Johansson´s Pocketbike

[Johansson]

I have a clear idea of how to modify the flame tube now. The tube is marked for drilling, I have ZZ Top in the earplugs and Ernest & Julio Gallo in my stomach so the evening is turning out great! *LOL*

//Anders

[Fricke]

With ZZ Top then it should go good! *LOL*

The coil is working... It packs a nice punch... *lol* So soon you´ll have a small and nice coil + driver...

Keep the good work up Anders! I´m looking for a 110CC bike now... =)

[Johansson]

Great! 5x10^12 big thanks to you my friend!

//Anders

[Fricke]

But I´m thinking of keeping the coil... It´s soo sexy and small.. =)

And the company refunded the shipping cost.. And the parts cost not more than a beer... So bring some Norwegian beer with You when You are this way next time, And i´ll get some nice Sort Guld... So I´ll sponsor your bike... And i want my name on the belly of the bike... =) "Fredrik, said tha t it wouldn´t work!" *ROTF*

Did I mention that My brother is an Undertaker? *LOL*

[NickC]

what is different with propane fed and lqiuid fueled GTs? I guess the actual tube dimension would be different, but what is different about the holes?



could you explain your fuel system?

[Johansson]

The main difference is that with a liquid fuel you need to find a way to turn the fuel into a very fine mist before it can burn, since propane is already a gas (unless running on liquid propane, then you might need to preheat it) it is ready for combustion as soon as it leaves the injector. The holes must be positioned carefully to produce a bit of recirculization in the top of the combustor so the fuel/air mix gets more to mix and burn, that was the part I forgot about when first designing my flame tube... *LOL*

The first way of turning liquid into mist is atomization by high pressure and spray nozzles, and the second is vaporurization by heat exchange inside the combustor. I use both systems in my bike:

I have separated the fuel system into two independent ones, the idle system runs of one EFI-pump and is fixed (it only gives the predesigned fuel flow) through a single spray nozzle in the combustor. The flow and characteristics of the nozzle is chosen so that the engine can maintain idle speed with it, and at the same time does it preheat the four vapour tubes surrounding it.

When the engine is idling I can flip the main system switch and start another EFI-pump, it gives fuel to the four spray nozzles that sprays fuel into the vapour tubes. If the throttle is in neutral the system just pumps the fuel back to the tank without any fuel reaching the combustor, it does that because the throttle is a ball valve on the drain line back to the tank and a pressure safety valve (1.5 bar, standard plumbing equipment) sits between the valve and spray nozzles.

When the throttle is increased (ball valve closes) the pressure rises in the system until it reaches the 1.5 bar that is the opening pressure for the safety valve, then the valve opens and lets fuel through to the combustor. I measure the fuel pressure just after the safety valve since the system pressure will be 1.5 bar higher than nozzle pressure. The throttling range has been found to be 0.5 bar - 7 bar, after 7 bar the pressure starts to bounce up and down since the pump can´t handle any more.

I chose this kind of system mainly because I didn´t want to use propane for preheating the combustor, and I was curious if it could work. I haven´t throttled the engine while it is running yet so it might not work as well as I´ve hoped for, but I guess that I will find out soon...

//Anders

[Nick]

Anders,

the more i read of this project the more impressice it is.
You should maybe do an "e-book" on the build, the how's and why's pics etc. I know i'd buy it!

Nick

[Anders Troberg]

Or even better, let the Chinese borrow it for a while, then we can all buy one over the counter after they start manufacturing copies!

[Nick]

:shock:
such synicism in one so young!!
He he
:D
Nick

[Johansson]

Ha ha, it IS a chinese bike. It just comes with a twist... *LOL*

I have rebuilt the flame tube after John´s instructions, a bunch of 6 mm holes angled towards the cap to provide recirculation and slightly larger secondary and dillution holes. I am eager to find out how the modifications turns out, but it will have to wait until tomorrow.

The crappy welds is caused by an almost empty Argon bottle, I will have to get it refilled this week...

//Anders

[Johansson]

I am by the way going to build a portable starting tank this week if I can get the Argon bottle refilled. I will use the same kind of tank as I used to make the combustor, a 6 liter Halon fire extinguisher (spelling?) that is tested up to 25 bar.

I have read that the Sofia J-450 engine used a 10 liter tank for starting and it lasted for 10-15 starts, so with my engine of twice the thrust and a smaller tank I could perhaps get 2-3 starts out of it.

The construction will be very easy, a ball valve with a male shop air connection fitted to the tank and a pressure gauge. The tank can be filled from any compressor and carried around very easy thanks to the lightweight tank. A female-female connection (those are nice to look at... *LOL*) on a small lenght of hose will couple the tank to the bike when it is time to start it.

//Anders

[Dang911]

You need to run a compressor off the turbine to keep your starting tank toped off!!

[NickC]

whoa, whered the other posts go? oh well, anyhow what spring load strength have you found to work best for your preload? I've never really seen your preload setup? could you post and explain some detailed pics of it?

[Jmitchell]

I think the forum exploded, and many posts got sucked into a quantum singularity.

[Johansson]

Hmm, strange. Many posts are gone I see... :-(

The preload is a wave washer sitting inside the bearing house which pushes the rear bearings outer race backwards, the pressure can be set by schims depending on how compressed the washer is. At the moment the preload is 66N which should be plenty.

//Anders