3DHELINUT

My Feedback: (3)

I got the gear upgrade and a new belt today and installed it.

These are the steps I took to install the new gear.

1- remove the tail boom, makes it easier to work on the heli.
2- remove the fuel tanks
3- disconnect the EGT sensor, glow plug wire and electronics box. (the box with the HP5 label), Be carefull when you remove the electronics box as the hall effect sensor is located on the back.



4- remove the turbine, disconnect all gas and fuel lines



5- remove the lower gear and bearing block assembly
6- loosen the starter assembly



7- remove gear from shaft, there is a 4mm bolt holding the gear to the shaft. you will need to heat the gear for removal and there is an insert that has to be removed from the gear. the insert is milled with a lip and limits the gear from sliding off the shaft.



The original gear is a 23/76 tooth gear and the new gear is 25/76 tooth. You will need to apply some locktite to the shaft and insert because the gear is not keyed to the shaft., you will also need to heat the new gear to install it on the shaft as it is a tight fit.

Now reverse these steps and your finished. You will need to adjust the belt tension and alignment of the lower gear assemble, I used a dial caliper and measured the distance between the top and bottom of the gear and the side frame as a reference.





I adjusted the top and lower belts to what I think is the same tension, I used a metric ruler and measured the amount of flex between both belts.

' HP5s came with both 267 and 270mm lower belts. If you had one with a 270mm lower belt already you might need to slot the holes for the engine to raise it up. This will misalign the starter. All you need to do is loosen the starter and re-center it to the compressor nut and your good to go.' Thanks for this info BOB


I took my time and had the upgrade done in just over an hour.




Alan....

cat-boi

My Feedback: (10)

just curoius, what are you doing to upgrade the rotor head? 1.8's are not meant to turn over 1200 or so, the effects can be disaterous when they hit 1400. NIce work btw...

3DHELINUT

My Feedback: (3)

I am running metal blade grips and the axle bearing with 825mm blades, to date I have logged 3 hrs on the ship with no ill effects or wear on the rotor system. The jet copter will now loop effortlessly and perform rolls, split s, 180 stall turns and inverted flight. The added head speed greatly helps with autos as well. The rotor system can handle even higher rpm's with no problem. Vario is too conservative with there max rpm per rotor diameter.

My Xcell Fury Extreme with an OS 91 and running 190 grams 710mm blades are turning 1950 rpm, The Jetcopter is running 235 gram 825 mm and turning 1460 rpm's

There may be an issue with the Graupner rotor system as they employ a GRP rotor head. But i have had no exposure with the graupner system and i may be wrong?


This is just my two cents and i will stand by it!

cat-boi

My Feedback: (10)

hey, youre the one whos gotta stand next to it... just be safe.

wojtek

My Feedback: (73)

I have my Jetcopter running the speed up gear also, and in fact i have been using the Graupner blades that they sell for the NH 90. I have beaten the crap out of this heli, doing several full speed / full controll deflection manouvers, loops, etc ... and no problems at all. Its actually much crisper to fly at this head speed. I have one of the Graupner heads for the HP5 for another heli, and im not sure im going to go to the higher head speed ... then again, i think deflecting the blades to 18 degrees at a lower head speed is equivelant to a typical 12 at the 1400 head speed.

With JetcatUSA backing the unit, im not worried at all, they stand behind their product and would not sell a speed up gear if it was not safe ... I do not believe jetcat germany will support or waranty changing out the gears on their units ,,,

Wojtek

cat-boi

My Feedback: (10)

I was referring to the rotor head, not the integrity of the gears(if you read my post)
the grips take a lot of centrifugal force at those speeds and are subject to wear/fatigue. I wouldn't worry about the quality or support issue , since that is not going to cause a failure. my point was that parts of the head can let go in time due to the much higher loads placed with them under those conditions and to be just safe and responsible about maintaining the rotor system and making sure its up to the job.

wojtek

My Feedback: (73)

as for the rotor head, my point was, stress wise, whats really the diverence between 1400 rpm with +- 12 degrees pitch, or 1200 rpm with 18 degrees pitch as is claimed for the NH90 with HP5 ?

its just a diferent part of the rotor head you are stressing ... with higher head speed, its the spindle bolts that take more stress as well as the thrust bearings and blade bolts, with the 18degrees pitch, id say thats wher the rotor grips take some more stress, as well as the linkages and entire controll system (swash plate, etc .. )


I do have to say its impresive how much stress our helis hold up to these days .... hey, look at the 90 sized 3d machines !! i think they put a lot more stress on the rotorheads than most turbine helis ...



Wojtek

3DHELINUT

My Feedback: (3)

Wojtek Your right about the stress factor with 3d machines, My fury Extreme has grp blade grips and the carbon blades are using a 4mm single bolt. I can safely say that i am putting more stress on my fury's rotor system then i ever will put on the turbine and as for wear of the head well that is why we do maintance on our machines! I change my blade bolts every few months and i perform maintance every month on all of my machines.

In most cases if a rotor head is to fail in flight it was due to manufacturing defects or poor maintance from the owner!



