RCM&E May 2002
There's a gulf in terms of performance and quality between 'budget' engines and their revered expensive 'peers'.
Says who?........... Malc Pinnock reports on the latest Chinese delicacy
ASP has been with us now for some 10 years, they were the first of the imported (quality) Chinese copies.
ASP are part of a very large multi billion $ organisation that produce items for a wide range of industries, including military applications
I had a preview of a 36 earlier this year, but the test engine has been much improved cosmetically and internally than the earlier product. Lets have a look at what makes it tick.
ASP 36 Crankcase and Back plate
The crankcase and back plate are high quality items; both are pressure die-castings from alloy with the final finish being by vapour blasting.
Both the castings are very crisp with machining were necessary to the high quality we now expect even on the budget engines, with no pock marks blow holes or casting flash being evident.
The crankcase is very compact for a 36 in fact not mach larger than a 25, to keep the size down ASP have angled the transfer and exhaust porting inside the case to keep the transfer passages to the optimum size.
To do this the cylinder fins are stretched lengthwise on the case and are oblong in shape with the sides being rounded rather than straight when viewed from above, looking at the case from the boost port side we notice that the boost port casting is not centrally cast on the case but towards the front, with the rear transfer port starting just in front of the upper back plate mounting bolt, this as mentioned earlier helps to keep the case slim.
The manufacturers name ASP that has a shiny machine finish is cast on a plate that bridges the ports, with the country of origin cast on just below the engine mounting lug, moving forward we notice the case has two axially cast stiffening webs running between the mounting lugs and front bearing housing, with further web running centrally at the bottom of the case. The large carb-mounting boss that has a web from the front silencer-mounting lug to the rear of the carb-mounting boss takes care of stiffening at the top of the front end.
Looking at the case from the exhaust side we notice the large exhaust mounting flange, this has part of the front transfer port passage cast into it and has been bored at the front and rear for the two M3 silencer mounting through bolts, like the O.S 32 so a wide range of silencers and pipes are available, the engine size 36 is cast on this side between the exhaust flange and the mounting lug, round to the rear of the case, this has been drilled and tapped for the 4xM2.5 allen capped back plate bolts, there are two set of upper bolts supplied with the engine, the longer set is required when the remote fuel needle is used .
The crankcase has been fitted with two high quality smooth running bearings, both bearings being steel caged, with the front bearing being of the sealed type. From the top of the case which has been drilled and tapped for the 6xM2.5 allen capped head mounting bolts, we also notice the small pressed in pin for correct positioning of the cylinder liner on assembly, a small but important detail that used to be found only on the more expensive engines.
Lets round up the case with back plate, as mentioned earlier pressure die cast with a vapour blasted finish, this sits deep inside the crankcase with a flat at the top for liner / piston clearance and is sealed with a plastic gasket.
Liner / Piston and Conrod assembly
The liner is of the schneurle port variety, turned from brass bar stock and finished internally on its working surface with a good coating of hard chrome, that has been finished by grinding and lapping, the large bridged exhaust port has a transfer port cut each side with a single boost port at the rear opposite the exhaust, the liner has a wall thickness of 1.20mm and has a taper of 0.15mm from top to bottom.
At the top of the liner there is a retaining lip of 2.5mm thickness that has a small slot for the liner alignment pin that is pressed into the top of the crankcase.
The piston is of the die cast type, made from high content silicon alloy, with a finely lapped finish, and has been machined with an oil groove 2mm below the crown, the piston skirt has been machined at the front for flywheel clearance, with further machining internally to the bottom 6mm of the skirt for lightness, the 5mm dia chrome steel gudgeon pin has been bored for lightness, and is supported in the piston by two large cast in webs. The gudgeon pin is of the fully floating type and is inserted from the rear of the rear of the piston, there is a small lip internally at the front of the web to retain the gudgeon pin at the front and a pressed in PTFE pad at the rear.
The conrod has been CNC machined from high tensile alloy, and has been fitted with bronze bushes to both big and small ends, with single oil hole bored centrally at the top of the rod for small end lubrication and two oil holes for the big end.
Crankshaft and Prop Driver assembly
Last of the engines hard working internals, the crankshaft is machined from a single billet of chrome steel, and has a final finely ground finish to the big end and shaft bearing surfaces.
Starting at the big end and moving forward, the big end has a dia. of 5mm and a bearing surface length of 6.15mm, with a counterbalanced flywheel that has a dia. of 26mm and a thickness of 7.70mm, with the big end flywheel being hardened by heat treatment. Moving forward to the main shaft, this has a dia. of 12mm and a length 29.70mm, it has been machined with a 12.5mm x 10.00mm timed intake port leading into the centrally bored 8.15mm gas passage. The next portion of the shaft steps down in dia. to 9mm for the front bearing and prop driver, the prop driver has been machined from alloy bar stock, with a dia. of 23.90mm and a length of 7.55mm it has a 2mm wasted portion centrally, and has been helically knurled on its driving face. At the rear it has been machined internally for the 1mm thick by 1.5mm deep dirt shroud for the front bearing, the prop driver is of the floating type, and is retained in place by the two opposing flats machined on the shaft.
