Allison V1710 E verses F type

[dfethers]

Hi all,
wondering if we might have a couple of Allison engine specialists on the forum. I am looking at whether the V1710 'E' type engines can effectively be turned into an 'F' type engine by simply fitting the reduction gear from the F onto the E block. For those not familiar the E type was produced for use with an extension shaft to a remote mounted gearbox and propeller (P-39 etc). The F is the traditional reduction gear bolted directly to the crankcase.
I have had a look at the bolt patterns and they appear to be identical. Just wondering what else (accessories?) might need relocating.
David

 

[MIflyer]

Yes, I believe that is the case. The engine had a "short block" with a removable accessories section in the rear and a gearcase in the front. The right and left turning versions could be converted into the other version by simply changing a single gear in the reduction gear section.

My friend Ward Duncan, WWII Maintenance chief of the 9th PRS in India, said that one of the engines supplied with their F-4 (no suffix) recon models appeared to be an earlier C model engine modified with a F series gearcase. He said it had a cooling water hookup and pump that was unlike any of the F series. He assumed they were pressed to get the engines out and they modified a C series with an F series gearbox. He did not trust that airplane, though, so they used it as a hack and even modified it into a fighter in an attempt to intercept a Japanese Dinah that was making regular recon flights overhead and even taunting the Allies over the radio. They did not have radar warning at first and so the armed F-4 did not get the Dinah but a stripped down P-40 eventually did.

 

[wuzak]

The right and left turning versions could be converted into the other version by simply changing a single gear in the reduction gear section.

I believe there was more to it than that.

The camshafts had to be flipped end to end, and maybe the crankshaft too.

The engine itself actually rotate in the opposite direction - it was designed to do that..

The accessories section (including the supercharger) could not work in reverse rotation, without the expense of building opposite hand units, so an idler gear was placed in the accessories gear drive.

 

[MiTasol]

Yes - depending on the submodel group everything aft of the reduction gear mounting flange is the same.

Have a look at these Allison training school manuals. SSH-5 is already on this site but I could not find it to link to.

 

[MIflyer]

Well, Lt Col Ward Duncan said, "You just had to change one gear in the gearbox." And I am sure he knew better than anyone else I've ever talked to.

 

[MiTasol]

and the manufacturer says you also need to flip the shafts and change magnetos and starters but what would they know, they just designed and built the bloody thing

 

[dfethers]

Much appreciated thank you. I am building a full size Spitfire replica in Australia and looking at engine options. David

 

[Skyediamonds]

Dfethers,
It would be much appreciated if you could perhaps share with us more detail of your project. Sounds very interesting. Any photos?

 

[emu27]

The right and left turning versions could be converted into the other version by simply changing a single gear in the reduction gear section.

There is a little more to it than that. Given to me by an Allison overhaul shop many years ago.

To make a left hand engine from a right hand engine, you have to reverse the crankshaft, replace a regular gear with an "H" gear (this is a gear that skips over a gear that was used), and add a standard gear to reverse the prop rotation after you skip with the "H" gear. Every Allison engine has the ability to be reversed if you have an "H" gear and the added gear.

The right hand bank as viewed from the distributor end (rear of the engine) must have several spark plug leads interchanged because the cam lobes are backwards. It works out the same for the left-hand bank, somehow ... no left bank changes to the firing order
Basically, to make a left from a right, the engine must be almost disassembled because you must be able to get to the gearcase in front and must split the case and disconnect all the rods to reverse the crankshaft.
However, if you are BUILDING a left or right from parts, the difference in build up is trivial, assuming you have an "H" gear, the new gear, and you know the plugs to interchange (this means rewiring the ignition harness on one side ... so it is MUCH easier to simply build a left or right wiring harness than it is to change one that is already wired).
The "H" gear:
A Standard gear is just a gear with a keyed center. An "H" gear looks like two standard gears joined by a small cylinder in the middle to skip over the gear that was formerly meshed by the standard gear. The new gear you add is to turn the skipped gear in the other direction. All gearcases have the ability to turn either way ... the gear bosses are in all of them, internally.
For both left and right engines, the cams turn the same direction and the crankshaft is reversed and turns backwards.
There is no other engine I know of from WWII that as so easy to make turn in either direction when being built up ... two gears, turn the crankshaft around, and change the right bank firing order ... that's it.
You need a starter that turns the other way, and you need an idler type gear to reverse the direction of the cam towers.

