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In a new departure for OTW we have a modern engine test that reflects those carried out by the likes of Sparey and Warring in the late 40's. Thanks to Dick Roberts and SAM 35, what follows is a detailed description and bench test of a brand new Rowell 60, no less than sixty years after it left Dundee. The article originally appeared in 'SAM Speaks' for June 2008.

"THE ENGINE EAR" No 7.

Rowell 60 Ignition. This engine is on loan from Richard Short who has kindly (foolishly?) allowed me to run it for our enjoyment. The engine tested is the Mk1 sparkie, Serial No 150. According to information received from George Blair there are two other versions, the Mk 2 Series 1 which has an upwardly inclined carburettor, Dooling like, and extended disc pivot bearing.

The other one is the Mk 2 Series 2 in which the carburettor inclination angle is increased from about 40 to 60 degrees. The Mk 1 was available either as a Sparkie or as a Glow and I would imagine that the later ones were also. No idea of how many made, but production started in 1948 and went on for some 5 years.

Like a Nordec, the engine was very expensive, quoted prices being £12-00 for the basic spark engine including a KLG plug, plus 7/6 for a prop driver, £3-10 for a centrifugal clutch etc. At that time, my Father was on about £8-10 a week and considered to be "quite well off"!

The engine, as can be seen in the photos, is a fairly conventional two ball bearing rear induction device, rather like a McCoy 60 on steroids. Bore is 15/16" and stroke 7/8", like the McCoy, but the whole structure is much bulkier & thus heavier, resulting in a weight of 19 ¼ ounces! From the literature, it is apparent that it was designed primarily for car use, as was the McCoy of course.

Front & rear housings, crankcase, timer frame & cylinder head are sand cast in a high grade aluminium alloy, subsequently heat treated. The engine is made to very high standards, all fits & finishes being excellent. Connecting rod is of light alloy and, rather surprisingly, is unbushed. A great deal of effort has gone into reducing crankcase volume in order to get lots of mixture through into the cylinder, but the transfer passage, like most others of the period is a bit on the small side. The liner has three transfer ports and 6 exhausts, all of moderate dimensions and there are two "boost holes" in both liner & piston to assist mixture transfer. Exhaust timing is approx 130 degrees and transfer 110 degrees, by no means "wild". Rear disc induction is open for some 170 degrees, the disc pin being well supported in the bronze bushed rear housing. Choke is 3/8" bore, with a 2mm needle across it, providing a sensible area to admit air, without the need for pressure feed.

The crankshaft has a fully circular web with a crescent shaped counterweight machined in and in addition, has three heavy metal slugs pressed into the web opposite the pin to improve balance.

Compression ratio is claimed to be 12 : 1, very high for the period, but no doubt aimed at using a non nitromethane fuel, a fuel component that was almost unobtainable at that time! Combustion chamber is fairly orthodox, the piston having a baffle isolating transfer from exhaust and a part spherical hump, whilst the head has matching recesses. All screw threads appear to be BSW rather than BA, presumably because that is what was available in the works!

The contact breaker incorporates a nice adjustment feature, difficult to describe, but visible I hope in the photos. The fixed point is mounted on a pressed metal bracket that rotates about the moving point pivot. It is restrained from rotating by a nut & bolt through the timer frame and a slotted hole in the bracket. Clearance is adjusted by firstly slackening off the clamp bolt & secondly by then rotating the fixed point assy slightly. The clamp bolt is then re tightened. Minor snag with this arrangement is in trying to achieve the desired .006" clearance by rotating a fairly big bracket a microscopic amount! I tried putting the feeler gauge in and then making the adjustment, but it did not work as the moving point spring is not strong enough!

Baffled piston and matching head. Contact breaker. Rear disc valve assembly. Crankcase and conrod.

Once the engine was cleaned off, lubricated & re assembled, I put it on the test stand, initially with a glow plug in order to find a needle setting. I used a 12" x 6" APC propeller and 80%/20% fuel and the engine started very nicely by hand, something of a surprise! It runs very well and the needle controls fuel mixture in a sensible fashion, being reasonably responsive.

Once I was happy that all was in order and that there were no nasty residues coming from anywhere, I set up the spark ignition system. Plug used was an NGK with a gap of 0.008" and the contact breaker gap was set at 0.006", opening 0.17" BTDC. Starting proved to be reasonably easy using the electric starter, but impracticable by hand, not really surprising with fixed ignition timing! On sparks, the engine was notably faster & smoother than on glow and felt easier to needle. The instructions do say that glow performance can be increased by the use of Nitromethane in the fuel, and presumably, like a Dooling, the spark performance can be similarly enhanced by the same means.

Vibration is notably absent, unlike some other early engines, due no doubt to the care taken to determine the counterbalance requirements. Everything stayed tight, even the mounting bolts only needing a minor tweak and no leaks anywhere.

I ran the engine on two different props, recording 10,560 RPM on the 12" APC = 0.97BHP, and 11,780 RPM on an 11" X 6" APC = 0.96 BHP. These are remarkably good figures for 1948, beating the Nordec by a mile and very close to what I understand a Black Case McCoy 60 of the period churns out! This is without any special preparation and standard fuel, with the engine almost certainly needing more running to bed it in properly. All in all a very nice engine indeed, with stacks of power, easy operation and top quality manufacture. My thanks to Richard for the loan of this excellent engine, it is very much appreciated.

R W Roberts

©copyrightRWRoberts2008

Footnotes: Interestingly, the .97bhp recorded in the 2008 test confirms the figures quoted in the 1949 test. Whilst the engine is complete with box and all documentation, the serial numbers do not match, and the box indicates that it was originally for the glow version of the motor.

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