Bristol Hercules 759 Running Frame





We soon realized that we could not run with a front support like the 216 , as the nacelle is in the way and the prop is to close to the front edge of the nacelle. So we designed extra bracing for the rear mounting frame, then passed that over to to Dom and he cut it out on his CNC Plasma cutter.

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We used 5 mm steel to make the extra side mounts with internal gussets .

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Then a couple of extra stays back on to the lower frame.





We plan to mount the tanks more to the side , which will cover  up the extra steel work and leave the center section open so the rear of the engine is visible.img_5174 img_5175 img_5178img_5254


New Tank mounts have been made just like on the 216 but offset to the outside.





Note the extra casing that is fitted to this 759 to allow electrical connection to the prop hub,as there is limit switches inside to allow interlocking for prop thrust reverse.


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With my very helpful wife Gill the prop hub and one blade was mounted to check clearances. As you can see the blade in full feather would touch the frame. After a bit more measuring , we decided that 60 mm needed to come out.

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After Chopping the frame back by 60 mm, it was all clamped back up and welded up. Next job make up the tanks.



Sleeve Valve Demonstration Uinit

At the shows, there is always two questions asked from young and old.

1. How dose a Radial engine work

2. How does a Sleeve Valve work

So we decided to make a display unit that can be taken to shows and people can have a hands on demonstration of both of these questions.img_4837-copy img_4846

We had a old 264 engine that we had removed all useful parts, so we decided to use this to make our display unit. First I cut up the front crank case section then the timing case cover using a reciprocating saw.







Next I fitted a Cylinder and five sets of timing gears




Next job was to weld back together the master rod, as this had to be cut to strip the engine as that cylinder would not come off.



Next I cout down the front half of the crank manaton and make a replacement crank pin to allow the master rod to be attached.

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The last job was to make a cranking handle , it works a treat. Over winter Pete will tidy the casing up and crankshaft on the milling machine, then all we have to do is make a perspex box to go over it , as there is plenty of finger trapping gears and sleeve valve ports etc.


2016 Shows

May 8th & 9th

The first show as usual is the Flying man Festival at Pocklington and the 102 squadron reunion

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May 15th Kelso

The show was at Kelso show ground in the Scottish Borders, we showed along side William and his Merlin



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Nice tow vehicle Will


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June 11th Scruton Village Fete near Northallerton

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June 12th Breighton Airfield fly in



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July 17th & 17th Farnborough International Airshow


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July 23rd Bagby Airfield



Aldborough & Dishforth Show held at RAF Dishforth

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August 5th & 6th Croft Nostalgia Weekend


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September 10th End of season BBQ at ours


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Peter and Graham turned up with a Merlin , It had not been run in ten years, but it ran fine.

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Ken Rusby who we met at Crof talked to us at Croft about his Dad who lost his life in a Albemile crash in WW2 , he was born three months later, he has don a lot of research into the crash and was chuffed to bits that we arranged to have a plaque fitted to the engine frame in memory of his Dad and crew mates that lost there lives. After the very touching speech he made he then brought out an actual Bristol Hercules Cylinder from his Dads crashed plane, To see him stood there with that cylinder against the 216  just makes the long hours of work worth while.





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The Following day after tidying up after the BBQ we decided to invite Mike Hemmingway to remove two old Mags from a scrap 264, after a couple of hours he was chuffed to bits with his afternoons work.

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We would like to thank everybody we met this year for the kind words and encouragement. Now its time to finish off the 759 ready for 2017! , then we can make twice the noise…….

Bristol Hercules 759 Rebuild Completed

As the Christmas holiday break is nearly here I decided to push on and get the 759 put back together and sealed up, as this weather we are experiencing cold then very mild is causing a lot of condensation and that is the last thing we need inside a Hercules Engine.


As with all of the sleeves, plenty of grease was applied to protect them.

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On No. 4 cylinder head, we found that part of one of the sealing rings was missing, this has been missing for quit a while, but no damage to the sleeve was found.


We have plenty of new head rings in stock , so new ones were fitted.


There was only one more head that had worn rings, as you can see from this picture the original ring has lost a bit of it’s shape compared to a new one.



Once all the heads had been fitted and torqued down, all of the lock tabs were set again.

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Next is was the painstakingly steady job of refitting all of the air defectors and exhaust, it’s not a quick job but once you figure out the order of assembly it’s straight forward….