 

[MIflyer]

But still, only one part has to be changed in the engine. Which is what Ward Duncan said.

In contrast, when they rebuilt that XP-82 they were very lucky to find a suitable left turning Merlin engine. I rankled some people I guess when I pointed out that for the Merlin you needed a Completely Different Engine for the left turning installation. In aircraft maintenance terms a V-1650 that turns the other way is a different part number and nothing can be done in the field to change that. The fact that it has a lot of parts in common with the other more common engine does not matter.

 

[dfethers]

Thanks for the info everyone. For those who are interested you can follow my progress at - EAA Builders Log

The basic design is from the original Clive de Cros plans which have been re-engineered to accept the Allison V1710. More details and some other builders at Spitfire Aircraft Workshop

 

[emu27]

But still, only one part has to be changed in the engine. Which is what Ward Duncan said

As the first paragraph of my post says, there are two new gears needed, the "H" gear plus an idler. From the Allison maintenance manual,

(3) One spur gear train from the flexible member of the vibration damper drives the accessory housing camshaft drive mechanism and the supercharger. In right hand rotation engines, this gear train is geared directly to the damper. In left hand rotation engines, an idler gear is used between the gear train and the damper. A second gear train is used to drive the generator, vacuum pump, the fuel pump, and the coolant pump. In right hand rotation engines, this gear train is driven through an idler gear from the damper, while in left hand rotation engines the train is driven directly from the damper.

Ignition leads also need to be changed, firing orders.

Right Hand Engine 1L 2R 5L. 4R 3L 1R 6L 5R 2L 3R 4L 6R

Left Hand Engine 1L 6R 5L 2R 3L 4R 6L 1R 2L. 5R 4L 3R

Plus a starter that rotates in the opposite direction, unless you want to use the Armstrong method.

Where abouts in Oz are you D dfethers once Covid clears could possibly catch up, built an RV-4 and helped out on another and an RV-6.

 

[Jugman]

The right hand bank as viewed from the distributor end (rear of the engine) must have several spark plug leads interchanged because the cam lobes are backwards. It works out the same for the left-hand bank, somehow ... no left bank changes to the firing order

That's because they share the same firing order ( 1-5-3-6-2-4 )per bank. Only the phasing between the banks in reference to crank rotation is swapped. If we use 1R as the reference for the V-1710-L the firing order is the same but with opposite bank signs.

 

[GregP]

To change from RH to LH there is an idler gear, a left-handed starter and clutch, and you have to change the ignition harness or it won't run very well, and yes, flip the crankshaft. Check the firing order for RH and LH. So, it's easy to build a RH or LH from parts (assume you HAVE LH parts!), but it requires some major disassembly to change one from RH to LH rotation.

 

[dfethers]

Thanks Greg. Any thoughts on the original topic? Is it fairly doable to convert the E to an F?
I see there are some minor changes to the oil scavenging system around the reduction gear, but other than that I can't see any show-stoppers. That being said I also can't find any literature that confirms my thoughts.

 

[MiTasol]

There are several Allison manuals in the engine manuals thread - including at least one service school handbook

 

[GregP]

Easy to convert an E to an F. You need an E-series front case and the bearings and gears thaht go in it. Simple change.

 

[wuzak]

Easy to convert an E to an F. You need an E-series front case and the bearings and gears thaht go in it. Simple change.

Does the E-series nose case have gears?

 

[MiTasol]

Go to the Allison Service School Handbook in the manuals section and you can answer that question for yourself

 

[GregP]

I believe there was more to it than that.

The camshafts had to be flipped end to end, and maybe the crankshaft too.

The engine itself actually rotate in the opposite direction - it was designed to do that..

The accessories section (including the supercharger) could not work in reverse rotation, without the expense of building opposite hand units, so an idler gear was placed in the accessories gear drive.

A less well-known difference, the middle two spark plug wires have to be swapped for a left-turn engine.