The G-Mark .061 Family

I believe they also made a .15 and a .30 twin. Unfortunately for me, I only have the .03 RC.

For those who don't know the story (that I have read), the rights and tooling were sold to a company in the US. The tooling was sent but the ship was caught in a storm and all of the tooling was destroyed by salt water corrosion. The new owner decided to let it go (probably insurance) as a loss.

Of course this is just what I read, additions/corrections welcome.

George

gcb wrote:I believe they also made a .15 and a .30 twin. Unfortunately for me, I only have the .03 RC.

The .03 was unique for its day and I heard favorable reviews of it as a miniature RC engine.

For those who don't know the story (that I have read), the rights and tooling were sold to a company in the US. The tooling was sent but the ship was caught in a storm and all of the tooling was destroyed by salt water corrosion. The new owner decided to let it go (probably insurance) as a loss. Of course this is just what I read, additions/corrections welcome. George

I heard the same, George, just couldn't place where I heard it. There was considerable disappointment over that. The G-Marks were phenomenal engines for their time.

GWILLIEFOX wrote:G-Mark came out with a sweet little 1 cc (.061 ci).  Using parts from it, they produced a 2 cc (.122 ci) Boxer twin, and the 5 cc (.305 CI) radial in Ian's post.  Cannon RC System imported them in the 1980 time frame.

Yes, that is what I remember, it was Bill Cannon, the then miniature RC proportional servo proprietor (I remember his two servo receiver brick system) one who was marketing these engines.

The 2cc twin is a great little engine.
I built a F/F 2in to the foot Farman Moustique for mine getting onto 20 years ago. Still have the model with engine in it hanging up in the workshop.....engine well oiled of course.
It starts up with a flick when both plugs are lit up and will even start up with one plug only lit up, then when the other plug gets a touch of battery it's away on both cylinders.
I have a Tatone F/F timer to have it at full chat on launch then 20 seconds on to drop it back to idle for the run home.

I still have one of the .03 R/C NIB ad three of the .061,which are great little engines.Not screaming powerhouses but they idled really well , one was on on a Carl Goldberg junior falcon three channel the other I had on a House of Balsa four channel P 51 Mustang.I put a pressure tap on the muffler.The Jr Falcon had nose gear steering so I would start in the pits taxi to the runway takeoff fly around, land then taxi back i just like the big boys. The Mustang has the Canon micro RC receiver and servos . I still have both planes and a few of the Canon systems. When you bought the engines he also sold plans for a model that was designed for the engines called the Griffin. The Griffin was a four channel tricycle gear model designed around the G Mark engines and the Canon micro RC systems one set of plans were designed for the 06 and the other for the 03 I think I have a copy of the plan for the .03 if anyone is interested,just pay the postage.

I have one .030 and three or four of the .061, plus the .12 twin (in plain Aluminium, not the black one).
Haven't run the twin yet though.

From memory the .061 had the power of a regular reedie at around twice the weight. Seems like they need a better glow-head to wake up...

An adjustable airbleed would help too.

Back in the latter 1970's to early 1980's I was in college when these engines were available. A Cox reed valve engine was easily half the cost or less of the G-Mark. Thus for a couple bucks I installed an Ace R/C throttle sleeve on a Black Widow and purchased the Cox .049 R/C Bee. Although throttle response was non-linear, I had engines that could idle. They had decent power wide open.

The R/C Bee went on the Sterling Minnie Mambo. The throttle sleeved Black Widow went on the Airtronics Q-Tee. I flew both on Ace Pulse Commander Rudder only with KRD sequenctial quick blip throttle. Later I replaced the Ace installation on the Q-Tee with two channel rudder and elevator. Radio was Charlie's R/C (Bill Cannon's wife) 810 kit on 72 MHz wide band with Cannon mini servos. (Now these are called park flyer servos.)

I carefully drilled a hole in the servo arm inside their carefully placed holes for standard RC carburetors since the throttle sleeve had a shorter stroking range. Servo 180 degree long stroke normally for transition from low to high, I had it go from idle to beyond wide open to closing off the opening somewhere between 1/3rd to 1/4th. This got me mid range. A servo 90 degree turn got me full throttle. I got idle, mid, high back to idle, opposite of the standard throttle sequence, but I had throttle.

By the time shortly after I started working out of college, AFAIK these engines were no more. Bill's radios were no more. (Kit radio experience was Bill's way to get rid of the unsold inventory of parts for his sport 4 channel radio.) I bought a Futaba 6 channel sport system with dual rates on the old wide band 72 MHz.

I wouldn't buy another half-A engine since until the Norvels became available.

Although these G-Mark engines weren't power houses, I gather that they were very user friendly with good throttling response, made good sport engines, something not common with half-A's at the time.

I'd be interested to know if the Enya .049 RC engine was also a decent engine. With muffler it would appear to be a heavy bugger. OS had .049 and .06 engines (in the Pet series), but I don't know if they had an RC version of it.

It is understandable why Cox continued to dominate the half-A market with their powerful yet light inexpensive reed valve engines, until the demand for the smaller models evaporated along with profitability, to be sold to the Estes company.

