Almost Anything Goes

speytime

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Yes I think they make some cracking photos.
I'd been at the quarry and was on my way home, it's was a hassle to get my phone out for a photo but the sunset that evening was worth it.

Al
 

speytime

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My son wanted one for his 10th birthday, he's left the nest a few years ago and I got left with him, he's got character, something I didn't associate with reptiles.

@flyfisher222 is there a huge difference between the gas turbine and a piston engine?

A
 

flyfisher222

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View attachment 25447View attachment 25449
My son wanted one for his 10th birthday, he's left the nest a few years ago and I got left with him, he's got character, something I didn't associate with reptiles.

@flyfisher222 is there a huge difference between the gas turbine and a piston engine?

A
My wife would be terrified of that. Where can I get one? :)

Yes, piston engines and turbines are not related at all. A model turbine is just the same as a full-size jet engine but much smaller and like the full size run on paraffin and have a built in electric starter. There's a one litre fuel tank between the air intakes which lasts about eight minutes at full throttle but you only use that for take off and if you want to go straight up so in use it lasts much longer. and there's an alarm on the radio transmitter that beeps when it's getting low.

The engine is British, the radio control is German, and the compressed air operated retractable undercarriage, which works from a small metal tank you pump up with a bicycle pump, is American.
I made the toy plane itself from a kit from Vietnam,. For some unknown reason they make a lot of kits there. It's balsa and plywood. I've been building toy planes since I was about ten years old.
 

speytime

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My wife would be terrified of that. Where can I get one? :)

Yes, piston engines and turbines are not related at all. A model turbine is just the same as a full-size jet engine but much smaller and like the full size run on paraffin and have a built in electric starter. There's a one litre fuel tank between the air intakes which lasts about eight minutes at full throttle but you only use that for take off and if you want to go straight up so in use it lasts much longer. and there's an alarm on the radio transmitter that beeps when it's getting low.

The engine is British, the radio control is German, and the compressed air operated retractable undercarriage, which works from a small metal tank you pump up with a bicycle pump, is American.
I made the toy plane itself from a kit from Vietnam,. For some unknown reason they make a lot of kits there. It's balsa and plywood. I've been building toy planes since I was about ten years old.
If you don't mind l,ve got a couple of questions about the jet engine, is the fuel injected from a central jet or is it a rail with multiple injectors?
afaik there's a main fan and a compresser fan, how or where does it compress, a jet is open ended? I think?
Eta, how does I climb will maintaining a fuel supply, is it a mechanical pump or electrical or neither 🤔

Obviously it quite a serious piece of kit 1ltr of fuel = 1kg that's a lot of fuel to be carrying.

Thanks Al
 

flyfisher222

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If you don't mind l,ve got a couple of questions about the jet engine, is the fuel injected from a central jet or is it a rail with multiple injectors?
afaik there's a main fan and a compresser fan, how or where does it compress, a jet is open ended? I think?
Eta, how does I climb will maintaining a fuel supply, is it a mechanical pump or electrical or neither 🤔

Obviously it quite a serious piece of kit 1ltr of fuel = 1kg that's a lot of fuel to be carrying.

Thanks Al
The combustion chamber is 'annular' (only one, centred around the compressor/turbine shaft) and has several 'shepherds crooks' (bent pipes with holes in them) in the chamber. This is standard practice on many engines of all sizes.

The compressor is centrifugal and the turbine is axial. They are both on the same shaft.

There is a 'glow plug' to initiate combustion, a thermocouple just behind the turbine to monitor exhaust gas temperature, a gas sensor to monitor the air/fuel ratio for starting and an optical RPM detector in front of the compressor. On the front of the shaft is the brushless three phase AC permanent (neodymium) magnet starter motor and clutch.

There is a FADEC (Full Authority Digital Engine Controller) about the size of a matchbox to run everything. This uses standard software used on a lot of turbines of all sizes from 747s to toy planes, but is adjustable to suit any engine and is done by the engine manufacturer.