Finally the last split pin is fitted and the exhaust is complete!.

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Next job was to reassemble the nacelle. The inner panels were cleaned and then fitted.

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And there we have it , all re-assembled and seal up , now we can get back to finishing off the ground running frame for the 759.

759 Rebuild

After speaking to our friends over in Canada, we managed to acquire two spare sleeves and pistons.


First job was to make a new “O” ring for the base of the cylinder.


Using a pair of modified cir clip pliers , swapping the piston was a quick job.


We got a new piston ring compressor from Snap-on , It works a treat.

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The replacement sleeve was fitted and secured.



Before the cylinder could be fitted, the induction belt was refitted.


No.3 cylinder being refitted, plenty of EP2 grease was smeared allover the sleeve as it may be a few months before we fire this old girl up.IMG_2331

After the base nuts were tightened down the induction pipe was tightened up, time for another beer. The next cylinder to be fitted is No. 5 and that will complete the back row.


759 Strip Down

After finding out we had a couple of rusty sleeves in the 759 it was time to do a partial strip down and fix the problem.

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First job was to remove the center section of the nacelle, this was done in minutes as these are attached with quick release catches.

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First we pulled off No.14 head as we knew that this was one of the affected cylinders.

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After we took the head of we removed the cylinder which came off easily, then we removed the two nuts securing the sleeve to the sleeve drive joint. Tip of the day tape on your socket so it cn not drop off into the bottom of the engine case.

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This is when we encountered our first problem, the sleeve was seized onto the piston , we managed to pull it up so far but we could not rotate the sleeve to get it lined up with the opening of the engine case. The engine was still seized , so we had to start removing more cylinders to allow the engine to turn enabling us to remove no. 14 sleeve.

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We realized that No.5 was also stuck so we started to remove that one.


The problem we had here is that even though the cylinder was coming off quite easily, we could not turn it to clear the nacelle. So the induction belt was removed to give us clearance.


I the end we had to remove six cylinders before the engine would turn, besides No.14 and No. 5 sleeves being rusty , it was the fact that the oil had dried out between the sleeves and the cylinders on the upper cylinders.


We had to make a very strange looking spanner to get one of the sleeves off.

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After cleaning all of the cylinders, one of the cylinder rings had to be replaced, we used one from a spare 264 cylinder, it was a bit fiddly but we got the ring replaced. As you can see in the upper picture the bit of surface corrosion build up on the cylinder, this did not take much effort to remove.



Considering we thought that the 759 was a quick fix, we had to take off a lot of parts, time for a beer I think.


216 Finished, Show time

Well we have had a very busy few months finishing off the 216 and attending a few shows this summer,

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Our first outing was at the old RAF Pocklington Airfield where we had been invited to the 102 Squadron reunion  on the 9th and 10th of may, where the Merlin that we had cleaned up was unveiled

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On the Sunday we invited an 93 year old Halifax Pilot of 102 squadron Tom Sawyer to start up our 216, we didn’t have to ask him twice! he was chuffed to bits.


The next outing for us was at the Duxford Flying Legends 11th and 12th of July, before we went down we made a new tachometer from a Land Rover defender speedo. and a new air intake and fit some new guages.

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We modified the Land Rover speedometer  drive spindle to fit the square drive on the Hercules, then made a brass bush to hold it in.IMG_1628 IMG_1629

And here we have the finished article, the original tachometer drive altered to drive a Land Rover speed transducer which then drives a 80mm Land Rover Defender speedometer, we used a pulse multiplier bought from ebay to allow us to calibrate the speedometer.


We used an old Snapon timing light to calibrate the tachometer.

The next job was the air intake.

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This was made from a stainless steel 6″ bend split in two then spaced out to suite the intake.

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Pete made up a flange on the milling machine to fit the engine.

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Once welded up and polished , it certainly looks the part.

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We then fitted some new Gauges and a new cover over the hydraulic controls for the trailer .


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We had a great weekend down at the Duxford flying legends where we got through a lot of Av-Gas! Before we went down we fitted a couple of brass plaques, One for my Dads crew and the other for Peter Blackburn’s Dad.

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We ran the engine every 45 mins during Saturday and Sunday up to 13:00 just before the Air Show starts, It certainly drew a lot of attention.

