liftbag
12-11-2011, 07:29 AM
Rather than a guide, this post is a way of gathering information already published in this forum and maybe to become a reference point for further tips and tricks that are born of helifreakers inventiveness.
Regarding the general considerations and controversies about this mod, you can refer to this thread (http://www.helifreak.com/showthread.php?t=359879)
To achieve the shortened main shaft, there are many different ways.
If you start with a stock main shaft, a good tip is indicated by pakk in this post (http://www.helifreak.com/showpost.php?p=3460279&postcount=38). You can use 1 mm drill bit for the shaft, but if you use Microheli head, better you enlarge the hole to 1,1mm, or at least you have to screw and unscrew the original E-flite screw (to enlarge the hole).
Personally I use the Jim Stoll Stuff to make my own shortened main shafts.
http://img823.imageshack.us/img823/461/jimstollstuff01.jpg
tntburnett has created a nice video (http://www.helifreak.com/showthread.php?t=349805) where he makes a careful review of this tool.
You can refer to this post (http://www.helifreak.com/showthread.php?t=349814) to order the tool.
My tool is the most complete among those that Jim built and allows you to create shortened main shaft of 3 mm...
http://img714.imageshack.us/img714/5548/jimstollstuff02.jpg
... or 2 and 4 mm and of course to replicate the original main shaft (Top to Top)
http://img140.imageshack.us/img140/2249/jimstollstuff03.jpg
The advantage of using a tool like that, is that you can have perfectly repeatable main shafts, with holes perfectly aligned with the main shaft axis, and also to eliminate the risk of ruining the rotor head if this is used as a drilling template.
I create my main shafts starting from the 3 mm carbon tube, or from the 120SR tail boom.
Using the tail boom of the 120SR you already have available the flattened part to lock the gear.
If you use a tube purchased separately, you must first create the flat. I use the exacto knife
http://img192.imageshack.us/img192/1590/jimstollstuff04.jpg
The next step is to make the hole for the locking collar.
To do it in a precise manner, I put the main gear on the shaft and mount it in the main frame.
Then use the anti-rotation collar to mark the drill point. Then complete the hole with the Stoll Stuff.
http://img171.imageshack.us/img171/210/jimstollstuff05.jpg
In the photo I purposely used RKH frame because this frame requires a non-standard measurement between the flattened part and the hole for the anti-rotation collar.
Using the Stoll Stuff to create the hole for the rotor hub.
In this picture I'm creating a main shaft shortened by 4 mm
http://img267.imageshack.us/img267/2504/jimstollstuff06.jpg
Finally the shaft is cut at the same distance from the rotor hub hole of the stock shaft.
With a shortened main shaft, you need to level the swashplate again.
Screw the link is not enough, you have to move the pushrods into the lower hole of servo arms.
The bottom hole is 2.5 mm lower than the highest.
Even if the shaft is shortened by 4 mm, it's possible to level the swashplate without bending the pushrod, simply screwing enough the pushrods.
The alternate holes of the servos arm should be enlarged with a 0.8 mm drill bit (better 0,75 if you find it).
Thats all. I described my method. It would be useful to the community have even other methods.
Paolo
Regarding the general considerations and controversies about this mod, you can refer to this thread (http://www.helifreak.com/showthread.php?t=359879)
To achieve the shortened main shaft, there are many different ways.
If you start with a stock main shaft, a good tip is indicated by pakk in this post (http://www.helifreak.com/showpost.php?p=3460279&postcount=38). You can use 1 mm drill bit for the shaft, but if you use Microheli head, better you enlarge the hole to 1,1mm, or at least you have to screw and unscrew the original E-flite screw (to enlarge the hole).
Personally I use the Jim Stoll Stuff to make my own shortened main shafts.
http://img823.imageshack.us/img823/461/jimstollstuff01.jpg
tntburnett has created a nice video (http://www.helifreak.com/showthread.php?t=349805) where he makes a careful review of this tool.
You can refer to this post (http://www.helifreak.com/showthread.php?t=349814) to order the tool.
My tool is the most complete among those that Jim built and allows you to create shortened main shaft of 3 mm...
http://img714.imageshack.us/img714/5548/jimstollstuff02.jpg
... or 2 and 4 mm and of course to replicate the original main shaft (Top to Top)
http://img140.imageshack.us/img140/2249/jimstollstuff03.jpg
The advantage of using a tool like that, is that you can have perfectly repeatable main shafts, with holes perfectly aligned with the main shaft axis, and also to eliminate the risk of ruining the rotor head if this is used as a drilling template.
I create my main shafts starting from the 3 mm carbon tube, or from the 120SR tail boom.
Using the tail boom of the 120SR you already have available the flattened part to lock the gear.
If you use a tube purchased separately, you must first create the flat. I use the exacto knife
http://img192.imageshack.us/img192/1590/jimstollstuff04.jpg
The next step is to make the hole for the locking collar.
To do it in a precise manner, I put the main gear on the shaft and mount it in the main frame.
Then use the anti-rotation collar to mark the drill point. Then complete the hole with the Stoll Stuff.
http://img171.imageshack.us/img171/210/jimstollstuff05.jpg
In the photo I purposely used RKH frame because this frame requires a non-standard measurement between the flattened part and the hole for the anti-rotation collar.
Using the Stoll Stuff to create the hole for the rotor hub.
In this picture I'm creating a main shaft shortened by 4 mm
http://img267.imageshack.us/img267/2504/jimstollstuff06.jpg
Finally the shaft is cut at the same distance from the rotor hub hole of the stock shaft.
With a shortened main shaft, you need to level the swashplate again.
Screw the link is not enough, you have to move the pushrods into the lower hole of servo arms.
The bottom hole is 2.5 mm lower than the highest.
Even if the shaft is shortened by 4 mm, it's possible to level the swashplate without bending the pushrod, simply screwing enough the pushrods.
The alternate holes of the servos arm should be enlarged with a 0.8 mm drill bit (better 0,75 if you find it).
Thats all. I described my method. It would be useful to the community have even other methods.
Paolo