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ecos
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[*] posted on 21-2-2018 at 05:29
Jet Bike


Hi All,

I saw a youtube video for a Russian guy who use a small jet engine to drive his bicycle. It sound really crazy but it was very cool idea.
I saw before people adding a small motor to the bicycle but this need a lot of modification to the bicycle( not a simple thing).


I searched internet but it seems a small jet engine with good thrust costs a lot :/ (from $2000 to $3000). I was thinking to make the engine but I couldn't find much information ( step by step) on how to make a reliable one. do any one have some resources here?

I was also thinking about the control circuit for the engine. I think i need :
1- temperature sensor to avoid overheating
2- fuel pump control to control the speed
2hedoqo.jpg - 137kB

Ref : https://www.youtube.com/watch?v=_O4mw0OMukE

did anyone try something like this before?
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Bert
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[*] posted on 21-2-2018 at 05:50


You'd need to be a pretty good machinist of reasonably exotic materials to make a jet engine I would have thought. A rocket bike however....

https://www.youtube.com/watch?v=bKHz7wOjb9w

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LearnedAmateur
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[*] posted on 21-2-2018 at 06:37


It would be a small turbine from a model aircraft and they are very loud, I used to fly model aircraft at a specialised field and a few members owned them, fun to watch and very expensive (AUD$3000-5000 for the lower end builds). If you live in an urban area then I would advise against this idea, an electric motor or a small two-stroke may be more practical and easier to configure. If you need some information, it may be an idea to poke around some RC forums since it’ll be pretty much the same setup, just that you’ve got wired connections instead, but I doubt it’s something you could make yourself.

[Edited on 21-2-2018 by LearnedAmateur]




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[*] posted on 21-2-2018 at 08:51


Turbojets built at home are an awfully tall order.

Getting decent thrust is harder than you'd think from the simplicity of the principles.

And without those expensive materials mentioned above, they don't last very long.

However there are always pulsejets. They're cheaper and simpler, so the fact they burn out if made from cheap materials matters less. I think there were some manufactured for model aircraft back before miniature turbojets were practical.

Motorjets are simpler than turbojets too, but I doubt the claims that you can get useful thrust without a decent compression ratio: I don't think spraying gas into a fast moving air stream like from a leaf blower motor would give you much of a kick.

Motorjets that have high speed axial compressors, and positive displacement blowers, have been used in a few aircraft successfully. Maybe some Soviet fighters from the 40s, and that Caproni prototype from before the war.

One other thing: If you get this running be sure to check your local regulations.

Many places have laws against use of rocket or jet powered vehicles on public roads.




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[*] posted on 21-2-2018 at 12:27


Many thanks for the replies.

I found this book: Home Built Model Turbines


I will get this book and have a look. it seems interesting !

@SWM, you are correct, I need to check regarding local regulations.


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[*] posted on 21-2-2018 at 12:51


This is an interesting read: http://www.pulse-jets.com/valveless/
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[*] posted on 21-2-2018 at 13:28


The other way is to build a turbine based on a used truck exhaust turbo - plenty of internet resources for that. You only have to build the combustor, as all the spinny, high speed stuff, bearings and housings comes with the truck turbo.
Instead of just directing a jet of hot gas out the back (which is a rather inefficient way to create thrust), an alternative is to have a third turbine connected to the bicycle wheel and use that to extract power from the exhaust gas. I can't recall the exact term for this, but it works in a vaguely similar fashion to a torque converter.

Pulsejets ... say goodbye to your eardrums!




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Corrosive Joeseph
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[*] posted on 21-2-2018 at 13:35


Quote: Originally posted by ecos  

I will get this book and have a look. it seems interesting !


Here is your book - "Home Built Model Turbines "

Attached


/CJ

Attachment: Home Built Model Turbines.djvu (4.2MB)
This file has been downloaded 169 times




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[*] posted on 21-2-2018 at 14:41


"Turboshaft". Thats the term I was looking for.



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[*] posted on 22-2-2018 at 02:51


My dreams are over :(
those engines require a lot of effort and skills!
NOT EASY :'(

@Twospoons, I think Turboshaft engine is for devices that require high RPM but doesn't deliver enough torque.

sounds like I will give up.

I will try to build electric bike using electric motor. it will be much easier than those engines!
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[*] posted on 22-2-2018 at 05:27


I had a look on the basic design of diesel and petrol engines.

I see the process as : inject air , compress air, inject fuel , ignition, release exhaust.

I think it is the same process of the jet engine. I don't see much difference ! any comments?

I would imagine the difference maybe because jet engines has high compression ratio but if this is true, why don't they use the same concept in cars !
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[*] posted on 22-2-2018 at 08:42


Power choice for aero use and ground/water use are governed by weight as well as efficiency, maintenance and other costs. You will find tons of gas turbines in aero applications, light weight per output and reduction of reciprocating parts and the associated wear/extending engine maintenance intervals related to such wear are big factors in this choice.

The only major use of gas turbines for a production land vehicle I know of right off hand is the prime mover of the M1 Abrams MBT.


[Edited on 22-2-2018 by Bert]
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[*] posted on 22-2-2018 at 08:56


FIAT, Rover, Chrysler and some others worked at turbine car design during the post WWII period.

Prototypes were built and tested, and Chrysler even ran off a few dozen cars for extended consumer testing trials back in the 60s.

But no dice. They just weren't practical then, and nobody has really pushed for them since.

I suppose a comeback may be possible though. One thing that made turbines tough to engineer for the road was the highly variable loading. That problem goes away if you mount the turbine in something like a Chevy Volt where it can just run steady-state and produce electricity. Save a bit on reduction gearing too.




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Kind of a waste as I'm having my immune system erased in a couple of months and will need another one.
And a DPT, and an MMR, and etc.

Pity I can't get my smallpox renewed, but those are hard to get these days. Maybe they'll give me cowpox if I ask real nice.
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[*] posted on 22-2-2018 at 13:00


Quote: Originally posted by ecos  
I had a look on the basic design of diesel and petrol engines.
....
I think it is the same process of the jet engine. I don't see much difference ! any comments?


Looks up the differences between the Diesel cycle, Otto cycle and Brayton cycle, especially the pressure / volume and enthalpy / entropy diagrams.

Notable differences are jet compression is 'constant volume' , and jet combustion is "constant pressure".

All are approximations to the Carnot cycle, which is supposed to be the ideal heat engine cycle for efficiency.




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