More 2.5cc Diesels
08-07-2012, 12:52 AM
#51
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RE: More 2.5cc Diesels
Hmmn-I must get some readings then-if it's timed too low, then a shim under the liner might see some improvement-there is no exhaust flange per se, so presumably (I've never had it apart) the liner seats on a ledge in the crankcase-and this ledge determines the vertical location of the liner-and hence the timing-similar to a lot of the Taifun diesels of the era. The latter used to seat on a copper washer to seal, so by making up a few washers of different thicknesses, we could experiment. The nice thing-with a diesel you just have to screw the contra further down to compensate-with a glow you'd have to machine the head to increase the depth inside the liner to maintain the same compression ratio..........
I must measure up the timing as well-including the drum valve.............
CJM
I must measure up the timing as well-including the drum valve.............
CJM
08-07-2012, 08:24 AM
#54
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RE: More 2.5cc Diesels
ORIGINAL: ffkiwi
Disappointing to hear that its no good for Classic T/R! Not much you can do about cylinder timing-presumably it must be timed too high? Can you give any details on what the perceived limitations were? Otherwise the liner could be shimmed.... If it was induction, then a new drum could be madeI've only bench run it-on F/F style props-and didn't tach it-but the handling is impeccable.............next time I run it I'll try and remember to tach it on a few different prop sizes............I didn't get it new-it came from a deceased estate via a third party-the purchase documentation is still in the box-it was purchased from Engines Unlimited in the UK , Feb 7th, 1997. It hasn't had a lot of running I estimate-but is run-in.
ChrisM
'ffkiwi'
Disappointing to hear that its no good for Classic T/R! Not much you can do about cylinder timing-presumably it must be timed too high? Can you give any details on what the perceived limitations were? Otherwise the liner could be shimmed.... If it was induction, then a new drum could be madeI've only bench run it-on F/F style props-and didn't tach it-but the handling is impeccable.............next time I run it I'll try and remember to tach it on a few different prop sizes............I didn't get it new-it came from a deceased estate via a third party-the purchase documentation is still in the box-it was purchased from Engines Unlimited in the UK , Feb 7th, 1997. It hasn't had a lot of running I estimate-but is run-in.
ChrisM
'ffkiwi'
I don't understand the low performance reported about this engine. My preliminary testing with a very
tight and not run-in engine was very promising. My moth-eaten documentation shows 15,500+ rpms
with a Russian 8" X 4" prop. The engine ran very smoothly; so I gave the fuel line a pinch for several seconds
and the tach showed rpm spikes over 16,000. I lost interest in everything concerning model testing around
that time. I'm retired now and old modeling urges are sneeking up on me again.
I forgot to mention that my two Pfeffer replicas are different versions. The version I test ran is just like the
ones you've pictured. My other un-run version is the "Special Edition" Team Race version that comes with a
spinner and integral fuel shutoff, also a display stand and plaque. I think they're serial numbered 451-500 or something.
Tony
08-07-2012, 12:11 PM
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RE: More 2.5cc Diesels
Tony-interesting comments-I didn't know there was an even more exclusive version of the replica! As I previously indicated, I was very impressed with the engine when I ran it-but didn't take any tach readings at the time-it was several years ago (before I moved from Christchurch to Wellington) and it was only one of several engines I was running. All I recall was the ease with which it started from cold, set, and hot restarted. The figures you report for an 8x4 are very good-and would put it right up there with with a good Oliver, Eta or Webra Mach-II performance-wise. Josef Pffeffer was no fool when it came to engine design and manufacture-and in the late 50's (I have 1957 stuck in my mind as the year the original appeared) he would have had the Oliver Mk3, the Webra Mach-1, Taifun Tornado and Blizzard, PAW Special and tuned versions of the ED Racer for comparisons with-I doubt he would have designed and developed a low production engine that fell below par with these... [I deliberately exclude the Frog 249 BB as even though contemporary, it was notoriously thirsty-not a desirable attribute in team race!]
