JET-POWERED - Maverick Blackout V2
Discussion
Fugazi said:
How fast, very fast, stupidly fast.. a simple, back of the fag packet calculation gives a rough estimate of 90 mph. Biggest factor is the drag of the car, which is probably huge as it has the aerodynamic qualities of a chest of drawers. 90 mph may not sound 'that' fast but if you're stood still then it will disappear into the distance at a rate of knots. However I found my car, (looked very similar setup to yours) was very, very twitchy as the speed increased and I ended up just letting it accelerate for a few seconds before spinning it around to dump the speed. If you had a quiet road and followed in a car, you might have better luck 
As you've noticed the thrust curve isn't linear, so you can program the transmitter to give a better profile. One thing to remember though, if you do get high speeds is the engine, even at idle, is always producing thrust. Some of the first rc jet engine powered models were unable to land unless the engine was shut down due to this residual thrust. My car wouldn't move at idle, but once rolling the thrust at idle meant it didn't stop. But looking at those tyres I think you'll be fine.
OMG - no, no - 90mph is plenty fast enough!! Even as a two-stroke engined affair, I had to be seriously respectful of its speed (I think 40mph). And - indeed - it has no brakes, I had to decommission the brakes for reasons too long to go into, but it was with experience in mind of the car when it could do 40mph - I could always get away without having to use the brakes, just lapping it instead in a very, very large field (empty, flat country park). It had transmission disc brakes, and if I needed them to operate the car, I'd burn through them quickly, and they're a pain to change, and a consumable I didn't want to get into (discs not always in stock). So again you've inferred totally accurately, that I rely on the car's [what's the opposite of inertia?] proclivity to come to a standstill, because of aerodynamics (lack of) and mud-plugging tyres, and going on grass. And thankfully for me, at idle, the car's not being pushed at all notably - feels almost the same as with no engine on - doesn't want to move. The perfect solution would be 90mph laps, not straight runs. Let's see what lateral traction allows!As you've noticed the thrust curve isn't linear, so you can program the transmitter to give a better profile. One thing to remember though, if you do get high speeds is the engine, even at idle, is always producing thrust. Some of the first rc jet engine powered models were unable to land unless the engine was shut down due to this residual thrust. My car wouldn't move at idle, but once rolling the thrust at idle meant it didn't stop. But looking at those tyres I think you'll be fine.
Edited by Fugazi on Tuesday 8th July 11:58
Fugazi said:
The compressor on an average turbocharger (approx 60mm dia) requires around 7 Kilowatts of shaft power to spin at 120k+ RPM so I suppose you could use a model tubo-shaft engine and use it to drive a second compressor. However the design and construction of such an engine wouldn't be a trivial task. A turbocharger is simply a gas turbine where the heat source is the piston engine instead of a combustor.
Have you heard of hyper-charging? Essentially it is a combustion chamber attached to a turbocharger, so at low engine RPM the turbocharger runs like a jet engine and most of the air bypasses the engine and is burned in a combustor, as you throttle the car engine a valve diverts the high pressure air to the piston engine. So you have maximum boost at any engine RPM. However it is not very fuel efficient as you can imagine, but for something like a hill climbing car then it's worthwhile. These small gas turbines will use around 200 to 300ml of fuel per minute at full chat, 2 litres of kerosene usually lasts around 8 to 10 minutes of fairly spirited flight in a model plane.
The reason I think apu's are used, is that you could possibly bleed some compressed air from the system without incurring temperature or running problems in the gas turbine.
I hadn't...goes off to learn about hypercharging. Presumably though there issues with it or it'd be used on pretty much all turbo-charged hill-climb cars.Have you heard of hyper-charging? Essentially it is a combustion chamber attached to a turbocharger, so at low engine RPM the turbocharger runs like a jet engine and most of the air bypasses the engine and is burned in a combustor, as you throttle the car engine a valve diverts the high pressure air to the piston engine. So you have maximum boost at any engine RPM. However it is not very fuel efficient as you can imagine, but for something like a hill climbing car then it's worthwhile. These small gas turbines will use around 200 to 300ml of fuel per minute at full chat, 2 litres of kerosene usually lasts around 8 to 10 minutes of fairly spirited flight in a model plane.
The reason I think apu's are used, is that you could possibly bleed some compressed air from the system without incurring temperature or running problems in the gas turbine.
Thanks.
You might struggle to find much as it's a very niche subject, but I suppose the modern version of hypercharging would be anti-lag. This article describes a setup that looks closer to the definition of hypercharging http://www.motoiq.com/MagazineArticles/ID/2771/Ext...