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After Duxford our next show was a local three day family music festival called the DeerShed Festival only two miles away.

Last year we took the 216 just to show it as a static display, and the amount of people that asked us when we were going to start it! so this year we were invited back to run the engine and it was great success.

We decided before the DeerShed festival that we would take the 759 with us also, so this meant getting  it out of the pod and mounted on a frame! nothing like a bit of pressure, we only had two weeks to do this!

The first job was to make another frame.

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After a dry fit of the steel work, Pete milled in the mounting holes for the engine mounts.

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Once the mounts had been done the whole frame was welded up ready for the 759


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The first time the 759 has seen daylight since 1971, even as Peter was watching the engine come out of the pod a Swallow had a fly by.



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When we got the engine fitted to the frame , it was time to re-hydrate the engine before we lifted it onto a trailer ready to take to the show.


At the show we fitted a full size Rotol Prop, this has put an idea into our heads, should we design a frame to fit a 14 tonne truck so we can run a full size prop at some time!

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At the end of the show a friend of ours Ben Potter brought his 9 foot wingspan Steller’s Sea Eagle called Camillia over to have it’s picture taken next to the Hercules with all of our Grand Kids and friends . Ones born to fly ones built to fly!



Our next trip out took us to the Scottish Borders Agriculture Show at Duns on the 1st of August.

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A lot of local people had a lot of knowledge of the engine as there was two local Airfields that used to be home to Beau-fighters.

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At the Show there was a 1944 David Brown Airfield tractor tug, so thought that we would introduce them!


A young future pilot i think!

After the engine run,Gill my wife did a bit of house keeping and cleaned the prop blades.

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Our next job is to sort out the 759, when we had the full size prop on it , we tried to turn it, it was stuck!.

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Using a Snapon endoscope camera we looked inside the cylinders, all were like new as to be expected except No.14

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It looks like this one had missed the inhibiting oil!, we have took the head off and the sleeve is too rusty, so we will have to renew that one.

New Engine Stand Build Up


First we lifted the engine off the new stand.

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Then we prepped and primed the new stand.




After the engine mounts wear cleaned and painted we refitted them using a very clever mounting pins.

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After the frame get its top coat  silver and lacquer, we refit the engine.

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Also we refitted the bump stop underneath the engine to absorb shock loads while on the road.

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Next we refitted the tank and actuator mounts after being  zinc plated coated.

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Now it was time to assemble the fuel control tank and the fuel tank. The left hand tank houses the priming pump and control valves.


After quite a few hours welding we had them finished.

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Last job on the left hand tank was to fit the access door.


After testing the fuel tank for leaks, the tp was welded on and the filler cap fitted.

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The tanks were now fitted to the stand using stainless steel straps.


New Engine Stand

Well Since September we have being busy building a new engine stand for the 216



We Got the Steel cut to size by a local steel supplier which saved us a lot of time and effort.

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Pete has added another toy! to his workshop, a CNC milling machine, he quickly got stuck in and bored the holes in the box section for the mounting pins.

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Ensuring everything is square before welding the base together.

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Next we put together the rear mounting arch, which is designed to take our already fabricated oil tank.


While I was fabricating the frame, Pete started making the four mounting pins.


After tuning the pins down they were then slotted and shaped on the milling machine.


One of the finished mounting pins being test fitted.



After the engine stand was put together, we made a “A” frame to all us to lift the engines on and off the engine stand, It was designed also to lift and engine mounted  stand, this will allow us to lift the stand with engine on and off the trailer.

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The first job for the “A” frame was to lift off the old engine stand with engine from the trailer.


The next thing to do was lift the engine off the old stand.

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Now we can fit the engine to the new stand.

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To allow for shock loads while the engine is moved on the road, we fitted a rubber front support.


We decided to design and make two cylindrical tanks for the rear of the engine frame, one for fuel, and the other to house priming pumps and valves etc.

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Dominic made up some brackets for the tanks on his CNC Plasma cutter.

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At the same time we made up the oil tank,control box and linear actuator mounts.


Now you can see what the tanks are going to look like!

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We decided to make some new control cranks or the throttle, constant speed control and fuel shut off.

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Pete enjoyed getting stuck unto his CNC milling tasks!





After the cranks were made he then mounted the actuator mounts.


Next Pete made some brass bushing for the cranks.


