"Active Flooding" this floods the engine with coolant, snuffing out the engine, and rapidly cooling the engine, with this method we have cooled the engine from 700 degrees to roughly 80-100 degrees Celsius.

How about thermal stress caused by rapid contraction of the engine? Could cause structural problems unless this is used only in an emergency?

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5 hours ago, Atlas2342 said:

How about thermal stress caused by rapid contraction of the engine? Could cause structural problems unless this is used only in an emergency?

Yes this is the last resort, if we use this at max thrust you will most likely crack the metal :/

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