Super Tiger G3250 Gas Conversion by Jamshed Ishrat
Super Tiger G3250 which is originally a Nitro Engine was converted to Gas by Flt. Engr (R) Jamshed Ishrat. Read the complete process in his own words….
I have different nitro engines shelved for so many years. Inspired by Lambert RC systems, I decided to convert one, my Super Tigre 3000.
Replacing the con rod big-end brass bush with a needle bearing.
The bush bearing requires 17—20 % of oil. To bring it down to the usual 3% and to reduce the mess we need to install the needle roller bearing. The bearing size that fits in the big end of the con rod is 11x07x08 mm. The ID of the big end of con rod has to be shaved off a little to house this bearing.
The ST con rod is aluminium and is weak and delicate. To house the bearing the inner of the big end must be ground (grinding)
Replacing the carb…
The ST 3000 carburettor was removed. A 4 cm dia aluminium stock was used to turn the saddle of standard Walbro carburettor.
A hole was drilled at the matching place that would draw crank case air to pressure the fuel pump. I drilled a hole to house a 3mm nozzle in the aluminium saddle for the fuel pump.
I used the usual Walbro carb installed on the DA 50 or DLE 50 engines. Pressure was routed from thee engine crankcase to the carb.
The spark Plug
The Ignition coils available in the market have 10 mm (CM 6) cap. Where as all the nitro engines use a ¼” micro glo plugs. The existing ¼” hole in the cylinder head must be widened and threaded to house a CM 6 plug.
Incidentally on great public demand, the RcExel Electronics of China did manufacture a ¼” mini spark plug which fits and screws to the hole without drilling a new one.
The cap that comes with RcExel Ignition system also has the ¼” fitting.
The Ignition Timing
Modellers have different views on ignition timing on a single cylinder 2-stroke engine. It could be anything close to 28° advance of TDC.
There are many gadgets available from CH Ignitions or RcExel Systems to mark and install the magnet and the hall sensor. I choose the simple way. Print out a 360° protractor from the Internet and paste it to a used CD disc, laminate it and drill appropriate hole to fit your engine.
How to find the TDC, how to mark the magnet position on the prop hub and where to position the hall sensor are all available on the internet, I will not discuss the procedures here. I inserted a neodymium magnet in the prop hub. The RcExel hall sensor was used to pick up the spark.
For engine break in I used the unleaded 90 petrol with 1:30 synthetic oil. For regular use I switched to 1:40.
Following is the video for the Test Bench Run
Following is the video of the maiden Test Flight on a Sukhoi Model Aircraft
More details will be updated soon.
If you need any guidance or have any query regarding this conversion you can contact me on firstname.lastname@example.org