Take a look-see at what I got bottom fishing on Ebay

May be not true bottom fishing, but I just won this with only 1 bid and 5 watching, no other takers: Gmark .061 RC w/muffler for $35 + $7 US shipping. I guess that is pretty good figuring that these are hard to come by. AFAIK, they weren't the most powerful, but still are nice RC engines. It's a little grungy but should clean up nicely, will know more when its arrive.

Nice acquisition George-give it a good clean and you'll be pleasantly impressed-and actually they ARE reasonably powerful-not quite up to TD standard-but not bad-the only published test I am aware of was done by Mike Billington in Aeromodeller, and published in the Jan 1985 issue and delivered 0.113 BHP @19,000 on 25% nitro fuel....this would put it directly comparable to the Fox 049 FAI Special. He also indicated that it responded well to higher nitro-a couple of spot checks suggested the power curve would be raised to about .13BHP-so within cooey of the TD....and equally positively-the muffler caused very little power drop-and at lower revs up to 16,000-actually increased power over the open exhaust level-the review specifically comments on this point.

He also notes that more power could be extracted by shimming the cylinder to increase exhaust and transfer timings with an .020 shim-though the head insert depth would consequently require adjusting to compensate.

Personally-I think this is one of those engines that might well benefit from a better head setup-such as a Nelson or turbo plug setup.

Personal experience (I have 6 of them...!) suggests that they DO require a considerable break in however-unlike a Cox....

ChrisM
'ffkiwi'

I picked one up a couple weeks ago. I was hoping it was an MP Jet but the G Mark is OK too. It would not turn over, or the Bees either, but they come out good. Funny how the shipping here is $18 from Canada to Canada. Mine is the control line variety, and came with two Babe Bees, one for parts. I drilled the hole bigger in the muffler and have plans to make a turbo head for it as mentioned. It does look like a pretty low compression dished head. Insulating the garage ceiling right now so kind of busy. Next week is warming up finally to test out a couple things I picked up bottom feeding.

Thanks, Chris on the positive inputs for this Gmark engine, gave me confidence I had made the right purchase. Since it is muffled will go a long way towards use in more restrictive locations. Just curious as its only been 2 weeks, but has the NZ Post Office delivered the Fox parts yet?

Aspeed, I'll be interested to hear how much of a performance improvement is provided with your turbo head conversion.

No sign of them yet George. Since it may be of interest I will scan the test article and post it here when I get a chance.

ChrisM
'ffkiwi'

As promised here is the scanned G-Mark 061 engine review from Jan 1985 Aeromodeller

ffkiwi wrote:As promised here is the scanned G-Mark 061 engine review from Jan 1985 Aeromodeller

well they don't want to load for me-sorry. George see if you can do them from your end...

Chris, the CEF import engine seems to handle photos sized under a megabyte. At roughly 2 megs each, perhaps this is why the pages didn't load.

I used photo editing software to reduce the resolution by 1/2 from 300 to 150 pixels per inch and halved the vertical and horizontal pixels, converted colour to grey scale. This made each page 600 kb. Tweaked the contrast a little to darken the text. Here it is, and thank you so much for providing this engine test article for the G-Mark .061:







In Sceptre Flight, Model Engine Tests / Cox Tee Dee 049, the Cox .049 Tee Dee achieved 0.145 HP at 21,000 RPM (December 1961 Model Aircraft) on 30% nitro. G-Mark .061 achieved 0.133 HP at 19,000 RPM on 25% nitro, which indicates that the G-Mark does have decent power at the Tee Dee level.

The G-Mark's power silenced is 0.109 HP at 17,200 RPM. In Sceptre Flight, Model Engine Tests / Cox 074 Queen Bee (2), The Cox .074 Queen Bee put out 0.1 HP at 18,000 RPM. Fuel used is not mentioned, but speculating may be more likely 25%.

Here's where the G-Mark shines. It's weight silenced is 2.6 oz. whereas the Queen Bee is 4.0 oz.

Good effort George-thanks. I didn't get any error messages from the website that the files were too large or anything-when I tried to post them-just a big lot of nothing happening-most of the other websites I use will tell you if a file is to large on attempting to post or upload...

ChrisM
'ffkiwi'

Almost jumped on this TD .020 carcass. https://www.ebay.com/itm/223455494731 But where is the piston?

