Calidus prerotator problem

[twistair]

Recently we got a failure on a Calidus while training its owner: on a prerotation I felt jerks on a mast, stopped prerotation and found that prerotator gearbox has certain problems inside it. This machine has about 40 TT, ca. 60-70 prerotations only, mostly 240 RRPM, sometimes 250-260.
I e-mailed manufacturer about this problem, got a reply that POH limits prerotation under 220 RRPM though earlier Calidus designer e-mailed me that I can "easily prerotate up to 260 RRPM". Since they refused to replace damaged gearbox we ordered a new gearbox directly from manufacturer http://maedler.de/Product/1643/1331/1978/1337/1339/1341.aspx
When it came I found that it needs some upgrade to fit Calidus which was made in few hours. During the story I contacted some other local Calidus owners and they all told they also had same failure. After reading technical info on this gearbox it came clear that this gearbox is definitely too weak for the purpose:
manufacturer of this gearbox limits its rpm to 1400 while in Calidus it sits directly on engine crankshaft and reaches 3200-3500 rpm when rotor reaches 200-220 rpm. Max torque on prerotation is also at least twice higher than manufacturer 's limit.
I disassembled damaged gearbox and found that everything is OK inside it less pinions which were trashed. Today we installed new gearbox and will try to see how long it serves if turned not higher than 220 rrpm on prerotation. My guess is no more than 100-120 prerotating cycles :(
I wonder if other owners got same problem and how you fixed this?
This failure was a disappointment while I must tell that the design of the whole assembly (pneumo clutch+gearbox) is very elegant and works exciting: one single touch of the activation button engages clutch soft and effective.
Now I wonder how to make gearbox more durable...

[PTKay]

Now I wonder how to make gearbox more durable...

Hi Alex,

by all due respect, why do you wonder?
Why should it be your business to fix such basic flaw
on a machine worth over 100k$?

If you claim, the gearbox is under engineered for the task
by factor two (2x), how do you expect to solve the problem
without the manufacturer carring the responsibility?

Are you going to buy a new gearbox every 100-120 take-offs?

[twistair]

There is none ideal design in modern gyroplanes, Pavel. Any gyros have their own problems - some more, others just a few. Last couple months I had a chance to flew some hours in Xenon and to see it more carefully. I can tell that Xenon has way more design flaws and their factory support (including even simple technical information) is way far behind Germans. Some things in Xenons look like they were made without serious ingeneering at all - just like a shadow tree mechanics.
As for this particular problem - I just wanted to share it with others with no goal to rain on manufacturer. This time I'm not affiliated with any company selling gyros so I'm free to evaluate them basing on my own experience.
BTW, the most well-balanced gyro I flew (among 15 different types I flew) is likely MTOsport. I like MTOsport best of all for fun flying and primary training. This doesn't mean it has no things which could be designed more reliably but all in all I'd prefer it for most kind of gyro flying. If it ever had DW or Vanek rotor and better landing gear for rough field operation, it would be definetely the best. But again - it is also far from ideal.

[ckurz7000]

Hi Alex, I read about your problem and can't really help you with it. I haven't had that problem but I'm also not prerotating higher than 220 rrpm. The second important thing to keep in mind is to engage the prerotator only with the engine in idle (< 1600 rpm).

-- Chris.

[twistair]

Thanks for the input Chris. Yes, I know about starting from idle =) But since these were mostly training flights with newbee owner so sometime he made it not very gentle. Anyway now we will be more careful and will see how long it lasts. Can you estimate how many prerotation cycles you have on your Calidus to the moment?
I also noted that clutch efficiency on different Caliduses may slightly vary: first one I flew here (red) never made it above 220 at all and slipped at 220. This white Calidus made 260 with ease, though I never tried to prerotate higher.

[MichaelBurton]

I looked at the prerotation procedure as outlined in the POH. I noticed several differences in the way that I was shown and the procedure. This could have an impact on the failures.

