New experimental impossible tilt for the BabyTri

[Terje]

I’ve made an impossible tilt version specific for the BabyTri. Find it at thingiverse (https://www.thingiverse.com/thing:2869393).

It is made for the original Emax RS2205 2300Kv motors, and may require you to trim the servo mount plate depending on the make and model of your props. It has indicator markings for easy center and 40 degree deflection calibration.

This version also allows for easy replacement of the tilt mechanism as the wires do no longer pass through the tilt mechanism.

Attachments:

1. 

   impossible-tilt-babytri.jpg
   

[Kevin_Erik]

Any chance of a version for the 2207 & 2208 motors?
If so, I’ll have my local print house burn me 2-3 of them.

[LitterBug]

@dkdarkness, (aka @Terje)
Nice! Need to get this on one of my baby tris. Firing up S3D and giving it a go! Played a little bit with printing the impossible tilt with PETG for my mini, but was having meh results. Going to just throw PLA at it for some quick sample prints.

Cheers!
LitterBug

[jihlein]

@dkdarkness, I’ve got it printed. FWIW, I don’t know if it’s subtle differences in the different servos, but I could not make your rear mount work, it wasn’t tall enough. I went back to the original square one I threw together and it fits perfectly with my servo, no binding. The “half circular” motor mount i genius, now I don’t have to mess with the motor wires. Thanks for posting it!

Pictures to follow after I get servo wired back in….

[Kevin_Erik]

Quick question… why arn’t we using Servo savers?

[Terje]

@Kevin_Erik be adventurous, print it at see if it fits your specific 2207/2208 motors.

Servo savers introduce latency in the tilt mechanism resulting in oscillations from the PID loop.

[Terje]

@jihlein your problems may be a result of “elephants foot” on your print of the servo mount. Try cleaning up all the edges and see if it fits. It may, however, be a result of me using my pre-production babytri frame for reference 🙂

[Kevin_Erik]

For the sake of discussion, lets assume that the Servo-Savers “latency” is based off its Point of Release. (PoR) Far as i can tell I’ve gone through 6-8 Servos this year alone, 2/3rds of which are the result of indirect impact. In many cases there is no damage to the copter itself or to the propellers. Yet the Servo gets trashed from the inertia of the copter slamming the motor towards the point of impact. Now if a Saver were found that could work for “our” torque range without slippage then it would be well worth the investment.

Note: As i understand it, the PoR is determined by a wound spring thats held inplace between two mountings. Normally the PoR is set to a fixed value but there are high end ones that are semi-adjustable. Will research this more later but suspect that its adjustable by a simple screw pushing against the spring. This would is effect trigger the PoR early or later based on the screws position.

As for printing the tilt-mech, I’ll first need to deside if the mount you’ve shown will fit. Will perform a side by side comparison via Fusion-360 and the motor template I’ve created for the 2207. Kids are in school so after i tidy up the house, i may have a spare hour or so.

[Terje]

For sake of my sanity, lets do less discussion, and more action? It’s a 2 hour print, with most printers unattended, so kind of a no-brainer. You do not need to write a masters thesis to decide if your motors will fit. Print it, it is less than $1 worth of materials, and see if they fit.

If you want to experiment with servo savers, by all means do it. Emphasis on DO it. You might find this thread helpful: https://rcexplorer.se/forums/topic/how-to-protect-the-servo/#post-26004

[Kevin_Erik]

@Terje

Already did a detailed verification, the 2207 motor will 100% fit the new mount.
https://farm1.staticflickr.com/819/27706225978_b6952f9229_b.jpg

Keep in mind that I don’t have local printing and must reply on a Print-House. This usually takes about 3-5 days not counting shipping. Hence why I am being difficult, just want to get it right the first time. I’m sure you can appreciate that part being from a tech background.

Overall, the only issue I saw is that the BMS-385D Servo I’m using is a bit wider than the Servo holder will is designed for. (13 mm vice 12mm for David’s BMS-210D) I have a work around for this just using a plastic bit that’s stuck to the frame via double sided tape and thicker zip ties (3 mm vice 2.5 mm). Been doing this with my current build and it’s worked good so far.

I do have an suggestion for the next update: The Rear-Holder and the Servo-Holder are separate entities, where it could be possible to join them together. It should allow for a stiffer tail-mech, while still allowing for the Servo-Holder side of things to fail when over stressed. The downside is that this may make things more difficult to print as well as requiring the entire assembly to be replaced if it does fail.

[Terje]

If you go through 5-6 servos a year, consider getting a BMS-210DMH Servo with Feedback wire – Stainless steel shaft instead – might save you some headaches in the long run. It is purpose made.

I started out making a all in one version, but the solution prohibits using different servos as in your case, it is not possible to use the key-in slots and the layers would be too weak on the servo holder.

[Kevin_Erik]

Tail-Mech on order…

100 um Markforged Onyx Nylon and Kevlar print, should allow it to flex a little but not break or shatter.

https://farm1.staticflickr.com/873/27706664858_14686e4da4_z.jpg

[Kevin_Erik]

I was using David’s servo but for the first half of the year but opted to try something else to see if it’s more robust. Thus far I’m uncertain as failures were not partial or intermittent but absolutes. Big downside to using a 3rd party servo is that I have to add a custom feedback wire to the Potentiometer. Luckily I can soldier to the mini level without the use of a Microscope. Can do micro-work and multi layer repairs if i had the equipment but I suspect the wife would get pissed if I turned a room into a solder lab.

[Terje]

I opted to use the new stainless steel servos, and order spare gears, as it takes less time to replace the gears than to replace the servo. Haven’t flown much tricopter the last year though.

[Kevin_Erik]

Most of my failures from David’s servos were the motors burning up as the Gears were in perfect shape. The Other servo I am using is the exact opposite, I’m blowing out gears but the other internals look fine.

[Author]

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