APS/Ω Gas turbine bike build

[Mobacken Racing]

Anders;

Wouldn't a "lost wax" casting process be more accurate than sand cast?

Regards, Neil  Tucson, AZ

A sand cast part is more than accurate enough for this, and a lost wax casting with mold making, cost of wax etc would be both very expensive and time consuming.

Lost foam would probably work, but then I would have to make the pattern manually and in case the casting turns out flawed I would have to go through the whole pattern making over again. With the sand casting pattern made I can make hundreds of castings with a minimum of effort, so that is by far the best method for making a part like this.

[manta22]

That makes sense, Anders. Your project is amazing!

Regards, Neil  Tucson, AZ

[Mobacken Racing]

That makes sense, Anders. Your project is amazing!

Regards, Neil  Tucson, AZ

Thanks Neil!

[tauruck]

Anders;

Wouldn't a "lost wax" casting process be more accurate than sand cast?

Regards, Neil  Tucson, AZ

A sand cast part is more than accurate enough for this, and a lost wax casting with mold making, cost of wax etc would be both very expensive and time consuming.

Lost foam would probably work, but then I would have to make the pattern manually and in case the casting turns out flawed I would have to go through the whole pattern making over again. With the sand casting pattern made I can make hundreds of castings with a minimum of effort, so that is by far the best method for making a part like this.

I used to be involved in the lost wax casting thing in the late 80s. Made molds for a sculptor who did horse racing trophies in Bronze. Not a fun job!!!!. Once the wax is gone you're OK but the process getting there is for crazy people. I won't touch that stuff anymore. Stick with the sand Anders.

[wobblywalrus]

Anders, it is a good idea to make your male plug a bit oversize to compensated for casting shrinkage.  Also, it helps to make the plug large enough to produce a casting you can machine down to final size.  My guess is all surfaces would be machined except for the sides of the blades and the cavities between them.

Figure on making a few castings.  Usually it takes several tries to get a good one.

The surface on those rotors might be shot peened or bead blasted.  It is a good idea.  It makes the surface under compression and it reduces the chances of a fatigue failure.   

[Mobacken Racing]

Thanks for the hints and tips guys, I appreciate them. Just for the record the cast part is a stationary part of the engine and won´t rotate in any way, so the surface quality and balance is not critical.

This week I decided to make the water tank for the upcoming water injection system, a couple of evenings ago I made a styrofoam mockup to find the right size and shape for the tank. The idea is to make it double as a chest rest so I won´t have to hang all of my mighty 67kg´s on my arms...



With the shape decided I started making the tank tonight in 1mm aluminum.



Not the best looking welds exactly, it would probably have helped if I had bothered to clean the oxide and dust from the aluminum before welding...



Oh well, it ended up leak free and that is all that matters. There is also a AN4 fitting welded to the bottom of the tank.



The result ended up the way I had pictured it, the water tank isn´t in the way for my helmet and with some padding on top I will have a nice rest for my arms while covering up behind the wind screen.



I ordered a water pump, pressure regulator and a high flow spray nozzle on Ebay last weekend so when I get it I can hook everything up and do some flow tests.

Cheers!
/Anders

[Old Scrambler]

Nice work .........Maybe the 'gas-cap' should say WATER ONLY

[Mobacken Racing]

Well, things would turn interesting very quickly if the tank was accidentally filled with kerosene. Pushing the water injection button would instantly double the fuel flow into the engine.... *boom!*  

[Mobacken Racing]

The exhaust pipes on the bike have been less than perfect, they aimed the exhaust jet straight out from the sides which probably caused lots of extra drag. Time to do something about it.



I´ve just started to make the new extensions, they are meant to angle the exhaust backwards and have an increasing cross section to increase the flow through them. Even the smallest decrease in back pressure for the freepower turbine adds horsepower.



After an hour and a half I had one side ready to be spot welded together, the exhausts stick out just as far as my leg so they won´t cause any extra drag.



Here you can imagine just how much better the flow will be, now it can leave the power turbine in a much straighter line than before.



Cheers!
/Anders

[sofadriver]

Anders, your work is so awesome but you really have to do something about those numbers!   

[Mobacken Racing]

Anders, your work is so awesome but you really have to do something about those numbers!   

You are right about that, I totally forgot about them at the race so I had to use vinyl tape to get them on there just before the race was on.

I´ll make them a bit prettier (and less prone to drop off...) this winter. 

[Frank06]

Looks pretty warm for the feet!

[tauruck]

Anders, your work is so awesome but you really have to do something about those numbers!   

The bike is so fast it pulls the vinyl off!!!!!

[Mobacken Racing]

Looks pretty warm for the feet!

It is pretty ok actually, I have a stainless heat shield between the engine and feet that keeps most of the radiant heat away.

[Mobacken Racing]

Last night I made the second exhaust pipe and welded them together, the aluminum tape is my poor-man root gas.



I seem to have managed to make both pipes the same angle and length, way to go Anders!



Then I turned my attention to the aerodynamics, I started making skirts for the rear fairing to enclose the rear wheel.



I am aware that I am stumbling in the dark here since I have no way of confirming that it actually works until I race the bike next summer.



Here is my high tech sheet bending machine.



One side almost finished, one to go. Enclosing the rear wheel will keep air from the spokes that act like a fan at the high speeds they will be spinning and hopefully lower the drag.



With the left side made I trimmed down the lower edge until it was 21cm from the ground all around, there are some gaps that needs to be closed and so on but that can be fixed later. It was only 5 hours left until I had to get up for work so I dropped the tools and headed for the bed.



Cheers!
/Anders