Johansson´s Pocketbike

[Fricke]

It would be less fun to become aware of that dilemma through a turbine exploding up my rectum... *LOL*

Yepp... *LOL* Safety first!!!

Or a good mechanical shop could have a suitable grinder setup... The ones that do molds and stuff like that... And I think that when You tell them of your project they do it really cheap... =)

I hope to get some videofotage of my trialrun of the kart either to day or in the week ;)

Edit - spelling correcting...

[Johansson]

Here are some pics of the newly bought shaft and wheel, very pretty indeed! Next weekend I will try to get the shaft posted to the company that will grind it down to shape, after that I can start manfacturing the shaft tunnel...

//Anders

[Johansson]

The shaft has been delivered for grinding and balancing, the guys at the shop became very interested when I told them what it was for so I might get a slight discount on the work... ;-)

//Anders

[paul skinner]

Hi Johansson.

Thought you might be interested in this project bike. Slightly related to your worthy effort. I'm posting this as a link vs. a PM, just in case there's intrest.

Paul.

http://www.badbros.net/jetbike.html

[Johansson]

I´ve seen that homepage, I hope that he gets his combustor problems sorted out so he doesen´t toast his turbo. It will be a challange for him to fit everything inside that small frame, it will be quite tight for me too and I don´t have to make room for a oil pump, tank and cooler...

I made a quick mock-up on the bike today to see how much space there is for the combustor inside the frame, and it won´t be a problem to fit a 25cm long combustor if the turbo is mounted low enough.

//Anders

[Johansson]

The shaft is now grinded down and balanced to a well better value than needed for ball bearings, I will pick it up on thursday on my way back from work. A couple of EFI pumps have also been bought for the fuel injection system.

One thing I CAN do without having the turbo assembled is to start making the fuel tank and mounting pumps and gauges. Since the fuel consumption at full throttle will be aprox. 0.4 l/min a fuel capacity of 4 liters should be enough for a 15 minute run since I won´t be running flat out all the time. The fuel tank will be built to fit inside the tail of the bike in order to hide it as much as possible.

The gauges needed for now will be two air pressure gauges, one for P2 and one for the exhaust nozzle pressure, a fuel pressure gauge for the main fuel system, a TIT gauge, a TOT gauge and a temp gauge for the bleed air after the bearings. When the pressure in the exhaust pipe is measured at max TOT the TOT gauge can be removed.

When the power turbine is built a wastegate will be made to keep the max pressure between the turbines below the earlier measured value, in that way I can throttle the engine up to max P2 even if the power turbine is not spinning without the risk of overheating the engine. The wastegate bypasses the power turbine and dumps the pressure out in the exhaust pipe after the power turbine and the spring loading will be adjustable so the dump pressure (and therefore the power of the engine) can easily be set.

//Anders

[racketmotorman]

Hi Anders
You have me intrieged by your suggestion of a wastegate after the gas producer and between the two turbines , theres no need to worry about overheating things if you happen to give full throttle without moving . Neither the bike or kart had any "unloading" mechanisms between turbines , the karts bypass nozzle was simply a means of matching flow capacities of the turbines , the karts freepower was too small for the flow out of the gas producer.
Save yourself some work and don't make it , all you need is the correctly sized freepower ,and with all the gases going thru it , power output will be at its best :D
If you look at the bike vids on Nicks site , the vid of just the instruments during a run , you'll notice the inter turbine temps (ITT) going up steadily despite the P2 being at max right from the time she starts to roll , it takes some time for temps of various components including thermocouples to rise despite a sudden increase in gas temps , by that time, you're away and things are spinning .
Cheers
John

[Johansson]

Hmm, you have a point there. I will start with fitting a temp and pressure gauge to find out how much a not-spinning power turbine affects the TOT. (I won´t start the construction of the PT until the turbine is up and running, so by that time I have probably changed my mind about how to build it 7 times... *LOL*)

I picked up the shaft today, and it was made to a very close fit for the bearings. So close that I might have to take a few 0.001:s of it to be able do take the engine apart without trouble, the bearings must be able to move on the shaft since it will be spring loaded.

