Five Cylinder Radial With Ohc

[Brian H]

On full size engines Lycoming- Continental. ETC. this is the standard, position.
so I had no qualms about using it. however as you will see later i am in the process
of changing it and going back to the original position behind the bulkhead. and other modifications,
but that's the purpose of development. I am a great fan of the Design it --Build it-- Brake it--Modify it
method of progress.
Brian.

 

[Brian H]

When I unwrapped this delivery my first thoughts where what on earth is the 7x12 going to do with that big chunk of tool steel.



So I adjusted drive belt so if I overloaded the lathe it would slip an set the autostop just in case.
and I was pleasantly surprised we even managed to make Blue swarf for the first time ever.




So on we went slowly slowly!!


At last the final polish will come when I fit the bearings - prop hub ETC
So on to the mill to machine the webs.







From the start of the project I have been worried about how to balance a radial engine. I investigated
every article and forum but came up with no easy answer. so I ended up static balancing the rod with a dummy
short crank pin, Then later checking the dynamic balance with a scope.



With the full length crank pin fitted the case was assembled What a relief.



Brian.

 

[Brian H]

Well I have spent hours looking for the photos of the pistons and it appears I have lost them . , Just one of rhe ring grooves being cut . and 3 pics of the last ops of the rings. these show the oversize tube of iron that was split then compressed in the lathe chuck a skim cut takes it to bore size a ring the bore size was fitted over the end and the ring parted off.
the case was then assembled and each cylinder was tested to ensure that TDC did happen every 72°

 

[Tozguy]

Awesome!

 

[Brian H]

The next stage was to try and se if the balance was satisfactory so the engine was assembled with the cylinders and pistons but no heads. Again i have lost most of the photos of this operation. but I will try to explain the method.

A wooden platform on soft rubber mounts was fitted to the mill and the engine mounted on its back with the crank shaft driven by a flexible coupling
.


above the coupling is ring of magnets to give me degree markers the TDC mark was shown with a double magnet these are read by a hall sensor and displayed on a twin trace scope A vibration sensor is fitted to the case and also shown on the scope.

underneath the mounting plate on the crank extension shaft i placed a disk that I could add weight to and alter the direction.

On the run up vibration was felt below idling speed so this was ignored above idle the vibration felt was minimal.



I Tried weights on the crank extension at all positions but only succeeded in making it worse. my final conclusion was
that most of the the error shown came from the coupling and the natural frequency of the rubber mounts.
So I decided to leave it as it is. this was finally proven when the engine ran with hardly any vibration at all .

Brian.

 

[brino]

Thanks Brian,

I love seeing an analytical approach and a problem being solved with science.

I have occasionally wondered about building my own tire balancing machine to save a trip to the local tire shop.
It's not a tool I'd buy as I cannot justify the cost/use, but it sure would be convenient every few years.....

Brian

 

[Brian H]

Having satisfied myself that the engine was not going to tear itself to pieces
I moved onto the ignition system after much thought I decided on having independent systems for each cylinder.
allowing me to isolate each cylinder in turn to test its efficiency by measuring the RPM drop
I placed a magnet in a sandwich plate on the end of the camshaft pully and had a hall effect sensor to trigger the
coil driver. these came in kit form from Jerry Howell at Outpost Enterprises.


Soldering is not my favourite pastime
but we got it done in the end.




to find TDC on each cylinder I made an adaptor to hold a dial gauge in the spark plug hole. I reckoned that if this
method is good enough for Rolls Royce its good enough for me.





Brian.

 

[Brian H]

Next was another part i had been putting off making for a long while-- the oil system originally i envisaged
a plunger pump but finally decided on a gear pump.
The engine has two areas that require an oil feed-- the main crank case and the gear case that drives the cams
the crank case feed is simple just a spray bar in the top of the case.


but the gear case required a separate feed that did not interfere with the belt drives.
my solution was to allow the usual leakage from the gear pump shaft to pass through the
extension shaft bearings and into the gear case then drain into the lower part of the crank case



The pump worked very well during the test runs. Two Well in fact even when I opened the pressure bypass fully I still
had far to great an oil flow into both areas, this is now being changed. More later on this subject.

Brian.

 

[Brian H]

After much deliberation it was decided to try a modified diaphragm carburettor fed by a electric pump .


Also a nice throttle handle was found on E Bay . and the whole thing finished with a home made rev counter.







All that was left was to make a device to start the beast.

 

[Brian H]

Originally the propeller was retained by 6 bolts (yellow) and a sandwich plate (blue) so 3 of these where replaced
with longer bolts (green) to retain the spinner this made a strong assembly capable of taking the torque loads from a starter.


I don't have a ball turning attachment so i decided to adapt my taper turning attachment fixing points to make a profiling
attachment. a master profile was mounted behind the bed and a stylus of the same radius as the cutter was mounted on
the cross slide and the slide feed screw removed. the compound slide was turned 90° to control the depth of cut. hand
pressure is used to keep the stylus in contact with the master.







All told a very satisfying result. Brian.