Hks 700t

[Av8r3400]

Not for an IVO. They flex quite a bit.

[Mnflyer]

Agree not for an IVO in fact IVO says not to worry about tracking or at least they did a few yrs back.

[Geowitz]

I think I may have found the culprit and I'll be an idiot if it's what is causing the problem. At this point though I'd rather be an idiot and this fix work than it be something serious. I'll report back tomorrow after another run up to check.

Thanks for the comments. I'm so close now!

[Geowitz]

Well, I may be an idiot, but my thoughts were incorrect and I have not fixed my issue yet. I have noticed though that on subsequent starts everything is rather violent and shakey until the prop gets up to speed. I mean bucking bronco type engine violence. Is the moment of inertia of the medium IVO too much for the 700T? I'm starting to lean this way which is unfortunate because I had high hopes of the IFA taking full advantage of the turbo. Might have to give that up for a lighter prop. Idle should be around 1600 rpms. At this speed the prop will go back into bucking mode with violence. Around 2000 rpm is somewhat bearable, but my panel is shaking like it's doing the jig. Above 2000 I can almost feel numbness in my body from the vibrations and see the panel shaking. It smooths out relatively above 3000 rpms and gets better the higher I go. Got it to 4300 rpm today.

Any thoughts? If I had a prop with too much MOI what would be the dead give away symptoms other than ripping my gear box apart after continuous use? Anyone have any clue what the MOI is for the medium IVO?

[rwaltman]

... on subsequent starts everything is rather violent and shakey until the prop gets up to speed. I mean bucking bronco type engine violence
... Idle should be around 1600 rpms. At this speed the prop will go back into bucking mode with violence. Around 2000 rpm is somewhat bearable, but my panel is shaking like it's doing the jig. Above 2000 I can almost feel numbness in my body from the vibrations and see the panel shaking. It smooths out relatively above 3000 rpms and gets better the higher I go.

A few data points, different engines, (HKS-700e non-turbo) different propellers, (3 blade powerfin in my case).

(a) Mnflyer reports "I can idle mine at about 2000 for warm up and after a flight for cool down it idle very nicely at 1700. "

(b) In the few engine runs I did on my KF I observed the same and had the same concerns. (Instrument panel turning into multiple instrument panels?) The shaking was too much until ~2200rpm, it could be called "smooth" above ~2500.

Waiting to get it back from its annual (this is turning into another litle horror story, the plane is not at fault.) to start experimenting with carbs and propeller balancing.
I am beginning to wonder if that may be intrinsic to the 2 opposite cylinders design

Anyone have any clue what the MOI is for the medium IVO?

I went through that some time ago. The only reference I could find is for the ultralight, not the medium. Also, it is from a competitor, use it as an unreliable lower bound.

From http://www.powerfin.com/features.htm:
"A 72" – 3-blade Ivoprop Ultralight propeller is about 4,500 kg/cm2"

If everything else fails, there is an article here on how to measure it:
http://www.800-airwolf.com/pdffiles/ARTICLES/part31.pdf

Roberto.

[Geowitz]

Roberto,

Thanks for your personal experience reports. I have been scouring the net for anything and had seen what you posted for the IVO light prop and how to measure it. Might try that soon actually. The 700T has a c type box that is spec'd to handle up to 6000kgcm so the hope was that with all the 912 ULS's running them(even if they were over that MOI which I suspect) that the 700T had a good chance too. While it is only 80hp it's 80hp at 2000rpm prop max(5300 engine) because of the gear reduction. This thing has no problem spinning it up and all of my high rpm runups have required the upper half of the medium blade's pitch range.

Took the prop off totally and it ran fine. Everything else seems to be in order and prop appears to be balanced. Is there anything else that can cause this kind of violence and vibration?

[rwaltman]

...Is there anything else that can cause this kind of violence and vibration?

Wild guess: Engine rubber mounts too rigid, or torqued too tight?

Thinking of other potential sources of information, I assume you know about the HKS group in Yahoo: http://groups.yahoo.com/group/HKS-engines/

Are there any groups dedicated to airplanes where the HKS is the norm rather than the exception? (Thunder Odyssey?)

Roberto.

[Mnflyer]

Hi Geowitz, the HKS will not run smooth at 1600 R's at all, my 700E is good around 2000 on warm up 2200 smooth as needed but below 2000 ruff, after flying and at cool down I can and do idle down to 1700 R's and its smooth will idle forever just purring away. Not to discourage with the IVO but I tried a 2 blade quick adjust on my Kitfox HKS and had no good results after 20 min of flt the CHT's were at max, I had removed the 3 blade GSC to try the IVO reinstalled the GSC and temps were no problem. After that I installed a 2 blade 68" Warp Drive and it has worked great engine idles better climb inproved as did cruise and temps stayed excellent. Incidentally I found no upside with the IVO when I tried it did not help getting into the air or climd nor cruise, I fully understand wanting the IFA capability though I do believe that with the HKS torque curve that an IFA prop would be great.
PS I noticed a big inprovement in smoothness when I removed the 3 blade GSC and installed the 2 blade Warp Drive.

[Geowitz]

With the turbo and lower compression there should be a possibility of a lower idle though. Not that it really matters. I'd be fine with 1800 rpms or even 2000 if everything proved to be smooth enough from there on out. Before I give up on the IVO I'm gonna try it in two blade and see what happens.

I'll check my mounts again. I actually tightened them after the first start because I thought they were too loose. Thinking more about it I don't remember as much violence or vibration in the seat of my pants on the first start when the rubber mounts were more loose. Perhaps I didn't notice because I was so excited otherwise. I'll try backing off them a little to where they were before and try again.

[rwaltman]

I'll check my mounts again. I actually tightened them after the first start because I thought they were too loose. Thinking more about it I don't remember as much violence or vibration in the seat of my pants on the first start when the rubber mounts were more loose

The installation manual for the 700E specifies the torque: "The tightening torque for the four 10mm bolts or studs is 4.8kgm. (34ft.lbs)"
(Have not read the 700T manual.)

Roberto.