On a radial engine, you’ve only got one true connecting rod per row of cylinders. It’s called the “Master Rod” and the cylider which holds the piston it’s connected to is called the “Master Cylinder”. All of the other pistons are connected to the Master Rod by rods called “Articulating Rods” and they are attached by “Wrist Pins”. I’ve coloured the master rod yellow and an articulating rod red.
Because the master rod is the only one attached directly to the crankshaft its the only “big end” which follows a truly circular path with the crankshaft, all of the others follow an elliptical path. This means that there are timing errors on all the cylinders except the master cylinder. When your setting up the engine after say, a Magneto replacement, everything is set up on the Master Cylinder.
KeithMac
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By: keithmac - 3rd October 2002 at 19:11
RE: ConRods!
Hi Merlin. I suppose the biggest difference between car engines and aero engines, even inlines, is that in most cases the cylinders are separate from the crankcase and can be removed individually, or in the case of some inlines as a block. Car engines usually also house the entire oil supply within the sump in a “wet sump” while aero engines have a large oil tank to contain a large quantity of oil which also acts as an internal coolant. This is known as a “dry sump” system.
KeithMac
By: Merlin3945 - 2nd October 2002 at 23:41
RE: ConRods!
Thanks Keithmac
I was working to the same principle a car work on where usually have to drop evrything out the bottom and the push the piston out the top of the block.I understand better now. There is a better way of access to the top of the piston.
Merlin
By: keithmac - 1st October 2002 at 19:12
RE: ConRods!
Hi Merlin. In a word – No! If you want to remove the piston in the master cylinder, you remove the spark plugs and any baffles around the cylinder, turn the engine until the piston is at the top of the stroke, undo the ring of bolts which secure the cylinder to the crankcase and slide it clear, disconnect the sleeve operating crank and slide the sleeve clear, remove the gudgeon pin which attaches the piston to the master rod and finally take off the piston!
(It takes longer to do than to describe!)
KeithMac
By: Merlin3945 - 1st October 2002 at 18:52
RE: ConRods!
Keithmac would I be right in saying that if you wanted to remove the master piston that you would first have to release all the articulating rods first in order to release the Master.
Merlin
By: keithmac - 30th September 2002 at 21:29
RE: ConRods!
Hi SeaFuryFan. In a piston engine the Connecting rod is indeed the rod which connects the piston to the crankshaft and turns the up/down motion of the piston into rotary movement of the crankshaft. On inline engines they are called connecting rods, but on radials its a master rod and articulating rods. The master rod is a sigle piece with lugs onto which the articulating rods are attached by the wrist pins.
KeithMac
By: Seafuryfan - 30th September 2002 at 20:39
RE: ConRods!
[updated:LAST EDITED ON 30-09-02 AT 08:39 PM (GMT)]Keithmac, now I think I understand what a ‘conrod’ is. It’s the connecting rod (the ‘master rod’,)which connects the master cylinder to the crankshaft.
All the other connecting rods follow an elliptical path, because they are not connected to the crankshaft, but to what appears to be a circular piece of metal attached to the crankshaft.
Is that correct?
I’ve heard about ‘conrods’ breaking in the past in engines so this is helpful.
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September 30, 2002 at 7:00 pm