CNC Machining Craftsman—Clen Tomlinson

11 Май 2015 | Author: | Комментарии к записи CNC Machining Craftsman—Clen Tomlinson отключены
Kawasaki Square Four 2 Stroke Prototype

Clennell Clen Tomlinson

to museum: 10/31/03

CNC-machined engine masterpiece

Clen is here at the 2003 Pacific Rim Model Engineering show in with his nearly-completed Napier 18-cylinder engine. (Click on for larger image.)


I had Craig add Clen to our Craftsmanship I did so with the express idea to the question, “Is a craftsman still a if he uses CNC tools along CAD/CAM programs?” Just a at the magnificent project that is in the works” by Clen and one should the answer, and it should be a definite In the hands of a great craftsman CNC is another tool, and Clen the same amount of respect as any craftsman.

(To read Clen’s on CNC vs. Manual Craftsmanship, CLICK .)

What especially impressed me Clen and his project was he wasn’t a who grew up in the computer age; he was a who was willing to take on a seemingly project and use every tool at his to accomplish his goal. I’m forward to the day when Clen’s roars to life. —Joe

Impressive engine attracts at American model engineering

While looking at the engines on at the 2003 PRIME show in Joe Martin was particularly impressed the work of Clen Tomlinson. on a model engine project of magnitude is no small task, and the on this model are simply Although it is not yet complete, we felt visitors to this museum want to see what has taken so far and will follow the progress of project to its completion along us.

Another aspect where project varies from in this museum is that it is almost completely using CNC technology. In the past we have CNC work in favor of the hands-on of non-computer controlled tools.

In case we made an exception for two 1) The level of complication of this meant that even the help of Computer-Aided Drafting and Computer Numeric Control machines to make the part, the of knowledge and skill required to make the parts is in some more demanding than them by hand, and 2) CNC machining is the way shops now work and the way in which in the future will be making As projects get more highly some parts such as blades simply cannot be any other way than with the of computer control. What you see is a preview of the direction model will be heading in the next or two.—Craig Libuse


training lays the background

Clen Tomlinson is a 71-year old Electro/Mechanical engineer, living in Sussex England. He started his life as an apprentice in the motor industry and is qualified as a Motor Technician. His experience includes commercial vehicles, agricultural and equipment, civil engineering and equipment and motorcycles.

Clen has and built many special-purpose including road and race and bikes. He has also managed and racing car departments. In middle of time he spent two years Service (Draft) in Royal Air He spent 13 months—5 days a 8 hours a day in the classroom being as an aircraft flight and navigation technician.

He says, I learned more in period of my life than in my to that point!

In the mid 1960’s he a change into scientific and spent three years small, high-speed (500,000 turbines and free piston used in cryogenics for liquifying He then took training in and joined a large manufacturing to set up and run an engineering training school. He to Group Training Manager and to Group Personnel and Training

The company designed and built electro-magnets for atomic particle research. He also specialized in new and refurbishment of underwater weapons and and built ion implanters for the electronics industry.

In the early 1970’s, joined with three senior managers and set up new company in similar areas. The company into one of the leading magnet in the world. As Engineering Director was for tendering, design and manufacture of

He designed and built large and super-conducting magnets and associated for atomic particle and fusion research projects throughout the

Clen has been involved in projects in the USA including the Brookhaven Laboratory, Long Island New NAL, Chicago; the super-conducting collider in Texas and Boeing, program.

Hobbies with a slant

Clen has always making or “improving” things many relatively simple engines, both steam and IC. In he had been slowly developing his and enjoying life. Then his died very suddenly four years ago.

He I needed something to totally my head for some time, and is where the Deltic came in. I had thinking about it for some

He is currently completing the restoration/improvement of a old BMW 30Csi coupe he has owned for 20 He has another BMW car and 2 motor-cycles to look He also has 2 grandsons to “train.” The model engine will be Napier; The Sabre. This is an “H” sleeve valve unit.

He is on the design, and it is some challenge!

new technologies

Recently Clen us up to date on some more of how he got into CNC machining. Here is he had to say:

“I spent most of my life with pencil and “T” square, log and trig tables and a rule. I progressed easily to the but a little more reluctantly to the Towards the end of my working life I get an engineer to work for me unless I him/her a PC on the desk. I was still with a pencil and thinking this technology has arrived too for me. Then I thought, “Hang on a non of them are not that bright.

It be that difficult.” Surreptitiously I put a PC on MY Word processing; no problem! there are was draughting. This CAD is impressive, but that’s beyond my brain.

Then I think, on a minute—-”. It didn`t take too and I was doing that too.

On the floor the handles have from the machines to be replaced by panels and screens. My God, kids today are bright! retirement, I found two Denford CNC machines.

They had no computers or software, and it a challenge. I think, “Hang on, I had to learn the hard way, but the is history as they say.”

and Hardware used

Clen AutoCAD 2000 and tends to toolpaths. He then prints off and manually programs them the Heidenhain 151 controller of the Bridgeport 1. This is a relatively recent to his shop. Most of the engine was on a Denford Starmill benchtop 2.5 axis machine.

