DT520 3-blade tail experiment

[TheBum]

I'm really encouraged by the results. I think any of the three materials would suffice, but the UV resin print looked the best and had the tighter tolerances. Here it is installed:

3D-printed DT520 tail slider for JR 3-blade tail (0 min 19 sec)

[dunkonu23]

Great job, Alan!

Scott

[rspiegel]

Looks like you won to me!

[TheBum]

Yes, I believe I did. I was pleasantly surprised that my first attempt turned out so well. I don't see a need yet for a second attempt. I'll let you know how well it flies, of course.

When I was attempting to jam the bearings into the bored-out stock slider housing, I managed to dent the shield on one of the bearings. It's a little rough and I'm concerned about vibrations and extra load on the motor, so I ordered new bearings.

[dunkonu23]

If you're happy with the fit, I'd order a couple more parts. That way you have spares.

Scott

[TheBum]

Originally Posted by dunkonu23

If you're happy with the fit, I'd order a couple more parts. That way you have spares.

Scott

I still have the other two materials. While not as precisely printed as the one I decided on, they would likely suffice in a pinch. They have a rougher surface and the bearing fit is still snug, just not super tight.

[TheBum]

The maiden of the 3-blade tail is in the books. It performed stupendously! I immediately noticed the improvement in tail authority.

The only issue I had was CG: with a 5300mAh pack, I was not able to get the CG where it should be because I ran out of space under the canopy. Despite that, I didn't notice any behaviors that would indicate it was excessively tail heavy.

[Atomic Skull]

Originally Posted by TheBum

I just have to decide if I want to bore an 11mm hole all the way through or keep the narrowed portion for a spacer that I'm making out of a K&S thick walled aluminum tube; it really only helps in getting the sleeve in and its absence shouldn't have any other adverse effects.

The purpose of that sleeve is to prevent the center race of the bearings from being squeezed together so that the slider can be screwed together tightly without binding up the bearings.

Some chinese helicopter manufacturers apparently don't know this and make helis with that sleeve omitted or slightly too short to do it's job.

"Flexible strong plastic" is laser fused nylon and is probably better for this application than UV resin which is hard but brittle.

Originally Posted by TheBum

When I was attempting to jam the bearings into the bored-out stock slider housing, I managed to dent the shield on one of the bearings. It's a little rough and I'm concerned about vibrations and extra load on the motor, so I ordered new bearings.

I've started using rubber shielded bearings in my helicopter tails, for some reason the tail box bearings and pitch slider bearings seem to be dirt magnets and rubber shielded bearings don't get all crudded up the way the metal shielded ones do.

[TheBum]

Originally Posted by Atomic Skull

The purpose of that sleeve is to prevent the center race of the bearings from being squeezed together so that the slider can be screwed together tightly without binding up the bearings.

Some chinese helicopter manufacturers apparently don't know this and make helis with that sleeve omitted or slightly too short to do it's job.

I guess I should have said "JR sleeves". Yes, the width of the new slider housing was to accommodate the inter-bearing sleeve, but the larger diameter of the new slider housing's bearing holes was to accommodate the 7x11x3mm bearings necessary for the JR 7mm diameter rotor shaft sleeve. That sleeve on the DT slider is only 6mm in diameter.

"Flexible strong plastic" is laser fused nylon and is probably better for this application than UV resin which is hard but brittle.

One problem was resolution. The ridges I designed into the holes for the outer races to rest upon were severely rounded off in the "strong and flexible plastic" and the aluminized plastic slider housings. They were sharp and well-defined in the UV resin print. Would the softer plastic ones have worked? Probably, but they were also uglier with very rough surfaces, almost like sandpaper (especially the aluminized one), and I didn't feel like sanding them down.

The only way I could see the resin-printed housings shattering is if the heli was crashed tail first on pavement. I made them pretty robust.

[Atomic Skull]

Originally Posted by TheBum

I guess I should have said "JR sleeves". Yes, the width of the new slider housing was to accommodate the inter-bearing sleeve, but the larger diameter of the new slider housing's bearing holes was to accommodate the 7x11x3mm bearings necessary for the JR 7mm diameter rotor shaft sleeve. That sleeve on the DT slider is only 6mm in diameter.


One problem was resolution. The ridges I designed into the holes for the outer races to rest upon were severely rounded off in the "strong and flexible plastic" and the aluminized plastic slider housings. They were sharp and well-defined in the UV resin print. Would the softer plastic ones have worked? Probably, but they were also uglier with very rough surfaces, almost like sandpaper (especially the aluminized one), and I didn't feel like sanding them down.

The only way I could see the resin-printed housings shattering is if the heli was crashed tail first on pavement. I made them pretty robust.

Shapeways also does laser fused aluminum so maybe you could have it done in that once you work the bugs out. From what I have read they use a casting alloy for printing aluminum because it becomes stronger when printed while 6061 is weaker when printed.

[TheBum]

I read the description for the aluminum prints and it mentioned that the final cleaning process would round off sharp edges.

[dunkonu23]

Alan,

I have to say I'm very impressed, bro! I can't wait to see this at IRCHA!

Scott

[Atomic Skull]

Originally Posted by TheBum

I read the description for the aluminum prints and it mentioned that the final cleaning process would round off sharp edges.

They often do the same process on CNC parts. The "rounding off" is only very slight, i.e. the edges aren't knife sharp anymore.