PAW 80 and possible use

Hello Chris,

Thank you for all the information. I don't know if this engine is an .049 or 80. I will have to look at the box. I also have some either .049's or 80's with carbs already. I will just swap engines if I decide the plane needs a throttled engine.

What did you mean when you said that the engine needs to be given its head like a Tee Dee?

I was very pleasantly surprised at how high this little engine revved up when I went to a smaller prop.

Thank you again for all your help.

Bob

Bob -your engine is definitely either an 80 or a 100....with absolute certainty-the three screws holding the cooling fins to the crankcase confirm this-the 80-and slightly larger 1cc '100' appeared in the early 80s-and were the first new PAW designs for about 20 years-joining the earlier 149, 249 and 19 displacement diesels. A bit later on, the 0.55cc PAW 55 appeared-itself the PAW interpretation of the long lived (30+ years in production!) Allbon/Davies-Charlton 0.55 cc 'Dart', which finally ceased production around 1984. This was a screw together engine-and PAW adopted a n identical form of construction for the '55'-which immediately distinguished it from the rest of the PAW range-and made one significant improvement-they fitted a rear ball race to the shaft-which as I noted in my earlier reply, improved starting and handling-which in any case was always fairly good in the case of the Dart anyway-compared to other small diesel.

The 55 was very well received by the modelling market-just as the Dart had been a generation earlier-and sold very well.....aided of course that by this time it was the only game in town if you wanted a 0.5cc diesel-and there are a vast number of model designs for 0.5cc diesels-and the Dart in particular. The PAW 55 was a real winner because it dropped straight in where the dart had originally fitted-having an identical mounting hole spacing and crankcase width.....and about 40% more power.

PAW then decided this layout was such a good idea they applied it to the larger '80' and '100' sizes-redesigning them to be screw in liner, screw on fins and a single rear ballrace. Initially the 049 was supplied with a very nice mauve anodised set of fins, and the 06 with a dark green set-but the anodising has been subsequently dropped.....as an economy measure.

This is why I have no doubt in identifying your example as one of the earlier 80/100 series......but I cannot say for certainty which of the two it is.....but don't panic-YOU can find out-have a look in the backplate well-the capacity will be stamped there-in very small letters-either '80' or '100' ...this feature was introduced by PAW once the 100 went into production, as there was no external difference between the two models and some positive form of identification was needed-especially if used in competition. The same applies to the larger 15/19 models. I do not have any of the LATER non anodised PAW 049 and 06 models-[mine are anodised...]-but I would expect that PAW would have reverted to stamping the capacity in the backplate with these now....and for the same reasons

ChrisM
'ffkiwi'

fit90 wrote:

What did you mean when you said that the engine needs to be given its head like a Tee Dee?

Bob

I'm gonna' guess that Chris meant "fuel head".. or having the optimal tank-height/placement for the venturi to draw fuel.. but not so much as to flood the engine? I'm not sure if this is correct though...

EDIT: After re-reading Chris's post where he mentions that; I'm not correct at all..

By 'given its head' I mean allowed to rev on small diameter props-nothing to do with fuel head and tank location. PAWs are high revving engines-in comparison with other brands of diesel-timed and ported to deliver peak power at significantly higher rpms than most similar plain bearing engines of their era-to illustrate the point most plain bearing diesels of the late 50s and early 60s peaked at around 12,000 13,000-with ball bearing ones a little higher say 14,000-15,000....the PAW 149 for example-which appeared in 1959 peaks at over 17,000rpm-and that was a plain bearing engine. That propensity for high rpm has continued in current PAW designs-which have been through a lot of evolution in the past 60 years. This general rule applies to most of the smaller engines in the PAW range-that is below .29 cu ins-the larger ones-.29 and up-are intended essentially for R/c rather than general use-delivering their power at more moderate rpms.

In practice-you might expect to use an 8x3 or 8x4 prop on a 0.8cc diesel-perhaps dropping to a 7x4 if max power was needed-that is certainly what you would do with a Mills 75 or a DC Merlin...to give two very well known examples of that capacity. In contrast a PAW 80 (or 100 or 049 or 06) would need to be propped down to about a 5x3 to get to the peak power band. See the performance figures in this link: https://www.eifflaender.com/technical-details

you will note that the 55 is an exception and delivers its power at a moderate level-probably because PAW were trying to emulate the DC Dart-which did likewise. In that aim they succeeded well, whilst still producing a more powerful unit

The advantage of the design of course is you can stick a big prop on it, and chug away at 10,000 rpm or even less, producing plenty of thrust, for scale or vintage use-in which case performance would be on a par with earlier types of sport diesel-or drop down to a size that allows the engine to reach its peak and scream,...which those early other brands would not be capable of doing- if the type of model being flown needs that approach-such as FF duration, or CL racing or combat or even RC racing events-though most R/C PAW use is generally relaxed sport or vintage flying.

ChrisM

I love the link to the PAW page that provides prop information. Lots of good info on that page thank you for sharing, Chris! I messed up on my opening post. I said this engine might go in a Cox Scorpion. The plane is actually a Cox Mantis. Eventually, a throttled version of this engine might end up in this plane. I did a post on this plane several years ago. It has been beaten up pretty badly both in my garage, from having multiple engines on it and from rough flying. But, it still flies pretty well. This weekend I will look at the box for this engine. I know it is .049 displacement. I think it is a PAW .80. I will find out soon.

This engine is an 80 MK II

fit90 wrote:This engine is an 80 MK II

That matches up-from memory there were the PAW 80, PAW 80 Mk II, and the PAW Vintage Classic 80. I have about half a dozen PAW80s-all but two were obtained second hand-so without boxes...and PAW were never forthcoming on what the exact differences were.. Its possible that the Mk2 had the rear race, and nothing else. An examination of a std and BR PAW 80 reveals they use the same basic die-or rather the BR die is modified to add about 4mm in length to the case front-but the ventuti location remains unaltered. The Classic 80 however also has a rear ball race and is optimised for large props and moderate revs...as you might expect from the name....it also is quite distinguishable by only having a single rear exhaust port, and two transfers, rather than the usual PAW 3+3...needless to say it also makes a good FF scale motor...which is where mine is destined .. I have not checked the shaft timing vis a vis a standard 80-but I would not be surprised to find a shorter induction period on the Vintage Classic version.

ChrisM
'ffkiwi'