Monthly Archives: December 2013

Piston removal

The first job is to clean the bore of the sleeve below the piston,

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then placed the sleeves in containers and flooded the back of them with our Special Brew.

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After only a couple of hours the Special Brew had started to work its way through.

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While these are soaking, Pete machined up a base plate to fit our 20 tonne press, so the sleeves will sit square and hopefully we can push the pistons down out of the sleeves.

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Since it’s New Years Eve, the top shed got a new sign, time for a little light refreshment,

Happy New Year everybody….


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The rear case came of quite easily, we used a chain pull to extract the case through bolts.

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Once all of the bolts are extracted the rear case is lifted off, then the rear maneton bolt is removed, now that was tight!

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The rear row of cylinders can now be lifted off.


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Now it is time to remove the pistons. First we placed in a 20mm spreader  plate on top of the piston, this should spread the up to 20 tonne pressure across the face of the piston.

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After a little pressure the first sleeve gave birth to a piston!

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A couple of the pistons were a bit on the tight side,so we filled the sleeves with special brew and warmed them up in front of the space heater, which worked a treat.

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The last pistons to remove was the master rods 4 and 11, these were a little bit more tricky to clean, as there was less space to work in.

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Pete altered the base plate to allow for the master rod.

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And there we have it, the final piston removed.

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All the children safely tucked up in bed ready for cleaning.



Supercharger casing removal

Now that the engine is vertical it was quite straight forward to remove the engine mount ring.

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Next undo a few locating 1/4″ nuts on the supercharger casing and lift off the supercharger! except one of the through bolts was seized in the rear casing.

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So in the end we lifted off the casing with that stud still seized in the casing, it will be easier to sort that out later on the floor.

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Move the stand out of the way and transfer it to Mr Hoist…

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yet again the internals of the engine are in remarkable condition.

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Just six more studs to remove and we can remove the rear crank case and finally remove the rear sleeves and pistons.



Crankcase Stand

We decided to make a crankcase mount addition to the engine stand. this will enable use to rotate the engine into the vertical position to allow us to remove the engine mount ring, supercharger, rear section of crankcase and finally the back row of con rods and pistons with sleeves.

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First thing we did was make some plates that mount onto each side of the middle section of the crank case  at cylinders 4 and 12.

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After tacking some box section onto the plates we then fitted 40 mm shafts into the box and using a laser to ensure the shafts align through the engine.

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Next job was to build up a frame each side to mount a pair of bearings.

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We then added a pair of bars to enable us to lock of the engine in the vertical position.

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We drilled holes in the box section to allow us to plug weld the shafts.

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The moment of truth! take the weight of the engine at the rear and remove the engine mount, then rotate the engine into the vertical position.

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We then added a couple of extra steady posts, next job removal of engine mount ring and supercharger.

Crank Case Strip Down

One of the reasons we have to dismantle the crank case is, we need to remove the sleeves, pistons and con rods as one unit, as the pistons are stuck in the sleeves. The condition of the sleeves below the pistons is in very good condition so they should push out with little effort.

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Removing the magnetos was straight forward

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Also remove the coupling shaft

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Starter removed, as you can see the internals of the engine is in very good condition.

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Next job was to remove the Hobson Injection System. As Pete was away driving a A340-600 to Sydney and back I used the third member of the team to assist , Mr Engine Hoist.

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Next job was to remove the reduction gear, as per the manual a little tap with a hide hammer and it came off.

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The condition of the reduction gear is excellent , and turns freely for the first time in thirty five years or so.

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Next to come off was the reduction gear drive gear.

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Take off the locking ring.

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Then take of the left hand threaded lock nut (good job I read the manual!) then remove the gear with the inner race of the front cover.

Next we will remove the front cover to reveal the wonders of the Bristol Hercules engine, the timing gears.

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And in we go! Pete spent a good day in the workshop and stripped down the timing cover and gears.

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The wonders of a Bristol Hercules, you can not stop admiring the mass of timing gears but in fact it is quite simple.

