Johansson´s Pocketbike

Johansson · Post by **Johansson** » Fri Feb 23, 2007 3:22 pm

I fitted the throttle wire to the bike today, it works just fine with a throttle lenght of 4 cm which is just the distance I am able to twist the handle without changing grip.

The bike is just a few hose clamps away from a test run, but it will have to wait until I feel better. I have cought a serious cold so I had to give up and go home after a few hours in the garage, the head aches and the skin burns at the moment so I will have to take it easy the rest of the weekend... :-(

//Anders

_Rahul_ · Post by **_Rahul_** » Fri Feb 23, 2007 4:19 pm

Man .. that's AWESUM!!

Johansson · Post by **Johansson** » Sun Feb 25, 2007 2:38 pm

I felt much better today so I decided to assemble the bike and try the throttle, so after welding a new fuel return connection to the tank and hooking all hoses and cables up I gave it a spin outside the garage.

Since I use diesel with 5% quality oil as lubricant instead of the much thicker mix I used before the metering jet flows a bit more, the puffing noices in the video are caused by this excessive oil that puddles up and burns when it gets through to the turbine housing.

I didnÂ´t keep the engine running for long above 5 psi since I havenÂ´t got a rev counter and the steel bearings might break. At 6 psi the bearings made a noice like they lost preload or something, might be ball skidding caused by too much lubrication...

The engine has a fair bit of throttle lag, it is caused by the spray nozzles and high pressure, it takes a second or two to build pressure in the system before the nozzles starts to flow fuel and when the throttle is closed it takes just as long for the pressure to drop. Anyway, if I wanted instant throttle response I would have kept the piston engine... ;-)

http://www.youtube.com/watch?v=1W6urp2w4Q4

//Anders

Ash Powers · Post by **Ash Powers** » Tue Feb 27, 2007 1:10 am

Very nice! I'm still in love with the startup of that engine - once I get my CC sorted out I'll get to building the electric start for mine in hopes to have the same success as you do with getting her fired right up - very impressive work bro!

Washout661 · Post by **Washout661** » Tue Feb 27, 2007 1:52 pm

Would it be possible to connect a pressure release valve actuated by a solenoid to release excess fuel pressure when closing the throttle? Using a microswitch which is pressed when the throttle linkage is closed, momentarily actuating the solenoid and realeasing some fuel to allow the pressure to drop. This could be recycled back to the fuel tank for economy purposes, or alternatively vented into the jet exhaust & ignited to get a potentially cool looking backfire/afterburner effect... might require flame proof undies considering the position of the jet exhaust though.

Steve.

Fricke · Post by **Fricke** » Tue Feb 27, 2007 3:23 pm

Remove the rubber hoses in the fuel system and use copper / SS tubes.

Johansson · Post by **Johansson** » Wed Feb 28, 2007 6:00 pm

Ash: Thanks a lot! The start procedure is the least sophisticated I can think of, I start the idle pump at the same moment as the air impingement solenoid opens and ignition starts, no stepping or anything. Since it revs up pretty quickly the temps havenÂ´t got time to rise to a harmful level. In fact, the EGT gauge needle wonÂ´t even move until the engine approaches idle revs.

Washout661: Hmm, that might be a way to get rid of the lag. I will do some more tests once I get back home from work in a couple of weeks, but I believe that with the throttle tweaked and the operator a bit more experienced I will not find the throttle lag annoying at all. Since the idea is to fit a power turbine to the bike once it is sorted out on pure thrust it will have a certain amount of lag anyway before the power comes, so it is not really a problem...

Fricke: I know that the radient heat from the combustor at higher P2Â´s will soften the hoses, but it will take some work before I can run the engine at those pressures so until then I will stick to the old 20 psi fuel hoses.

//Anders

Fricke · Post by **Fricke** » Wed Feb 28, 2007 9:05 pm

Johansson wrote:I know that the radient heat from the combustor at higher P2Â´s will soften the hoses, but it will take some work before I can run the engine at those pressures so until then I will stick to the old 20 psi fuel hoses.