Enya did both a .049 and a .06 RC engine with optional mufflers. There is also an .08 and .10 engine mentioned in a data sheet, but I don't have any of those...
The engines are pretty old-school and use a regular glow plug, so their are really more for the enthusiast than for everyday flying now I guess.

I really like their AAC and ABC engines,  these are very well made and smooth runners, they range from X.11, X.19, X.21 and so on...

Here is some engine info that came with the .049 engine:




And a .049 on the left and the .06 to the right;

Thanks Kris, yes those are the ones. How does the Enya .06 compare with the G-Mark .06? Are they about the same power?

I don't have any experience with the Enya Schneurles, but I have heard favorable comments. Another with favorable comments is the Fuji .15 Schneurle. I've got two Fuji .099S-II RC ABC engines, older cross scavenge with low compression of 5.5:1. Those are heavy sport engines.

Seems we've been spoiled by the higher powered Tee Dee's, Black Widows, Norvels, small A-sized Schneurles and etc. due to their higher power to weight ratios. It is not hard to see, even though how neat these other engines were when they first came out, have fallen to the historic occasional use nostalgia category.

Looking back, although I've had my share of fun, the smaller lighter powerplants won out. They are just more fun to fly.

I like the 061 single. It shares the triangular crankcase shape of the .03 "Humming Bird"



It gives the engine a certain uniqueness.

The twin is a little beauty - well not so little compared with my other twins.



G- Mark recommended 10 -25% nitro fuel for this but I found it ran better on 0% nitro and a hotter glow plug. I found this out by accident - I selected the wrong fuel, filled up my test tank and then couldn't be bothered to empty it. I hadn't fitted the plugs and had a couple of hotties handy.

It has a very pleasing sound to it.

GWILLIEFOX wrote:...The Boxer really screams.  The 5 has a sound of its own.  Check it running on my youtube page GW MOHRBACHER

Hey GWilliefox, did you know there is a place in your profile editor where you can add your Tube channel? It will place an icon with a link under your avatar.
Rusty

ian1954 wrote:The twin is a little beauty - well not so little compared with my other twins. G- Mark recommended 10 -25% nitro fuel for this but I found it ran better on 0% nitro and a hotter glow plug. I found this out by accident - I selected the wrong fuel, filled up my test tank and then couldn't be bothered to empty it. I hadn't fitted the plugs and had a couple of hotties handy. It has a very pleasing sound to it.

Ian, that G-Mark .12 is a nice looking twin. It would look good, very scale-like on the front of an Aeronica C-3 cabin. Is the engine mount bolt pattern the same as with a Cox .049 reed valve tank engine?

Regarding running well on no nitro / low nitro fuel, I read an interesting discussion on I think Stunt Hangar. Seems some fliers were having problems with their Schneurle engines running hot and poorly in the summer heat. When nitro content was reduced to 5% from the 15% to 25% they were using, their engines settled down. This is interesting, because traditionally over here in the colonies, because nitro costs were less, higher nitro fuels have been pushed by the flying community. It is nice that this trend at least in this case has been debunked.

The G-Marks when they were available had favorable comments toward them. I think it was not regarding greater power, but toward the user friendly throttle-ability and that they had mufflers, too. They were usable engines on half-A airframes.

Since as a college student I couldn't afford the higher costs of these engines, I opted for the then new Cox .049 R/C Bee engine at about a third of the cost of the G-Mark .061 R/C. Although with a throttle sleeve muffler, it was revolutionary at the time with integral clunk tank of greater capacity than the Golden Bee / Black Widow. Whereas I would get something like 2.5 - 3 minutes flight time with the Black Widow, I got more like 4 minutes with the R/C Bee.



One thing I quite did not understand is why they had such an odd clunk configuration. It used a very thin fuel tubing coiled inside, which was very thin walled, so it could move. The engine was only made a short time, then discontinued in lieu of the .049 Dragon Fly. I don't know why they changed the Bee name. They could have called it the R/C Bee II. I view it as the decline of Leisure Dynamics as owners of Cox, prior to selling to Estes.

When they came out with a heavier .074 Queen Bee, making it reed valve instead of front valve rotary, they were definitely in decline. (If they had simply made a lighter weight QB with standard reed back venturi and exhaust throttle muffler, shorter crankcase for lighter weight, they would have still had a winner.)

Since the R/C Bee was discontinued early, the fuel tubing was no longer available. AFAIK, Dragon Fly was fairly short lived, also.

Nowadays, I am told I can salvage the silicon insulation off facilities wiring. Since I was flying single channel with auxiliary throttle, clunk action was of less importance, and so I used the stiffer small Sullivan blue silicon fuel line tubing as a replacement.

I put sufficient mileage (flight time) on that R/C Bee engine, that I wore out the cylinder / piston fit. This was on mostly Sig Champion 25% with 50% Castor oil. Later I bought a replacement piston / cylinder, which restored the compression.

Thus I would say the R/C Bee was the last of the truly great Cox products, but also a clue that Leisure Dynamics was on its way out.

The mounting pattern on the twin isn't the same.

