My Goblin 770 Build with Photos

[CeeveeSiN]

Mine is almost built would be 100% if I had not have had 1 minor issue.
My tail servo hole was just a tad too small.
bummer now I need a dremel and a drill.

other than that the 770 was even nicer build than the other 3 I've built.
Like the new Canopy guide bumpers..
Love how one of my least favorite steps is now done for you ( the screws for the tail assembly were already mounted perfectly)
Love the new Battery tray.
and my boom and canopy were flawless other than the hole being just a tad too small.

[busterboy]

Originally Posted by CeeveeSiN

Mine is almost built would be 100% if I had not have had 1 minor issue.

My tail servo hole was just a tad too small.

Damn I had the very same issue with my 770.

Took longer to fit the tail servo than build the whole boom.

[mmarmouz]

Originally Posted by CeeveeSiN

Mine is almost built would be 100% if I had not have had 1 minor issue.
My tail servo hole was just a tad too small.
bummer now I need a dremel and a drill.

other than that the 770 was even nicer build than the other 3 I've built.
Like the new Canopy guide bumpers..
Love how one of my least favorite steps is now done for you ( the screws for the tail assembly were already mounted perfectly)
Love the new Battery tray.
and my boom and canopy were flawless other than the hole being just a tad too small.

I just finished installing my TORQ 9188 using the supplied 2.5x12mm bolts, had no problem at all, i used some electric tape to wrap the servo cable, i now need some hot glue to fix it in place, i just bought a gun and some glue for 7$ on ebay .. lol

I did not put the horn yet, it's in they way !

[aramb]

Originally Posted by snemi00

Reminder on tail rod length https://www.helifreak.com/showthread.php?t=480577

He is absolutely correct. The dimensions are 4 mm too long. I mocked up my control rod this afternoon without the CA just to make sure. I will post photos in a bit.

[rctintin]

Originally Posted by mmarmouz

Do you have any picture with the brass sleeve in place ?

I dont have one of my Goblin, but here is one from my recent build thread of the Diabolo

[mmarmouz]

Quick question, the 2 holes in the front bottom of the boom in the 770, are they there to pass the servo cable on them ? or they have another function ?

[CeeveeSiN]

Originally Posted by mmarmouz

Quick question, the 2 holes in the front bottom of the boom in the 770, are they there to pass the servo cable on them ? or they have another function ?

they are from the boom construction rig.

most people use them for a tie wrap to tie the tail servo cable down inside the boom too,

[snemi00]

Originally Posted by aramb

He is absolutely correct. The dimensions are 4 mm too long. I mocked up my control rod this afternoon without the CA just to make sure. I will post photos in a bit.

Thanks for the vote of confidence
The whole first batch is like this, but please read my post before being drastic and ripping your tail rod apart if you've already assembled it and glued it in place.
Its not too late if they're already glued in, You can just cut off a few mm from the end of the steel threaded rods. There doesn't need to be exposed threaded rod between the plastic and the carbon.

Of course if you read this heads up ahead of time, you can just cut 4 mm off the length of the carbon rod as I did. No real difference it all accomplishes the same thing.

[aramb]

Sorry for the delay in getting these photos up. I have been unable to upload photos to HF all day today. I finally just decided to host the photos elsewhere so I could get this posted.

The next portion of the tail assembly requires hardware from Bag 9 as well as the bell crank lever assembly, tail rotor assembly (both assembled earlier) as well as the CF tail plate and vertical fin.



The support posts are installed on the tail side plate along with the bell crank assembly.



The vertical fin is bolted to the other side of the support posts.



Now the tail rotor shaft is slid in place along with the 25T pulley. Make sure to wrap the belt around the pulley before installing it in the assembly. The tail box is now complete.



The next step involves preparing the tail boom and requires the hardware found in Bag 10.



The manual divides the details of the boom assembly into three parts. The first part involves the installation of the two boom spacers which make up the lower part of the boom support. I used thick CA for this step.



Next, the tail linkage support is installed. The manualr recommends threading the screws into the plastic tail support before trying to install it in the boom. This is highly recommended, as it took a lot of pressure to get the screws to thread.



The final step of the boom prep is already completed at the factory - installation of the locking element for the tail box. I understand that in the 700 this was not factory installed. Now the tail box/vertical fin assembly can be attached.



The manual now suggests building the carbon tail control linkage. Due to some posts I had read earlier regarding the dimensions potentially being incorrect in the manual, I decided to skip this step until I had the tail servo in place. Parts for installatin of the tail servo are found in Bag 13. This is left out of the manual. The screws required to install the servo in the boom are part #HC026. This is also inadvertently missing from the manual.



