Bringing Inhibited Engines Back to Life (e.g: DB601)

Just a question from me,…

Seeing as there was the “Flug Werk” thread going also…

How does the RR Merlin compare with the DB601’s for stripping and rebuilding, parts rarity aside ?

Does the fact that the DB601 appears “upside down” make a difference ?

Cheers
Chris

peter

Is there any easy way to do this?

Speaking to a UK based Merlin engine rebuilder his feeling was that providing an engine was correctly inhibited you still wouldn’t want to leave it standing for more than 10 years before pulling the bearings out to make sure there was no corrosion build up between the bearings and the crankshaft etc.

Wot about this then??

What about ground running an engine that has not been stripped down for inspiection but was inhibited by the air force in the 60s and reinhibited in the 80s? iIt has been given a top end inspection by a qualified merlin mech?

Originally posted by Seafuryfan
WarbirdUK – might you possibly be able to illicit views from any engine specialists at RR?

The watch word here should be ‘Never assume!’ however, a good record of work & items replaced should be kept as it is not uncommon for some ‘over haulers’ to asset strip a good engine & replace the good with not so good. Some years ago an engine was sent to the States for an inspection as the engine which had test hours only on it had sat in a crate for many years & had minimum paperwork so, off it went, It came back looking very good with all the right bits of paper so it was put in the aircraft where it flew for around 160 hours then it broke with metal in the filters big time! so the engine was stripped & lots of wear was found to the extent that the case hardening on some of the gears was almost worn through! after 160 odd hours? I don’t think so but how do you prove it?
A couple of years ago I had the pleasure of unpacking an inhibited Merlin from it’s packing case & then disassembling it into large bits to help the overhaul shop that was going to strip & re build to check everything, once the 50 odd years of muck was cleaned off the paint looked rough but on removing the cam covers & cleaning up the rocker gear & cams it looked new As was the rest of the engine, I think the bearings were replaced as a caution & apart from new gaskets & seals the engine went back together & has run beautifully! But they must be checked!
Cheers………………………

Interesting point Wombat.

I agree, but an intreguing twist came up recently, in that there are certain grades of metal, required for W.W.II a/c that aren’t manufactured any more. This was for wing spars and engine parts (two seperate conversations with restorers) and the point was, yes, you could do it, by paying a helava lot for a small batch, but that (high) grade of metal, the manufacturing recipie had been lost., so the reverse engineering would be v. difficult. Wing spars on the Blenheim for instance, used the last of a batch that were ‘in store’ and are now unobtainable.

Also talking to ARCo, their comment ws that the Bristol engines from the early war period were a) handmade b) to far to high a quality than made sense in a war economy. LCT Rolt (Biographer of IK Brunel) went to work from RR at Derby during the war, and in his autobiog ‘Landscape with Canals’ says he left in disgust because RR were just mass producing engines and there was no ‘craftsmanship’ in their work (!)

Cheers

I talked to Allison employees and they told me they were under alot of pressure to get them out the door.

What was the original quality control like?

Given the pressures of war, I have often wondered if Merlins and Griffons were built to the famous Rolls-Royce standards. Were they simply brilliant engine designs, or did their performance arise from a combination of brilliant design and outstanding engineering and manufacturing quality?

Even if the manufacturing standards were the very best possible at the time, the quality of metals used would be far less than is available today, and the stresses to which they were exposed could have caused serious wear which must be detected and rectified prior to flying again. Is it feasible to replace original parts with identical modern components, using more modern materials?

Wombat

Thanks for your thoughts.

Galdri, I have not assumed that engines in service have not been stripped, but I was wondering to what degree this occurs. Articles I have read in Warbirds Worldwide indicate that companies can carry this out to a very high standard, but those same engines still appear to fail – or if it’s not the engines, it’s an ancilliary sytem associated with it (e.g. cooling).

Is it that a proportion of these powerful motors, operated to high tolerances, are bound to fail – similar to well maintained modern systems, operated to similar high tolerances, which fail in modern military aircraft?

Damien and Ant – yes, I remember hearing about the problems of German armament build quality in the latter part of the war. I’d like to know how Flugwerk will tackle these new engines – and how they got hold of them!

Eddie – interesting comment on your last post.

WarbirdUK – might you possibly be able to illicit views from any engine specialists at RR?

Re: Bringing Inhibited Engines Back to Life (e.g: DB601)

Originally posted by Seafuryfan
Engine failures which have been documented in past warbird accidents come to mind. I include the non-modded carb from the port Merlin of Mosquito RR299, and the crankshaft failure to Spitfire ‘EE606’.

As far as I know – these were both due to a rebuild by the same company?

And I believe that RR299’s carb was simply incorrectly adjusted, because the person who’d set it didn’t understand how it worked (!).

“Absolutely – particularly with WWII German kit, which was hardly built using the best quality metals or workmanship, particularly later in the war.”

As an example to add to Damien’s comments,a production line was set up in France to build the BMW 801 for the Fw190’s which were also being built in France.The French workers frequently sabotaged these engines as they were being built,practically every engine produced was duff.
An unfortunate twist to the tale is that the French decided to keep Fw190 production going after the war (they renamed it the NC.900) and these machines utilised spare French-built BMW 801’s produced during the occupation.This meant that the rates of engine failure were extremely high,and many a French Fw was brought down by French sabotage!

Well, I may not be an expert, but in my opinion NO aeroengine, be it IO-540 out of a Chiftain or DB601 out of a Messerchmitt, should be put back in use after a prolonged period of inhibitation without a detailed examination.

In the case of the DB601’s I think they should be torn down to basic components and each one of them measured to servicable limits and NDT’s (magnafluxed, ultrasoned, x-rayed where applicable). When reassembling the engine it should be brougt up to the lates mod-status- thought that might be a bit difficault with something like a DB601.
You never know where these engines have been, their prior usage and service history, so the only way forward is to make sure they are up to serviceble standards as per factory limits. Just poking your finger at them (‘well this LOOKS ok’) then putting them in a flyable aircraft and flying them is pure lunacy if you ask me!