Qazimoto-I've dug out the engine test-it shows a BHP peak of 0.34 at 15,500-so about the same as a std Oliver. The test review notes the short transfer timing with no overlap caused by the ports being so wide (but doesn't indicate whether it is the transfers or the exhaust ports! )So obviously the relative timing geometry can not be altered by pushing the transfers higher-so shimming the liner and playing with the drum valve timing would be the only options available in getting more performance-though if the published report is typical, the power is quite adequate. In any case, shimming the liner is going to increase the exhaust duration even further, so may not help at all since it appears that short transfer timing is where the design falls short of ideal.The report also notes the excellent handling-so this seems to be a consistent characteristic of the design.
I wonder if people have fallen into the trap of making invidious comparisons with modern T/R engines-after all, no one would think it fair to compare a Super Tigre G20 with a Nelson 15 for FAI power..........?
ChrisM
'ffkiwi'
Qazimoto-I've dug out the engine test-it shows a BHP peak of 0.34 at 15,500-so about the same as a std Oliver. The test review notes the short transfer timing with no overlap caused by the ports being so wide (but doesn't indicate whether it is the transfers or the exhaust ports! )So obviously the relative timing geometry can not be altered by pushing the transfers higher-so shimming the liner and playing with the drum valve timing would be the only options available in getting more performance-though if the published report is typical, the power is quite adequate. In any case, shimming the liner is going to increase the exhaust duration even further, so may not help at all since it appears that short transfer timing is where the design falls short of ideal.The report also notes the excellent handling-so this seems to be a consistent characteristic of the design.
I wonder if people have fallen into the trap of making invidious comparisons with modern T/R engines-after all, no one would think it fair to compare a Super Tigre G20 with a Nelson 15 for FAI power..........?
ChrisM
'ffkiwi'
08-07-2012, 12:59 PM
#56
RE: More 2.5cc Diesels
ORIGINAL: earlwb
One thing I noticed with the model diesel engines is that they tend to cool off when you go to low throttle with a RC version. Then when you go back to WOT you have to wait for the engine to heat up and start running faster and faster. So you have to be careful of the needle valve adjustments, compression etc.
One thing I noticed with the model diesel engines is that they tend to cool off when you go to low throttle with a RC version. Then when you go back to WOT you have to wait for the engine to heat up and start running faster and faster. So you have to be careful of the needle valve adjustments, compression etc.
How effective this is depends on engine and fuel of course. Give it a try.
George
08-07-2012, 03:49 PM
#57
RE: More 2.5cc Diesels
ORIGINAL: ffkiwi
Qazimoto-I've dug out the engine test-it shows a BHP peak of 0.34 at 15,500-so about the same as a std Oliver. The test review notes the short transfer timing with no overlap caused by the ports being so wide (but doesn't indicate whether it is the transfers or the exhaust ports! )So obviously the relative timing geometry can not be altered by pushing the transfers higher-so shimming the liner and playing with the drum valve timing would be the only options available in getting more performance-though if the published report is typical, the power is quite adequate. In any case, shimming the liner is going to increase the exhaust duration even further, so may not help at all since it appears that short transfer timing is where the design falls short of ideal.The report also notes the excellent handling-so this seems to be a consistent characteristic of the design.
I wonder if people have fallen into the trap of making invidious comparisons with modern T/R engines-after all, no one would think it fair to compare a Super Tigre G20 with a Nelson 15 for FAI power..........?
ChrisM
'ffkiwi'
Qazimoto-I've dug out the engine test-it shows a BHP peak of 0.34 at 15,500-so about the same as a std Oliver. The test review notes the short transfer timing with no overlap caused by the ports being so wide (but doesn't indicate whether it is the transfers or the exhaust ports! )So obviously the relative timing geometry can not be altered by pushing the transfers higher-so shimming the liner and playing with the drum valve timing would be the only options available in getting more performance-though if the published report is typical, the power is quite adequate. In any case, shimming the liner is going to increase the exhaust duration even further, so may not help at all since it appears that short transfer timing is where the design falls short of ideal.The report also notes the excellent handling-so this seems to be a consistent characteristic of the design.
I wonder if people have fallen into the trap of making invidious comparisons with modern T/R engines-after all, no one would think it fair to compare a Super Tigre G20 with a Nelson 15 for FAI power..........?
