RunRyder - GSR 260 Main Gear, Clutch and Motor Tolerances

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Gasser Model RC Helicopters > GSR 260 Main Gear, Clutch and Motor Tolerances

KarbonBird
Key Veteran
Location: Australia

Just checked the mesh and alignment of the GSR and found one side of the clutch is lower than the other. After several attempts to correct this problem I was able to line the clutch and bell BUT then there was way too much tolerance in the meshing to the main gear (unless it should have noticeable play in it normally).

One thing though the clutch spins freely and doesn't bind at all despite the one side being about .25mm longer. Is it self-aligning perhaps so this doesn't matter?

Is there a solution to this perhaps - maybe another gasser type helicopter has similar issues?

01-06-2008 11:59 AM

copperclad
Elite Veteran
Location: ..

hi Ross
i agree , the angle you are seeing is bad , you want to get it corrected before you fly , the first thing i would look at

is the clutch pinion shaft parallel to the main shaft

or is the engine crank parallel to the main shaft

if the clutch pinion shaft is parallel to the main shaft then it is the engine that is cocked

and if the engines crankshaft is parallel then it is the clutch pinion shaft that is cocked

and of coarse it could be both that need work

the main shaft is the base and everything is brought up to it , or alligned in a sequence starting from the maingear , so i would start with loosening the engine , or if you can pull it out of the frame ( i know you don't want to hear this ) it will only interfere with positioning the clutch pinion shaft

this will let you focus on mateing the clutch pinion shaft in the correct position to match the main gear , and verify that it runs smooth with the correct lash

once the clutch pinion are correctly placed , and locked down, then bring the engine into position to line up with the clutch pinion , you may need to shim the engine baseplate fit to correct the lineup between the engine and the clutchbell , HTH , dana

01-06-2008 04:39 PM

HOMEPAGE

KarbonBird
Key Veteran
Location: Australia

The news is bad ...

Scored clutch and no lining ...

Update pics - cleaned up .. maybe not so bad after all???
==========================================================

Just checked the measurements top of the bell (without lining, no wear area) = 45.2 mm and the bottom (bell opening, with wear) is 45.5 mm so it seems that there was some wear on it - will it be usable as a temporary fix whilst I wait for parts to arrive?

01-06-2008 11:34 PM

aambrose
Elite Veteran
Location: Pana, IL

Rossco,
How did you remedy your alignment problems both with the clutch in the bell and with the mesh of the bell pinion and main gear? Also, how do the teeth on your main gear look? Are they wearing properly?

Here's my dilemma:
I noticed the teeth on the main gear look like they're wearing on the side of each tooth (possibly from a loose mesh and the bell pinion teeth digging into them). The starter shaft spins freely BTW. To check the mesh, I used a strip of heavy-duty aluminum foil about 2" long and the width of the main gear to pass between the main gear and the bell pinion. This gave a good representation of the gear mesh.

If I loosen the 4 bolts on the bell pinion bearing block, I can move it approximately 1.5mm fore/aft. If I slide it back toward the main gear, I get a nice mesh (even peaks and valleys on the foil) and the starter shaft spins freely but the exposed clutch under the bell is ever so slightly uneven (exactly like Rossco showed in his photo). The GSR manual states that .5mm should be exposed. I can see .5mm exposed at the front of the bell but it tapers down to maybe .25mm exposed at the rear. Again, exactly like Rossco's photo.

If I slide the pinion bearing block toward the front (away from the main gear), I get a looser mesh (peaks and valleys are not uniform on the foil) and the starter shaft still spins freely but the exposed clutch under the bell is an even .5mm front to back. This is where it was when I was getting the questionable wear on the main gear teeth.

So, should I leave the bell pinion bearing block in the position that gives the better gear mesh and shim the engine to even out the clutch misalignment in the bell? If so, what's the best method for shimming the engine?

Thanks!

Tony

07-02-2008 07:14 PM

aambrose
Elite Veteran
Location: Pana, IL

A few photos to show the clutch alignment and the main gear teeth.

With the clutch in the uneven position shown, the teeth mesh evenly.

BUT...the teeth shown in the photos are the result of loosening the pinion bearing block and rocking the clutch bell slightly forward until the clutch has even exposure along the bottom of the bell.

Any suggestions?
Thanks!

Tony

07-03-2008 12:27 AM

aambrose
Elite Veteran
Location: Pana, IL

I think I may have solved the gear mesh/clutch alignment problem. It was pretty simple actually (once I discovered it

). I haven't flown the heli so I can't say for sure that everything is perfect at this point. I just know the alignment issues seem to be corrected. It didnt involve any reaming of mounting holes or bending the "L rails" on the bottom of the frames.