//Anders

[racketmotorman]

Hi Anders
Be very careful when removing metal from the shafting for the bearings, it always seem to be too much, too quickly, whenever I do it , I found the best way is to spin the shaft in the lathe ,and using some fine "wet and dry" paper lubricated with a bit of kero and held against the shafting bearing land underneath a large piece of ground tooling steel to keep everything flat , and slowly remove very small amounts at a time , with frequent size checks and cooling periods to equalise shaft and bearing temps , the removal of metal will slightly heat the shafting compared with the bearing and will give false fitting clearances .
Slowly slowly :-))
Cheers
John

[Johansson]

Thanks for the hint. I´ve noticed the problem before while making the test bearing tunnel, it is just about right so only a tiny bit more......damn! *LOL*

When the PT is running I will have to couple a generator to the shaft, the two fuel pumps will probably have drained the battery well before the bike runs out of fuel. The main idea with the project is to have a bike that can just be refuelled between the runs without tons of equipment to get her going. A scuba tank for the air starter cannot be avoided though.

Does the Kamps book cover the kind of GT based on a turbocharger shaft? Otherwise I won´t get much help from him with the bearing issue...

//Anders

[Johansson]

I did a mock-up with the two fuel pumps this morning and found out that they can be fitted side by side under the seat, this is great since they then will be next to the fuel tank with a minimum of piping needed. I was worried that I would have to fit them directly above the turbine with the risk of kerosine leaking on the turbine, but now they are hidden well behind the place where the power turbine will be.

I am not worried about lack of space now, I might even fit a first-aid kit and a thermos with hot chocolade... *LOL*

My total lack of drawing-skill is the reason why I haven´t posted a drawing of the mockup, a 5-year old would probably do it better than me so I won´t bother...

//Anders

[Johansson]

After some measuring with my new digital caliper I found out that the massflow is better than I thought before.

Fuel consumption 0.4l/min or 6.4GPH
Compressor massflow is 0.676lbs/sec
The turbine PR is 2.07 which is enough for a P2 of 30.5psi or 2.1kg
The exhaust nozzle diameter should be 4.82cm and gives 28lb or 12.6kg thrust.

The power turbines measurements:
Inducer diameter 102mm
Exducer diameter 82mm
Wingtip width 15mm
Hub diameter 28mm
PR = 1.97

The turbine: Trim 65.3, Exducer 61.25mm, Inducer 75.8mm, Hub 26.5mm, Wingtip width 9.4mm

The Compressor wheel: Trim 39.4, Exducer 82.70mm, Inducer 51.90mm, Hub 19.00mm, Wingtip width 4.15mm

//Anders

[Fricke]

Johansson !

You will need a big first-aid pack! And an even bigger thermos (And You could use some clever system to keep the chocolate warm with the turbine) to fix the burns and to comfort You - When I beat You with my turbine powered Ural! *hehe*

On the more serious side: I think it will work really good, 12kg thrust is alot of power for that small bike... ;)

//Fricke

[Johansson]

If you get that Ural working I can just imagine the headlines in the newspaper:

Russias answer to the american Y2K bike

If that thrust figure is correct it will be quite fun to ride even without the power turbine fitted. We skip the gocart race and concentrate on the bikes instead!

//Anders

[Fricke]

Yeah! *LOL* 200kg thrust and 150 A.Hp To put on the rear wheel... *grin*

Well I´m looking for a used and cheap PocketBike... But all the Nimrods want to much for them...

I´ll have to build it myself...

GasTurbines are so much better than those fuel hungry and redglowing and too loud pulejets... ;)

And if I have enought inspiration and don´t get bored in the middel of the build it will be ready to the summer...

I´m thinking of ressurecting my kart in a couple of weeks... I´m building a new turbine for it... It will be shaft driven and use some form of CVT if iI can find a suitable transmission...

And I still have two barrels of JET A1 to burn up =)

//Fredrik