It had only 170 mm in X and 90 mm Y travel, and the tooling was a nightmare to Clen.

Making the Napier engine

by Clen Tomlinson


The prototype for this is the NAPIER “DELTIC” opposed 2-… cycle, Diesel range, used primarily in fast patrol boats and today, but also to power two of English Electric Diesel-electric The engines were produced as units (3 banks of 3 cylinders) or, as the of this model, as an 18-cylinder (3 banks of 6cylinders).

The principle has its in a German Junkers aero engine of the late 1920`s-1940`s. engine was an opposed piston, Diesel with 1 bank of 6 arranged vertically with two crankshafts;1 at each end of the cylinders.

D. Son Ltd. had a license to develop unit as the “Culverin” aero in 1935 but it was not until after the 2 nd war that a use was found. The project was by in the hands of the English Electric who were looking for a light high speed marine engine. This application a couple of inspirational design

The first was the realization that if one crankshaft were added, two more banks of cylinders be added in the configuration of an equilateral The second was that if you arranged to one crankshaft in the opposite direction to the two, then the relative of the whole assembly for port “fell into place” design produced an extremely strong but lightweight unit almost perfect natural

With 18 cylinders having a of 5.125 and a … of 7.25 per or 14.5 per cylinder, this had a swept volume capacity of cubic inches or 88.3 There were 3 stages of from the initial design engine driven blower for then being turbo-charged, with charge cooling and “Compounding” using an axial unit within the triangular void.

The performance ranged 1,650 bhp at 1,500 rpm for locomotives, to bhp at 2,200 rpm “sprint rating” for (bmep 92.lbf/in 2 ) both blown, to 3,700 bhp at 2,200 rpm 130 lbf/in 2 ) when turbo-charged and cooled. Note that the “Deltic Compound” prototype 5,600 bhp output on test 1956.

T he Model

The working is an 18 — cylinder, opposed 2 — …, spark engine. The model is based on, is follows, the design principles, of the DELTIC Diesel engine to a 1/8 scale. The design was produced a single cross section of the marine version as published in T he M Engineer plus the bore and dimensions.

This drawing was photocopied and onto several A4 sheets with a different scaling

Here is the drawing upon Clen based the model. on the image above to see a larger (File is 251 Kb.)

The internals of the are to scale, that is the bore, connecting rod length, porting and dimensions are accurate to within 5%. ( off metric equivalents of inch This gives a model of approx 160cc ; hence the 160” logo on the crank

The following is a list of the major from the prototype design:

cylinder cent er s have increased to allow greater volume around each

2.The connecting rods do not split big ends due to scale restrictions. This has involved the of a built-up crankshaft with bearing main and big end bearings.

the design has changed to accommodate distributors, spark plugs and oil pumps ( 1 pressure and 3 scavenge). A deal of external decoration has been added.

The engine has 3 of 6 cylinders arranged on the sides of an triangle. There are 3 “V12” assemblies, one at each corner of the There are 36 connecting rods and with 6 pistons operating in one set of and opposed by pistons from the at the opposite end of that cylinder

The exhaust and inlet ports in the walls are “opened and closed” by the

Current state of the building

The model is approximately 90% complete the major structures in place crankshafts, connecting rods, liners, timing/phasing gearing, blower, exhaust manifolds, plugs, distributors, oil and water

There are no castings used. T he model is machined from bar stock and “made to look castings.

The engine is currently with tight slide fit (without rings) installed to the accuracy of machining and assembly and to that it is possible to assemble the with all piston assemblies to the rods. I am happy to report it does go together and that it freely.

The oil pumps together the full flow filtration are complete together with the for the oil spray to the crankshafts and scavenge from the two top crank cases. The pump, with feed and plumbing is also complete. The blower together with relief and control regulators is now in The current project is the ignition

The 18 spark plugs are fitted and if the is to run at the modest speed of 5,000 rpm it require 90,000 sparks/min. If it ever to get to 20,000 rpm (it is tiny that would be 360,000 I am building a six-element infra-red trigger unit to mount on the end of the crank. Each of these will control one of six CDI modules. The major project will be the pistons with the 144 rings ; 2 and 1 oil control.

In practice I may not populate all of the

C ylinder B lock and Liner

The cylinder blocks are machined in 3 the centre section, the exhaust and ends. Annular rings the ports are machined into the faces, the exhausts exiting to the as per the prototype but the inlets to the inside

The cylinder liners are machined grade 17 cast iron and are of the design as the prototype with 4 grooves machined over the for cooling water. The two central are inter — connected by a of axial grooves. At each end of the and between each annular there is an “ O ” ring.

Each liner has a discrete cooling with water entering via a ed hole through the block and the ring to the outer end of the exhaust Water then passes drillings in the block to the first of the grooves, and into the second groove via the axial grooves. here it has to pass out of the block on the face through external fittings to pass over the porting and back into the annular groove then out via a drilling.

The liners are located in by threaded bushes through the which also receive the plugs. The block assembly is together by 28 M4 cap head screws into the centre section.