Alan...

wojtek

My Feedback: (73)

Hey Alan, I heard you were looking to build also NH90 but V-east could not come up with one for you (i had the same deal) I got a place overseas that will get one to you if you still want it, in under a week, and for like 20% less .....



Wojtek

3DHELINUT

My Feedback: (3)

I just might have to look into this after i finish my Vario Giant Hughes 500!

cat-boi

My Feedback: (10)

That was my main point about maintenence keeping and eye on expendable parts, but also excessive pitch like what we use 18 degrees does not increase centrifugal loads, spinning them faster exponentially increases load with every step up in rpm however.If you look at actual load calculations it would scare the cr*p out of you. If you speak with the expert designers like I do on a regular basis you realize that even though something holds up, does not mean it will forever... just like the blade bolts as a perfect example, factor in the heavier rotor mass and even the smaller metal grips or blades can pull through. by smaller i mean standard size.
The first sign of this being an noticable enlongation of the blade bolt holes themselves... even ships that are desgined for a specific set of blades can fail if proper attention is ignored.I am glad you guys are keen to this and know what you are dealing with.

f.y.i we run 12 mm shafts with 10 mm cross axles for these types of loads along with mamouth grips..much larger
than previously available units.
These systems will be shown here soon...
http://www.v-eastonline.com/ScaleJetmain.htm

CopterDr

Gee Guys............I just had to share what little knowledge I have on the subject since I work on full scale 206L1's and 3's and love the heli hobby too.

For sure, centrifugal force is directly related to RPM, not to pitch. That force is vertical. Our ships turn 394/5 rotor rpm period. The system is designed for 10% increase for autorotations, and we as mechs, make sure during test flights that the PC links (pitch links) are adjusted accordingly.

I can truly say I lived through a grip failure on my beloved Benzin Trainer a coulpe of years ago. Stock rig, turned the main rotor at 1300 (via rotor tach from a friend). Right before the "event" I was running her up after a good preflight and had a recv. glitch (for lack of a better explanation) that caused a rotor overspeed. (I'm guessing close to 1900 rpm.....O* pitch). After changing my pants, I did a through postflight insp. Other than worried about the engine, I checked everything, espeically the grips, blade bolts, etc.

Conviced all was OK, I tried later that afternoon for a little hover time. Fired her off.....made all the flight control checks......and spooled her up. She lifted of as always in a rock solid 4' hover, 10' in front of me. As she set there, about 2min,... I only heard a loud crack.....and she was on the ground so fast, I never saw it fall. As I looked down in total disbelief......nothing but a twisted unrecognizable pile of parts lay there in a heap with the engine running smoothly at just above idle. I reached over and hit the kill switch.
Now a deafening silence hit me.......never heard my kids come out of the house. As I was trying to figure out what happened. My son said he saw something white about 60 yards out in our then strawberry patch out in front of where the heli was hovering. He brought back one blade,intact, with a slightly bent, not broken, blade bolt, nut still on. A pang of fear fell all over me. The neighborhood kids usually come to watch when they hear me flying........thank God they weren't around that day.

I found one blade grip with a third of the outboard radius (top and bottom equally) gone. I could only assume the overspeed had caused fatigue by the high cetrifugal loads.

My point is, the designer/engineer's take rpm limits seriously and pushing that envelope can be disasterous. The cetrifugal loads can be unbelievablely high at just a few hundred rpms more than normal.

I was lucky that no one was hurt, or worse. The bird was absolutely totaled, with less than 60 hrs of scale like flying on it.

Hope this sheds a little light on the subject.

Play it safe..!

wojtek

My Feedback: (73)

centrifugal force is one thing, but the controll system (swhash plate, rods, etc) are what is afected by pitch (of course combined with head speed) it is the controll system i am more afraid of failing rather than the rotor grips themselves. for the hell of it, i might take an old rotot head and see how much of a cetrifigual weight it can hold .. (using a ratchet winch and scal, NOT ON THE HELI )

On my Jetcopter witht the 1400 head speed, i have the all metal blade grips. I still think the original GRP ones will hold ( Alan, which ones you using ? i know you had the extreme head at one point )


As for head speed, im contemplating weather or not to go past 1200 on my 4 blade head on the EC-135. With the turbine, i will have constant RPM, so a moving phase window wont be an issue. In the case of the vario multiblade heards, cant beat them. twin bolts per blade, and masive center hub.


Wojtek

cat-boi

My Feedback: (10)

you should run 1400 on the multi, the blades do not have the mass of the huge two blader and should be just fine at those rpms, especailly with the gov.
the two bolt vario multi head is all grp. molded construction.

wojtek

My Feedback: (73)

ill experiment with the pod and boom set up with the 4 blade head first, but ou are right, the blades are not as masive ...



Wojtek

Phil Cole

The centifugal force is proportional to the square of the RPM. Running at 1400 RPM instead of 1270 increases the radial load on the grips by 22%. I did see load ratings on the Vario USA web site. It was something like 1000 kg for the GRP grips and 950 kg for the metal grips.

Overspeeding to 1900 is another thing entirely. The increase from 1300 to 1900 is 113%.

