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

[brw0513]

I would really like to see the shape of the torque and power curves for these GT15HZ variant engines with the OS Boost pipe and as well as the Hatori pipe. In my tiny mind, the sweet spot for these engines would be to have them run at a speed somewhere between the point of max power and max torque - probably closer to the point of maximum torque. That way when the head speed slows under load the available torque is actually increasing at a reasonable rate to help recover the situation. I think if these engines get run at the point of maximum power then they don't have the torque available at that speed to recover in reasonable time.

Of course this is all conjecture on my part It's so easy to be an expert on the interwebs. If I was a rich man I'd keep throwing money at the well known engine builders until one of them gave in and committed to putting these engines on a dyno so we can all learn.

Sadly I'm not a rich man But I do have a BNIB GT15HZ600 I'd be happy to temporarily donate for the purpose. I'd also be happy to contribute US$50 for the effort. No doubt Joey could make any freakin' adaptor required to mate these engines to a "Zenoah" dyno.

Maybe these engines could be happiest at 14,000rpm with the Hatori pipe?

More progress please Joey. This public holiday on Monday should be a great chance.

[Sowa]

Got any more flights in, on the 570, Joey?

[brw0513]

Hiya Joey,

Any updates? I'm hanging out for the next installment

Is it time to buy a 570 kit now?

[jc23cl]

Originally Posted by brw0513

Hiya Joey,

Any updates? I'm hanging out for the next installment

Is it time to buy a 570 kit now?

Hey Guys,

Just a quick response.

Been flying the bird last weekend, flies really well. Idle up-1 at around 2400 HS, its just fun.

Motor has been really strong, vibration levels really good, definitely has more poke than my electric T550 with Rail 556's.

BUT......

At low RPM cooling is effective and temps don't go over 100 degs, at just above hover the temps start to creep and it takes around 4-5 mins before we are past 150 degs.
At higher RPM the temps stabilise and the fan can keep up with the loading.

So in a nut shell, there is a big dead band of efficiency with the 5 blade fan at around mid stick. Not Ideal.

I have ordered and is sitting here ready to go a DR Madthrust 10 blade unit, probably should of designed this guy in the first place.

Blade efficiency apparently goes up exponentially with the addition of blades apparently, so the 10 blade should yield much better results. I just have to make a new shaft for it, the new fan has a 6.5mm mount instead of 6mm.

So "hopefully" I can find an hour to turn up a new shaft and Install it on the weekend.

I would say this though, I have flown in Idle-up for at least 5 mins at 170 degs, way too hot but the OS took it ( just plain fun ). The spiral rings seem to be doing there job, but lets get the temps down to a max of 150 deg with an Ideal of 130 degs.

I am optimistic the new fan will give a much broader efficiency spread, but will report back as soon as possible.

Thanks guys. Joey.

[Sowa]

That's good to hear, last weekend my temps were between 160-170C. I was however taking my temp readings by the exhaust port. Somehow my sensor moved itself during the spiral clip install. Motor took the higher temps well, no ejected parts.

[jc23cl]

Hey mitsudriver274,

Are you using a Futaba temp sensor or other ? I have my sensor tucked b/w head and 1st cylinder fin on exhaust side.

I would note that I had higher temps when measured at the back of the head out of the air stream.

Do you think the motor would of thrown the standard retainer at this temp ?

Thanks for the feedback, Joey.

[Sowa]

I'm using a spektrum telemetry sensor. Because of the Hatori exhaust originally installed I couldn't go one fin down, it's sitting at the very top, between the case and head. I usually read opposite to the exhaust 2 fins down, so naturally it will read higher in that location.

It's hard to say. I did some simple thermal calcs and it doesn't seem like the groove expands much. I think the issue is a combination of tolerance stack up and incorrect installation. Causing the retainer to rotate in the groove and eject when the opening reaches 3 or 6 o clock due to the inertial forces.

I'll be damn surprised if someone throws a spiral retainer, given it was properly installed.

[brw0513]

Hiya Joey,

Maybe one of these "under plug" temp gauges would be good to correlate readings:

http://www.poweredparagliders.com.au...s/TTO_CHT.html

[Sowa]

Every location you read temperature will be different. Likely to see temps around 450F (~230C) under the spark plug.

For us to be able to really correlate temp readings we would all have to use the same method of measurement as well as the same location.

Even then I'm sure the accuracy of these telemetry units leaves much to be desired. Sometimes I get readings as high as 450F which would lead me to think I'm very lean, but the motor sounds healthy and doesn't hang on the pipe.

[Doug Darby]

I ran the TT gauges for 2 years on my Zenoahs using the cht ring under the plug...as Mike says I saw 380 to 430 deg max on many well tuned flights... after I ran an eagletree logger I found out that the Max that was displayed ALWAYS occured in the 25 seconds AFTER I landed and shut the engine down...The engine temp rises about 15 deg every time without exception. When you turn the engine off... I verifed tbis earlier tbis week breaking in a new TRMVX300TT on the test stand.
telemetry is the way to go.
going to be logging temps while breaking in my GT15HZ600 on the breakin stand...

