Oops, I did it again...........570 Goblin Style

[jc23cl]

Hey all,

Now that the Goblin 700/630 kits are underway, I'd thought I'd share my latest tinkerings.

Fairly self explanatory, shoe horn a GT15HZ-600 into a 570 and hope the Power to weight speaks for itself !

I recently built a 570 for a good friend and of course took some key dimensions for feasibility.....I am now happy.

It will utilise existing motor plate, where the drive/clutch bearings will sit, custom side frames, T700 fan, T700 clutch adapter, Lynx Gas Clutch and so far custom dedicated GT15HZ-600 fan shroud.

Now this point is Important as I have also modelled in so far a T700 fan shroud and although I can make it work, the canopy will require eyelets to be cut into sides to let shroud width to stick out 10mm/side. Functional but not the ultimate in maintaining the 570's gorgeous lines IMHO. Economics may dictate the outcome, and some feedback of course.

So I will at least do BETA's with an open source 3D printed ABS custom version as shown. I have already test printed many variants and it is right on for strength, geometry and mechanical stability, only hard testing will tell the whole story.

Any I am finalising the side frames now, but you can see in pics the original frames, to see there will be not much size change from the original.

Anyway enough bla, bla.......enjoy or not (as always happy to hear comments positive and negative)














Some final comments, I am not 100% convinced with the plastic landing gear as they are pretty weak just above the mounting screw, don't ask how I found out on my maiden electric flight......( SAB, these are sooo clever and Innovative, just take material off the mold and strengthen these guys...please )

And anyone who has any experience with the GT15HZ and cooling, feedback please regarding further development of the shroud if needed, thanks all.

Kind regards Joey.

P.S. big thanks to Jockstrap....he knows and Carey for the constant encouragement, thanks guys.

[LoveToFly1]

that looks awesome man! keep up the great work! I hope to one day own a goblin gasser too!

[Doug Darby]

Very nice.... And an interesting project...
I love the concept but wish there were other more reliable engine options.. I have not followed all the engine failure threads but my feeling is based on the sheer number of threads discussing issues... Maybe it has been improved?

I flew my Goblin 700Gas yesterday and I was shocked at how it performed. I was not expecting such a signuficant improvement over the Whiplash G that I have flown for several years...

So im confident this design will be just.as superb... (my 570 is sitting on the bench waiting... lol)

I wonder if you could resolve the engine fan shroud and canopy issue by going to an electric cooling fan on the shroud and remove the engine fan and its parasitic load all together?
Bizarre idea I know... just thinking...lol

[fastflyer20]

Great to see innovation!

Agree with Doug, if this is "as good" as the 700G, you will have another winner!

Hopefully the OS GT15HZ 600 has a happier life that the original one, time will tell. If the engine is good, this could be the hot "small" bore conversion.

Cooling will be critical. For the fan shroud, how about formed plastic to cover the cutouts in the canopy?

[HankAz]

Oh man I haven't even got home to start my Gas700 yet and I want one of these. When the 570 came out I figured I would not get one but you just changed my mind. LOL one more heli to get. Put me on the list...

[Rudy]

I like the Goblin kits, and I like your conversion. I how ever do not trust the OS 15 engine. I have yet to hear of anyone getting that engine to last more then 2 or 3 gal of fuel before it eats it self.

[brw0513]

Joey,

Nice idea!!! This engine deserves a good home and the Goblin 570 could be it.

Please consider thinking outside the square for cooling duties. IMO, by themselves, these crank mounted fans and bent shrouds just don't have the efficiency needed to address the heat generated by these OS gas engines. At best, such a fan will only move air over the fins on the plug side of the head - and then not evenly.

What about an electric fan ala Compass Odin 90? Or a belt driven fan within a shroud ala Kyosho Calibre 90?

Another option, used by others before, could be a 50mm EDF for cooling duties - they certainly move a lot of air and can have a low power consumption. I've done some bench testing with a GT15HZ and an EDF in combination with a CSM CarbSmart so that the fan speed varies based on sensed head temperature. The experiment wasn't really successful - my test stand was hastily put together and didn't allow me to load the engine to any real extent or capture much in the way of useful data. The next incarnation will be better. But the EDF sounded really good speeding up and slowing down to moderate the engine temp.

My left field ideas are:

1. Water cooling. Not necessarily with a pump but small pumps with potential are available. A sealed "natural convection" system may be enough. If you have a look at the underside of the head, there is a nice space between the cooling fins and the circular boss - I bet a 1/8" copper tube could be fitted in there with thermal epoxy as a coupling medium. An aluminium spiral coil could be strategically located on the model to create a heat pump. I think this idea using glycol/water mix has been used in our hobby many years ago. All air would need to be purged from the system but that shouldn't be too hard to achieve.
2. Using one of those disposable Soda Stream CO2 canisters and an expansion valve to create a cold "atmosphere" over the head. A bit like using a fire extinguisher to cool a 6-pack of XXXX Gold.
3. Rotate the head on the crankcase by 60 degrees (courtesy of the bolt hole pattern) and get a good airflow over all of the fins.