It looks like he is taking air from the compressor and diverting into the combustion chamber to produce large amounts of hot gas to drive the turbocharger turbine. So the turbocharger is giving maximum boost off the line. It's certainly not a setup you'd want for day to day use
It looks like he is taking air from the compressor and diverting into the combustion chamber to produce large amounts of hot gas to drive the turbocharger turbine. So the turbocharger is giving maximum boost off the line. It's certainly not a setup you'd want for day to day use
I estimated the drag coefficient and cross sectional area but that doesn't take into account the friction from those tyres etc, it's purely an aerodynamic estimate whereby your max speed occurs when your thrust equals the drag. It will probably be far less, but I've seen push bikes with gas turbines exceed 30 mph, so it wont exactly be slow
Oh and Arif110 we need videos
Oh and Arif110 we need videos
Edited by Fugazi on Tuesday 8th July 13:50
Videos! Indeed! I'm hoping that it's as easy as uploading photos now? Else - I do have an Imgur account, or could figure out how Youtube works!!! I'm actually a complete Luddite!
I initially wasn't going to record a simple static start & run, but someone here said that that'd do for now/better than nowt - so I'll look to sort that tonight. Obviously, visually, there's virtually nothing to see more than the photographs afford - so here's hoping that the sounds make up for that a bit!
I'll only get around to actual videos of ground runs when I find someone trustworthy enough to do a good video, with me focusing on controlling the thing!
I initially wasn't going to record a simple static start & run, but someone here said that that'd do for now/better than nowt - so I'll look to sort that tonight. Obviously, visually, there's virtually nothing to see more than the photographs afford - so here's hoping that the sounds make up for that a bit!
I'll only get around to actual videos of ground runs when I find someone trustworthy enough to do a good video, with me focusing on controlling the thing!
Quasi-technical update: I'm going to programme the engine to top out at a level of thrust that results in about 50mph. I know I was okay handling it at that speed when it was a two-stroke, but with the current programme, it's so sht-scary approaching the higher engine speeds, that I never even get to cruise at 50, always backing off - so continuously scared of going past that speed (as it's all in the last 20% of throttle trigger travel). This will then allow me the confidence to do a video!
Dear Professor!
Fantastic to hear from you and indeed on these boards! Good one for remembering the search terms!
Before I forget - can you PM me your mobile please!
Collective - myself and the Prof (Rob) met in the most macho of circumstances - Ante-Natal classes! Seven years ago now.
So - on to updating the Collective.
I've been quiet lately, but what's been happening is:
1) I haven't yet posted a static video, because that is of course all about the sound, and the really odd thing is that once it gets much past 40,000RPM, the microphone simply ceases to be able to interpret the noise AT ALL, whatsoever - and instead completely invents a noise very much like that of playing with an old-fashioned radio dial (high-pitch/low pitch affair) - it's literally nothing to do with the sound being output.
2) I've been sourcing and testing on rugby fields so far, for safe straight runs, with enough left over to come (steer) to a standstill. One of these I will certainly video - perhaps now with the Professor's help. I've simply been looking for someone worthy to be taking that first video! And I suspect that at a distance, the video's microphone should hopefully just pick things up as they are really sounding.
3) I've just written to Santa Pod - with a view to assessing top speed. The clincher is, it really needs to be followed in a car, to ensure no going out of transmitter range. The Prof's now got dibs on that job - and to boot it will therefore be in his (proper) Audi S8, no less!! 'Jet-powered scale car has top speed assessed using an Audi S8'! (Shhhh - it'll prob only get up to 80/90mph)
4) I'm also in talks with a few parties who do custom bodywork for left-of-field vehicles and motorbikes, with a view to creating bodywork to pick up on what someone here said - that it looks a bit like the Tumbler from behind! And feck me, it really does! One of these sources is connected with the Fast & Furious team, who use scale radio-controlled models (I think it was both third and fifth-scale) for the movies - however, I reckon I'm going to have more luck with the more sane resources on that one - have to go to Kent for that! If any of you have any contacts in that regard, please do say - I'm looking at maybe fibreglass or carbon fibre for the middle onwards - the back end might need metal.
5) I've just today picked up a small drum of Mobil DTE Oil Light - from fellow PH'er Norbert's (Dentressangle) Crick depot - to use instead of synthetic two-stroke (at 5%). This seems to be the recommended oil. I'm hoping Fugazi checks in here soon - as would like to know his thoughts on that - the thing being that two-stroke is designed to be burned (but (therefore?) has been leading to gummed bearings, even for me), but DTE is not - so I'm planning on using it at a lower percentage (3%). The entire point of adding oil, is to lubricate the bearings - so one that does not burn off seems to have a logic behind it.
So - next post will hopefully be a video!!
Fantastic to hear from you and indeed on these boards! Good one for remembering the search terms!