ChrisM
'ffkiwi'
The usual Oz VA TR test prop is an APC 7 x 6. A good competitive modern MOD OT, "fixed up" CS OT, or an R250 will turn +17K on the bench with a 3.6 mm venturi. The R250 having a clear edge.
The R250 will also do 60-64 laps on a 15cc tank.
The Webra Mach 1 was as fast as an Olly I believe but had about half the range. This may be why the Pfeffer hasn't been a great success in vintage team racing. Someone must have tried it.
Would a PAW liner fit?
Are you interested in Vintage or Classic TR? From what I've seen most people are using modern style engines (Fora 15 Junior) in the latter in the UK and Oz anyway.
Ray
08-07-2012, 05:12 PM
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RE: More 2.5cc Diesels
Ray-useful data-I will put an APC 7x6 on it for some benchmarking-and on some of my other 'period' engines such as the Mach-1, Mach-2, Taifun Orkan-so I have feel for how its contemporaries performed relative to it. Webra Mach-1s were a bit thirsty I believe-but small and light so must have gained some benefit from frontal area aspects-or was there a fuselage cross section rule in place at the time? The Taifuns of course were physically quite a lot bigger. 17+K on an APC 7x6 I suggest is a lot more than 0.35BHP-I must look up the calibration charts that were published in AM in the early 90's.
A PAW liner wouldn't work-the Pfeffer one screws in-and though I haven't had it out, the lower part seems to be significantly larger in diameter than is typical-so I doubt a Taifun or Webra one could be substituted. I suppose I could approach NBN (if they're even still in business) about spares-or even a blank liner-but given it was part of a limited production (only 500 copies) replica produced 15 years ago-I'd say the odds of finding any spare parts now are astronomical.....
Classic T/R remains more a possible pipe dream for me, though over the past few months I have been given serious consideration to taking up C/L seriously (as a second string to my current modelling) if my club accedes to a request to put in a circle at our R/C site-which is only a couple of miles from home. [I didn't suggest it, but have supported the proposal at club committee level.] In contrast my FF site is 1-1/4 hours drive away, and currently too wet-after a wetter than normal winter- to even get on.
I can't see the point of putting modern engines in Classic Models-it makes things farcical-and there are always the attempts to weaken the rules. About as sensible as putting a Wankel in a Model T Ford and entering it in a Vintage car rally. I've seen the same attempt to weaken the rules here in Vintage-and it's invariably because people are too damn lazy to obtain suitable engines. I've fought hard against it at various AGMs over the years, but it's generally a losing battle. I have absolutely no issues with the use of replica engines in such events, but I draw the line at modern engines. The NFFS in the US have managed to keep things under control by having a list of approved engines for Nostalgia-which is pretty much the same era, and I see no good reason why the same approach cannot apply for Classic.
I don't know what the NZ rules are for Classic T/R-and what engines are allowed-easy enough to look up on the MFNZ website though.
ChrisM
'ffkiwi'
A PAW liner wouldn't work-the Pfeffer one screws in-and though I haven't had it out, the lower part seems to be significantly larger in diameter than is typical-so I doubt a Taifun or Webra one could be substituted. I suppose I could approach NBN (if they're even still in business) about spares-or even a blank liner-but given it was part of a limited production (only 500 copies) replica produced 15 years ago-I'd say the odds of finding any spare parts now are astronomical.....
Classic T/R remains more a possible pipe dream for me, though over the past few months I have been given serious consideration to taking up C/L seriously (as a second string to my current modelling) if my club accedes to a request to put in a circle at our R/C site-which is only a couple of miles from home. [I didn't suggest it, but have supported the proposal at club committee level.] In contrast my FF site is 1-1/4 hours drive away, and currently too wet-after a wetter than normal winter- to even get on.
I can't see the point of putting modern engines in Classic Models-it makes things farcical-and there are always the attempts to weaken the rules. About as sensible as putting a Wankel in a Model T Ford and entering it in a Vintage car rally. I've seen the same attempt to weaken the rules here in Vintage-and it's invariably because people are too damn lazy to obtain suitable engines. I've fought hard against it at various AGMs over the years, but it's generally a losing battle. I have absolutely no issues with the use of replica engines in such events, but I draw the line at modern engines. The NFFS in the US have managed to keep things under control by having a list of approved engines for Nostalgia-which is pretty much the same era, and I see no good reason why the same approach cannot apply for Classic.
