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HelicopterKasama Srimok 90 › Start shaft dial indications, YS 91, what did you guys get?
01-01-2010 09:23 PM  7 years agoPost 1
husafreak

rrKey Veteran

Livermore, NorCal

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I spent a couple hours trying a good runout on my start shaft. I was unable to get better than 4-5/1000 runout which seems bad to me. Hopefully one of you can give me some insight. First, the manual says not to use a washer between the motor (YS91SR) and fan bot this did two things to mine. One, it made the fan scrape against the motor case (bad) Two, the start shaft then is a tight fit at its base on the unthreaded part of the motor shaft giving a consistent 7/1000 runout at all clock positions (bad). So I put the 1mm thick washer provided for the OS engine on and this allowed the start shaft to bottom out on the fan. The best runout I got with this arrangement was 2/1000 at finger tight but when I torqued it down I got 4-5/1000 again. I torqued the assembly down at many diffeent clock positions and this was the best I could get. This leads me to a couple questions.
Is it OK to use a shim or washer between the motor and fan?
Is 4-5/1000 an acceptable runout?
should I buy a bunch of fans and or start shafts and try to find a perfect combination(not!)
Should I just close my eyes, build the damn thing, and pray it works?

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01-01-2010 11:05 PM  7 years agoPost 2
fr8brkr

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Asheville,NC

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I was able to achieve between .001-.002 with about two hours of tapping the shaft with a bronze bar and checking and re-checking. The spacer is used in the OS shaft I believe because the OS and YS output shafts are slightly different in length. I have a YS91SR and without the washer it is a very close fit between the bearing in the motor and the fan. If the output shaft of your motor is beyond 2-3 thousandths it may make it very difficult to minimize the run-out. I know at my first build attempt I had 6-7 thousandths and had considerable foaming in the tank - It smoothed out a great deal after minimizing the run-out. The hard mount engine mount dampeners also helped in getting rid of any excessive vibration.

Problems ? -- Mine are flown in fresh daily

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01-01-2010 11:12 PM  7 years agoPost 3
gonkulator

rrApprentice

Sutter, ca., usa

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I put the washer on my engine with the
fan. It works fine. I have some .031 thou
shim washers that I use instead of the
washer that comes with the engine and
it works great. I will mail you one if
you like? Also, I turn the bottom of all
my start shafts (take off just a thou or two)
just a little to make sure they are truly
perpendicular to the shaft. I can do that
for you also if you send me your shaft.
gonkulator

Is this fun or what :)......

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01-02-2010 02:04 AM  7 years agoPost 4
husafreak

rrKey Veteran

Livermore, NorCal

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Thanks and Happy new Year! I see what you mean about opening up the end of the start shaft where it engages the motor shaft, I will do that. I have the 1.4mm/.055" shim from the kit and also the YS shim which is 1mm/.041", I will PM you my address if you can send me a .031" shim that would be great, thanks. I am amazed by the idea of hammering the shaft but if it works it works! At least now I know that I can use a shim and that I should keep trying for a better runout.

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01-02-2010 10:11 AM  7 years agoPost 5
The Old Guy

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UK Surrey

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[quote] I am amazed by the idea of hammering the shaft but if it works it works!
I did not use a hammer to tap it but i did use a ring wrench over the shaft just below mid point and "tweaked" the shaft till i got zero runout.

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01-02-2010 02:53 PM  7 years agoPost 6
Dr Lodge

rrElite Veteran

Guildford, Surrey - UK

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I have learned not to assume that the crank is straight. After some hours trying to get minimal run out I checked the crank and found it was out! Think I used a socket set on the crank nut to apply some gentle leverage to straighten the crank. Then once the crank is straight, you can dial the clutch

Vibe 90, Vibe 50, Vigor CS x2,
Dyna-x, Knight 503D, Logo 10,
TRex 500, Furion, Gaui EP200

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01-02-2010 04:13 PM  7 years agoPost 7
husafreak

rrKey Veteran

Livermore, NorCal

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I did dial the engine shaft and it was straight, thanks though. I also dialed the start shaft on the engine without the fan, it was .007 out at all clock positions. Probably due to the very sloppy thread fit and the tight fit at the unthreaded part of the shaft pushing it out of position. The fan seemed to stabilize it down to 4-5 thou. But my fan is out 4-5 thou. at its outer edge vertically so I think I may have to try and shim the shaft at its base (or bend it). There is little I can do about the fan... I'll keep at it but it is my fist try at dial indicating a shaft and it's a PITA to fix a bad one.
I noticed yesterday Kasama's website shows pics now of his CNC machines, proof that he as them! But I still think a lot of his earlier kits have parts made from various suppliers, how else to explain the variety of different sized parts we have found in our group. Harder, higher tolerance parts would have helped a lot of us but I am enjoying all this as a purely academic excercise

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HelicopterKasama Srimok 90 › Start shaft dial indications, YS 91, what did you guys get?
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