Has anyone tried MAH 810 blades?

[DDragon]

Hi,
decided to switch my wren/pred back to 810mm mains from 710mm.

I was only able to find MAH 810 locally. usually I use rotor tech, but it was a nice weekend and I didn't want to wait. So I bought them.

I noticed right away that they are wider and perhaps heavier than my rotor tech.

After installing them and spooling up I notice a shake/vibration that got worse as the head speed increased. I tried hovering about a foot from the ground brought it down immediately.My fuel tank and battery literally slipped out from the velcro and was hanging by the fuel lines and battery wires.

I figured the dampers needed to be replaced... I'm also going to check the tightness on the main bolts.

Does anyone have any ideas? They seemed to be tracking ok.

Thanks.

[Cletus]

I've got MAH 810 blades on my Bergen Intrepid Turbine and I like them a lot !
Dampers could be an issue, you could also try switching the blades around if the vibe is slight sometimes just that makes a difference. Also, the blade-grip bolt torque sometimes is an issue. I like those blades and I'm going to changeout the NHP 800 I have on the gasser real soon.

[cbergen]

You may want to check your headspeed also.

The difference in lift of these blades may have changed where you lift off in relation to stick position, which then would have changed your headspeed at liftoff.

[DDragon]

Originally Posted by cbergen

You may want to check your headspeed also.

The difference in lift of these blades may have changed where you lift off in relation to stick position, which then would have changed your headspeed at liftoff.

Thanks Chris. I'll look into that as well. I didn't think of it, but these will have massively better lift than what I'm used to.

[DDragon]

Originally Posted by Cletus

I've got MAH 810 blades on my Bergen Intrepid Turbine and I like them a lot !
Dampers could be an issue, you could also try switching the blades around if the vibe is slight sometimes just that makes a difference. Also, the blade-grip bolt torque sometimes is an issue. I like those blades and I'm going to changeout the NHP 800 I have on the gasser real soon.

Thanks, I'll give that a try. I was originally looking for NHP800 blades. But could not find any.

Cheers

[DDragon]

Well, I took a part the head today and discovered that the feathering shaft is bent. I put it on my lathe and it had a slight bend...maybe 2-3mm out of true.

I assume that would cause head wobble?

I haven't rebuilt the head in about two years, so I figured I've change the bearing and dampers while I was at it.

[helibeli]

If you've not had an accident,how on earth did you manage to bend the feathering shaft?

[cbergen]

WOW! 2-3 mm is HUGE for a bent feathering shaft!!

[DDragon]

Originally Posted by helibeli

If you've not had an accident,how on earth did you manage to bend the feathering shaft?

Actually I did in the spring... haven't tried flying it since then since I had the 744. I lost tail control (linkage popped) and I was forced to bring it down quickly. It came down on a slight angle and the main blades hit concrete. Didn't think it damaged the feather shaft at that time. Looked ok.

[DDragon]

Originally Posted by cbergen

WOW! 2-3 mm is HUGE for a bent feathering shaft!!

LOL... well. THAT would explain the vibration then! I order a new one.

[DDragon]

OK... as an update. I replaced the feathering shaft and dampers. But I still get a vibration. It may not be as bad a before but it still makes it difficult to fly.

It appears that tracking may be off by 1/8 to 1/4 of an inch. BUT with 710 blades (these Mah are 820 I believe) there is no vibration and the tracking seems fine.

What do you think? Anyone... does the tracking show up more because these blades are wider and longer?

[cbdane]

Originally Posted by DDragon

It appears that tracking may be off by 1/8 to 1/4 of an inch. BUT with 710 blades (these Mah are 820 I believe) there is no vibration and the tracking seems fine.

What do you think? Anyone... does the tracking show up more because these blades are wider and longer?

It is not uncommon for tracking adjustments to be required with a new set of blades.

[helibeli]

If you bent the feathering shaft in an accident then chances are the main shaft will be out of true as well.Try rolling it on a flat surface to see.Also rpm/blade size is much more critical in feathering shaft type heads than it ever was with underslung see-saw type heads. Personally I much prefer the see saw type.(I'm only a scale flier)

[fallafalla]

Also check the headblock if its alu, ive bent a few, but usually been able to spot it pretty easy.

[DDragon]

Thanks Guys, I'll check these things out. What I find confusing it it flies WITHOUT vibration using smaller/shorter blades.

[cbergen]

Are you flying the heli at different headspeeds with the different size blades?

IOW did you change the gear ratio, or are you just throttling down?

[DDragon]

Originally Posted by cbergen

Are you flying the heli at different headspeeds with the different size blades?

IOW did you change the gear ratio, or are you just throttling down?

Hi Chris, When I originally setup the heli I was running 800mm blades and had everything setup for that. When I put the 710 blades on, I didn't touch the settings. I then left it till now and didn't bother touching it until recently. So the settings should be the same. But I could be mistaken.... the Max rpm is set to 145,000 and the throttle has a gradual curve from around 70% to 80%. Gearing hasn't changed.

I'll check the tracking this weekend, and if that doesn't work I can lower the rpm in case I changed it.

[cbergen]

What headspeed are you running with the 810's? With the 710's?

[DDragon]

Originally Posted by cbergen

What headspeed are you running with the 810's? With the 710's?

I think both are running around 1450 but I'm not sure. I need to check.

[cbergen]

1450 with 710's? As heavy as the bird is? hmmmm...

I would have suspected a low headspeed wobble at that rpm with 710's unless you have a REALLY soft rotor head...