The hoses act as an accumulator (not much but it does) by switching to tubes you will reduce the lag a bit. Using switches and solenoidvalves only add to the stack of possible faults later on...

Your safety wrt to using hoses for fuel that close to the hot bits is not my main concern... haha...

ItÂ´s just my thoughts about it...

Johansson · Post by **Johansson** » Thu Mar 01, 2007 2:49 pm

Aha, I get the point. If I find the throttle lag too annoying I will change to copper tubing, but since that is going to cause me a lot of extra work I will stick to the spongey hoses for now.

Thanks for your concern of my personal safety by the way... *LOL*

//Anders

Johansson · Post by **Johansson** » Sun Mar 11, 2007 9:43 am

I ran the bike again this friday and made some minor adjustments to the throttle, now it behaves better with less lag. I took the engine up to 8 psi P2 with a wildly bouncing pressure gauge needle (I have to fit a restrictor to the pressure hose to dampen the pressure pulses) but above that the same bearing noice as last time appeared.

I also experienced a few flameouts while taking it up to 8 psi and quickly shutting the throttle, when I disassemble the engine later I will try to find a clue inside the combustor by watching the heat marks on the vapour tubes.

Multispool has offered me a set of better lube restrictor jets to solve the problem with over-lubricating the bearings, 1000 thanks to him for that! The bearing noice might be caused by an excessive amount of oil in the bearing tube that makes the balls skid in the races, so it will be interesting to run the engine with the new restrictor fitted!

The external air tank that I made earlier seems to work by the way. I filled the tank with 5.5 psi and after the start the pressure had dropped to 2 psi, the tank is stamped at 25 psi so if I fill it up to 10 psi I might get two starts out of it...

//Anders

Fricke · Post by **Fricke** » Wed Mar 14, 2007 6:58 pm

Johansson wrote:Thanks for your concern of my personal safety by the way... *LOL*

*LOL* You know that IÂ´m concerned about your safety, IÂ´m going to beat you and your tiny pocketbike racer... IÂ´m collection parts for my own GT pocketbike. All that I lack is the pocketbike *lol*

How is the Suzuki going?

//Fredrik

Fricke · Post by **Fricke** » Wed Mar 14, 2007 7:00 pm

Johansson wrote:The external air tank that I made earlier seems to work by the way. I filled the tank with 5.5 psi and after the start the pressure had dropped to 2 psi, the tank is stamped at 25 psi so if I fill it up to 10 psi I might get two starts out of it...

I hope that itÂ´s 25 bar or kg/cmÂ² and not PSI!?

//fricke

Johansson · Post by **Johansson** » Wed Mar 14, 2007 7:26 pm

Fricke wrote: I hope that itÂ´s 25 bar or kg/cmÂ² and not PSI!?

//fricke

Ooops, my bad. Bar it is!

The turbo-project is progressing well, I have sorted out the turbo now so this weekend I will fix the leaky front springs and machine two nylon pucks to stiffen the swampy suspension a bit. At the moment the front wheel hits the turbo with the fork compressed, not good on the road...

http://www.youtube.com/watch?v=MhzopEF1pZY

The first video of the bike before I fixed the oil return, the smoke is oil going through the shaft seals due to a narrow return line. I have a project thread at http://www.sporthoj.com/forum/showthrea ... 55&page=13.

IÂ´m going to beat you and your tiny pocketbike racer...

You wish! :-)

//Anders

racketmotorman · Post by **racketmotorman** » Fri Mar 16, 2007 6:50 am

Hi Anders
Your P2 gauge shouldn't be bouncing around , thats surge ,
LOL...no wonder the engine is sounding strange :-))
Better do something quickly to relieve the surge otherwise the engine mightn't last long .
Cheers
John

Johansson · Post by **Johansson** » Fri Mar 16, 2007 7:49 pm

Strange, what could be causing that? With a snail housing for the compressor and a decent sized turbine I never dreamed of getting surge...

//Anders

www.pulse-jets.com

Johansson´s Pocketbike

Throttle lag - potentially daft idea

Throttle

Re: throttle