The servo is no installed. Make sure to install the ball on the servo arm prior to installing the servo, or the arm will need to be removed from the servo in order to install the ball.



At this point I took a measurement from the tail servo (arm centered) to the bell crank arm (centered) and decided that the measurement in the manual might actually be incorrect. In my case I determined that I only needed about 2mm between the ball link and the carbon rod (not the 4mm as advertised in the manual).

[aramb]

At this point the main structure, swashplate, and main rotor head will be mounted in the frame. The hardware required is found in Bag 12.



First, the main structure is bolted into the frame.




Next, the swashplate and rotor head are added.

[mmarmouz]

Originally Posted by CeeveeSiN

they are from the boom construction rig.

most people use them for a tie wrap to tie the tail servo cable down inside the boom too,

Ok good ! i will put a tie wrap to secure the cable in place.

Thanks

[byter182]

Originally Posted by aramb

Sorry for the delay in getting these photos up. I have been unable to upload photos to HF all day today. I finally just decided to host the photos elsewhere so I could get this posted.

The next portion of the tail assembly requires hardware from Bag 9 as well as the bell crank lever assembly, tail rotor assembly (both assembled earlier) as well as the CF tail plate and vertical fin.



The support posts are installed on the tail side plate along with the bell crank assembly.



The vertical fin is bolted to the other side of the support posts.



Now the tail rotor shaft is slid in place along with the 25T pulley. Make sure to wrap the belt around the pulley before installing it in the assembly. The tail box is now complete.



The next step involves preparing the tail boom and requires the hardware found in Bag 10.



The manual divides the details of the boom assembly into three parts. The first part involves the installation of the two boom spacers which make up the lower part of the boom support. I used thick CA for this step.



Next, the tail linkage support is installed. The manualr recommends threading the screws into the plastic tail support before trying to install it in the boom. This is highly recommended, as it took a lot of pressure to get the screws to thread.



The final step of the boom prep is already completed at the factory - installation of the locking element for the tail box. I understand that in the 700 this was not factory installed. Now the tail box/vertical fin assembly can be attached.



The manual now suggests building the carbon tail control linkage. Due to some posts I had read earlier regarding the dimensions potentially being incorrect in the manual, I decided to skip this step until I had the tail servo in place. Parts for installatin of the tail servo are found in Bag 13. This is left out of the manual. The screws required to install the servo in the boom are part #HC026. This is also inadvertently missing from the manual.



The servo is no installed. Make sure to install the ball on the servo arm prior to installing the servo, or the arm will need to be removed from the servo in order to install the ball.



At this point I took a measurement from the tail servo (arm centered) to the bell crank arm (centered) and decided that the measurement in the manual might actually be incorrect. In my case I determined that I only needed about 2mm between the ball link and the carbon rod (not the 4mm as advertised in the manual).

Great build thread Aramb,


This is gonna be my first time building a Goblin and a bird of this size so your walk-through and PICS are a tremendous help. I'm very excited about starting my build and have subscribed to this thread.

One quick question though... I noticed above you took apart the main rotorhead and regreased/relocktited it all back together. However, do you recommend doing the same w/all the factory assembled parts?

Sorry... 2 quick questions... Noticed that the tail rotor blade grips have a pretty decent amount of slop in them... Is it just my kit or are some of the other kits coming that way? How are we correcting for this problem or does this not affect the 770's performance?

[Slyster]

I really am appreciating this thread.. as you are just a few days ahead of me. Thumbs up!

[aramb]

Originally Posted by byter182

Great build thread Aramb,

This is gonna be my first time building a Goblin and a bird of this size so your walk-through and PICS are a tremendous help. I'm very excited about starting my build and have subscribed to this thread.

One quick question though... I noticed above you took apart the main rotorhead and regreased/relocktited it all back together. However, do you recommend doing the same w/all the factory assembled parts?

Sorry... 2 quick questions... Noticed that the tail rotor blade grips have a pretty decent amount of slop in them... Is it just my kit or are some of the other kits coming that way? How are we correcting for this problem or does this not affect the 770's performance?

Other than the main rotor and tail rotor assemblies, all of the other pre-assembled items from the factory can be inspected for proper assembly without taking them apart. The key reason to take apart the rotor assemblies is to verify the thrust bearings are greased and installed properly. Neither my Fusion or Trex kits had any grease on the bearings when I pulled them apart. The SAB kit was greased and assembled correctly. Other SAB owners have indicated the same on their kits, so perhaps it is not necessary, but I still think it is a good idea to verify. Its best to find that you got a problem before you try to put something this big into the air.