[jc23cl]

Originally Posted by Doug Darby

I ran the TT gauges for 2 years on my Zenoahs using the cht ring under the plug...as Mike says I saw 380 to 430 deg max on many well tuned flights... after I ran an eagletree logger I found out that the Max that was displayed ALWAYS occured in the 25 seconds AFTER I landed and shut the engine down...The engine temp rises about 15 deg every time without exception. When you turn the engine off... I verifed tbis earlier tbis week breaking in a new TRMVX300TT on the test stand.
telemetry is the way to go.
going to be logging temps while breaking in my GT15HZ600 on the breakin stand...

Thanks Doug,

Make a note where Carey has mounted his (I have it there now also) so that we can reconcile results etc.

Thanks Joey.

[Sowa]

I'm jealous of your test stand Doug!

Do you think you could do all of us a huge favor and record temps in different locations on your Gt15HZ, once it's tuned? It would be nice to have some sort of baseline readings of a tuned engine. I'm still fairly new to tuning gassers. Nitro is so much more forgiving.

Maybe to make it easier for newcomers, and the community, it would be wise for us to at least all measure temp from the same location to be able to compare notes on temperature readings. At least if someone is able to place a temp sensor at location X, then one could compare temp notes to others and get a ball park figure of where they stand.

Edit: Joey, I'm assuming you are referring to this location:


That's the current location I have my sensor mounted, I normally measure 180 degrees from that point as the exhaust port gets very hot. However, logically it makes sense to monitor the hottest location, but I do feel it is not accurate to the temps stated by OS. This is a hunch though, I could be wrong.

[brw0513]

Thanks for the update Joey. I'm sure you've got good help so keep going.

It would be great if the 10 blade fan is the answer.

Ay idea how temps would change if the needles were richened up a touch?

Could your fan blades be variable pitch like a fenestron tail?

[jc23cl]

Originally Posted by brw0513

Thanks for the update Joey. I'm sure you've got good help so keep going.

It would be great if the 10 blade fan is the answer.

Ay idea how temps would change if the needles were richened up a touch?

Could your fan blades be variable pitch like a fenestron tail?

Hey brw0513,

Its funny that you ask how temps change with needles.

Just before I brought it down for the second last flight I gave the main needle 2 clicks and I swear the temp dropped 10+ degs. Almost to the point of dis-belief and doubting myself.

This is also what I will log next time out, because i reckon it plays a big part in high temps, just how much i don't know yet. But i will chart this behavior for next report !

Cheers Joey

p.s. mitsudriver274 - Yep exactly measured there as well as Carey with Futaba sensor.
p.s.s "Could your fan blades be variable pitch like a fenestron tail?" - Yep that would be the ultimate, but the complexity would outweigh the benifits. I'm afraid if I cant get the 10 blade to work, and then refine the shroud, I will be going back to radial fan concept.

[brw0513]

Originally Posted by jc23cl

Just before I brought it down for the second last flight I gave the main needle 2 clicks and I swear the temp dropped 10+ degs. Almost to the point of dis-belief and doubting myself.

I've got an older heli mag here somewhere that reviews the CSM carbsmart, IIRC, on a 90 size nitro motor. The CSM carbsmart allowed a change in mixture based on measured temp. From memory it did a good job of maintaining a constant head temp and showed around a 15 deg C reduction in peak temps. Seems to back up your finding.

[fastflyer20]

Based on what we have seen on the test stand and learning the signature of heat rising after peak power and the cooling ability of a RC engine, I cool down Zenoah's at the end of a flight. Flip to normal and fly a bit then let idle before shutting the engine off. When breaking in engines on the test stand they will drop by 30 degrees F when running 7-8000 rpm and allowed to idle at 4000 for 30 second or so. There is even a more dramatic difference at higher RPM's. This may help the OS if it is seeing even higher temps.

[Sowa]

Any news on the cooling system revision?

[brw0513]

Originally Posted by mitsudriver274

Any news on the cooling system revision?

Keen for an update too!

[jc23cl]

Originally Posted by brw0513

Keen for an update too!

Ok Guys,

Finally had time to test new fan (been just to busy to get "man cave" and backyard ready for the Missus's 40th in Dec)

Anyway, spent a few hours on Sunday running way rich to way lean temps were better and held at b/w 155-160 Deg's.

Heli was hard pitch pumped, with 30 ft climb outs continuously and temps held.

Heli was Flown in Idle up and quite frankly not treated well at all, but it just flew strong.

So, the newer Impeller was better, not a quantum Improvement but definitely better. I could feel the heat with some force coming out from the shroud, and really hot.

I would be confident to just fly this bird as it is, but I am now re-designing the shroud to relieve back pressure and allow more flow. My feeling is this will Improve the temps by maybe 5-10 degs but I don't think I will ever see 130 degs as per manufacturers recommendations.

I'm wondering if anyone is achieving 130 degs flying hard, please let me know !

So I'll re-design and print a new shroud this week and test on the weekend, let you know.

p.s. outside temp was a cool breeze and sunny 25 degs !

Also, if I didn't have to change out the retainers, I'd say what a great little engine !
Any feedback from others on the retainer mod (to spiral rings) !



miscellaneous : )




Heli pad.....

[Sowa]

That's good news. My motor has always been running between 150-170C range with the temps taken from the same spot, that's even with the trex cooling system. It's hard to say where OS pulled that 130c operating temp from. You will see spikes up to 220C under the plug, but that doesn't mean the motor is running lean or overheating.

Spiral retainers are holding strong, haven't heard of any failures from the people that are running them.

Joey, are you still running the OS pipe?