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Post by Radialicious on Dec 2, 2008 22:43:39 GMT 12
Yeah it is a good souvenir of an afternoon in Bristolville. Maybe you could post a shot of the shirt?
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Post by nzompilot on Dec 3, 2008 8:39:06 GMT 12
Yeah it is a good souvenir of an afternoon in Bristolville. Maybe you could post a shot of the shirt? Its been through the wash a couple of times so doesnt look as good. And anyway it was far better at the time with the whole package me covered with oily gunky crap from head to toe.
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Post by Radialicious on Dec 9, 2008 20:52:45 GMT 12
I've been making steady progress on the problem on the STBD engine. The problem I have been having is a decaying oil pressure that takes a few minutes to manifest itself after start. With much head scratching, I have worked my way through the entire external oil system and the internal scavenge system. First up was the indicating system to the cockpit. To eliminate the whole pressure transmitter/wiring/guage thing, I fitted a direct reading gauge to the oil pump pressure outlet. This was relatively simple to do and showed that these systems were OK. The oil feed from the tank was looked at next and to do this I removed the electrical actuator from the main oil feed isolation valve. When the valve core was moved by hand, it became crystal clear that there was no lack of oil flow to the pump! Messy messy messy.... I started to suspect the lack of oil cooling on the STBD side and the resultant change in viscosity. As there was a clear leak from the core of one of the coolers and their outlet shutter controls were inoperative, I decided to bypass them after her first few ground runs. If air couldn't be passed through them, I considered that they wouldn't be all that effective. Replacing the damaged one would be a difficult job because the leading edge has to be removed and its screws are well and truly rusted in place. However, I began to wonder if the oil temperature had something to do with decaying oil pressure. To troubleshoot this, I reconnected the one serviceable cooler (or so I thought....) It was pretty clear after Wayne Tantrum started her up for me, that I had chosen the wrong cooler. The inboard one which looked like the leaker, only appeared so because of the dihedral of the wing made the oil run out of its shutters. That wasn't a drama and I soon hooked up the good one and isolated the leaker. However the result was the same and the pressure started to drop off after three or so minutes. If oil temperature wasn't the problem, I wondered again if there was a starvation problem going on. With the feed to the engine proving to be OK, I launched into the scavenge system so see if it wasn't being returned to the tank in time for the pressure pump to send it out and about again. There was a sense of triumph when I found the gauze scavenge screen to be almost completely blocked with untold years worth of carbon and scunge that had found its way from the sump. I had cleaned a lot of scunge out of the sump as I prepared it for its first run but there was obviously a lot more in there. The sump really needs to come off to be cleaned out properly. Again that is a job that is made very difficult due to a lack of access caused by rusted fasteners. I cleaned the scunge from the filter and as much as I could from the cavity that it sits in. Todays run of the engine showed that double the period of time was needed (about 7 minutes) between 1300 and 1500 rpm before the oil pressure started to drop. I also came to realise that perhaps, the oil pressure that I was expecting at idle, simply isn't achievable. The two Bristol sisters on the wing are chalk and cheese when it comes to internal condition. The port one, while in need of a bit of adjustment in the fuel mix department, has never given an ounce of trouble and soldiers on with nice strong oil pressure all day. However, she has had none of the problems that the other one has had. I don't like to see the STBD oil pressure drop below 80 psi because that is what the placard suggests the minimum should be. However, that is with rpm above 1400 and I don't spend much time up that high just yet. The ground setting is meant to be 100 +/- 10 psi at 2500 rpm with oil at 90 degrees C. I'll do a bit more research to see if there is a rock bottom minimum oil pressure that the engine can accept. There is every chance that what I am seeing on this engine is normal for what might be a worn out old time expired engine that is unlikely to perform like its sister on the other wing. Today I may have found the source of the leak from the outboard one. The centre 'nut' of the cooler has evidence of a leak from a rigid gasket and its backwards lockwiring certainly isn't helping! I'll have a look at the manual and see what can be done. I may be able to repair it and hook them both up. The winterisation plate that can be seen on one of the two coolers in the photo above was also removed today. It covered up probably half the oil cooler core. That may make a difference. I was surprised how hot the oil gets. After the run today, I drained the sump (all 20 litres of it) to again get access to the scavenge screen. It was a lot cleaner than yesterday but I will check it regularly. Pat and my 150 litres of Avgas is now part of the atmosphere and I'll need to find some more so that I can keep up these troubleshooting runs. It was heartening to see Avgas drop by 24 cents per litre today...........
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Post by Radialicious on Dec 10, 2008 18:52:58 GMT 12
I just had a closer look at the close-up photo of the oil cooler core. If you look eight holes in an anticlockwise direction from the small screw, you can see an arrow stamp pointing at a small crack. There was obviously a problem in the cooler before the aircraft was retired. I have been told anything to do with oil coolers was typically given to the apprentices to inspect and repair. The piston engine equivalent of inspecting compressor and turbine blades.
