The Internet Craftsmanship Museum Presents:
Clennell "Clen" Tomlinson (Part 2)
Timing/Phasing Arrangements
The timing and phasing of the crankshafts was designed to be identical to the prototype. The entire design was taken from the single cross section drawing shown at the beginning of this folder. When viewing the engine from the front (non-drive, blower or free end) the cylinder blocks are identified A,B and C clockwise with A to the left, B at the top and C to the right. The bottom crankshaft is therefore designated C/A and runs in the clockwise direction with A/B and B/C running counter-clockwise at the top left and right respectively. Number 1 big end of each shaft is at this end. All of the pistons are of identical design but are required to perform the secondary function of opening and closing either the exhaust or inlet ports in the liners. Again, when viewed from the front, the exhaust ports of block A are at the left bottom, those of B left top and C right top.
The firing order for each shaft in my engine follows standard 6-cylinder practice at 1,5,3,6,2,4. They are, however, 600, not 1200 shafts as this is a 2-stroke. Each of the 18 cylinders fires once in every revolution of the engine or a power impulse every 20°. I have subsequently discovered that the prototype engine has non-standard crank sequences with the order of numbers 6 and 4 reversed giving the crank order of 1,5,3,4,2,6.
The firing sequence in each triangular bank of cylinders is identical, cylinders B,C and A firing at 40 degree intervals. The firing intervals per bank are therefore: 0°, 40°, 40°, 280°. The firing order for my complete engine is;
C1, A4, B1, C5, A1, B5, C3, A5, B3, C6, A3, B6, C2, A6, B2, C4, A2, B4.
For the prototype all the 4’s should be changed for 6’s and visa versa.
As with all modern internal combustion engines, the valve timing is designed with “lead and lap”. To this end the exhaust piston leads the inlet piston of the relevant cylinder by 200 of crankshaft revolution. This means that the effective TDC position; i.e., when the crowns of the two pistons in a cylinder are at their closest, does not occur when either of the big ends is at it’s TDC position. The exhaust is 10° after TDC and the inlet 10° before. It is easier to express all of the port timing in relation to BDC of the piston related crank.
The port timing for my engine equates to:
Ex opens 71° BBDC. (68°)</SPAN>
In opens 54° BBDC. (53.5°)</SPAN>
Ex closes 71° ABDC. (68°)</SPAN>
In closes 54° ABDC. (53.5°)</SPAN>
If this corrected in relation to effective TDC, the port timing becomes;
Ex opens 81° BBDC.</SPAN>
In opens 44° BBDC.</SPAN>
Ex closes 61° ABDC.</SPAN>
In closes 64° ABDC></SPAN>
The exhaust period is, therefore, 142° (136°) and the inlet period 108° (107°) The exhaust lead is 37° (34.5°) and inlet lag 3° (5.5°).
The figures in parenthesis above are the actual values from the prototype which are published in relation to exhaust TDC and have been adjusted to the same base as my model.
Finding the right materials
It is always a challenge sourcing materials for engine components without spending a fortune. For the Deltic pistons Clen wanted the correct high Silicon/low expansion alloy and went looking for some scrap pistons from big diesel engines that he could cut up and make the model pistons from the crowns. His searches took him to a marine breakers in Portsmouth where he had been told they had dismantled some Deltic engines. No luck, but he did find racks of dozens of brand new pistons for large Paxman Marine Engines. These are approx 11" in diameter and 13" long. The skirts are 7/8" thick. Stamped into the inside are the material specs and all QA data. Perfect for what he needed. They cost £25, but what a bargain! A Paxman piston can be seen in some of the photos below. It is shown for size scale because all 36 model pistons will fit around the skirt of one of these large pistons.
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Clen is also an associate member of the
Bay Area Engine Modelers of San Francisco, CA. This is how he happened to be displaying his engine at the show in Oregon along with the club and how the model came to the attention of the museum.
(My apologies to Clen for "Americanizing" his English spellings to conform to the conventions on this American web site.--Craig)
Here are photos of Clen Tomlinson's engine:
Napier Deltic engine as seen at the PRIME show in Oregon, September, 2003.
Left side view of the assembled engine
Right side view of the assembled engine 
Three crankshaft main bearing frames—The main bearing frames are the center of the crankcases which form the “corners” of the triangle and bolt to the three cylinder block assemblies to form the main structure.Three sets of cylinder block components—Each cylinder block is assembled from three sections to allow the machining of the internal water, inlet and exhaust passages.
