Merco 61 Glow Engine (Single plug version)

[Dave Millard]

Hi Folks,

Resurrecting a Piper J3, she’s an old bird but worth bringing back to life, I’m not familiar with an engine this old. I’m looking for any specs for the engine, especially the Glow Plug heat spec for this engine. It’s not been run for about 24 months, so some work required. Is there anybody outside here who can help?

Dave M.

[Engine Doctor]

An Enya No 3 plug will be fine on a Merco 60 . If it hasn't been run then it may be gummed up or worse still the dreaded rust may have got to the bearings or the piston ring making it stick in its groove . Squirt some fuel down the the carb and turn it over , As It frees up check if it feels smooth . If it has any roughness or feels lumpy then change or get the bearings changed. Better still if you can remove the engine easily from the airframe then remove the back plate and visually inspect the crank and bearings . Any rust can be seen it like brown grease on the bearings and crank . The bearings can then changed before any damage is done to the rest of the engine .

[ken anderson.]

hello dave and welcome from me.the merco is a fairly old engine and the era it was designed in...the plug choice would have been limited...my advice would be try a model technic's no 3 or 4...should be perfectly happy with that...others may advise different.....have fun..

ken anderson...ne....1....merco plug dept.

[Former Member]

[This posting has been removed]

[SIMON CRAGG]

We used to use Taylor idle bar plugs, which was the default plug atthe time. Not sure they are still available, but and idle bar plug seemed better.

[Former Member]

[This posting has been removed]

[Dave Millard]

Cheers Everybody,
Thanks for the tips, looks like a good source of knowledge to draw on out there. Will be Using this alot more.
Thanks again.
Dave M

Edited By Dave Millard on 23/12/2018 18:00:31

[Martin Harris - Moderator]

What's the AUW Dave? I'm not an advocate of overpowering Cubs but my fairly hefty 18 pound one flies nicely on a 160 four stroke twin but is not overpowered on an 18 x 6 prop.

[Dave Millard]

Hi Martin,
Still in the process of bringing her into the 21st century, fitting servos and such, but I'm sure the AUW shouldn't exceed 12lb.

[Stearman65]

I don't think anyone else has mentioned the proposed model. I think you would be pushing your luck to try to use a Merco 60/61 in a 1/4 scale piper cub. Back in the day I had one in a senior Falcon which I think was the limit for that engine.

[Martin Harris - Moderator]

That's why I was asking Dave the likely AUW, S65. As a guide, these are the specs for the Hangar 9 ARTF Cub which is likely to be as light as most versions - and manufacturers figures are often rather optimistically light.

Weight 14.5 - 16.5 lbs

Engine 1.00 - 1.60 cu in 2 stroke

You haven't said whether yours is a traditional build but even at something well below the lower figures, it might struggle on an older .60 - do you know if it was ever flown successfully on the Merco? You do have the benefit of a lot of wing so it may fly OK - Cubs typically had 65 hp engines but have flown with engines from 37 up to 180 or more hp - but I would think it will be very sedate and my feeling is that to replicate the character of the original, a little extra power to simulate the lack of inertia in a model is useful.

[Former Member]

[This posting has been removed]

[SIMON CRAGG]

Posted by Percy Verance on 23/12/2018 17:11:38:

Better until the idle bar came adrift that was....... And no I don't think they're available anymore Simon.

Banggood do them for £1.00 a pop. Must say never had a bar come adrift, and I am still using up my stock.

[Denis Watkins]

Have just noticed the thread, and the lads are right with the motor power concern Dave.

The Merco 61 is good for a 10lb model, on synthetic fuel

And

would be very marginal on a 1/4 scale as said earlier.

Unless, back in the day, the Cub was a real lightweight

[Dave Millard]

The aircraft came with the Merco, it's a traditional balsa wood build, the chap who passed it on has flown this aircraft successfully for a number of years. It has a large wing area, over 7ft although the coverings are in need of replacement eventually. Thankfully the engine is in good shape.

[David Davis]

If it's any help DM, I rescued my first Senior Telemaster from an old bloke in Wales. The model had an eight-foot wingspan and the wings and tail were covered in Solartex. I built the fuselage out of pine strip bought from B&Q.My Merco 61 powered it adequately enough. It's just a big trainer after all.

 

Edited By David Davis on 24/12/2018 09:57:39

[Dave Millard]

Well she has been interesting to work on, even the wire operated rudder system. One thing that is a curiosity is how the wings were secured to the airframe, although there are wingspars forward and Aft, there is no obvious securing points to keep the wings from sliding on the spars. Needs to be considered how to put right. Portability if the wings are fixed could be an issue for sure.

[Martin Harris - Moderator]

Posted by Dave Millard on 24/12/2018 09:47:50:
The aircraft came with the Merco, it's a traditional balsa wood build, the chap who passed it on has flown this aircraft successfully for a number of years. It has a large wing area, over 7ft although the coverings are in need of replacement eventually. Thankfully the engine is in good shape.

Ah - sounds like it's not quite 1/4 scale then - or is it a clipped wing version? Wing area of a 1/4 scale J3 is just under 11.5 square feet - or if you meant a 7 foot wingspan, then it would be a couple of inches under 9 feet. That may explain the performance with the Merco...

Whatever, a Cub is a rewarding model to fly although not quite as easy as many people assume due to susceptibility to crosswind handling problems and many models needing a fair amount of rudder co-ordination. Mine has scale Frise ailerons and needs surprisingly little work with the left thumb.

[Engine Doctor]

Re the OP for glow plug choice. Indeed an idle bar glow plug would be an excellent choice if you can find one. I have never witnessed the urban myth of the dle bar coming adrift ! Back in the 1970 / 80s their were a load of rubbish plugs usually sold at the shows . They were very cheap and often blew the seal after a few minutes run so perhaps the idle bar version of these were the "dodgy" plugs that started the myth ? Has anyone personally had an engine damaged by an Idle bar plug ? Taylor glow plugs were/are great quality plugs all assembled by one man. They are not available now unless you can fin old stock hidden away somewhere. Good luck with your restoration.

[Alan H]

Back in the day my first "large" engine was a Merco 49 then a Merco 61. A nice easy to handle engine of modest (by today's standards) power. Something like an Enya No 3 plug or similar should be fine. Handling is definitely improved with some nitromethane in the fuel, around 5 to 10%

[Martin Harris - Moderator]

Posted by Dave Millard on 24/12/2018 10:15:06:
Well she has been interesting to work on, even the wire operated rudder system. One thing that is a curiosity is how the wings were secured to the airframe, although there are wingspars forward and Aft, there is no obvious securing points to keep the wings from sliding on the spars. Needs to be considered how to put right. Portability if the wings are fixed could be an issue for sure.

Closed loop rudder is normal - and scale - and is a very efficient and light system.

Cubs are positive G devices - mine relies on the struts for both retention and controlling twist in the wings. At the root, they simply slide on to piano wire stubs, are retained gently by springs between the wings and flying loads hold the wings firmly in place in operation. This made for an interesting 30 seconds or so when the 3mm (rather than 2mm as specified in the kit instructions) bottom strut fixing clevis failed - although bent quite badly, the piano wire held the port wing at a jaunty angle for long enough for a very gently flown emergency landing.

I don't fly mine inverted or subject it to negative G - which doesn't prevent me looping, stall turning and barrel rolling - all of which I've seen evidence of the real thing doing...

Edited By Martin Harris on 24/12/2018 13:15:58