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Next job was to strip down the gears. It says in the manual “Provide provision to catch the 74 needle rollers from each transfer gear” that is an under statement! as Pete found out! But they are all accounted for.

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All the gears off now, next job is to remove the front section of the crank case, this will allow us to split the front section of the crankshaft.

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The front casing removal was quite straight forward, just get ready to catch the rollers from the front casing bearing.

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The next task is going to be a bit fiddly! we need to get the bolts out of the front part of the crank to allow us to remove the first row of con rods with the master rod, then we can remove the bottom pins from the master rod to release the rest of the cylinders.

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First job undo the maneton bolts, using special tool FB.168782 or in our case a 3/4″ drive ratchet and a six foot scaffolding pole! they where FT or very tight!

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The rear  bolt of the front maneton came straight out, the problem with the front bolt  was that it fouled No.6 sleeve. First we undid all of the sleeve ball joints, which gave us about 10′ of rotation of the engine, this was still not quite enough for us to get the front bolt out.

So we had move No.6 sleeve down a bit to give us clearance. We mixed up our special brew of Forte Diesel Injector cleaner and Variable Vane Turbo Cleaner 50/50 mix and flooded the back of No.6 piston.

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After a twelve hour soak, the special brew had worked its way through and was dripping out of the sleeve.

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Next we had to make up a puller to move the sleeve, we altered one of the cylinder removal tools by milling a slot in it to allow us to fit it at the base of the sleeve around the con rod.

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We then welded together some old puller legs to fit around the sleeve, inserted a plate on top of the piston along with the push jack. The hydraulic connection just happened to come out of one of the ports! That was lucky……

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We only needed to move the sleeve about 1.5″ down to give us clearance.

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With a bit of gentle heat from a heat gun it soon moved down.


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With both maneton bolts removed, it was a fairly straight forward job to remove the front part of the crank. We then removed the front row master con rod and all of the slave rods as one unit, we then removed the circlips on the wrist pins and dismantled it.

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Next job make a crankshaft stand addition to our frame, this will allow us to rotate the engine unto the vertical position, this allow us to strip down the rear section of the engine, gearbox, supercharger and rear set of sleeves etc.

The last of the heads and cylinders removed

Well we finally got there, we have managed to remove all of the remaining heads and cylinders. Typically the last head to remove No.3 was a tad on the tight side, but with the aid of a couple of bottle jacks it soon gave up.

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Cylinders 6,7,8 and nine came off very easily due to the oil seeping down the sleeves over the last thirty five years or so.

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No 9 actually came off as per the manual, remove base nuts and slide off!

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The last base nut removed

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The last cylinder to come off was No.3 , like the head it was a bit reluctant to come off, but with a bit of pressure from the 30 tonne jack we teased it off.

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And there we have it, phase one completed.

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Time to re hydrate!

The next few jobs are to remove the magnetos and carburetor,  then we will start stripping down the front of the engine.



New Rotol 4 Blade Prop

Well look what we have found!

A brand new Rotol 4 blade prop, totally complete. Obviously we will not be running this prop but will trade it for parts we will require.

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We would like to display an engine with the full size fourteen foot prop on next year at a memorial service held by the RCAF only a mile from us at  Skipton on Swale , it should look mighty impressive.


Heads 6,7,10 and 14 removed, also cylinders 12,13 and 14 removed.

Well steady progress this weekend with a few more heads removed and three more cylinders removed.

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Here we are using the air line adapter to aid a head removal, obviously this can only be used when the piston is at , or near TDC.

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Here we are using our “C” spanner that we  made to slacken of the induction pipe rings, when they have move a quarter of a turn, we can use another “C” spanner with out the extension handle.

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It was time to try out the rotating engine frame! So Pete requested a rotation to starboard of  51 degrees 25 minutes and 43 seconds exactly!

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Not a problem the frame works a treat!

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With the engine tilted over we can have a good peak at the carburetor, it is

nice and clean inside and all moves freely.

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Shelve’s are filling up with more and more parts.