The SAFE apprentices also became quite good at servicing spark plugs from what I hear....
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Post by kiwithrottlejockey on Dec 10, 2008 19:41:02 GMT 12
If you look eight holes in an anticlockwise direction from the small screw, you can see an arrow stamp pointing at a small crack. There was obviously a problem in the cooler before the aircraft was retired. There is also an arrow stamp pointing at the fourth hole (in a clockwise direction) from the small screw.
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Post by lumpy on Dec 10, 2008 20:31:21 GMT 12
Sounds like your on to the pressure problem . Symptoms sound like an old car car engine with worn mains , runs fine with thick ( cool ) oil , but the warning light flickers at idle when hot ( when the oil gets so thin , it pours past the worn bearings ) . As you say , probabally going to be the nature of the beast . Only solution ( other than a rebuild ) - use as thick oil as you can , and keep it cool as you can .
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Post by baz62 on Dec 11, 2008 16:42:03 GMT 12
Al I mentioned your oil pressure problem to my exRNZAF workmate and he was wondering if the oil pressure relief valve was sticking? Baz
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Post by Radialicious on Dec 14, 2008 20:23:48 GMT 12
Yeah, I'm hopeful that that is the guts of the oil pressure problem - an old worn engine. It does make me mindful of how she should be operated from now until the airshow. Baz, I forgot to mention the oil pressure regulator. It was one of the other things I checked early on. I was suspicious that the regulator valve may have frozen at a position that is suitable for thick cold oil but not warm thin oil. However the sliding element of the valve was free and the spring was intact.
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Post by baz62 on Dec 15, 2008 14:18:50 GMT 12
Ah. That clears that up then. Do you have the engine logbooks that point to the hours run after its last overhaul? Also I seem to remember running an oil in the Avenger described as a "detergent" oil. My memory is a bit unclear here but I think it had anti foaming properties but was it to clean out any "crap"?? I do know that foaming can cause low oil pressure but not sure if it applies to something like the Hercules. Actually if she is foaming the temperature would be higher. Baz
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isooctane
Leading Aircraftman
Petroleum Chemist
Posts: 2
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Post by isooctane on Dec 16, 2008 10:55:30 GMT 12
Hi Al, Its with fascination I've been following your progress over the past year. I grew up in Wellington near the airport in the 70's and can well remember the Bristol Freighters rumbling through the skies along with F27's, Viscounts and the occasional DC-3. I know where I'd be after work if I lived in Blenheim... Last week I went to the Moorabbin Air Museum here in Melbourne. They also have a Bristol Freighter (and Beaufighter) that has sat outside since it was parked after retirement in 1979. 30 years has taken its toll and definite evidence of animals living within the cowlings. Sound familiar? I'm going back later in the week, this time with a camera. I passed on your story, it would be great if it could inspire some action over here.. Re the oil pressure issue with the starboard engine, I notice it blows a lot more smoke than the port one. It reminds me of an experience I had with a Mini 1275 engine once. Same symptoms, fine oil pressure on start up but slowly lost it as the thing warmed up, 50 at idle went to 10 or so. Went thru usual checks eliminating all leaving only the pump etc. With reluctance stripped engine and found centre main bearing spinning in its housing, journal completely r@#ted... Have you thought of talking to some oil company reps and see if someone can organise a used oil analysis for you? Then you could get an idea of what wear metals are present in what quantities etc and help you diagnose the problem. Perhaps an oil company would also be prepared to donate some oil/ fuel for a good cause. A "proudly sponsored by BP/ Shell" sticker would look good for them on such a fine old machine that is now getting a lot of exposure worldwide via the internet...
Congratulations on your achievements so far and also to all the people who've crawled out of the woodwork with stories, knowledge and experience, not to mention Bristol bits!
Best wishes Michael
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Post by Radialicious on Dec 16, 2008 20:35:12 GMT 12
Hi Michael, thanks for your letter. I'd love to think that we could inspire some life into another B170 in your neck of the woods. It is quite a big ask to bring one of these things back to life but by jeez what fun it can be! Get those who can, to get a team together and hook up a battery cart. That will give you the most obvious indication of how much work you have in front of you. ZK-CPT woke up with probably a great deal of suprise but rewarded my interest with a real keen-ness to get rowdy again. I have had very little to do with the electrickery of CPT and with its cooperation, the results were a lot easier than if she had become a 12 ton short-circuit. The video clips of Big Bird running do suggest a more smoky start from the RHS versus the left. I can assure you though, Old Lefty is just as smoky as the right if she is left to sit for a while. The Stbd one was up until recently, suffering from oil siphoning from the tank into the engine. This would eventually swamp the sump and the remainder would settle into the lower recesses of the crankcases. If left for long enough, this oil would find its way past the piston rings and into the cylinders. The oily burp would leave the undercarriage leg black with oil and the remainder would take quite a while to burn off. If for example, both engines were run and then run again the next day, there is smoke (not much) but in equal amounts.