Before I forget - can you PM me your mobile please!
Collective - myself and the Prof (Rob) met in the most macho of circumstances - Ante-Natal classes! Seven years ago now.
So - on to updating the Collective.
I've been quiet lately, but what's been happening is:
1) I haven't yet posted a static video, because that is of course all about the sound, and the really odd thing is that once it gets much past 40,000RPM, the microphone simply ceases to be able to interpret the noise AT ALL, whatsoever - and instead completely invents a noise very much like that of playing with an old-fashioned radio dial (high-pitch/low pitch affair) - it's literally nothing to do with the sound being output.
2) I've been sourcing and testing on rugby fields so far, for safe straight runs, with enough left over to come (steer) to a standstill. One of these I will certainly video - perhaps now with the Professor's help. I've simply been looking for someone worthy to be taking that first video! And I suspect that at a distance, the video's microphone should hopefully just pick things up as they are really sounding.
3) I've just written to Santa Pod - with a view to assessing top speed. The clincher is, it really needs to be followed in a car, to ensure no going out of transmitter range. The Prof's now got dibs on that job - and to boot it will therefore be in his (proper) Audi S8, no less!! 'Jet-powered scale car has top speed assessed using an Audi S8'! (Shhhh - it'll prob only get up to 80/90mph)
4) I'm also in talks with a few parties who do custom bodywork for left-of-field vehicles and motorbikes, with a view to creating bodywork to pick up on what someone here said - that it looks a bit like the Tumbler from behind! And feck me, it really does! One of these sources is connected with the Fast & Furious team, who use scale radio-controlled models (I think it was both third and fifth-scale) for the movies - however, I reckon I'm going to have more luck with the more sane resources on that one - have to go to Kent for that! If any of you have any contacts in that regard, please do say - I'm looking at maybe fibreglass or carbon fibre for the middle onwards - the back end might need metal.
5) I've just today picked up a small drum of Mobil DTE Oil Light - from fellow PH'er Norbert's (Dentressangle) Crick depot - to use instead of synthetic two-stroke (at 5%). This seems to be the recommended oil. I'm hoping Fugazi checks in here soon - as would like to know his thoughts on that - the thing being that two-stroke is designed to be burned (but (therefore?) has been leading to gummed bearings, even for me), but DTE is not - so I'm planning on using it at a lower percentage (3%). The entire point of adding oil, is to lubricate the bearings - so one that does not burn off seems to have a logic behind it.
So - next post will hopefully be a video!!
Arif110 said:
4) I'm also in talks with a few parties who do custom bodywork for left-of-field vehicles and motorbikes, with a view to creating bodywork to pick up on what someone here said - that it looks a bit like the Tumbler from behind! And feck me, it really does!
This needs to happen!Silver Smudger said:
This needs to happen!
Don't worry, I won't let the idea go without execution! Interestingly, the Tumbler was based partially on a chimeric hybrid of a Lamborghini Aventador & a Hummer - however I feel it's landed with a visage which looks much more like the Predator (alien)! The Tumbler to my eyes positively has 'mandibles'! UPDATE!
Okay - so I'd been engineless for about three months, waiting for the newer version of the engine to arrive.
So this now has the Wren DCi100 - same thing externally, largely - but now much is fully internalised - such as pump valves and main brains of the ECU. Also - the starter motor and fuel pump are now brushless, making for much more accurate fuel-control, and overall RPM control as a result, as well as faster spool-up.
PICS
While the carcass was sitting there devoid of an engine, I decided that I needed a bigger fuel tank - hence what you see now, versus how it looked on Page 1 of this thread.
VIDEO
https://www.youtube.com/watch?v=bBtSnW5_fHo&fe...
Okay - so I'd been engineless for about three months, waiting for the newer version of the engine to arrive.
So this now has the Wren DCi100 - same thing externally, largely - but now much is fully internalised - such as pump valves and main brains of the ECU. Also - the starter motor and fuel pump are now brushless, making for much more accurate fuel-control, and overall RPM control as a result, as well as faster spool-up.
PICS
While the carcass was sitting there devoid of an engine, I decided that I needed a bigger fuel tank - hence what you see now, versus how it looked on Page 1 of this thread.
VIDEO
https://www.youtube.com/watch?v=bBtSnW5_fHo&fe...
Fugazi buddy!
Glad to have elicited comment from you on this, sir!
The video's a bit naff, plus I was one-handed at the time, hence some awkward re-positioning of the camera, at points! Really - my next video will be of it actually moving, too.
The engine's super-lovely!! It starts in about 30 to 45 seconds - and seems almost to 'skip' steps I was used before to witnessing - e.g. rise-to-temp while you hear the flames swirling inside, leading to Switchover once it reached the designated temp (200degrees) - this one switches over and starts ramping even as low as 50degrees - I simply can't see the delineation - it just starts almost in one very quick sequence - I'm looking for Switchover - and it's idling already!!
