Johanssons Jet-Cart

[racketmotorman]

Hi Don
Just an update on the PJ turboprop concept , she fired up this arvo , noisy as buggery , but the turbine wasn't getting up to speed so there wasn't a lot of power/noise being extracted in the few seconds I ran her each time .
Cheers
John

[serverlan]

Oh John, you make me feel so normal!
(and jealous)

That bike is amazing.
how long did it take to build?

Re the pulsejet,
I get the feeling they are more to do with poressure impulses than large amounts of gas flow, so may not be suitable.
I'd guess you would need some form of chamber to spread the pulses out to give a nice steady push that a turbine would prefer.

I am near Canberra.
I'll have to drag the wife kicking and screaming up to visit you some time!

I'm a bit of an "ideas man"
i.e. all thombs and talk, no product,
but hey, thats me.

Don

[racketmotorman]

Hi Don
The bike took about 12 years from the time I starting back in about 1990-1991 until she was sorted and running well .
There was a lot of uncertainties in the early days as I didn't have much info to go on , just a coupla books on full sized aircraft engines .

The kart only took 7 months , I'd learnt a bit by that time :D

This PJ experiment is rather enjoyable as its all unknown territory, theres not even some rough data available on freepowers being added to PJs.

I'm flying blind :shock:

You'll be made most welcome if ever you're up my way .

Cheers
John

[Johansson]

60Hp? Hmm, it would be fun to convert it into a diesel fueled turboprop cart... *smile*

The problem with making a freepower for an engine that size is to find a turbine shaft big enough for the job, I suppose welding one together like you did for the pulse-turbine could work but it would aquire lots of work before it could run without vibrations at 30-40krpm.

If that engine should be able to produce 60 or more hp, just how much power could I get in theory from the pocketbike turbine which will produce a massflow of 0.643lb/s and 12.1kg max thrust? I have decided to build a gearbox for the freepower turbine to gear it down to between 3-4:1 to have the free turbine spinning at a decent speed and not stressing the chain drive too much...

//Anders

[racketmotorman]

Hi Anders
I was getting a theoretical 140 hp from 2 lbs/sec mass flow in the bike , even allowing for losses and "unknowns" I'd have to be getting at least 100 hp at the rear wheel to be able to get the acceleration times I did with only a single speed gearbox .
With your mass flow of around 1/3 rd of my bikes , and allowing for reduced efficiencies from the lower mass flow , I can't see any reason why you shouldn't be able to get at least 25 hp , possibly considerably more if everything is being pushed to their limits .
The freepower on my kart was only a Cummins truck turbo turbine with a 3.5 inch dia exducer , and it was capable of flowing around 1.1 lbs/sec or 0.5 kg/sec .
With a gearbox on it , (rather than the direct chain drive) and it being able to reach its designed rpm (for the thermodynamic energy available) of around 40-45,000 , >60 hp was possible .
Cheers
John

[Johansson]

That much power should get the bike close to the magic 1:1 power/weight dry if I make most of the cold parts out of aluminum and thin stainless, perhaps 0.8:1.

I have ordered Thomas Kamps book now, it should arrive in december so I won´t start with the bearing housing before I have read it. The annoying thing is that I can´t make anything with the bike before I have the turbo assembled so I know the measurements for the engine mounts, so there won´t be much done to it before Santa arrives...

//Anders

[racketmotorman]

Hi Anders
Thats good news about Thomas' book , it really is very good value for anyone contemplating what you intend doing .
Read it through at least 3 or 4 times before starting any construction , I still refer back to my copy from time to time .
Cheers
John

[hagent]

Hi Johansson,

I was wondering how an Aero Spike type of exhaust nozzle on the afterburner would work for your turbine? Would be a very interesting project.

Think there would be any benifit?

Cheers,

Hagen

[Johansson]

I don´t know so much about Aero spike nozzles, but I doubt that it would make much difference on this kind of engine. The cart is built for sub-sonic speeds *LOL* so it would probably be a waste of both time and sheet metal...

They look good though!

//Anders

[hagent]

I don´t know so much about Aero spike nozzles, but I doubt that it would make much difference on this kind of engine. The cart is built for sub-sonic speeds *LOL* so it would probably be a waste of both time and sheet metal...

They look good though!

//Anders

I was looking at some specs, and compared to the standard bell shape rocket nozzel the Aerospike has more thrust at the lower altitudes and just as much at the near space altitude. I may be wrong but I don't think a low vehicle speed should make any difference. I just wonder if it would make any type of improvement over a standard afterburner.

[Bruno Ogorelec]

I doubt that the aerospike would work. If I understand it right, it depends on the Coanda effect. I think the gases coming out of the simple turbojet, with an afterburner or without it, are too turbulent for the Coanda effect to work properly. You'd need some kind of a flow 'straightener' first.

[Fricke]

Hi... Well I think that making a "areo spike" is overkill!

And the AB is based on the "dump" type. the area of the pipe is increased and to get the maximum use of a spike you´d need to have a spike infront to get the flow out and then the fabrication of a spike is quite difficult to make, the metalspinning involved in forming the two spikes would cost more than the increase in thrust.

Our turbines are not made of exotic materials like the commercial turbines.

16kg of thrust is awesome for a DIY-turbine in that size that Johansson have! Well done Anders!!! =)

[hagent]

Thinking about the Aero Spike further, you guys are probably right. I forgot that that the pressure needed to get the Aero Spike working in the AB would end up stalling the turbine.

Great Job on the Cart!

Did you see the Rocket boots video?

Anyone know what turbines were used and how much thrust they produced?

Thanks,

[Lugebob]

The Boot turbines are Artes Rhinos at 36 lbs of thrust each.

http://www.jetartes.com/


bob

[Mark]

A modest fellow. ha
Mark