The next job for Pete was to make the crank control shaft mounts.

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Test fitting the mounts.

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And there we have it, ready to be fitted to the new stand.


The next job is to remove the engine from the frame and paint it, also remove the engine mount tubes and have them cleaned and painted, while this is being done we will finish off the tanks ready for assembly. We hope to have it all done by the first week of May 2015.






The Big Day, First run of the 216

On the 27th September 2014 we asked a few friends and Bristol Hercules fans to come along and enjoy a beer or two and a bit of a Bar BQ.

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Brian Mills brought his 216 along to keep ours company..

We had a practice start the previous night just to test all of the control systems and we developed a major oil leak from the prop hub. So there was only one thing to do, put a pair of head torches on and strip it down in the dark!

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The problem was the seals that the four actuating rods go through wear split, luckily we had some spare ones from the other prop hub.

Here is a clip of the first start up and you can see when the oil seals let go, as the oil gets sprayed all over the exhausts.

This next clip is the final run of the day when we had both 216’s running together,  now that is a moment in time everybody there won’t forget in a hurry. Brian had a bit of a technical start up issue, he forgot to turn on the fuel, easily done as we made the same mistake the previous night!

After the final run we retied to the marque and enjoyed a few beers and food.

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Peters wife Jackie did a great job of the cakes they look familiar!

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Also the table decorations consisted of a Cylinder , Sleeve, Cylinder Head and Piston from the 264, Thanks again Jackie for your green finger touch.


For all you Bristol Hercules buffs you may of noticed that our 216 was running a bit rough! well to tell you the truth is was only running on 8 cylinders!. There was not a lot we could do about it on the day but we found out that it was one of the mags was hardly working and the upper ignition harness was badly corroded and had water in it. That’s what happens when you leave these old girls outside!!!

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On first inspection, the upper ignition harness was corroded and seized into the distributor top on both sides.

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There was only one way to get it off and that was to brake it off!

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We chain drilled the remnants out with the view of making a new insulator.

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But as luck would have it , in and among our 264 parts we acquired when we got our first 264 there was a lower ignition harness for a 216! with one good magneto connector on it.jet art 002 jet art 010

Because we only had one harness to Mag connector we contacted Chris at Jet Art as we new he had one new mag and a few good serviceable ones. We acquired the new left hand one and a good right hand one. A big thank you to Chris on letting us have a good look round his big boys sweetie shop.

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Oh and look what we found! a Tornado F3 that Pete had flown in his RAF career, we thought we better not bring that home as the Gillian and Jackie might not of been to pleased!

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Once we had the new magnetos, we stripped down one of them to retrieve the missing connector.

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Once we got the coupling off, we slit it down the the side and teased it apart to get the coupling out.

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We got the upper harness removed then stripped it down.

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As you can see there was evidence of water everywhere!

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Once stripped, the upper conduit was fully dried out.

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Threading the new HT cable down the conduit was straight forward, just follow the instructions in the manual and label them as you go.

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Now you can fit the spark plug conduits and elbows.

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Now we can fit the spark plug insulators.

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Its a bit fiddly, but one you get the hang of it, it doesn’t take to long to complete.

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After fitting the magneto flexible conduit, it was time to terminate the magneto connectors.mag_harness 029

We fitted a set of plugs and tested it we the new magneto and a cordless drill drive! It.

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Pete made a nice little puller to remove the automatic advance unit of the back of the old magneto.

Once we had fitted the replacement magnetos and rewired harness, there was only one thing left to do, test it.

So sit back and turn the speakers up and listen to a Bristol Hercules running on 14 cylinders , we peaked at about 2000 rpm and -2 psi of boost.

The last job to do before we start building the new engine running stand is to connect up the constant speed unit control cable.

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As you can see the control cable had been cut off near the engine mount ring.

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After rummaging around the workshop I found an old Land Rover Defender wiper rack cable that had a eye at one end and a piece of power steering pipe that fitted over the cable and a length of Land Rover wiper rack tube.

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After stripping back a bit of the outer wound spring on the rack to reveal the center cable, I found that a piece of 3/16″ brake pipe fitted perfectly over the center cable and fitted inside the CSU outer control tube.

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After tinning the cables , the two parts wear soldered together.

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And there we have it, we have full control of the Constant Speed Unit.