The fuel pump use a similar motor to the starter motor and varying fuel pressure is the throttle.

START.
Close the throttle on the transmitter, switch on the transmitter and receiver batteries and the onboard engine battery.
Open and close the transmitter throttle. The FADEC takes over.
The motor spools up the engine to about 50,000 RPM.
The glow plug is turned on, after a couple of seconds the starter motor is turned off and the fuel pump turned on at 'idle' pressure.
As the RPM decays the air fuel ratio will optimise and at some point the engine will light.
The starter motor will start again and when the engine stabilised at about 70,000 RPM (idle) and a constant exhaust temperature the starter motor will turn off.
The FADEC flashes its external led which you usually fit under the cockpit canopy and will hand over control to you. Note you left the throttle at idle so nothing obvious will change.

This takes 15-20 seconds overall. Don't set your trousers on fire by standing behind it.

There is a separate fuel cut off tap operated by a separate transmitter control. Use it to stop the engine. The starter will engage now and again for about five minutes to cool the engine.
 

speytime

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Sounds interesting, I like that sort of extreme engineering it's very interesting, 70,000 rpm is a bit of a eye opener I didn't expect that, they must be extremely well balanced and strong to cope with the centrifugal force involved, that's phenomenal.
There's a group of people gather close to my club water that fly rc planes, I've stopped and watched but never spoken to them, i most likely will in future.

Thanks Al
 

flyfisher222

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Sounds interesting, I like that sort of extreme engineering it's very interesting, 70,000 rpm is a bit of a eye opener I didn't expect that, they must be extremely well balanced and strong to cope with the centrifugal force involved, that's phenomenal.
There's a group of people gather close to my club water that fly rc planes, I've stopped and watched but never spoken to them, i most likely will in future.

Thanks Al
Just for interest here's a picture of the 'turboprop' version designed to drive a conventional propellor rather than being a pure jet engine. It's real nice but at a bit over 4000 quid it's more than twice the price of the regular jet. The 'base' jet engine (on the left) is reversed and its jet exhaust drives a 'power take off' turbine on a totally disconnected second shaft. The larger size of that second turbine together with its planetary gearbox (the round part in the gold-coloured 'cone') increases the torque and reduces the RPM from it full-throttle 150,000 RPM to a full-throttle 10,000 RPM at the propellor shaft. The whole thing from the tip of the shaft to the tip of the starter motor (extreme left) is about 12 inches.
It has a very high power to weight ratio. About 10 shaft horsepower and a weight of about 22 ounces.
wren-44-i-turbo-poster[1].jpg
 

Cap'n Fishy

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Think its best to wait a day or two.. :oops: for to try for leaping Salmon.

View attachment 31208
My mate and I were all set to go up today, Andy. The height looked like it was going to be perfect, coming down from a fresh spike yesterday. Checked this morning and could see it had a second big spike during the night and would be too high...



I added the red line to show what it would have been if it hadn't had that second spike. Needs to be around the 0.4 to 0.5 m mark on the Newtonbridge gauge for the best action. Much above that and they seem to sense it is pointless to attempt it... and they just swirl round in the froth, looking like blacks socks in an old twin tub washing machine! 😜

Best to check the gauge before heading up. ;)

Col
 

boorod

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My mate and I were all set to go up today, Andy. The height looked like it was going to be perfect, coming down from a fresh spike yesterday. Checked this morning and could see it had a second big spike during the night and would be too high...



I added the red line to show what it would have been if it hadn't had that second spike. Needs to be around the 0.4 to 0.5 m mark on the Newtonbridge gauge for the best action. Much above that and they seem to sense it is pointless to attempt it... and they just swirl round in the froth, looking like blacks socks in an old twin tub washing machine! 😜

Best to check the gauge before heading up. ;)

Col
Aye, my fault, should have checked the gauge Col,, was in the same frame of mind thinking that the levels would have dropped nicely, but rain early morning put paid to that, hopefully drop in the next day.
 
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