Discovering the problem:
First, I loosened the 4 bolts holding the bearing block for the starter shaft. Next, I loosely mounted the motor with just the 4 bottom bolts. After positioning the motor, clutch pinion, clutch bell, etc. to get a good mesh and an aligned clutch, I noticed a small gap (maybe .5mm - 1mm) between the motor mounting plate (at the 2 rear mounting holes) and the bottom of the "L rails". If I tightened the 2 rear bolts, the motor would tilt slightly forward and the rear portion of the clutch would get pushed upward into the bell as the mounting plate came up to meet with the "L rails". (see clutch bell photo in my previous post)

I removed the engine, then removed the starter rope assembly, then removed the 1/4" aluminum stamped mounting plate. I put a straight edge on the front of the plate (the edge which faces the front of the helicopter) and it looked pretty good. When I placed the straight edge on the rear of the plate (faces the rear of the heli), the plate had a slight (but very noticeable) bow in it causing the rear corners to bow downward maybe 1mm.

Fixing the problem:
I laid the center of the plate over a piece of 1/2" aluminum angle and gently tapped one half with a rubber mallet checking the bowed end of the plate with a straight edge after each tap until it was straight. I also gently filed off any casting irregularities on the bottom of the motor case so that it would mate better with the plate. I reattached the plate and loosely mounted the motor in the heli using only the 4 bottom bolts. Next, I adjusted the bearing block so the gear mesh was good then tightened the bearing block bolts and the motor mount bolts. This time the clutch remained aligned in the bell!

I also made sure the starter shaft spun freely. Finally, I installed the 2 side bolts in the motor.

Having three G26 motors on hand, I decided to look at the mounting plates on each of them. Two of the three had the bow in the plate! I'm guessing this is a result of the punching process at the factory or maybe when the plate is fastened to the motor, the process causes it to bow slightly. Regardless, the approximate 1mm bow in the plate seemed to be enough to cause the clutch alignment problem. I'll definitely keep an eye on the gear mesh, the main gear teeth, and the clutch alignment.

Thanks for all of you who provided input on this through PMs! I hope this helps save someone some frustration and time in the future by checking the mounting plate first.

Tony

07-10-2008 05:07 PM

meflyjeep
Senior Heliman
Location: On the ground and in the air ...

Quote
The GSR manual states that .5mm should be exposed. I can see .5mm exposed at the front of the bell but it tapers down to maybe .25mm exposed at the rear ...

may I ask the source of the manual ?

meflyjeep

07-11-2008 11:45 AM

KarbonBird
Key Veteran
Location: Australia

Well done Tony for finding the solution - definitely a good reference point for other GSRers in the future.

BTW I have just taken an impression of the teeth on aluminium foil as requested but I guess that's not needed to assist you any more.

07-11-2008 02:45 PM

aambrose
Elite Veteran
Location: Pana, IL

Quote
may I ask the source of the manual

If you didnt receive one with your GSR purchase, then Rossco (KarbonBird) has a PDF version in his gallery. The reference to the clutch is on page 11.

Tony

07-14-2008 02:24 PM

KarbonBird
Key Veteran
Location: Australia

Just a follow-on to Tony's post...

After suffering similar frustration with the alignment of the motor and clutch I decided to pull the motor out and examine the base plate. On removing the motor I noticed a very visible bowing of the base plate (verified with a straight edge).

I had an engineering friend of mine pop over this evening to check the extent of the problem and to see if he can fix it. He confirmed that it was indeed a problem and suggested that the rough edges/burring were caused due to machine wear on the pressing machine that punched the plate out of a sheet of aluminium during manufacture. He has taken the plate to the workshop and will sort it out for me tomorrow. I am certain that the problem will be fixed after everything has been trued up and straightened.

Will report back tomorrow with details of the outcome.

08-14-2008 02:31 PM

aambrose
Elite Veteran
Location: Pana, IL

Rossco,
That's good that you discovered it. I simply removed the plate then layed it on the bench with the bow facing upwards. I laid a piece of 1/2" aluminum angle stock under the plate (like this ^ ) directly inline with the center then held one side of the plate against the bench and made a series of light taps with a rubber mallet on the other side of the plate -- checking the plate after each tap. Once it was straight (with a straight edge), I screwed it back onto the motor. Everything lined up perfect after that. I noticed the edges of the aluminum looked a little ragged as well. Maybe a bad batch of stamped plates.