Most importantly, keep up the good work. I'm sure OS would pay attention if the GT15HZ or GT15HZ600 found a truly happy home!

[jc23cl]

Hey brw0513,

Thanks for the Input, I love the Innovative thinking ! I really do.

My professional business (away from helis ) is built exactly on this type of left field approach.

The 570 is however very special, in that there is just no room or allowable weight for some of your Ideas.

I will though see if a small GT2/3 timing belt can fit in place of the fan to drive an AXIAL 50mm ducted fan and custom housing. This should be way more efficient than the normal radial type. I can also amplify the fan speed with pulley gearing options.

What do you think ? Anyone.

On a side note, is the general consensus, that previous failures have been mainly attributed to inadequate cooling ? Anyone.

[Sowa]

Carey has two engines running with no issues, both new and old piston design. I have the feeling the walbro style carb may have been difficult to tune, but have no first hand experience. I will though next week with the 600 version.

However the only cooling setup I've seen for the 600 version uses a 600 fan in a 700 shroud. I'll find out first hand how effective the cooling system is and will be able to shed more light on the matter.

The biggest issue with this motor is weight, everything has to be very lightweight in order to get back into a reasonable disk loading. I will try mine out on rail 606s, then on edge 623s, I'd like to pick up a set of sab 630s as well to try out.

One benefit of the gt15hz is it only burns .5 oz of fuel every min at 16k. A 8oz tank should yield at least a 14 min fight. There is one area to save weight, PET plastic tanks are very popular in the airplane community for there weight and simplicity, I will be trying one out in a heli to see if they are applicable.

If this comes in around 7.5 lbs I'll have to put a for sale sign up on my 600 OS dfc airframe

[jc23cl]

Thanks, any feedback would be well received.

A quick layout tells me I CAN squeeze in an 50mm fanjet fan, driven from main shaft.
This should give significant cooling over radial, lets see.

Put it this way, I don't believe a radial fan configuration would ever give enough airflow/thrust for a EPO Jet to take off. Food for thought.

Thanks for the feedback so far, I'll post axial fan CAD progress as it develops.

Regards Joey.

[brw0513]

Maybe some ideas here:

http://www.hobbymedia.it/45688/gaui-...-ep-ircha-2013

[Sowa]

I was going to say gaui also went with a different cooling system than the standard setup we see these days.

[carey shurley]

Kyosho did this for the Caliber ZG LONG before GAUI copied it

K&S has a conversion for the GSR260 that uses it as well


caliber zg



caliber zg cooling system

[Calil]

I may be very wrong but I would never ever trust this tiny belts

[LoveToFly1]

I wouldn't either man.

[Rudy]

Originally Posted by LoveToFly1

I wouldn't either man.

Why there is no load on either one. One is driving a fan, and the other the generator.

[Sowa]

Originally Posted by Calil

I may be very wrong but I would never ever trust this tiny belts

I think they look small in relation to the engine. But for the given task they are more than adequate.

[jc23cl]

Hey all,

Quick update, as promised I have Investigated the "axial fan" design and can make it work.

I reserve that although technically feasible, other components or design Issues may prohibit this variant.

But here it is, 50mm EDF fan (5-blade), geared 4:1 so that at full speed, the fan generates almost 50K RPM. This equates to more than 450 grams of thrust, this wont act to lift the heli as the motor blocks this thrust, but gives you an Idea of how much cooling is available. The shaft and bearings are very rigid, as the the fan cowl is only acting to distribute cooling air, therefore no compromise there. The fan has no obstruction from post Impeller thrust so cooling should be optimised.

Anyway here's the pics....one note is that a 6mm 3GT belt is used, same as Goblin tail drives. Any doubt that a small timing belt cannot cut it, Google Belt Drive Planer and see what a standard Planer utilizes as its transmission ; )

[LoveToFly1]

Originally Posted by Rudy

Why there is no load on either one. One is driving a fan, and the other the generator.

bc I wouldn't.

[PPJHEN]

Originally Posted by jc23cl

Hey all,
Anyway here's the pics....one note is that a 6mm 3GT belt is used, same as Goblin tail drives. Any doubt that a small timing belt cannot cut it, Google Belt Drive Planer and see what a standard Planer utilizes as its transmission ; )

No pics ?