I did some calculations a while back and concluded that 180 g 680 mm blades at 1750 RPM was equivalent to 230 g 810s at 1500. I.e. grips and grip bolts that can take 1750 on a 60 are good for 1500 when used on an 1.8 M rotor. This was calculated using the blade CG position as a single point mass. The radius from to the grip bolt was included in the calcs.

The MA GRP grips do have more cross section that the Vario GRP grips, and a more substantial boss around the bolt hole so the above extrapolation needs to be considered carefully. I did measure the cross section of the (GRP) grips on a Robbe Cuatro, and that was in the Vario ballpark. The local Cuatro guy runs 1600 and more with 810 mm blades.

I calculate the actual radial force on 810 mm 230 g blades at 1400 RPM to be 252 kg. (1400 RPM = 23 rev/s = 146.5 rad/s. F = w^2 . m . r = 146.5^2 x 0.230 kg x 0.5 m = 2469 N = 251.9 kgf)

The guys with SPS Cuatros delight in telling me they can do 1900 RPM. (1900/1400)^2 x 251 kg = 464 kg. I don't know the load rating for the Cuatro grips. They get away with it so far, but I try to be at a distance!

For Jetcopters, there is no doubt that 1400 RPM (at least!) is necessary and reasonably safe. It's not a scale machine and just cruising around with a 1270 RPM fish-head that can't out-climb a 60 doesn't really cut it

Elliot

Hi Guys,

to run a rotor head with 1400rpm is sure not a problem. We run on the rocket up to 2000...., but with 1.60meters of rotordiameter...

Main problems with higher rotordiameter are:

1. blade holder aixle (8mm ? sounds not good)
2. main rotor mast (10mm ? sounds not good)
3. not known vibrations in the system
4. belts ? better not to think about it
5. rotorblades themselves
6. servos

I would never run a system anymore with a head speed which is not recommended for it, nor tested by the manufacture. This is dangerous not even for yourself, but for other people standing around as well.

We once run a Hughes 500 using a five bladed head. Recommended headspeed was 1150 max. We used 1250 because the heli was a little bit too heavy...the system simply exploded by hovering it...bad experience...

Take care, that`s the only advice I could give you. Use a rotorhead which is designed for diameters more than 1.80meters, not a tuned plastic head....

I would suggest a LSZ or even better a Nuova Cuatro head. Use a 12mm main mast, use a 10mm blade holder aixle, use 5mm rotorblade screws..., just to be safe enough..

Best regards,

Elliot

wojtek

My Feedback: (73)

the 1400 head speed IS supported and warantied by JetcatUSA. The actually also ship newer belts also for this set up if your unit does not have them. The problem used to be with the lower belt that was right of the turbine, where you had a high centrifugal force on the belt at over 90,000 rpm, and thats why units were being set to under the 90,000 with diferent gearing ..



Wojtek

Elliot

Hi !

Ok, I understand....the newer belts also guarantee the higher headspeed with all consequences for the blades, main mast, rotorhead, etc...

This makes sence to reduce the overall speed to get more headspeed...

Where can I get those ?

Elliot

cat-boi

My Feedback: (10)

thats a good thing and good luck with all of it. I would/will go with elliots recommendations anyway just to be on the safe side.just makes sense.

wojtek

My Feedback: (73)

Eliot, the new belts actually allow the turbine to run at a higher rpm, the propper gearing allowe for the higher head speed. You can get the parts from www.jetcatusa.com, cal Bob Wilcox there, he can help you out.

As for staying on the safe side come on !! like Phil said, ya wana be out flown by a 60 ? maybe i should switch to all 30 size machines ... there are so many HP5s flying at 1400 rpm, and several of them getting sevearly abused (like mine ). Hey Alan, i hear you rgularly loop, roll, and auto your JC ?

JetKat, are you flying a Jetcopter ? call JetcatUSA and talk to them about it, you will like your heli a lot better with the 1400 head speed.

Im thinking of setting up dial modes on my radio for my scale helis. 1, where the rpm never goes over 11-1200, and the pitch arnge is appropriate for this speed, and them another mode (condition on the WC2) for the 1400 speed, again, with an appropriate pitch setup ....

Wojtek

3DHELINUT

My Feedback: (3)

This thread sure has gotten a new lease on life, Thanks for all the tech data guys.

OK, i plan on using vario's 5 blade head, 12mm shaft and a diameter of 1680 mm with two bolts per blade @ 185 gr. Based on Phil's calculations i should be fine with 1400 rpm's. do we have anyone out there using a multi blade head on the HP5 with the speed up gears? what are your thoughts and how does this configuration perform?


Alan...

Bob_Wilcox

My Feedback: (1)

JetKat, are you flying a Jetcopter ? call JetcatUSA and talk to them about it, you will like your heli a lot better with the 1400 head speed.

Wojtek:

I don't think Sandy will fly a JetCopter SX!

wojtek

My Feedback: (73)

Ohhh , i did not realize it was Sandy, thanx Bob ..


hey Sandy ! whats up !


Wojtek

cat-boi

My Feedback: (10)

Hey Bob,
Your right I have too many helicopters already!
Most of the info here was pretty good...
Exhanging ideas can be a nice refeshing change once and a while