fiery

My Feedback: (2)

This has arrived. It bears serial number 385 lightly inscribed on the flank of its port side mounting lug, not visible in the photograph due to camera limitations.

It has poor to fair-ish compression but pleasingly no shaft play. Overall it is in fairly good shape. The correct prop nut is missing and the thread will need a die run over it. A couple of other minor issues will need sorting.

Advice from those knowledgable about these engines would be welcomed.

ffkiwi

Supposedly these were quite economical engines compared to the Frog 150 they derived from-and for a while were popular in the 80's for the UK's 'Flying 15' class-which was a UK type Texaco event. Being a sort of reed valve setup, they'll run either direction-I have two of them-which raises thoughts of a C/L twin one day and possibly opposite rotating props......
Performance wise they're better than the early silver head 150, (and better than a Sabre, Hornet etc) but not up to the later 150R bluehead

ChrisM
'ffkiwi'

PS I've never done a systematic test of their fuel consumption compared to the other Frog 1.5s.......another experiment to do one day.

AMB

Fiery you never cease to amaze me , you seem to come up with these rare vintage engines , at least one every 2 weeks congrads on an other find martin

fiery

My Feedback: (2)

Chris: Thanks for that advice, much appreciated.

Here is a link to a review:

http://sceptreflight.net/Model%20Eng...rog%20149.html

Martin: Engines seem to find me, I can't turn them away . The reality is I live in a seaside area popular with retirees. Recently it is not uncommon for old model engines to be given to me.

AMB

Fiery must be a goldmine of these down there, do not think diesels in the US every achieved the wide usage of the UK and Australia of course we had a few makers drones K and B and a few others. The biggest inroads here are the Davis conversions since 1975 and the PAWs my thought

Oh and the model names the Brits came up with Vibramatic sounds like a washing machine that would scare most American modelers away

brokenenglish

Fiery, you mention the wrong prop nut. Be advised that many engines were sold with a normal hex. nut, but there were also quite a few with a nice spinner nut, like this one of mine.
Another point is that the "name" "Frog 149" is only on one side of the crankcase. The other side is plain. They're nice engines, really good runners.

Dan Vincent

I have two of these Clack-Valve engines, plus a spare crank.

I guess the reed valve Cox engines of the early '50's caused diesels such as this Frog "Vibramatic," Elfin and the German Taifuns.

gcb

Here's my old oily one:

BTW, weren't there some India replicas of this engine?

ffkiwi

I think you're right Dan....BUT.....the Frog Vibramatic is quite different in its mechanism to reed valve operation-unlike the Elfins and the Taifuns-which pretty much copied the Cox 'annulus and tab' reed layout of the early Cox-and can definitely be described as reed valve. The Frog-if you read the engine test (url posted by fiery above)-and if you've ever had one apart-uses quite a different system-effectively a spring loaded valve sealing a double backplate plenum chamber. Yes the operation is similar to a reed valve in that it is sole determined by crankcase depression/compression-but different in that it does not reply on the flexible deformation of a thin metal or plastic reed element to open and close the induction tract.
I also note the engine test (which I've had for many years)[the Aeromodeller engine test, not the Model Aircraft one] mentions that the system did not work very well when applied to smaller engines-nor when the return spring was weaker than that fitted as standard.
It would be interesting-though of academic interest only-to see what would happen if you went the other way-applied it bigger engines....the Taifun Blizzard, Jena 2/2.5cc and Jasolka 2.5cc reed valves, for example.......

ChrisM
'ffkiwi'

AMB

Well that answers a question I was going to ask its NOT the Cox setup, sounds like this setup may be the same used in some larger 2 strk ( gas) in weed wackers, chain saws etc


martin

dennis

My Feedback: (90)

I always seriously wanted one of them when I was much younger. Part of the problem with diesels in the US was that they were generally considered 'dogs' in a time of really increasing performance levels of glow engines. Free flight scale liked them though. The Oliver and Rivers ETA et all came too late to reverse the perseption. Oh and the FROG 2.49 was one of my true favorites back then. Never broke a shaft on it. That the diesel is even considered in this country at all is in no small part due to Bob Davis who did most of the work re introducing modellers to the benefits of the diesel.