[twistair]

Calidus POH was changed some times, Michael. Now it describes prerotating procedure the other way it was 1-2 years ago. Manufacturer' website also has some info that now they replaced prerotator gearbox by another type which should be more durable. I didn't find yet which type is that gearbox, only saw some photos.

Some days ago a new Calidus arrived in our hangar so I hope to see the difference soon.

Cheers,

[flyover1974]

Hi, i know the problem with the prerotator gearbox. I'm owner of a MT03 with 600+ hours and neither I nor the previous owner had problems with it if you remain around 200 rpm.
More rpm only needs on short runways...my experience with the MT03 is that I take off maybe 15 to maximum 20m earlier with 250rpm.
If I fly solo, never more than 180 rpm because the grass strip i usually use is 400+ meters long on 3000ft msl and i need maximum 150m of it with poor weather conditions.
Anyway I thought about already, to build in stronger gears from a specialized company because only the gears are too weak, not the housing.
The second option is to build in a flexible shaft like that from Magni. Its aproved for 300 rpm.
ceers
Hermann

[mikeconcannon]

Copy the Magni set-up, it works.
Or just buy a Magni in the first place.

[WHUBBS]

I like my Magni.

Wayne

[davidchuyulin]

thank you ! yesterday my new Calidus with 40 hours had a pre rotator gear box breakdown ! thank you for let we all know !!! now i know why. David Chu

davidchuyulin@me.com

[davidchuyulin]

thank you again ! Twistair !!!! David Chu

[aerobatic]

I had problem with the bearing of the prerotator of my Calidus. They replace the bearing and the gearbox with the new version and everything is fine from that time.

Maher

[gao]

Mahar, is the new bearing and the gearbox from the same supplier, maedler.de as Alex said? I can no longer find the part on the link Alex provided. Is you new gearbox rated to 220RPM? Was the replacement part paid for by Auto Gyro? I thought Auto Gyro has made a very dangerous misrepresentation stating you can prerotate to 220 RPM.

[aerobatic]

All I know about the new gearbox is that the ratio is different. No need to push throttle to prevent the engine to choke in the coupling period. When the coupling is OK, engine rpm need to be pushed to about 3500 rpm in order to reach 200 rrpm.

I rarely prerotated above 200 rrpm since the airfield I'm accustomed are long enough.

I didn't pay for the new clutch.

Maher

[NoWingsAttached]

There is none ideal design in modern gyroplanes, Pavel. Any gyros have their own problems - some more, others just a few. the most well-balanced gyro I flew (among 15 different types I flew) is likely MTOsport. I like MTOsport best of all for fun flying and primary training. This doesn't mean it has no things which could be designed more reliably but all in all I'd prefer it for most kind of gyro flying. .

I'm with you there after having just flown a cross country trip in one. My choice by far to date.

I have to wonder why you are pushing the prerotation so hard in a single-mast gyro built with square tube. Do you have a death wish?

Put a piece of square aluminum 1/8" wall x 1" x 1" x 2' aluminum tube in a vise and rotate it at the top with a pipe wrench.

See how EASY that is to get it to deflect?

IMHO it is unwise to pre spin rotators on ANY machine with a single unit square element mast like this - 260 rrpm every time you take off - sir. I am no engineer, but these single mast square tube designs flex WAY too much to be safe to prerotate up past 180 RRPM routinely. Even 200 every TO is a scary thought.

[ckurz7000]

I am no engineer, but these single mast square tube designs flex WAY too much to be safe to prerotate up past 180 RRPM routinely. Even 200 every TO is a scary thought.

Can you tell me what the torque curve on prerotation up to 200 rrpm is for a 27' rotor?

How many masts have failed upon prerotation?

-- Chris.

P.S.: You probably DO need to be an engineer to assess this properly.

[davidchuyulin]

you are so right !!! my new Calidus' gear box broke down exactly 45 hours ! i never rotate it above 220 and it would not do it anyway ! what can i do now ?

[MichaelBurton]

Tell me your procedure for pre rotation and take off.

It will be a pain to change the pre rotator but you should order the parts needed from your dealer and get advice / support from them.