April 2000 Tech Feature www.virtualindian.org   
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    Inside the Ace Engine of 1926 - Part #2
   By Rohan Bradney
Part #1 (last month) gave a very brief overview of the history of the Ace motorcycle, and briefly examined some aspects of the Ace engine. Part #2 this issue will explore some of the oiling system, the crankshaft, the pistons and conrods. Some discussion will be directed towards a chronology of Ace parts and models.    

To the casual observer, most Ace motorcycles in the years 1920 through 1927 all look the same. But a detailed examination will reveal a host of yearly changes, to the point where very little of the 1920 model will even fit the 1927 model. Some discussion of the various models and parts would thus seem to be necessary.    

But first, a word on the Ace parts numbering system, and many models of similar looking bikes.

In the beginning, there was the Ace in its startup year 1920 and there was the letter A. So it was logical they went together. All Ace parts for the year 1920 are prefixed with the letter A, as are all Ace engine numbers (perhaps). The first part in the Ace parts book is A-2000 Crankcase Upper, and numbers for the 1920 year range from A-1200 (Oil Pump) to A-3037 (Generator Belt Hook). Plain numbers under 1000 are used for nuts, bolts, screws, washers, keys, cotter pins, rivets, etc. The bikes and parts for 1921 were as for the 1920 year, so retain the A-prefix letter in all respects.    

When some mechanical changes were made for the 1922 Model Year, the system adopted for the new parts was that the letter B prefixed the same part numbers. So the new inlet manifold was B-2300. The 1920 inlet manifold was A-2300, so only the prefix letter changed for a new part, and the number stayed the same. New for 1922 pistons were B-2005, new Schebler carburettor was B-2301,etc.    

When the Ace Sporting Solo was announced in December 1922 for the 1923 Model Year, the prefix letter for the parts was C, but the engines retained the B codes. So the new high-fin cylinders were C-2003, new aluminium pistons were C-2005-C, new inlet and exhaust tappets were C-2053, new oil breather was C-2265, etc.    

The 1924 prefix letter was D, and some examples of new parts were new piston pins with floating brass end-caps D-2010, new camshaft centre bearing D-2025-C, new Gas Tank and toolbox complete D-1555, new fork spings and rebound springs D-2889 and D-2890, etc.    

The Ace Motor Corporation went into liquidation in early 1924. Following much financial wrangling, it restarted Ace production as The Blossburg Corporation in 1926, so there was no 1925 production at all, as far as can be determined from this remote point in time. There was no code for the 1925 year, being completely omitted from the system.    

The 1926 production year code was logically an E. Parts introduced for this year were minimal, but a noticeable change was the one piece inlet manifold and 4 cage inlet valve assembly E-2300 and new Schebler carburettor E-2301, Schebler number DLX25.    

Big news for the 1927 model was the switch to pressure oiling lubrication, with a host of detail changes to permit this change. And a large number of other changes. A major development though was the purchase of the ailing Ace concern by the giant Indian Motocycle Corporation. While the 1927 year would have been year code F, Indian Motocycle changed the system slightly by prefixing the F with a V. So the 1927 year code for the Indian Ace was VF, and literally hundreds of new VF part numbers were introduced. Examples include new pressure feed upper crankcase VF-2000, pressure feed lower crankcase VF-2001, drilled crankshaft VF-2032, etc    

For 1928, the previous Ace part number system was completely overhauled. The previous Ace part numbers became "factory numbers", and Indian initiated a new system of part numbers commencing AA1 for the flywheel, AA150X for the upper crankcase, etc. Engine codes used a CA prefix. Items such as nuts and bolts which were common with other Indian models adopted their existing Indian part numbers. For example, the cylinder stud nut lock washer, which had been Ace number N214, became Indian P/N 19B114S, same as for other Indian models.    

To recap :    

example A-2001    

Year Code   
1920 A-   
& 1921    
1922 B   
1923 C    
1924 D   

1926 E   
1927 VF   
1928 AA 


Letter then numbers    
example A1202    

Year Code   
1920 A   
1922 B   
1924 D   

1926 E   
1927 VF   
1928 CA 


An Inspection of the Ace Crankshaft and Lubrication System.    

Ace4 - Splash Oiling   

The Ace4 engine 1920 to late 1926, immediate ancestor of the Indian4, utilised "splash oiling" for the engine. The Indian4 by contrast was a pressure-oiled motor, a system of lubrication used to this present day. The basic description of the Ace4 engine was a 4 cylinder engine, at first of 75 cubic inches, and later at 78 cubic inches. The undrilled crankshaft used 3 main bearings, and 4 separate  journals for the four cylinders. The gearbox also used plain bearings, and also relied on splash oiling. So what is splash oiling ??    

