View Full Version : help needed-changing belt
06-06-2011, 10:29 AM
I am having trouble changing belt on my atom 500
My belt slipped from the guide pulleys and consequently got scraped against the main frames..I dont know how it happened because the belt was not loose.
So, i want to replace the belt but am having a lot of trouble to dismantle the tail. It's all stuck with loctite and dirt.
To make things worse, i cant get the tail rotor hub out of the tail shaft because the set screw holding it is so stuck into it and in the process, the set screw head is stripped. I tried heating it up with a lighter to loosen it but it's still not coming out..
Is there an easier way to dismantle the shaft to remove that belt? It looks like the only way to do it is to get the rotor hub out? any kind soul can provide some help:dontknow
One more thing, how is the tail pulley held onto the main shaft? there are two holes in it and whats inside does not look like screws but more like some kind of guide pin..is that correct?
thanks a lot
06-06-2011, 10:56 AM
Tail pulley is held in it's place via roll pin. If you look closely at the pulley
you'll see a small 2 mm hole. Within it is the roll pin. To remove the pulley
you would have to tap the roll pin out. Re pulley guide, if you look for the side
the belt might not be totally parallel between pulley guide & main pulley. In my
case the belt was slightly lower at the main pulley from the guide. In order to
get it level, I had inserted a washer below the main gear to raise it up.
06-06-2011, 11:01 AM
thks for the advice..
so, to change the belt, i have to:
a) i still need to get rid of that tail rotor hub
b) remove that roll pin from tail pulley
c) slide everything out
that's it or is there anything else that locks the tail shaft in place?
I think am going to try and drill the set screw..i am still stuck with it.. I will change the tail shaft and rotor hub if needed then..
or anyone else has a better idea?
06-06-2011, 11:17 AM
Yes. Btw why did you loctite the tail housing to the boom ?
Tell you it's gonna be a real pain to remove ya. If you can't
remove it perhaps your last option is to cut the boom 1/2 an
inche away from the tail housing & slowly use a file to cut
a groove on the boom all the way into the housing. That after
slowly bend & peel the left over boom out of the tail housing
06-06-2011, 11:25 AM
i bought the heli second hand ..So, not too sure how the owner did the build and also, i havent dismantled the tail unit for more than a year.. So, i guess loctite and dirt made things worse..
but dont we have to loctite that set screw to the rotor hub
Yeah it is a real pain in the butt to remove these things now..think i have to change the hub and tail shaft and anything else that gets messed during the process..Tomorrow i will order some tail parts
06-06-2011, 11:46 AM
Grub screw yes. Try releasing the screws, slowly & firmly twist the tail housing.
If you have WD 40, spray some between the boom & the tail housing. The problem
with Atom tail & boom is that it is an interference fit design. That means that you
would have to use a little Kung Fu to remove it.
06-06-2011, 11:51 AM
Also, when you slide the shaft out, make sure you don't lose the shims that are also on the shaft.
06-06-2011, 08:15 PM
thks Bum and Jchen..i will do that tonite..
meanwhile, i ordered some parts for the tail just in case :)
06-17-2011, 11:24 AM
thks all for the help..I finally managed to change the stuff and get the tail up..
I didnt lock the tail case in a vice to insert the roll pin. Instead I placed it on a sticky mat and using a cable tie to lock the tail shaft in place, i managed to drive the roll pin within the shaft with a 3 mm hexagonal wrench.. Didnt have punch to use..So, i used my wrench instead
Anyway, now that everything is in place, there are 2 issues bothering me:
a) as i said, i had about 2-3 mm clearance between the belt pulley and the side of the tail shaft such that i could insert a cable tie in between.. Is that normal or is there supposed to be some sort of washer in between? I hope thats ok because i dont want to dismantle the tail again
b) there is a set screw holding the tail rotor hub to the tail shaft. Since the head was stripped and i had to drill it. I dont have any replacement set screw. I found a set screw somewhere and it fits nicely within the rotor hub. (its a 2 mm size set screw i think!)
but it cannot fit within the hole in the tail shaft. Is that ok? I checked the tail and it seems to be tight with the 2 mm set screw i am using..
thanks a lot
PS: sorry i forgot how the tail was before i repaired the heli.. its been so long i havent touched the heli...about 5 months
06-17-2011, 12:25 PM
a. Are you talking of play between the pulley & the tail rotor housing ?
If so, did you forget to place the spacer back in ? There should not
be any play & not 2-3mm
b. the replaced grub screw, did it screw in smoothly or did you had to
force it ?
06-18-2011, 05:01 AM
thks for the reply..
well it seems i forgot about the spacer..So i had to dismantle the whole tail again..this time was even worse to take out that stupid roll pin..
i brought the tail to the LHS and when i compared it to the atom tail over there, it looks like my tail pulley was slightly smaller too. I managed to fit a washer that fits just nice in there..
Not sure if the roll pin i have is correctly sized but it's a real pain in the butt to actually fit that in. Also, the stupid tail shaft keeps rolling at every strike.
I managed to put back everything but about 1.5 mm of the roll pin is protruding out. I really cant fit it any further..probably the roll pin got damaged along the length from the punches..
i gave up on it..1.5 mm off should still lock the tail shaft and belt pulley in place.well, hopefully!
06-18-2011, 06:11 AM
The roll pin should have a shamfer on one end & this is the side that
goes in first. Pin should be flush with the pulling.