rcmk cr300f

[bambini]

Hello,
I would like to start a new gasser conversion project, with a high power rc format engine. Are there any experiences with the rcmk cr300f (vibrations at higher rpm's, usable power-bandwith, temperatur issues, etc.)?

Many thanks!

Wolfgang

[martin_]

I don't know for the RCMK into heli, but according to the baja & goped world this engine is as good as Zenoah for durability, of course the RCMK deliver more power out of the box but a Zenoah can be modded to match that power.

Vibration wise, I don't know, they have their own cranckshaft, maybee it's better balanced.

I have a full mod Zenoah 30.5cc reeded case with big bore carb and a real tuned pipe, no doubt it have strong power to move my 800, 12deg pitch, aggressive cyclic and the motor is barely bogging, however I fly less than 10 min on a tank (power should come from somewhere) but the biggest issue is vibration that cause me all sort of problem.

Have a friend that have and identical 800 setup and his last vibration adventure was the carbon tail control rod popped off of the servo ball, he managed to land safely and we could not believe what have happened, we expected the ball link to be damaged, cracked, etc.. but no, we put it in place with the nice ''click'' sound as usual while scratching our head, and it happened again later, but this time he crash landed. I suggested to move the rod support a little to break the resonance and lower his rpm by 100 or so rpm.... if it can help.

Now we are stuck with those engine.... we will wear it, maybee the next time will be a smaller/smoother engine, but will I trade all that power for a smoother engine..??

[losi5t]

Apples to oranges here, but I put a rcmk 30.5cc full-mod in my 1/5 scale short course truck. I did a lot of research before I bought this engine. First, the cylinder are supposed to have the best plating out of the bunch. This will make any porting that you do a little bit harder for a diy person if you go this route (supposedly they chip the plating vary easily). The other nice feature I like is the four bearing crank (would assume this would help you in vibrations some? ) and then it also has six ports compared to four. The other thing I would look at is the exhaust port is larger than that of a cy/zen engines. But I'm a 100% noob to helicopters and was talking to a guy at the air show I just went to about them in helicopters. But I can tell you for surface side of things. This engine is great and price wise you can't go wrong Imo. Here's a picture of it installed,

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[bambini]

Hello,
I have found this dyno-results:
http://miraclehobby.com/shop/html/?999.html

The max power is reached at 17.000 rpm's. Mmhh I hoped this point would be at lower rpm's.

I think the biggest problem then would be the vibrations at high rpm's.

I found several tuned motors for rc cars:
http://www.gizmomotors.com/index.php...03-05-21-30-33

But I'm afraid, that this motors do a great job in rc cars but not in rc helis?

Wolfgang

[Doug Darby]

I am currently running a Toxic Al TRM VX270TT with a Quickdraw pipe that is 6+ HP at 14,800 to 15,000 RPM. It pulls 12-13 deg pitch on a Whiplash Gas Heli with 695mm Cyclone blades and I have never had any vibration issues.

[losi5t]

Originally Posted by bambini

Hello,
I have found this dyno-results:
http://miraclehobby.com/shop/html/?999.html

The max power is reached at 17.000 rpm's. Mmhh I hoped this point would be at lower rpm's.

I think the biggest problem then would be the vibrations at high rpm's.

I found several tuned motors for rc cars:
http://www.gizmomotors.com/index.php...03-05-21-30-33

But I'm afraid, that this motors do a great job in rc cars but not in rc helis?

Wolfgang

Gizmos is a great place to do business with. I would call them and try to talk to Bruce himself or Tim. If you're looking for lower the rpms for vibration he might be able to achieve this for you. It's worth asking them to see if he can?

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[turboracer]

Been there and done that. The RCMK cylinder uses the same number of transfer, exhaust, and intake ports as a Zenoah. The exhaust timing is higher than a stock Zenoah. The plating is better than Zenoah. The transfer ports suck. They need a tremendous amount of work to get them to run well. The intake port is too small as well. They do use a different crank. The 30.5 will vibrate badly at the rpms we run them at. You will destroy your airframe and electronics unless that motor is modified to run smooth at the rpms we run in helicopters. They do produce some good power when done right. All of the "stroker/big block motors" I tried were also really good at breaking things especially when unloaded at high rpms. Take Doug's example and consider it carefully. Al builds great motors that run smooth.

[Azalin]

I run a Zenoah G290RC on my Helibug 600. It vibrates crazy. I checked the airframe yesterday and noticed that 2 M3 bolts were missing. The power is just enough for the application (600 size) but it needs to modified to run smoother. I know lightened pistons can help reducing the vibration. I will try that.

[bambini]

Thank you for your comments...

It's worth asking them to see if he can?

I don't know the guys behind Gizmos and I don't know whether they have experiences with heli engines and the special demand on low vibrations at high rpm's.

I think, I will choose an engine, that is especially tuned for helis...

The TRM290 Special Edition sounds interesting. But it's not available at the moment, I understood and that is why not an option yet.

Does anyone know how munch power the TRM VX270 provide?
I found an other engine especial tuned for helis: Hanson 29 RC 3D Max

This two engines would be shortlisted for the moment.
Any comments about those two engines?

[Azalin]

The VX270TT provides amazing power. Perfect as a gasser motor.

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[turboracer]

Power production depends on if you choose to use a tuned pipe exhaust system or a tuned muffler. Tuned pipe exhaust will provide a significant power increase over a tuned muffler. The price you pay is more sensitive tuning. Either motor will run well. Both will make great power on a tuned pipe. I suggest that you call both motor builders and discuss your goals with them. Then choose the one you feel most comfortable with. They both do great work!

[rbort]

Does anyone know how munch power the TRM VX270 provide?
I found an other engine especial tuned for helis: Hanson 29 RC 3D Max

I use the Hanson G270 RC 3D Max motor as well as the G26 PUH 3D max motors between my 3 helis.

They make great power and are super smooth. The Hanson G29 motor in RC or PUH format makes more power the than 26cc motors if you need more but will also burn more fuel then the smaller engines.

Think of the G23/240 motor as the 4 cylinder, most economy, lowest power.
The G26/270 as the 6 cylinder, good economy good power
The G29 is like the 8 cylinder, least fuel economy, and most power.

To give you some idea from some testing I did some time ago:

G231 motor topped out at 1670 head speed on my heli at full collective
G26 Pro Plus motor spun the same head/pitch at 1730 rpms.
The G26 3D max turned at 1800 rpms.
The G29 I was unable to hold the engine back with the 3D had (not enough pitch), it kept increasing in rpms on the way up at full power. I ended up putting a tempest head on it and it climbed even faster with more pitch and a 34mm larger disk.

-=>Raja.

[mark196622]

I'm running the Hanson 290RC 3D Max in a Whiplash Gasser. It's very smooth and powerful. Close to 200 flights with no problems with the engine or heli.