Dennis

AMB

In the world of model engines at least in the USA Bob Davis is in the AMA hall of fame for his contribution to the world of model diesel engines martin

ffkiwi

This may well be true Martin-the pics below should give you a better idea of the internal workings of the 149 Vibramatic. As you can see-below the venturi is a sort of plenum chamber-the outlet of which is sealed by the steel valve disc-held in position by the return spring-which is itself held in a chamber with two outlet ports. As the piston ascends, crankcase depression causes the valve to move forward, slightly compressing the spring and allowing the fuel charge to pass from the plenum chamber past the spring into the crankcase, As the piston descends, the crankcase pressure plus the spring tension cause the valve to reseat. The key difference I suppose is that the steel valve does not flex or distort in the process like a reed does-it simply moves backwards and forwards against the pressure of its retaining spring. That being said, IMA (International Model Aircraft-the manufacturer of Frog engines and kits) must have had quite a challenge coming up with the spring specifications to achieve just the right tension..........

ChrisM
'ffkiwi'

AMB

Chris quite sure they did plus of course one that would not fail from the constant flexing movement would be miminal however not having the engine have never seen the setup martin


post note your pix explains it large spring hold up just about forever miminal flexing

quietflyer

My Feedback: (1)

Yes, the Indian replicas were sold as the K-149 (Kumar) in the 70's. It was my first engine, and my first diesel. The cylinder muff was anodised red like the original, and the overall quality was excellent. I had no problem running it on equal parts of Kerosene, Ether and Medicinal Castor. I had bought it for C/L use but never got around to it and eventually sold it to Rishi Kumar. I still regret that decision! Incidentally, there was also a K-150 diesel although I am not sure whether it was based on the Frog 150 or the AM 15.
Sorry for drifting off topic a bit, but it surely brought back some fond memories!

fiery

My Feedback: (2)

All sorted. Test run to follow. My thanks to David Owen for educating me on the nuances of this FROG; and for the skilled surgery undertaken.

It feels great. Ready to quickly bound away, like an energetic young FROG should.

ffkiwi

What nuances would these be, fiery? The delayed response to needle valve adjustment?

ChrisM
'ffkiwi'

fiery

My Feedback: (2)

Yes! ...

as well as:

propensity to start backwards if lazily flicked on small props;

no playing with the clack-valve spring tension;

never over -tighten the back-plate mounting screws (the somewhat delicate back plate tabs are prone to bending);

And ....

don't store it near a cute FROG 80, or there may be tadpoles )

JKinTX

Gotta a bunch of Froggies.
Have a restored "Vibramatic" too in one of the engine drawers. I always thought that was a terrible choice of name for an engine though!

I have two Mk II Frog .80s and a Mk I, all nice.

fiery

My Feedback: (2)

On the test stand. It starts and runs well but will not hold a steady setting.

Examination reveals it leaks fuel / air mix from worn back plate gaskets. Replacement gaskets will be made up from 1/32nd thickness gasket paper. It will then be re-tested.

http://www.youtube.com/watch?v=SxwW2UZakiA

Bill Adair

My Feedback: (1)

Very nice engine, and one I'd be proud to own.

Seems like I can actually hear the poppet valve in operation, or is that a trick of my much less than perfect hearing?

I've seen precious few of these on the US auction site, so I'm curious what they normally sell for?

Bill

fiery

My Feedback: (2)

FROG 149 is now healthy.

http://www.youtube.com/watch?v=8d_tq...ature=youtu.be

fiery

My Feedback: (2)

Images from and article by Chris Rowe in "Sticks and Tissue" No 57 - August 2011 edition, pages 24 to 32.

The aircraft is a F/F (restored and converted to R/C assist) 'Incubus' flown in the 1958/59 Australian National Championships. Designer is the late Ken de Bomford.

DeviousDave

Twin reed valves can be a problem as the reeds will resonate from both motors giving inconsistent runs. Be sure to plan for a motor swap in the engine compartment if you try this.

brokenenglish

Sounds unlikely to me. "Resonance" between engines a foot apart overcoming the crankcase pressure/depression cycle...