Also - the newest consensus seemed to be that Mobil DTE Oil Light was positively rubbish for the bearings (my previous one had started to whine quite early), such that Wren are now saying that if you use it, dose it also with two-stroke or something!
The elixir of high-temp bearing oils though seems to be Aeroshell 560 (quite new) - and it's made a world of a difference! Two-stroke would gum the bearings - whereas on this stuff, they keep spinning for a good while, after starter disengagement on cool-down.
It's supposed to output a tad more than 100Newtons - but that's unofficial - the official output is still the 100N.
Very happy overall - and believe or not - thanks to and for all the support from those 'jet-nuts' like yourself, and Ben (who's also got a thread here for his two jet cars) - it's made it worth it to get past all the aggro of setting these things up, and getting it all just so!
Glad to have elicited comment from you on this, sir!
The video's a bit naff, plus I was one-handed at the time, hence some awkward re-positioning of the camera, at points! Really - my next video will be of it actually moving, too.
The engine's super-lovely!! It starts in about 30 to 45 seconds - and seems almost to 'skip' steps I was used before to witnessing - e.g. rise-to-temp while you hear the flames swirling inside, leading to Switchover once it reached the designated temp (200degrees) - this one switches over and starts ramping even as low as 50degrees - I simply can't see the delineation - it just starts almost in one very quick sequence - I'm looking for Switchover - and it's idling already!!
Also - the newest consensus seemed to be that Mobil DTE Oil Light was positively rubbish for the bearings (my previous one had started to whine quite early), such that Wren are now saying that if you use it, dose it also with two-stroke or something!
The elixir of high-temp bearing oils though seems to be Aeroshell 560 (quite new) - and it's made a world of a difference! Two-stroke would gum the bearings - whereas on this stuff, they keep spinning for a good while, after starter disengagement on cool-down.
It's supposed to output a tad more than 100Newtons - but that's unofficial - the official output is still the 100N.
Very happy overall - and believe or not - thanks to and for all the support from those 'jet-nuts' like yourself, and Ben (who's also got a thread here for his two jet cars) - it's made it worth it to get past all the aggro of setting these things up, and getting it all just so!
Fugazi said:
Not had chance to look at the video yet, but I love the smell of burning B&Q's Paraffin in a morning...
Indeed!! I'd been without an engine for three months, and was seriously missing that smell of 'aviation' - literally the same smell as that of airfields. So now I go and bathe in it, much to the Mrs' chagrin!!In this weather, it's especially nice too. Garage-based heater - which actually ends up defrosting the entire car, if I'm playing with it for long enough (car parked on drive, facing garage opening).
Finally - a video of motion of some sort!
The microphone ceases to pick up the actual noise at certain RPMs, sounding more like trying to tune a radio.
On move-off, watch the tree-foliage in the further background. That was about 100,000rpm. The 'crash' into foliage was deliberate, to catch it safely as I concentrated on video and throttle. Oh - and it could easily have ploughed that stuff down and gone over it - but at much beyond 60,000 RPM, it's too loud to be that close to, without ear defenders. At full throttle, you can hear it a mile off, literally.
https://youtu.be/IguVcGxH15A
And another...I just blipped the throttle to about 70% power for a few seconds, the rest was momentum:
https://youtu.be/uCFKifDL-2U
And lastly - gentle movement!
https://youtu.be/nZ-0m8pty2k
Edited by Arif110 on Monday 18th May 01:18
Edited by Arif110 on Monday 18th May 01:29
Ha ha!! Thanks buddy!
The tank'll take 4.2litres (normal paraffin mixed with Aeroshell turbine oil at 5%) - and I get through it in about 40mins, or a fair bit less if full-throttling it a lot.
It idles at 45,000 RPM, full-throttle's 160,000RPM, and I've clocked it at 90mph on smooth tarmac (needed a 500m stretch) - however, I'm normally on grass.
If tootling along at a bit more than walking-pace, it has a range of just under 3miles.
I've never had so much fun - full stop, ever. The sound and the smell!
Arif
The tank'll take 4.2litres (normal paraffin mixed with Aeroshell turbine oil at 5%) - and I get through it in about 40mins, or a fair bit less if full-throttling it a lot.
It idles at 45,000 RPM, full-throttle's 160,000RPM, and I've clocked it at 90mph on smooth tarmac (needed a 500m stretch) - however, I'm normally on grass.
If tootling along at a bit more than walking-pace, it has a range of just under 3miles.
I've never had so much fun - full stop, ever. The sound and the smell!
Arif
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