The last 24mm of the shaft steps down to 6.50mm, for the prop-driving portion of which 18mm of the shaft is cut with a std. 1/4 unf thread for the chemically blackened steel prop nut and washer.
The deeply finned head is once again a very good piece of pressure die cast alloy, with the lower edges having a machined bright metal finish.
Looking at the head from underneath it has a shallow combustion chamber of the modified hemi type, surrounded by a 4.50mm wide squish band, the head has been drilled and tapped for the centrally mounted std long reach type plug, [a nice feature usually only found on more expensive engines is the brass bushed plug thread,] the head has been deeply recessed for the cylinder liner, and is fitted with a soft alloy head gasket. Finally head mounting is taken care of by 6x m 2.5mm allen capped bolts
Carburettor and ancillaries
The ASP 36 carb is of the two needle type and comes optionally with a rear safety fuel needle mounting bracket and fittings, [at no extra cost to the customer]
Both the needle mounting bracket and carb body are pressure die cast from alloy, with all nipples being of steel with a chrome plated finish, and sealed by fibre washers, the throttle barrel with its extended leaver mounting spigot is from steel with a finely ground working surface, and has been bored and tapped centrally for the brass idle needle, with the adjustable operating arm being of steel a chrome finish, initial opening of the carb venturi is 12mm tapering down to the choke size of 7.50mm, opening out to a double D in the 13mm carb mounting boss, that has been bored and tapped for its two chrome plated steel X head mounting bolts, sealing is taken care of by a rubber O ring, last of the carb fittings is the optional for position, steel needle valve assembly, the fuel needle has a fine thread for positive adjustment and is sealed internally with a rubber O ring, the needle has been centrally bored for an extension if required and side bored and tapped for a locking grub screw, the assembly is fitted with a positive pressed steel ratchet and all parts are finished by chemical blacking.
ASP 36 Silencer and options
The exhaust port on the ASP 36 has 35mm bolt spacing the same as OS, giving the ASP lots of after purchase options off the shelf, E.G.: tuned pipe Pitts type or in cowl silencers. The standard silencer that came with the engine is of the duel cone three part variety, the front and rear part being from die cast alloy with the centre turned from alloy bar stock, the front part has been drilled and tapped for the 2x m3 mounting bolts is heavily ribbed and has been fitted with a chrome plated steel pressure nipple, the tail cone has an offset exhaust outlet that can be adjusted for position, with the whole assembly being held together by a long steel through bolt and lock nut. There is a further option of a quiet silencer from Just Engines for around £5 so please state your requirements when ordering.
|Engine: ||ASP 36 A series 3|
|Configuration:||single cylinder two stroke|
| ||ABC liner/piston with schneurle porting|
|Displacement:||5.9cc (.36 cu. ins)|
|Bore and Stroke:||20.2mm bore X 18.4mm stroke|
|Power (manufacturers):||1.15 BHP at 17,500 rpm|
|Weight (with safety needle:||270grms|
|Weight with std. Silencer:||335grms|
|Supplied with:||safety needle assembly, 2x allen Keys, silencer and gasket, |
| ||full English operating instructions and two year warranty|
|Fuel Used in Test:||Flair Yellow Spot (running in) 20% castor, 5% nitro Flair Yellow/gold (performance) 5% castor 10% synthetic 5% nitro|
The ASP 36 is part of a very wide range of engines; .12-1.80 two stroke and .30-1.60 four stroke.
|8X6 RADIO ACTIVE (R A M) ||3,600 ||17,600 |
|9x6 R A M ||3,400 ||15,200|
|9X6 A P C ||3,400 ||15,400|
|9X7 R A M||3,200 ||15,200|
|10X6 A P C||3,000 ||12,600|
|10X6 R A M||3,000 ||12,800|
|10X7 R A M||2,600 ||12,400|
|111X6 R A M||2,600 ||11,200|
Plug used in test FIREBALL STD ( MED)
Average noise test at 7 mtrs. 84Db on STD SILENCER (Note, expect 82Db or less on quiet silencer)
Its getting very hard nowadays to tell the difference between, the budget engine and their more expensive counterparts, as the quality of the budget engine is continuing to rise all the time.
The latest offering ASP 36 Series 3 Aero, from Just Engines, narrows the gap still further and is nicely put together, offering a very good performance.
Right from the start the ASP was very smooth running. Upon stripping the engine after testing, for a period of some five hours of running, there were no signs of wear, just a nice matt grey below the piston crown showing the pistons nip point, with all the other moving parts being in excellent condition.
In my opinion the ASP is excellent value for money and should serve the buyer well, if care is taken when running in, with the extra £5 for the optional quiet silencer being a good investment, and helping to save our flying sites.
You can find more ASP engine reviews here.