Gap between fan and clutch driver.

[X]

The gap between fan and clutch driver on my is around 1.2mm. Does it seem too big? OS 91 szh ps.
Thanks,
x

[DavidH]

If you used the SZ plate. That is the correct gap.

David

[Zilly]

mine is about 0.9mm so I am sure you are close enough

Chris

[X]

Thanks,
x

[chrisvau]

Put your starter on it and spin it a few times it will seat and the gap SHOULD be good.

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

After the flight the gap was amost non existant. i could barely see any light through mine. I checked the fan and it had not moved up shaft. I also checked spacing between clutch assembly and bearing block and it was exactly per spec. ie .032. I could also see signgs of rubbing in flight.

I also have the right back plate. So for some reason my gap is too small. And yes I did use the OS not YS collet.

I am going to have to either get a thinner washer between engine bearing and bottom collet. (stock one with motor is 1mm exactly) or I will get some shimstock under the A-frame ladders and lift the top half by .25mm

Regards
Chris

[X]

chrisvau,
Thanks. will see if would be the same like your.

[heliroller]

If you need more space in between the units, here is a quick and easy way to do it without too much disassembly. I had that issue with C-Spec 91 where it was rubbing and locking out.. I took the backplate off the motor and used 100 grit sandpaper and took about 1mm off of it. You don't have to remove that much if not needed. Do the sanding on a perfectly flat surface. Use some 400 after that to smooth it off when the correct amount is removed. Worked like a champ and did not have to remove the fan, etc. That usually gives you enough space in between.. You might want to measure the thickness of the edge of the backplate before you start and measure as you go to determine when to stop. This way you can get the perfect fit.

[ChrisLaFollette]

How about just sand the washer under the fan?

[DavidH]

How about just sand the washer under the fan?

This is why

Worked like a champ and did not have to remove the fan, etc.


David

[ChrisLaFollette]

I wouldnt wanna be sanding my engine but hey it sounds like it works. I just kinda skipped through what he typed up. Sorry about that.

[chrisvau]

seems a bit extreme to sand the engine backplate especially a pumped one with nipple.

Does anyoen see any issues with just adding some brass himstock under A-Ladders to raise frame very slightly ?

regards
Chris

[ChrisLaFollette]

I dont completely understand what you mean... are you talking about moving the bottom CF piece further up from the top by shimming it? I dont think you would notice a difference but it would mean there would be more weight further down and have more of a pendulum effect if you understand what I mean but if nothing mechanical or anything would change and it would just raise the frames ever so slightly then I dont see a problem with doing that to make the gap bigger. We need a better alternative though IMO..... Maybe sand the face of the fan?

[heliroller]

Let me see if I can clarify this little issue:

1. If the clutch gap is too close, You need to make it wider!

2. Pulling the engine towards the bottom CF plate will accomplish this. One Engine backplate thinner on the outer bottom rim where the bolts go into the crankcase by what ever thickness will save you a lot of time. Also it's just the backplate.. You tap holes in these things for pressure fittings, etc. All you are doing is making the rim thinner. This will not harm the engine.

3. It's very easy!

ps - sanding the fan does however seem extreme!

You can go about it however you like, just trying to save you a headache with washers, spacer plates and the such which at times, don't actually measure out just right.

[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

[DavidH]

.032 is not too little of a gap. I would want the gap down to about .025 to .020. I run .025 on my helis.
First you do not want to sand the washer between the fan and the front bearing. That is a set distance. The crankshaft will run in the bottom of the clutch driver.
Also do not shim the frames. I don't know how that could be done without enlarging the bolt holes in the side frames.
It is normal for rub marks to be on top of the fan in the Stratus. The top frames flex from the bottom. It is designed that way.

The gap on the Stratus is set by the bottom motor plate. If the fan assembly is installed correctly. The gap should be within specs between the fan hub and the clutch driver.

David

[chrisvau]

Well I have an OS91 SZH Pumped. I have the right Engine plate, My fan is as far down on the bottom collet as it can go. My clutch assembly to bearing block gap (pink arrow in picture below) is spot on according to spec. I think it was .032

Yet my gap is too small. Am I imagining this ? No. Its almost touching. Only a few thousand of an inch gap at best. ie I can barely see any light though the gap. I am led to belive this gap is too small and that touching in flight can lead to RF noise and lockouts.

So options are.

1. Sand Washer
2. Sand engine back plate
3. Sand fan
4. Raise top frame assembly

The picture below with green arrows show where you can put some shims to raise top part of frame to increase gap. No re drilling or enlarging holes needed. Some $1 brass shim is all thats needed. I have done it now and it looks fine. Granted I have not flown it yet but cant see why brass shim exact same size as metal A frame in the location pointed to below would have adverse affect.

http://www.dslrfocus.com/stratus/shims.jpg

Hopefully this clears up the shimming confusion.

Regards
Chris

[DavidH]

Well in that picture. I don't know what you did. But the gap is quiet excessive between the fan and the clutch driver. I doubt the dampeners will last 30 seconds.
I thought you was talking about the gap between the fan hub and clutch driver was .032. In the above picture it appears to be about 1/2 to 3/4 inch. You have definitely assembled something wrong.
The gap between the clutch driver and clutch plates is not adjustable. That gap is set when the clutch and clutch driver are assembled with the bearing block at MA.

In your picture. The area I am talking about that is very wrong is the just below the pink arrow. You should not be able to see the delrin ball. That is the gap that should be .025 to .020.
I really don't have a clue what you have done or left out to have that big a gap.
Looks at X's pictures in the first post of this thread. That is how the gap should look between the clutch driver and fan hub.
David

[GM1]

I bet he has the is using only 4 of the 8 screws to link the upper and lower frames and has the upper hole on the bottom A frames connected to the lower holes on the top frames. REALLY excessive clearance.
Gordie

[chrisvau]

Woah lads I have my momenets but Im not quite that dumb. :lol:

That is not a pic of my machine, thats from the stratus manual showing the frames going together. I just used it to show the area that i was talking about shimming with green arrows.

Pic of mine is below. its not closeup so you cant see fan gap very well , but you can see there is no light visible.

http://www.dslrfocus.com/stratus/Radio1.jpg

Regards
Chris

[DavidH]

Gordie,
I think your correct. Really hard to tell from the picture. But it does look like the upper frames are installed too high on the A frame pieces. And the amount they are too high would make the gap correct if they were lowered.

David

[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]

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