We do oil analysis on our Nanchang and Tiger Moth and it is good to establish a trend of what is sifting around in the oil. I think in this case however, there is such a lot of old stuff swimming around, we would need to run her for a long time to establish a trend. We know nothing about this engine and it is likely that it may have been bolted on just to make CPT look nice. I'm giving a lot of thought to how she needs to be looked after in case she has 'special needs'. A few people have suggested that a fuel company be approached to assist with fuel and oil. We will be looking into this. I can't help but thinking that SAFE Air is enjoying some unexpected worldwide advertising too....
It's great to see that the leaky old rattler inspired you to join the forum. Cheers!
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Post by Radialicious on Dec 22, 2008 23:19:30 GMT 12
Last night, Marty and I towed the Bristol back on to her pad as the guardian of the Marlborough Aeroclub Clubhouse. Might I say that she well and truly dug her heels in. She was like a cat going to the vet as she was pulled off the airfield and back onto the concrete pads that were her home for 22 years. It was a bit of a shame as recently, she has been the backdrop for some foxy-as model shoot and the launch of some new Mazda. Mazda is on to a winner here. Just how bad could your new product look when parked next to a B.170? She enjoyed her time on the airfield but the security of the tie downs on her concrete pad make good sense as our nor-west season picks up. Before we parked her up again, Marty and I took her for a drive to the MAC hangar to settle the rumour that she couldn't fit in the doorway. Sure enough, as the RNZAF found with their B.170, she was about a foot too tall to go inside. I had thought it would be quite funny to surprise the aero club with the Freighter parked amongst the Tomahawks and Cherokees etc. She will spend some time in her element again soon over Easter. Bring on Classic Freighters 2009!
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Post by baz62 on Dec 23, 2008 15:06:39 GMT 12
Al I have on loan from my exRNZAF friend at work a pristine copy of the Bristol Hercules (Mark VI XI XVI XVII and XVIII covered). Very nice colour schematics of the engine and various sub systems. Under the low oil pressure trouble shooting guide: Obstruction in the oil circulation system or in the feed or scavenge filters.
Air leaks in the pipelines particularly on the suctions side of the pump.
Sticking or leaking oil dilution valves.
Defective oil pump.
A bearing may have failed (!!!!!!)
I think you have looked at these areas anyway but just in case... If yoiu like I can scan areas of interest for you. Theres lots of maintenance info and drawings.
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Post by baz62 on Dec 26, 2008 14:28:20 GMT 12
Heres a couple of schematics from the handbook :
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Post by b10m on Dec 28, 2008 9:11:02 GMT 12
How english is that. "held by seven stout bolts," like having stout shoes for walking.
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Post by Radialicious on Dec 30, 2008 19:40:48 GMT 12
In Bristolville, stout really means stout. I'm sure there are less stout bolts holding the Earth in it's orbit I have been meaning to reply to Baz62 and recently, Paul Hawkins who has had difficulty posting on this Blog. To do so and also provide a bit more discussion to those that are interested will do three birds at once. From Paul through Stu, l seem to have a real problem trying to post a message on the 'Wings Over Cambridge Forum' l have sent a few messages that just disappear into the unknown. l think l should let you know who l am as l am asking a favour of you. My name is Paul Hawkins and l live in Terrace, British Columbia. My two partners and l operated Hawkair Aviation's Bristol Freighter C-GYQS and Carvair C-GAAH until 1999 then ferried the Bristol to the Wetaskiwin Museum, Alberta in 2004 which was the last flight of the last airworthy B170. Sadly it will never fly again but as least it is in good hands. My suggestions to Al regarding his oil pressure problems.... Have you checked the Purolater filter which is on the pressure side of the oil system ? As the scavenge filter is collecting so much coke, sludge and other muck any small particles that the scavenge filter cannot hold will finish up in the Purolater filter. lt is situated on the left side of the engine just forward of the sump in the supercharger case. A cast aluminium cover held on by 8 to 10 five sixteenth studs when removed will expose the filter. lt is a very fine filter so could get very contaminated if there is a lot of crud in the system. I have tried pulling the Purolator filter and whilst the cover comes away easily, the element inside prevents it from coming completely off. I'll have another look at that in the new year. There is possibly something going on in there. However I do wonder if a blockage or restriction in the supply circuit could cause a low pressure problem. Particularly when the pressure tapping is directly off the pump and such a restriction should increase the pressure. In saying that, an internal blockage would then tend to send more oil through the external circuit to the front cover and the sleeve drive lubrication circuit. Clearly though, not being able to pull the filter suggests something is not quite right.ls the anti-surge-valve opening ? Two ways to check it. On the threaded cap that is removed to take the valve apart there are 3 or 4 small one sixteenth