Thanks, Chris. The particular server Jason is using doesn't for some reason give any thing but clues. I just learned what seemed to work and what didn't.

gkamysz wrote:Almost jumped on this TD .020 carcass. https://www.ebay.com/itm/223455494731 But where is the piston?

If you re-examine the photos, piston appears to be there but appears to be locked in the up position way beyond SPI. Owner mentions that con rod may be broke.

Greg, as GallopingGhostler mentions, there's the piston lodged!
GallopingGhostler: You have a very good view !!

Ah well, I guess i didn't look close enough.

You are welcome, Mauricio.

gkamysz, I'm wondering if perhaps the piston ball socket was never tightened and after gaining some time and may be overspeeding (prop loss?) allowed con rod to separate.
This is speculation, of course.

- George

Could be. I've never heard of it have you? Something certainly went wrong with this one too. This ended yesterday.

The G-Mark just came in today's mail. It is like a little jewel, impressive when compared to other engines like Fox. Previously I mentioned that compared with the similar in power Cox .074 Queen Bee, it is 1.4 ounces lighter. I think I will have fun with this one.

GallopingGhostler wrote:The G-Mark just came in today's mail. It is like a little jewel, impressive when compared to other engines like Fox. Previously I mentioned that compared with the similar in power Cox .074 Queen Bee, it is 1.4 ounces lighter. I think I will have fun with this one.

What are you putting it on? Mine is a control line venturi so I can't really think of a project right now. I spent a couple hours today making the new turbo head. If it doesn't blow plugs it should be better than the stock one. It is a bowl type with a standard plug, and .025" headspace. This one is .012" or so, and a tighter bowl shape that I copied from an old T Tiger .07. It worked good. Maybe tomorrow I can try it out. Got the ceiling of the garage insulated now so no excuses that I can think of now. From the review above, I can imagine a .020" shim to raise the liner, and drop the head another .020" to make a real screamer(ish?)

Haven't decided yet, aspeed, but I have a couple kits yet to build that it would work on, 34" DeBolt Livewire Kitten, 38" Jetco Rearwin Speedster, 36" DeBolt Livewire Champ, 32" HOB Stealth Sport, 41" Midwest Bebe Jodel.

Been impressed on the write up provided by Chris, the lesser known G-Mark is actually a good sport engine with a decent carburettor even with the glow plug head.

This year I hit 65, and I've slowed down a bit, plus with all the volunteer work I do, plus house repairs, fighting a few bouts of arthritis, have kept me away from building for the past 2 years. However, I haven't given up yet.

Just bought a 16 oz. big bottle of Titebond Ultimate Wood Glue, supposed to be water proof. Don't know how easy to sand like the original formula, but will find out.

Finally got the aluminium back flange mount for my Cox .09 Medallion R/C, for mounting in my 46" 1959 Berkeley Impulse that is already framed. It will probably be the next in line to be finished.

Also just in, picked up an HB .12 RC with muffler. Always wanted one, unique they have both the beam and firewall mount, considered decent power in its day and still is.

I'm feeling the age a bit too. I can still do what I always did, but seems like not as long, and get stiff for a couple days after. 60 now. Pretty good day today so I ran up the G spot .06. A bit slower than a TD until I put in the turbo plug head. Started with 14,400 using a Master Airscrew 6-4 on 15% fuel and got up to 17,500 with the turbo head, so that was worthwhile. I put on an APC 4 1/4 - 4" which I used to test all my other .049 motors, and it started with 18,300 and the turbo head went all the way up to 24,000. This compares to a TD .049 at 22,900 (using 10%) It seemed to like the turbo head better, as the other one lost rpm when the clip was detached, either way was a bit iffy starting, but that is the way the little motors are. The muffler did not take any rpm away. Whatever, I wish there was a throttle. You should enjoy yours. I would bet that leaving out the head shim and maybe lowering the stock head would help a bit.

LoLz, I have to ask which engine exactly "G spot 06" and just how hard is it to find?

Some decor for the living room? https://www.ebay.com/itm/Model-Airplane-Engine-Sculpture/202645486503

There is a TeeDee on there. Could be worth a shot if someone wants one. Will probably get it for the $25.