One could probably straighten the bow in a vise too. It wasn't much but enough to affect the clutch alignment.

Tony

08-14-2008 02:57 PM

andyman_sf
Senior Heliman
Location:

If this really is the problem, its a super easy fix. Just cut it with a fly cutter on an end mill and take off a small amount. That would gaurantee flatness. Repeat on other side just to be safe.

andy

08-14-2008 07:06 PM

KarbonBird
Key Veteran
Location: Australia

UPDATE:

Have just reinstalled the perfectly straight mounting plate and .... PERFECT. Fits like a glove. Will have to wait till morning to test it out

Thanks to Tony for identifying the fix.

KB

08-15-2008 04:50 PM

aambrose
Elite Veteran
Location: Pana, IL

Glad to hear that Rossco! Surely we aren't the only 2 who have bowed mounting plates.

I have three G26s and after careful inspection, I noticed two of them had bowed plates and they were purchased within the last year. The one with a straight plate is just over 3 years old. Might be a good idea to check the mounting plate when the clutch isnt lining up properly. The bow is minor but enough to throw things off up higher.

Thanks to you for starting this thread!

Tony

08-15-2008 06:58 PM

andyman_sf
Senior Heliman
Location:

thanks guys the plate problem resolved my alignment issues also. I took a couple passes using my mill and you can really see that this plate isn't flat at all on both sides. But it is NOW!

08-17-2008 07:52 AM

KarbonBird
Key Veteran
Location: Australia

UPDATE 2....

Just when I thought everything was fixed - the alignment problem seems to be back. This even after getting a friend to machine the bottom plate correctly.

Even with the mounting plate straightened,it isn't possible to lign the motor and bell up correctly as there is simply not enough movement permissable in the bottom 4 bolts to fix the alignment problem.

Hmmm - something funny here...

09-05-2008 06:10 PM

aambrose
Elite Veteran
Location: Pana, IL

Rossco,
I'm confused (imagine that

). How did the alignment problem present itself this time? Did the bolts loosen? I thought you had corrected it a few weeks ago?

Quote
Even with the mounting plate straightened,it isn't possible to lign the motor and bell up correctly as there is simply not enough movement permissable in the bottom 4 bolts to fix the alignment problem.

Dumb question here, but did you loosen the 4 bolts in the bearing block too when attempting to align everything?

Tony

09-05-2008 06:33 PM

AceBird
Elite Veteran
Location: Utica, NY USA

Quote
Dumb question here, but did you loosen the 4 bolts in the bearing block too when attempting to align everything?

Quote
the main shaft is the base and everything is brought up to it , or alligned in a sequence starting from the maingear , so i would start with loosening the engine , or if you can pull it out of the frame ( i know you don't want to hear this ) it will only interfere with positioning the clutch pinion shaft

Rossco, I can’t tell you what is wrong. All I can say is Copperclad is correct, first the main gear then the pinion then engine/clutch coupling alignment. If it is an angle alignment between the bell and the clutch that usually is how the upper frame is attached to the lower frame with other helicopters. Maybe it is the same for the GSR. Again that assumes that you have the main gear and pinion correctly aligned.

Sandwich construction with plates and spacers can be a pain in the butt if you don’t start out right.

Another concern I would have is that this heli suffered some damage a while back and possible frame members got twisted or stretched somewhat. Sometimes it is hard to tell unless you completely disassemble and match compare plates.

Ace
What could be more fun?

09-05-2008 09:34 PM

KarbonBird
Key Veteran
Location: Australia

Tks for the feedback Tony & Ace...

Quote
How did the alignment problem present itself this time? Did the bolts loosen? I thought you had corrected it a few weeks ago?

I haven't flown the GSR for a while now but when I did the alignment after the plate straightening, it was a fairly quick job (in between work on the new T-Rex 600 front mount). The problem was the tolerance!. Whilst the bell originally ligned up the tolerance was actually to much (about 1 mm play) so now that I have had a chance to really go over it ahead of a flight - that's the finding.

Will give it another go (top down again) and report on the findings.

09-06-2008 12:22 AM

KarbonBird
Key Veteran
Location: Australia

UPDATE

Managed to find the problem ...

I had loosened but not completely removed the bolt holding the exhaust onto the frame. Removed that and all is good.

I guess that will teach me to fiddle at 2 a.m. when I should be sleeping!

09-06-2008 04:01 PM

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Gasser Model RC Helicopters > GSR 260 Main Gear, Clutch and Motor Tolerances

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