Trex 700 Rear servo mount

[mattie-lodge]

Hi All,

Just spotted this from G-Force. Its a rear tail servo mount for a Trex 700.

New product from G-Force Heli! | RC Heli Resource

Now the benefit I can see for this, is to move some weight aft of the mainshaft therefore allowing you to run a slightly heavier (larger capicity) battery up front.

My only concern is how strong it would be as it only mounts on the two screws where the idler link went.

The reason why I'm considering this is because I only get 'safely' two flights out of a pack that I'm running which balances the model correctly.

Whats your thoughts???

[trillian]

It looks like a very well made part.

But if you have a nose-heavy issue that's the easiest thing to correct because all it takes is a very small bit of weight added back around the vertical fin or somewhere along the boom. I know you're probably thinking
along the lines of not wanting to actually add overall weight to the heli but the farther out the weight is placed the less you need.

I would find it annoying to only get a couple flights out of an RX pack.

I've never had to do that because my helis tend to be tail heavy generally (especially the Ely.Q)

[mark Taylor]

Great idea for the 700e
Not sure about using on a 700n ,
as my 700 is always covered in oil under the boom block,
which is going to cover the servo in oil.
Which in turn will eventualy kill your tail servo.
Just my thought matty.
I know it's a pain using a small lipo to get the 700 to balance correctly.

[mattie-lodge]

Trillian...I'm always concerned about adding weight to the tail because I fear it will decrease the tail performance. However I've not proved this


Mark.... Its a good point about the oil getting into the servo. I had overlooked that

[barney]

Have to agree mattie, its the last place you want a servo on a big Nitro. Worse still is the 700 tank with a YS pumping it can leak at the bung.

Be excellent on the Leccy versions

[trillian]

Trillian...I'm always concerned about adding weight to the tail because I fear it will decrease the tail performance. However I've not proved this

Well, the only answer then is taking weight off the nose to change the C of G.

Whatever weight it takes added to the tail to balance the heli will create the same amount of inertia regardless where it is located because the amount of weight required will be perportional to how far out it can be mounted. So in other words, it might take 100 grams added right at the base of the boom or on the back of the frame and the weight needed to do the same balancing act might only be 20 grams if placed at the very end of the boom by the tail fin. (just using these weights as an example, I'm not sure what the actual weight ratios would be depending on the length of the boom etc)

So in terms of making the tail slower, it will take the same amount of energy to move the 100 gram mass 5 inches for example whereas the far end of the boom might move 25 inches, but with only 1/5th the mass added, the energy to move it / stop it is the same. 'Hope that makes sense.

Some of that physics malarkey I learned in school actually stayed in my brain

[Grant_beltcp]

Almost right there lol. Adding a lower weight further out would increase inertia in the tail which could effect it more in comparison to a larger weight closer to the centre.

I personally wouldnt add weight to the tail as I dont like the thought of something possibly coming off and catching the tail blades.

[trillian]

Almost right there lol. Adding a lower weight further out would increase inertia in the tail which could effect it more in comparison to a larger weight closer to the centre.

Nope, it is totally perportional. It takes the same energy (and thus the same inertia is present) to move one weight a certain distance as it takes to move half the weight double the distance. This is just basic physics and applies to anything, there is nothing special about it being a helicopter tail.

If the lower weight added further out is actually truly in perportion (ie; what it actually takes to acheive the same c of g balance) it will make zero difference in inertia how much weight is used because it will travel perportionately farther. Adding more weight closer in will not give you less inertia, only moving the same weight closer in will do this. Trust me on this, it is not a matter of opinion it is the laws of physics, it's energy required to do a certain amount of work, mass and leverage.

Put another way; it takes the same energy to accelerate 100g to 1mph as it does to accelerate 10g to ten mph. On a heli tail you're trading mass for distance, if you lower the mass in the correct perportion the inertia stays the same but since they are both acting against a constant (gravity) they can acheive the same balancing action on the C of G.