drilled holes that act as indicators if the valve is stuck closed. lf oil is seen seeping from the holes then the valve is US. lt can be taken apart with caution to clean or change the seal. Best to use a vice or bearing press while undoing the cap as there is a big spring inside that will really get your attention when it flies out. lt is a very messy job to remove and if the bolts have nuts on and not anchor nuts you will have to get behind the feathering pump on the other side of the firewall. One of Bristol's many Monday or Friday stupid ideas! You could run with the chevron seal removed so the ASV is open all the time all it will do is increase your warm up time. One other way of checking the valve is to monitor the oil temp after start up. The temp will drop off a few degrees as the ASV opens. The colder the out side temp the greater the drop. I have another ASV from the generous donation earlier in the year. I really do hope that SAFE Air did modify the bulkhead to fit anchor nuts as plain nuts would really be a pain in the brain to access. I suspect the ASV is opening because of the leak from the leaky oil cooler. A slower warm up time and thus a longer 'cool time' is preferable in my case because we arent going to pull any serious horsepower. I will check the ASV out though and wonder if the thinner oil that we are running could be upsetting it. Thinner oil does explain why the oil is circulating though the coolers early on. As I am aware, the ASV recognises viscosity and relates that to temperature instead of the 'Vernatherm' system that uses a temp. bulb to measure temperature in the first instance.ls your engine oil temp rising as the engine oil pressure drops ? lf the oil cooler shutters are inoperative and closed the coolers will not work very well. lf you cant get the actuators to work try disconnecting the linkage so the shutters blow open. lf the oil temp is too low throw an old glove into the fairing on each cooler it disrupts the air flow enough to bring the temp up, it worked for us! The oil temperature system on the STBD engine is U/S but I am going to swap the bulbs between the two engines. Old Lefty is soldiering on like a locomotive and there is now a clear need for temperature indications on her sister. I have disconnected the outlet shutters on the STBD side and they sit open wide. There may be a need to bite the bullet and remove the leading edge and fit a replacement oil cooler in place of the leaking one. The more cooling is probably better in the long run.Just a couple of ideas that may help you but l think you are a pretty smart guy. l wont mention the pilot thing !! Anyway congratulations on getting the old girl running, you did a great job. Regards Paul Thanks Paul, it is great to have another wise voice to listen to!Baz, thanks for the suggestions, Obstruction in the oil circulation system or in the feed or scavenge filters. The scavenge and feed system seems to be a lot cleaner than it used to be and I'll be checking it often from now on.Air leaks in the pipelines particularly on the suctions side of the pump. I'll double check the hose joints on the suction systemSticking or leaking oil dilution valves. Not fitted! She already uses enough fuel!!!Defective oil pump. Possibly. I have wondered about the replacement pump and also the O-rings that were used when I fitted it. They were sourced and fitted from the best that I could find. I might try a bit harder to source the exact seal or an approved alternative. Searching so far hasn't turned up any matches for the part number in the parts catalogueA bearing may have failed (!!!!!!) Always in the back of my mind!!! That would possibly be the beginning of the end for that engine as I would be reluctant to run her if I knew that she was self destructing. It is a possiblility considering the dramatic return to life that she suffered back in June.It seems that I have enough to keep me going and I'm pleased these problems are occurring now instead of in front of an airshow crowd. Cheers guys!
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Post by Radialicious on Jan 2, 2009 21:24:13 GMT 12
[glow=red,2,300]5 OF 14 CYLINDERS AND SLEEVES FREE![/glow]
The 5th one came unstuck today and is the first sleeve to be able to be reciprocated through its entire range. It is is still too tight to be operated by hand but will clean up sweet as.
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Post by baz62 on Jan 3, 2009 8:22:10 GMT 12
Hoorah! Great news Al! When the last one is done you can have a Sir Edmund Hillary moment!! Thanks for answering all those questions it's really interesting to me(and everyone else!) since i'd enjoy bringing an old aircraft and/or engine back to life. I did wonder about the oil dilution valves being for a much colder climate. Baz
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Post by corsair67 on Jan 3, 2009 12:15:09 GMT 12
[glow=red,2,300]5 OF 14 CYLINDERS AND SLEEVES FREE![/glow]The 5th one came unstuck today and is the first sleeve to be able to be reciprocated through its entire range. It is is still too tight to be operated by hand but will clean up sweet as. Well done, Al - that is truly awesome news, mate. You must be feeling very happy about this? I love reading these updates too, especially as I know so little about the internal workings of these engines myself, so it is great to feel like we're in the loop with all your experiences.
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Post by Dave Homewood on Jan 3, 2009 13:52:58 GMT 12
Hear hear!
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