36 connecting rods—There are 18 inlet and 18 exhaust connecting rods of the fork and blade design. They are only 48 mm centers and are machined from Titanium. These had to be machined on a conventional milling machine as the spindle motor of the Denford benchtop CNC could not drive the cutter and the stepper motors could not drive the feeds. Each big end carries two miniature ball races; two together in the inlet and one on each side of the exhaust. The rods are so small that split big ends were out of the question, hence the built-up crank design.
36 pistons sit atop a Paxman piston skirt—The running pistons are machined from a Wellworthy high Silicon/low expansion alloy. They are only 16mm diameter and the Paxman skirt was 22mm thick.
A single model piston sits atop the skirt of a Paxman piston. This big Diesel piston had exactly the material composition Clen was looking for to duplicate the metal used in the original Deltic pistons.
Blower drive one-way centrifugal clutch—The blower is driven from the rear of the output shaft via a long flexible shaft through a six times step-up gearbox. This engine carries no flywheel and accelerates/decelerates very quickly. It was felt necessary to provide extra protection.
Cast iron cylinder liner—The liners are of the wet type and carry a series of circumferential “O” rings to separate the water and gasses. They are located in the blocks by a Bronze bush screwed into the centre section which the houses the spark plug.
Liner with dummy piston
Liners in block 2 
Crankshaft assembly fixture—This shows the relatively simple but very accurate assembly system.
Crankshaft assembly index plate (counter-clockwise)—See the crankshaft assembly fixture 4 photos above.
Crankshaft assembly index plate (clockwise)
Crankshaft assembly in case
Crankshaft assembly with dummy pistons in case—This and the following picture show the crankcase assemblies ready for assembly to the blocks.
Crankshaft in assembly fixture 
Cylinder block center section 2—This and the following 7 photos show the machining for the various gas passages within the blocks. They are secured together by means of cap head screws threaded into the centre section.
Cylinder block exhaust end 1
Cylinder block exhaust end 2 
Cylinder block exhaust end 3 
Cylinder block inlet end 1 
Cylinder block center section 1 
Cylinder block inlet end 2 
Cylinder block inlet end 3 
Engine assembly as of August 1, 2003
Exhaust and inlet connecting rods
Pair of connecting rods
Phasing gear assembly as of August 1, 2003—This shows the method of coupling the three cranks and taking the power out.
Pipe "bends" in manufacture—This illustrates the method used to form the very tight radius bends of the external water plumbing. Rather than bend pipes, the shapes were machined in two halves and then silver-soldered together to form a pipe.
Single counter-clockwise crankshaft assembly CA
Top of cylinder assembly 2
Two clockwise crankshaft assemblies, AB and BC
Miniature Engineering Craftsmanship Museum, Carlsbad, CAThe model Napier Deltic engine was shipped from England to the USA in March, 2011 for display for one year at the Craftsmanship Museum in Carlsbad. This gave us the opportunity to take some additional photos of the assembled engine. The first and second photos show the engine with its right valve cover removed so the workings of the pistons, rods and crankshaft can be seen. A 6" scale and US Quarter can be seen in the foreground for size reference in the first photo. The second to last photo shows the three Bakelite distributors, while the last photo shows some of the extra parts, some of which were machined using computer-controlled equipment. Many of the tubing parts were created as CAD drawings which were split down the middle and machined in two halves. Then the brass "tubes" were soldered together to complete the round cross-section while assuring that all the complicated plumbing would fit perfectly when assembled. In the lower right of the last photo is part of the delicately welded sheet metal exhaust system.
This engine will be on display in the Craftsmanship museum for one year starting in March, 2011. It will also be taken to the WEME show in Pleasanton, CA in August, and Clen will be here for a visit to talk about the engine in person.
To demonstrate the complicated motion of the Deltic's three crankshafts and 3 banks of cylinders Clen created this demonstration model. It features the original Junkers two opposed pistons in one cylinder on the left, the Deltic's triangular configuration (center) and the diamond shaped 4-crankshaft design (right) also tried by Junkers. The secret to getting the 3-crank motor to move pistons in the correct directions was to reverse the direction of rotation of one of the three crankshafts. The model is driven by sets of gears on the back and an electric motors powered by a model train transformer.
Clen flew out from England and spent a few days at the Craftsmanship Museum in Carlsbad before heading up to the WEME (Western Engine Model Exhibition) show held in conjunction with the GoodGuys Nationals hotrod show at the Alameda County Fairgrounds in Pleasanton, CA August 26-28, 2011. Here a video crew hired by the show promoters interviews clen for a video on the hotrod show. Getting the tiny engines in front of a new audience was part of the reason for holding the model engine show inside the huge hotrod show. According to the GoodGuys staff, they want the model engines back again next year. The display was very popular with the crowd.