Gap between fan and clutch driver.

[GM1]

Whew, that looks much better. My fan to driver clearance is .009 inches BUT I run an FAI model and do not load the model like hard 3D. After 4 months, there is not a single mark where the fan and driver are touching.
Gordie

[DavidH]

Yeah if you shimmed the bottom plate. I would think the gap is too large. Tim designed the Stratus to have as little gap as possible. So if your shimming to open up the gap your defeating the purpose of having the gap.

In X's picture above. You see he says his 1.2 mm. That converts to .047. I had not done the conversion till today. At .047 that is too much gap. Zilly mentioned his gap is about 0.9mm. That is .035 gap, that will probably be OK, but I would prefer it to be about .015 to .020

For a .020 inch gap it would need to be .5 mm
.4mm = .015 inches


David

[Zilly]

The Official line from Tim at MA is that the Gap should be between .030 and .035

Mine use to be a lot less than this despite using the correct washers etc, I then looked at the back plate of my YS and compared it to another YS and the rim of my back plate was about .015 thicker so I got a mate to remove .015 using a lathe.

I would not recommend sanding the back plate as you will not take off a uniform amount of material however get someone you know with a lathe to do it.

z

[Alfred]

Originally Posted by chrisvau

What I was suggesting is putting a strip of brass shim under the 2 metal A frames front and back that support top half of the frame and join them to the bottom half where the motor is mounted. This would lift the entire side frame assembly including clutch assembly (delrin ball and all ) up slightly thus increasing the gap). Lifting the top by .235 of a mm is not likely to have any noticiable ffect on heli in terms of pendulum effect.

My concern with sanding anything is that if for example you sand the washer, you may not get it 100% flat which when related to the motor may cause runout issues on the fan if the bottom collet is not sitting on a flat surface.

I would just prefer the gap to be right in the first place!!!!

Regards
Chris

I am with you Chris
In a normal sanding action, the chance of getting it not just dead flat, but also dead straight is very low, unless you use a milling mashine.
I have sheets of bras shims here at home in all sizes up to 0.5mm.
You can get them from your local bearing place.
At least until MA comes out with a fix.
I am sorry that you ended up with this much trouble on your new heli.
I still think that it is a great quality heli that has just those little faults as all new design helies have.
If we wouldn't want the risk that everything isn't 100% right from the start, then we can't ever by a newly designed heli that has just come on the market.

What if you take the small carbon backplate to your local engineering shop and have them mill it down by whatever amount you need?

[DavidH]

At least until MA comes out with a fix.

What kind of fix would they come out with?

MA has motor plates for the OS SZ, OS Cspec, YS.
As long as the gap is in the .015(.4mm) to .035 (.9mm) range. It is within acceptable specs.

David

[Alfred]

David
My understanding is that Chris's gap is basically none extisting and that he used the correct parts.
So, he obviously doesn't have the .015 gap.
Assuming all the above is as stated, then there is a Manufacturer's issue.
That's the fix they have to come up with.

[DavidH]

Chris wrote: And I believe the gap he is referring to is the picture of X's

I just put a new 91 szh PS in my new stratus and the gap looked exactly like yours before its first flight.

That would leave me to believe that something moved after the model was flown.
So I would think the gap was in the .030 range when he installed the motor. At least that appears to be what he is saying in the above quote. So if the gap was there when he installed the motor, don't see how that is a manufactuer issue. I don't think the parts add on material once they are installed.Also Chris has never mentioned the measurement of the gap. .015 is close enough that it would appear that light can not be seen thru it.

David

[Alfred]

Some of this is conjecture on both of our sides.
He didn't mentioned the gap of 015 but mine was originally 010 (with a YS91) and with a light coloured background I still could see the light through it.
I then changed mine to the mashined down carbon base plate and now the gap is .021.
The new rubber dampers are a lot harder but the pins also go in a lot easier, so I can't see the pins "working themselfs in" after a few flights.
As there are no vertical slots in the whole engine/clutchstack system, it can't have moved there.
There are no vertical slots anywhere between the top and bottom frames.
IF the engine/fan assembly would have come loose..well it would have been obvious.
I am going to fire mine up this weekend, so I will see if the gap changes for some reason on mine.

[Jaso]

I used a thin piece of plastic cut out as shims like the above mentioned method and put them between the A arms and the base of the frame . My gap was ok I just wanted to make sure that it couldn't touch during flight and casue a clitch or lock out issue .
The plastic I used was from a packaging of a TT part of all things .
From memory , it was about 10-12 thou think hard plastic , the clear stuff thats a real pain to open to get your bling parts out of . I think it had a alloy TT head block in it or something . I put it in once I had carefully cut out the shims and loctited the bolts in as per normal .
I don't think it's going anywhere by it self as it is trapped between the flat bottom of the A arm uprights and the carbon base plate .
I was a bit turned off of using a piece of alloy or brass shim so I searched the heli room till I found the plastic and give it the technical material test, ie , I stabed it with a knife , squashed it with pliers, cut it with some side cutters and made sure fuel didn't eat it . lol :mrgreen: :mrgreen:
Then when I was happy I made my shims . I havent rechecked my clearance but I guess it woold be around 35-40 thou which gives me a little safety margin and I doubt will adversely affect the dampeners . I'll keep an eye on it over time but I'm happy .
Cheers,
Jason .

[megotroulette]

isn't there a tool that you use for your fan, that you use to check the gap with?

i think its the fan tightener where you bolt it on.. its an ma one i think

Cheers.

[DavidH]

You use feeler gauges to check the gap. I don't think MA includes in the Stratus kits the piece of aluminum that is used to set the gap. It is .030 thick.

http://www.miniatureaircraftusa.com/....asp?prod=0546

You can see the gauge in the above link. It is the U shaped piece with the notch. That is what comes in the kits where the motor is adjusted vertically.

The gap on the Stratus is set when the heli is built. It will be correct unless something was assembled wrong when putting the fan on the engine and the correct motor plates are used.

David

[megotroulette]

i am starting to suspect i know what happened to my stratus which locked out and crashed, apart from a bearing poping out of the starter shaft block and hitting against its block and a hex adaptor,

after the crash when i took the motor out on top of the fan it was polished right up from rubbing... which i think may have caused it...

with my next stratus i think i will be very carefull and alot more cautious about that gap when setting it up i think...


i have been using a JR X3810 radio and the R900 Jr pcm Receiver... anyone else using this receiver? is it suitable for the stratus?? it cost alot of $$ too

What size should the gap be in mm.. since i am a kid and am not very smart... what the hell is a thou?

Cheers guys