Due to the relatively small and lack of space it was not felt to have split big ends to the rods. The crankshaft is therefore of the design. This has enabled an all bearing assembly to be designed.

this process it was not considered to press the components together the required degree of accuracy. The is, therefore, bonded together slide location fit components by threaded and bonded pins at joint. There are three axially at the main bearing to web and two radially at the big ends. Each of the 3 is assembled from 118 components

7 main bearing shafts

6 big end

12 crank webs

9 main races

24 big end bearing races

36 bearing locking pins

24 big end pins

A relatively simple but indexing assembly fixture was to sequentially bond the components from the drive end and followed by a big end with con-rods and the next from six down to one. On the assemblies spin freely in the and the main bearing frames.

A test assembly was first to test the bond strength. failed at one big end at a static torque of 17 This is more than to achieve my wildest dreams regard to power output.

the subsequent addition of the threaded pins I am confident about the strength of the assembly but remain regarding the high frequency stresses applied to the relatively and thin six cylinder shafts.

T /P hasing A rrangements

The timing and of the crankshafts was designed to be identical to the The entire design was taken the single cross section shown at the beginning of this When viewing the engine the front (non-drive, blower or end) the cylinder blocks are A,B and C clockwise with A to the left, B at the top and C to the

The bottom crankshaft is therefore C/A and runs in the clockwise direction A/B and B/C running counter-clockwise at the top left and respectively. Number 1 big end of each is at this end. All of the pistons are of design but are required to perform the function of opening and closing the exhaust or inlet ports in the

Again, when viewed the front, the exhaust ports of A are at the left bottom, those of B top and C right top.

The firing for each shaft in my engine standard 6-cylinder practice at They are, however, not 1200 shafts as this is a Each of the 18 cylinders fires in every revolution of the engine or a impulse every 20°.

I subsequently discovered that the engine has non-standard crank with the order of numbers 6 and 4 giving the crank order of

The firing sequence in each bank of cylinders is identical, B,C and A firing at 40 degree intervals. The intervals per bank are therefo re. 0 °. 40 °. 40 °. 280 °. The 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 all the 4’s should be changed for 6’s and visa

As with all modern internal engines, the valve timing is with “lead and lap”. To end the exhaust piston leads the piston of the relevant cylinder by 200 of revolution. This means the effective TDC position ; i .e. when the of the two pistons in a cylinder are at their does not occur when of the big ends is at it’s TDC position. The is 10 ° after TDC and the inlet 10 ° before.

It is to express all of the port timing in to BDC of the piston related crank.

The timing for my engine equates to:

Ex 71° BBDC. (68°)

In opens 54° (53.5°)

Ex closes 71° ABDC.

In closes 54° ABDC. (53.5°)

If corrected in relation to effective the port timing becomes;

Ex 81° BBDC.

In opens 44° BBDC.

Ex 61° ABDC.

In closes 64° ABDC

The period is. therefor e, 142 ° (136 ° ) and the period 108 ° (107 ° ) The exhaust is 37 ° (34.5 ° ) and inlet lag 3 ° (5.5 ° ).

The in parenthesis above are the actual from the prototype which are in relation to e xhaust TDC and have adjusted to the same base as my

Finding the right materials

It is a challenge sourcing materials for components without spending a For the Deltic pistons Clen the correct high Silicon/low alloy and went looking for scrap pistons from big engines that he could cut up and the model pistons from the His searches took him to a marine in Portsmouth where he had been they had dismantled some engines.

No luck, but he did find racks of of brand new pistons for large Marine Engines. These are 11 in diameter and 13 long. The skirts are 7/8

Stamped into the inside are the specs and all QA data. Perfect for he needed. They cost but what a bargain! A Paxman can be seen in some of the photos

It is shown for size scale all 36 model pistons will fit the skirt of one of these large

Clen is also an associate of the Bay Area Engine Modelers of San CA. This is how he happened to be displaying his at the show in Oregon along the club and how the model came to the of the museum.

(My apologies to Clen for his English spellings to conform to the on this American web site.—Craig)

Tomlinson’s Napier Sabre—A in Progress

It can never be said Clen Tomlinson takes the path. His current project is a of another very complicated by Napier, the 24-cylinder, 2-cycle . It has two crankshafts, one above the other, driving 12 pistons in arranged of six. Therefore, each head is six cylinders long and two

It is a sleeve valve design, the cylinder sleeves slide up and while rotating to expose the openings and the piston cycles the moving sleeve. The complicated cylinder head of the original all the passages for intake air, and cooling water. To duplicate arrangement, Clen machined the in layers of billet aluminum CNC technology.

The layers are then together virtually seamlessly to up the head. A complicated gear mechanism rotates arms at cylinder that have a universal joint to both and move the cylinder liners in and out at the time. The motion almost has to be to be understood. Shown below is a head that Clen us for display at the museum that has now returned to him.

We hope you got to see it it was here, but if not, here are photos. We look forward to the completed engine one of these

Overall views of the cylinder from various angles. on any photo to view a larger

Details of the gear-driven sleeve actuating mechanism.

(Left) openings can be seen in the cylinder (Right) The head was machined in to be able to duplicate the complicated exhaust and water passages in the casting. Some of the tight-fitting between the layers can be seen

Here are photos of Clen Deltic engine:


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