I don't know what the NZ rules are for Classic T/R-and what engines are allowed-easy enough to look up on the MFNZ website though.
ChrisM
'ffkiwi'
09-20-2014, 08:43 PM
#59
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NBN "1954 Pfeffer 2.5" replica, No. 448. NIB as received for running and setting up for a fellow diesel lover.
I like:
1. Clean, elegant design, backed up with good materials, fits and finish.
2. Rotating lockable venturi insert.
3. Free bottom end using two quality ball races.
4. Contra-piston fit is just right, unlike many Czech engines where they are too tight. Comp screw does not wander.
5. Easy to start hot or cold. Also LOUD. Like they should be, in this configuration.
I don't like:
1. Strange 40E 40 C 20K + up to 3% DII suggested fuel mix in the instructions. 35E, 25C and 40K + 1.5% 2-EHN sport mix used.
2. Cylinder kept wanting to unscrew when being run in, even after belt tightening hot. In the end, I used a precise spanner on the cooling jacket flats to carefully tighten it after a short peaked run. No bruising, so the alloy is up to the task.
3. Piston / liner fit on the example handled is a little 'average'. Slightly slack, and does not hold compression when warm to hot. That said, there is no evidence of scorching on the piston walls so fit must be adequate.
4. Compression screw thread is a little coarse.
5. Can't get over 12,500 RPM on sport mix with an 8 x 6 Master Airscrew grey scimitar prop fitted. So, performance is slightly disappointing even for a 1954 replica.
All in all a good effort, but not a prize winner. My best MARZ 2.5 would wipe it.
I like:
1. Clean, elegant design, backed up with good materials, fits and finish.
2. Rotating lockable venturi insert.
3. Free bottom end using two quality ball races.
4. Contra-piston fit is just right, unlike many Czech engines where they are too tight. Comp screw does not wander.
5. Easy to start hot or cold. Also LOUD. Like they should be, in this configuration.
I don't like:
1. Strange 40E 40 C 20K + up to 3% DII suggested fuel mix in the instructions. 35E, 25C and 40K + 1.5% 2-EHN sport mix used.
2. Cylinder kept wanting to unscrew when being run in, even after belt tightening hot. In the end, I used a precise spanner on the cooling jacket flats to carefully tighten it after a short peaked run. No bruising, so the alloy is up to the task.
3. Piston / liner fit on the example handled is a little 'average'. Slightly slack, and does not hold compression when warm to hot. That said, there is no evidence of scorching on the piston walls so fit must be adequate.
4. Compression screw thread is a little coarse.
5. Can't get over 12,500 RPM on sport mix with an 8 x 6 Master Airscrew grey scimitar prop fitted. So, performance is slightly disappointing even for a 1954 replica.
All in all a good effort, but not a prize winner. My best MARZ 2.5 would wipe it.
10-10-2014, 06:59 AM
#62
It doesn't sound too bad on an 8x6 prop to me, what would you expect, around 13500rpm on that prop?
10-10-2014, 12:17 PM
#63
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I have the AM magazine review of the NBN Pfeffer 2.5D replica. I have uploaded a copy of the engine review article in pdf format. Click on the links below and tab 'open'.
I was too harsh in my assessment. The reviewer only achieved 12,100 rpm on an APC 8 x 6; which is a heavier load than the same size Master Airscrew Scimitar.
I was too harsh in my assessment. The reviewer only achieved 12,100 rpm on an APC 8 x 6; which is a heavier load than the same size Master Airscrew Scimitar.
Last edited by fiery; 10-22-2014 at 09:28 PM.
10-11-2014, 02:10 PM
#64
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Hi Fiery,
I'd love to fly it. When? Don't really know. I'd like to build a TR or two and get back into U/C. Presently can't find anyone close by that's interested. Burlington has a U/C circle, but they require the use of a muffler.
Or, I do have a 1/4 Midget (Cox .15) RC that might work. We have a private field, noise is not a problem, but I'm not sure I can see well enough to keep it in sight. Added to the bucket list.
John
PS: 12k on an 8x6 I think is rather good. My Conquest only spins an 8x4 at 18k on the ground and is no slouch.