In the splash oiling system, oil is whipped up by the crankshaft and conrods rotating around and dipping into the oil troughs. Oil is splashed everywhere inside the engine, and trickles down into oil collection holes and thus lubricates the bearing surfaces. Sounds precarious, but was standard automotive practice on the majority of motor vehicles of the times. It worked - probably as long as there is no prolonged high speed running... Roads were mostly rough dirt tracks in those days, so high speeds were rarely even contemplated.    

Contrary to popular belief, while oil is stored in the deep and handsome aluminium sump, the splash oiling occurs in oil troughs located immediately under the crankshaft. In effect, a second pool of oil is held up under the crankshaft, and this pool is maintained and replenished by the oil pump. The oil in the base of the sump is only maintained as a cooler resevoir of oil to draw from - the externally finned sump assisting with the cooling. The inside of the sump was not finned at all, but is divided into 3 main compartments - engine, clutch and gearbox. The sump is not a structural part of the engine assembly - it just bolts up from underneath, to retain the oil.    

The oilpump is a single pairs of brass gears running together in an iron housing (a gear type pump), driven by the timing gears on the front of the motor. Oil is drawn from the base of the sump, through a coarse mesh strainer, and pumped into the oil troughs located immediately under the crankshafts. In the early Ace engines, a simple copper pipe with four holes drilled in it directed the oil into the four oil troughs. The oil is NOT delivered under pressure - the oilpump simply delivers the oil to where it can do the splash oiling.     

In the 1926 Ace engines, the copper oil-delivery pipe (lower edge of picture) has been organised so that oil is piped directly into the collection points for the 3 main crankshaft bearings. The excess oil delivered would flow down by gravity into the oil troughs, so that splash would deliver oil to the conrods to lubricate the big end bearings in the con-rods.    

Oil splashed up into the cylinder bores would lubricate the pistons. A number of pistons had been available over the years. First for 1920 was a cast iron piston of diameter 2.7" diameter (no details known). Next was a 2 ring cast iron piston of 2.75" nominal diameter for 1922 (?), the rings were 3/8" in width. Later followed a 3 ring cast iron piston for 1924 (?), (2 ring and 3 ring cast iron pistons compared) the 3rd (lower) ring being an oil scraper ring of sorts. Not shown is the Ace aluminium pistons fitted as standard in the engines for the Ace Sporting Solo Model - this performance model with the lowered handlebars had been available since January 1923. Finally, a view of the Ace cast iron piston compared to a later Indian4 aluminium piston - the Indian4 has thinner rings, more rings, bigger wrist-pin, taller piston and is cam ground.    

Ace4 CrankShaft   

An Ace Crankshaft in the metal (pardon the rust). The clutch fits to the disk on the lhs end of the crankshaft. Note the use of all plain bearings. It looks deceptive, but this is crankshaft is flat when its is lying on the work-bench (i.e. is a single plane crank).   

A labelled version of the crankshaft, identifying each bearing. It has 3 main bearings, and of course has 4 big-end bearings, one each for the 4 cylinders.   

For an explanation of the red arrow, see the final image on this page.   
The red arrow in this picture points to the thinnest part of the crankshaft - below shows how this thin design shows as a weakness !! The thinnest cross-sectional area of the crank is right next to the heavy clutch and flywheel assembly. This picture shows the results of jerking the bike into 2nd or 3rd gear with a few revs up - as for example if the gear does not engage completely and jumps back out again. Not good crankshaft engineering - modern crankshafts are frequently thicker adjacent to heavy flywheels, or at the power delivery end of the crank. Broken Crankshaft.   

Thanks to Per Erik Olsen of Norway for the spare crankshaft images,   
and for sharing some previous owners misfortune with us.   

Eagle-eyed readers will have observed that the cam, valves, valve gear and combustion chambers have not been discussed. Maybe next issue... 

1926 Ace engine   

1920 Ace parts list   

1922 Ace parts list   

1928 Indian Ace parts list   

Ace crankshaft (back to text)   

Ace sump (back to text)  

 Part # A-2001 (back to text)   

Ace sump with oil tray   
(back to text)    

Ace sump (back to text)   

Ace oilpump back (back to text)   

Ace oilpump front (back to text)   

Underside of sump tray with mesh strainer second from left (back to text)  

Ace bottom end (back to text)   

Ace conrod (back to text)   

Ace conrod (back to text)   

Ace 2-ring piston (back to text)   

Ace iron pistons (back to text)   

Ace/Indian pistons (back to text)   

Ace crankshaft (back to text)   

Ace crankshaft explanation (back to text)   

Oops... (back to text)