Whittle V8

[Peter Twissell]

This is a mostly retrospective build thread, as I started in March and the engine is now complete.
I detailed the build on the Whittle V8 group here: [email protected] | Topics

I have built the engine mostly to Eric Whittles drawings, but with a few variations of my own.

The crankcases start as a length of 2" aluminium 2014A, which is faced to length and split into two with a slitting saw.
The cam tunnel is drilled and reamed at this stage. It is a long, small hole and as such is the feature most likely to 'wander'. The hole is then used as the datum for further machining of the upper crankcase.

 

[Peter Twissell]

The lower crankcase is fairly simple. Fins in the underside were cut with a slitting saw.

 

[Peter Twissell]

The upper crankcase is a little more complex, with a lot of bores and internal machining.
Upper and lower halves were screwed together to finish the front and rear bores which locate the end covers.

 

[Peter Twissell]

The end covers house the ballraces at either end of the crankshaft. There is also a plain bearing at the centre.
The rear cover also houses the cam drive gears.

 

[Peter Twissell]

Tappet guides are made from aluminium and tappets are from steel.
Bronze bushes in the end covers locate into the cam tunnel and support the camshaft.

 

[Peter Twissell]

To ensure that the centre main bearing is concentric with the ballraces, it is finish bored with a bar which runs in the ballraces.

 

[Peter Twissell]

The crankshaft is first turned as a blank, with both ends left oversize.
An eccentric turning fixture was made to support the crankshaft while machining the journals.

 

[Peter Twissell]

The crankshaft was roughed out on the mill, leaving the journals square.

 

[Peter Twissell]

A small eccentric clamp at the end of the crankshaft provides centres at the two journal offsets. The flat allows for accurate repositioning of the crankshaft when it is moved along for the next journal.

 

[petertha]

Very nice, Peter. I always liked Whittle's design but felt it was beyond my skill level at least for time being. It is a nice rendition of an aero v8 with lots of practical build features. Keep us posted on your progress, the pics thus far are great.

 

[Peter Twissell]

I chose this engine specifically because I thought it was beyond my skill level.
I do try to pick projects which will force me to learn new skills and improve existing ones.

 

[Peter Twissell]

More crankshaft turning operations: Reducing the webs and the finished crankshaft.

 

[Peter Twissell]

The camshaft blank was turned from silver steel. A fixture was constructed to time the 16 cams correctly.
It took me some time to understand the way Eric Whittle had chosen to number the cams and then differently number the dowel positions on the fixture. The drawings call for the camshaft to be hardened, but in my experience of small engines, the forces in the valve train are so low that cam and tappet wear is not an issue.

 

[Peter Twissell]

The cylinders are from EN16T. The fins are formed using a 0.020" wide grooving tool, which I ground on an HSS parting tool. I am fortunate to have access to a surface grinder, which makes it a lot easier to produce the correct clearances.
The bored were finished with an expanding lap, made from cast iron. I also made a plug gauge, so I could ensure all the bores are the same size and avoid having to match individual pistons and rings later on.

 

[Peter Twissell]

The drawings show split connecting rods with bronze shims in an Omega shape foming the bearings.
In a departure from Eric's drawing, I decided to make conventional bronze shells. I split some bronze bar in half along its length with a slitting saw and clipped the halves together in the 4 jaw chuck. I machined the OD of the shells, then pressed on an aluminium ring to hold the halves firmly together while roughing out the ID and parting off the pair.

 

[Peter Twissell]

The rods were made in a conventional manner, using a simple fixture on the rotary table.
The shells are fitted with Locitie 620. Note that they are slightly rotated relative to the split line of the rod. This helps with alignment of the rod and cap on subsequent assembly.

 

[Peter Twissell]

Pistons are straightforward turning and milling.

 

[Peter Twissell]

The cylinder heads appear highly complex, but once they are broken down to a logical series of operations, there's nothing particularly challenging in them. I made a D bit to cut the small radii which give the appearance of four seperate heads.

 

[Peter Twissell]

In order to ensure that the cooling fins would align properly all the way round, I made a fixture block to raise the parts high enough above the vice that I could cut fins on all four sides at one height setting.
In another devaition from Erics design, I made the heads 1/16" taller than drawn and counterbored the combustion chambers 1/16" deep to a tight fit on the cylinder ends. My heads have an extra cooling fin on the bottom face.
This arrangement replaces the steel plate and rubber gasket of the original design.

 

[Peter Twissell]

Valves are made from 316 stainless steel. They were initially roughed out in a series of steps, then stress relieved before final turning with the slide rotated so that the seat face can be finished at the same setting as the stem diameter.