We all have different opinions on engines and although I like all Cox engines (including the Queen Bee) I often find it difficult to compare them with other engines. The RC Bee is a nice motor but short lived because of the difficulties Cox had dealing with a cast crankcase. Setting one up to machine with the vagaries of a casting on a production line must have been fraught. I do like the casting though. I believe it was introduced to reduce costs but ended up increasing them.

I can understand the choice of an RC Bee if you are on a limited budget (I gave up aeromodelling while at University and for some time afterwards) but not comparing it with the G-Mark 061. The TD RC 051 is probable a better comparison in like for like categories with its silencer and throttle.

However, the TD RC 051 wasn't produced until 1995 after the Queen Bee and well after the RC Bee.

RknRusty wrote:

GWILLIEFOX wrote:...The Boxer really screams.  The 5 has a sound of its own.  Check it running on my youtube page GW MOHRBACHER

Hey GWilliefox, did you know there is a place in your profile editor where you can add your Tube channel? It will place an icon with a link under your avatar.
Rusty

I don't have an avatar

Ian, appreciate you sharing those photos of these "limited production" G-Mark engines, which have attained to collector status. If I had one, I'd be reluctant to use it as a regular engine, due to its historic value.

My comparison was not so much of engines of comparable power, but of availability and cost around the same time frame. G-Mark .061 versus .049 R/C Bee, regarding which is more powerful is not hard to discern. The G-Mark would win hands down. Sport flying within a budget, the Cox wins hands down.
(And, this is a Cox forum, is it not?)    

The use of the glow plug for the G-Mark would make it tamer. I would think the comparison in power probably would be similar to my Airtronics Q-Tee that I fitted a Norvel .061 Big Mig with MECOA glow plug head. I reduced the compression, but compared to performance with a Black Widow, it was still sparkling, moved out with authority.

No doubt if I had purchased the G-Mark then, I would have put it to good use. However, living in budget helped me to successfully complete college.

Since the G-Mark was a limited production engine, it now marches on as a collector item.

Peter Chinn tested the twin. He found the Glow Bee plug, standard type, not drop in, was hundreds of RPM better than standard plugs. I don't have the mag in front of me now, but I'll get the actual numbers. I think he used a long plug with an extra gasket. The engine was designed for the intermediate length common on Japanese engines. The extra gasket put the element in the correct position.

GallopingGhostler wrote:
(And, this is a Cox forum, is it not?)    

I keep forgetting. Perhaps I should post some pictures of the few Cox engines I have but this one is for you.

Actually Ian, I am glad that Admin removed other engines from the "Off Topic" category to "Other Engines". I gather that this is not to discourage others from posting about other engines, but to provide a forum for these as well, as this forum graciously although with emphasis on Cox products allows for other makes and models of interest as well.

Back plate is mounted backwards (but you probably knew that already). Yes, same box, I've still got the original paper box from college days.

Have you or anyone tacked the G-Marks? Is there an optimal prop that they run best with? Now that you mentioned a fairer comparison would be with the Cox rotary valve engines, I'm curious how they ranked.

My guess would be closer to the Medallion in thrust. Comments, anyone?

From memory (it has been a while since I ran one) a 6x3 prop is about right on the G-mark .061 but it will only spin it at around 14-15000rpm. That discouraged me from ever running the twin I have NIB...

"Nono Fulton" also did quite a lot of documented bench running a few years back, including the twin; https://www.youtube.com/playlist?list=UUc2htnYER0W2hlfvokWGL4g

Another thing nice about the G-mark 061 is it has a phosphor bronze bushing on the crank case. made to last. The one with the black crank case was known as the Seagull .061 (first Generation)

Those are some impressive engines i must say , wish i had one (( that comes from being a engine head i guess )))

Hi all, i resume this post because i just found this...i search a lot...and it is here...someone knows where i could buy gaskets, orings, plugs?
thanks

Just noticing the necrobump here, I can not help you with parts, other than telling you to making your own gaskets.  As far as plugs, I would like to add that I made a turbo style plug head that really woke up my engine.  It is a control line .06 model so things would be different from many of yours.  Surfer Kris was questioning if anyone had tried a turbo style head so I will post my results here.  I have done it elsewhere but forget which forums it may be in.  I think Kris may have already seen it.  Nevertheless my notes are stock with a 4 1/4 - 4 APC prop rpm is 18,300.  With a M/Airscrew 6-4 prop - 14,400 rpm.  This is with 15% fuel.  With the turbo plug I made up, the numbers increased a fair bit to 24,000 and 17,500 respectively.  It had a bit more tight chamber than the stock one, and of course the better seal with the turbo plug.  I used the Merlin plug because I have mostly those around.  I believe this would make the motor competitive with most other motors out there including the Cox.  Ya I know this is a Cox forum, but doubt this orphan will compete with Cox sales.  Being control line, I can not estimate the idle qualities on an RC version but guess it would be fine, as the carbs seem fairly good. I am guessing that I did the test without the muffler, as I normally do that do skip a variable when comparing engines/brands. I like to make a list and then choose which motor is suitable for any plane that I might scare up. I have not flown this one yet.