Azimut Challenger

[Navibot]

Hello all,

I have a issue with the challenger constantly pulling to the left, worse at higher rpm requires constant right hand steering... not ideal

any thoughts? I have re - aligned buckets and checked esc settings

Hello
have you exchanged/inverted the engines (right -- left) for testing?

[frenchi1]

Hi Likeomg

there are several causes for the problem, especially if the jet is running at it's physical limits.

Check first if:

1) Impeller on both side have exactly the same diameter on the same gap to the housing of jet. Water back slippage may cause higher differences in thrust.
2) Check if your impeller is sucking false air (Jet housing installation and shafts/tube unit must be leack free).
3) Check if shaft runs free
4) Check if dog drive unit for impeller does´nt slip on shaft (Probleme that often occurs with the Graupner jet)
5) Check if shaft/motor couling does not slip
6) Change right impeller with left one, verify that the pitch on both is exactly the same
7) Check if cooling water nozzle is leack free
8) Check if jet nozzle is broken or sealing surface is damaged

If everithing is OK and the probem remains, change as suggested by Navibot, left motor with right and vice versa.

May be that one of the drives is too early at its maximum torque (Inrunner Problem, low torque !)


Important: the Graupner Jet should run at absolute maximum of 15000 rpm. Above, there is a high risk of cavitation. Very small geometric differences on right or left jets can lead to cavitation that starts in one of the jets first. This could explain the problem at maximum speed, because the thrust breacks down (WORSE, CAVITATION CAUSES HIGH DAMAGES ON THE JETS).



I hope this will help you!

Regards

Christian

[Likeomg]

Hi Gents,


I’ve disassembled the left hand drive, some minor wear on the prop but nothing too bad


Checking for air leaks is a good idea - I will try and do that.


Shafts are both free,


Left dog drive is very tight on shaft - considering I have issue curving to the left I would assume right is fine


Motor couplers aren’t slipping - first run one was and could feel heat build up


Cooling is all good no leaks,


I will pull the right hand drive apart tomorrow and investigate.

I have already switched the esc around and ran today, still pulling to left - I need to use my radio sub trim to about 80 to get her to steer straight... I also have ordered some ballast to drop the stern a little more in the water


- I have also ordered a rpm sensor for my eagle tree, I will test that too when it arrives.

will report back once ive investigated the starboard shaft

[Likeomg]

my rpm should be around 17k max id say, but I don't use much more than 60% power as it's enough and she veers to the left badly the faster I go.

1577kv neu 1521 on 3s.

[frenchi1]

also have ordered some ballast to drop the stern a little more in the water

Dont use ballast, the jet need to eject the water free in air, not in the water. That' s the principle of the water jets.

Regards

Christian