I have noticed the slop in the tail as well. I have heard that it is not an issue.

Good luck with your build!

[CeeveeSiN]

Originally Posted by aramb

Other than the main rotor and tail rotor assemblies, all of the other pre-assembled items from the factory can be inspected for proper assembly without taking them apart. The key reason to take apart the rotor assemblies is to verify the thrust bearings are greased and installed properly. Neither my Fusion or Trex kits had any grease on the bearings when I pulled them apart. The SAB kit was greased and assembled correctly. Other SAB owners have indicated the same on their kits, so perhaps it is not necessary, but I still think it is a good idea to verify. Its best to find that you got a problem before you try to put something this big into the air.

I have noticed the slop in the tail as well. I have heard that it is not an issue.

Good luck with your build!

the "slop" in the tail is not slop it is by design.
all the Goblins have it.
its the bearing setup that allows it.

[Clinton1]

Originally Posted by CeeveeSiN

the "slop" in the tail is not slop it is by design.
all the Goblins have it.
its the bearing setup that allows it.

I got all the slop out of the tail. The bolt they supply to secure the tail grips is hitting the face of the spindle end before it touches the bearings. By adding a extra washer that fits over the spindle, you can tighten the bolt untill the bearings is pressing against the recess on the inside, without any slop or binding . Have about 50 flights on it, tail is still perfect without the slop. This is what worked for me. I dont think that if you look at all the other components on this heli, with the tolarences they have, they will design that much slop in the tail grips. Just my 2 cents.

[CeeveeSiN]

Originally Posted by Clinton1

I got all the slop out of the tail. The bolt they supply to secure the tail grips is hitting the face of the spindle end before it touches the bearings. By adding a extra washer that fits over the spindle, you can tighten the bolt untill the bearings is pressing against the recess on the inside, without any slop or binding . Have about 50 flights on it, tail is still perfect without the slop. This is what worked for me. I dont think that if you look at all the other components on this heli, with the tolarences they have, they will design that much slop in the tail grips. Just my 2 cents.

per Bert that little bit of play is part of the design.. take the play out by adding hardware and you may cause other issues.

[Mr.Gobler]

Originally Posted by CeeveeSiN

per Bert that little bit of play is part of the design.. take the play out by adding hardware and you may cause other issues.

yup.

[Clinton1]

Originally Posted by CeeveeSiN

per Bert that little bit of play is part of the design.. take the play out by adding hardware and you may cause other issues.

I hear what you say, but as i said, after 50 flights everything is still perfect, and heli flies like a dream. Can you please explain what other issues may be caused by removing the slop ?

[snemi00]

In order to have a properly balanced tail or main rotor assembly, the distance from the centre of the tailshaft to the mounting hole for the blades must be identical. This is almost always accomplished on a heli by using the end of the spindle or the spindle face as the reference plane.
So, when the tail is assembled correctly, the outer thrust washer face is to be perfectly flush with the end of the tail hub. The screw head, or as included in the new tail assemblies, the washer that comes with the screw, are only there to hold the components in from extending out past the end of the hub. This is why the washer that comes with the screw does not fit over the spindle of the hub. It should bottom out and create a nice square stop for the thrust bearing to bear on.

If you add a washer that fits over the hub, then you will be pushing the thrust bearing in past the end. You would have to do the exact same thing on the other side to make sure it is balanced. But, it is impossible, since you will end up removing all the slop on one side differently than on the other.

The slop, in and out axially along the spindle direction, does not matter because as the rotor spins the amount of centripetal force is HUGE. This forces the grip assembly out and both of them should sit perfectly balanced at the end of the hub against the underside of the screw head or washer if you have put it in. It really doesn't matter if you can push the grips in 1mm or 3mm or whatever, all that matters is how far out they go.

A washer under the screw head is now used in the assembly as it is creates a very nice square face as a datum plane for the thrust bearing to be pressing on. Although the screw head alone could work, the underside of some screw heads are not as square and consistent as others and also have less surface area than the beefy washer.

As a side note, if you have a chance to look at the new Compass Warp machine, there is identical slop in the main rotor grips in and out. This is for the same reason as the SAB tail grips. A single reference plane to keep tolerance on that increases accuracy while making manufacturing simpler and more consistent.
Unfortunately, it creates user confusion as it is unconventional.