I'd love to fly it. When? Don't really know. I'd like to build a TR or two and get back into U/C. Presently can't find anyone close by that's interested. Burlington has a U/C circle, but they require the use of a muffler.
Or, I do have a 1/4 Midget (Cox .15) RC that might work. We have a private field, noise is not a problem, but I'm not sure I can see well enough to keep it in sight. Added to the bucket list.
John
PS: 12k on an 8x6 I think is rather good. My Conquest only spins an 8x4 at 18k on the ground and is no slouch.
10-11-2014, 08:58 PM
#65
A good Oliver Tiger MOD 2.5cc diesel will turn a RAM 8 x 6 at 12K rpm. That's the setup for UK c/l "Oliver" combat. The venturi hole size will be on the smaller size for manoeuvring.
So the NBN Pfeffer isn't too bad. A RAM will be a heavier load than an APC 8x6 I suspect.
So the NBN Pfeffer isn't too bad. A RAM will be a heavier load than an APC 8x6 I suspect.
11-02-2014, 02:51 PM
#66
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AMZ 2.5 diesel
This appears to be a well made engine. Excellent fit, very smooth bearings.
The exhaust is dumped into a collector ring, then a muffler, and may not let the engine breath very well.
No, this one sits in a box and will not get used.
The exhaust is dumped into a collector ring, then a muffler, and may not let the engine breath very well.
No, this one sits in a box and will not get used.
11-03-2014, 06:13 PM
#67
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Llam A-2
Que es muy agradable y causa una grata impresión porque tiene muchos encantos o atractivos.
Last edited by fiery; 11-03-2014 at 08:15 PM. Reason: ella es hermosa
11-04-2014, 07:13 AM
#69
Hi Fiery,
I'd love to fly it. When? Don't really know. I'd like to build a TR or two and get back into U/C. Presently can't find anyone close by that's interested. Burlington has a U/C circle, but they require the use of a muffler.
Or, I do have a 1/4 Midget (Cox .15) RC that might work. We have a private field, noise is not a problem, but I'm not sure I can see well enough to keep it in sight. Added to the bucket list.
John
PS: 12k on an 8x6 I think is rather good. My Conquest only spins an 8x4 at 18k on the ground and is no slouch.
I'd love to fly it. When? Don't really know. I'd like to build a TR or two and get back into U/C. Presently can't find anyone close by that's interested. Burlington has a U/C circle, but they require the use of a muffler.
Or, I do have a 1/4 Midget (Cox .15) RC that might work. We have a private field, noise is not a problem, but I'm not sure I can see well enough to keep it in sight. Added to the bucket list.
John
PS: 12k on an 8x6 I think is rather good. My Conquest only spins an 8x4 at 18k on the ground and is no slouch.
11-05-2014, 04:01 PM
#70
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Thanks aspeed. I see you're closer to Windsor. I bought a ST .40 RC from a modeler in Windsor way back when they were "the motor".
I have a spot (family farm) in the Chatham area where I can fly RC or FF over the field. Noise isn't a problem. Actually, it isn't too far from where the Chatham Aeronauts have/had a secondary flying field just along the Prince Albert side road. Toronto is an option, but the traffic is a real killer. It gets worse every year.
So, maybe one day we'll meet up.
I have a spot (family farm) in the Chatham area where I can fly RC or FF over the field. Noise isn't a problem. Actually, it isn't too far from where the Chatham Aeronauts have/had a secondary flying field just along the Prince Albert side road. Toronto is an option, but the traffic is a real killer. It gets worse every year.
So, maybe one day we'll meet up.
11-05-2014, 08:33 PM
#71
We race the LA .25 racers just north of Dresden a couple times a year, along with F2D and slow (80mph) combat, stunt and I guess some scale too. Same schedule in the Toronto/Etobicoke field. I don't go there much any more because it is a bit of a drive. I used to be in Waterloo for 50 years. I would be the good looking tall guy if you come across me.
11-07-2014, 08:28 AM
#73
http://www.balsabeavers.com/ is a bit more informative on control line events in the area, even into some of the northern US. We normally get a showing of New York, Detroit, and even Chicago flyers sometimes. Sorry for getting off topic.
