Mini frame mod for experienced builders

[fGene]

The round parts (motor clamps etc) indeed need 4 axes to machine in their current state. If you can change the design to something that requires only three axes, the desktop CNC mill (about $2.5k) will be more than what you need.

In my opinion, 5 axis is a bare minimum, if we are talking about volume production. Unfortunately, I can't change the design so it can be easily milled on a 3 -axis, (or 4-axis for that matter) -- believe me, I tried my best, as I only have a 3-axis machine with separate 4th axis and love all kinds of optimizations. And the parts are not molding-friendly either.

Or maybe even SLS 3DP technology?

Sintering machines might provide superior resolution to regular printers, but AFAIK they are very picky about materials and the parts are not that durable unless "baked" afterwards (which is a main detractor). Not even sure if they would work with something like nylon or HDPE...

 

[Justinswidebody]

Maybe a resin 3d printer (dlp 3d printer )..... They are far superior in detail. I have 2 of them at the house. No layer lines, and can surely be stronger than the stock mini plastic....

Well stiffer than stock mini plastic but more brittle...

Look into it, a decent dlp 3d printer can be had for around $300 so not too expensive.

 

[Vaideeshwar]

Sintering machines might provide superior resolution to regular printers, but AFAIK they are very picky about materials and the parts are not that durable unless "baked" afterwards (which is a main detractor). Not even sure if they would work with something like nylon or HDPE...

You can print a Nylon part on a SLS printer. Another 3DP that produces really good resolution is SLA. If it is 3DP, it is going to have to either be SLS or SLA.

 

[fGene]

Thanks, I'll look into it.

 

[Justinswidebody]

Thanks, I'll look into it.

Look into the anycubic photon

 

[Justinswidebody]

I'm working on designing my own... I'll update when I have done.

 

[fGene]

I'm working on designing my own... I'll update when I have done.

I see you are planning to use existing rear pivots. The inside cavity in your part doesn't have to be as complicated as the original, a simple rectangular shape will do just fine.

 

[Justinswidebody]

First prototype came out really great!! Now just have 2 motor mounts to design and front pivot adapter.

 

[fGene]

Look into the anycubic photon

Indeed it looks promising from the resolution standpoint, and the resin doesn't seem outrageously expensive either. Can you please answer:

1. How durable the printed parts are? I understand it may be a far cry from a milled nylon, but is there any type of common plastic you can compare it to? Can the printed parts be bent without cracking?
2. What software are you using? Is it open-source? Will it accept regular Autodesk CAD files?
3. How long did it take to print the part you were showing in the previous post?

Thanks in advance.

 

[Justinswidebody]

Indeed it looks promising from the resolution standpoint, and the resin doesn't seem outrageously expensive either. Can you please answer:

1. How durable the printed parts are? I understand it may be a far cry from a milled nylon, but is there any type of common plastic you can compare it to? Can the printed parts be bent without cracking?
2. What software are you using? Is it open-source? Will it accept regular Autodesk CAD files?
3. How long did it take to print the part you were showing in the previous post?

Thanks in advance.

1. It's hard to compare... They are coming up with new resins every day... Some can be bent...
The benefit of the resin prints is resolution, and your part won't break at layer lines..
But resin isn't plastic so it doesn't flex or bend as much... It will chip like glass... I think it will work perfectly in this situation...

2. I use a online cad program called onshape. You can see it at www.onshape.com

3. It took 3 hours to print this. How you see it, is how it came off the printer. No supports were used, didn't have to clean anything up.

 

[Justinswidebody]

There is a resin that is flexible... People do 80/20 ratios to make stronger parts that resist breaking because now they have a little flex.

 

[scro]

I note in your original post that one objective was to improve the drone's wind resistance abilities. I see you've raised the height of the rear props and it would seem their thrust vectors are angled slightly further back. Were there any other aspects incorporated into the design to meet that objective?

From my observations of flying in strong winds the max ground speed does indeed seem to be software limited to 13m/s (29mph). I've seen tilt angles of just 10deg when flying downwind at a steady 13m/s ground speed.

 

[fGene]

I note in your original post that one objective was to improve the drone's wind resistance abilities. I see you've raised the height of the rear props and it would seem their thrust vectors are angled slightly further back. Were there any other aspects incorporated into the design to meet that objective?

I think I mentioned this in one of my earlier posts. Raising of rear arms increases overall stability, all but eliminates propwash interference (especially in forward flight) and consequently improves efficiency and noise characteristics (not in a major way, but noticeably). It also helps with landings and takeoffs on the grass.

The thrust vectors of front and rear pairs are angled because such configuration further improves stability -- in particular yaw stability in high wind. Relying on prop/motor inertia and air resistance only is insufficient in MM case when yaw is concerned, so I've added vectored thrust to help.

From my observations of flying in strong winds the max ground speed does indeed seem to be software limited to 13m/s (29mph). I've seen tilt angles of just 10deg when flying downwind at a steady 13m/s ground speed.

Same here. Thanks for confirming!

 

[scro]

Thanks for clarifying! I know what you mean regarding noise due to prop wash interference. I've previously noted that the standard MM is subtley quieter when flying backwards. The Spark has slightly inward facing thrust vectors - fine for assisting yaw, but perhaps not optimal for forward flight.

Your mod is pretty cool! Both practical and aesthetically pleasing. Sadly there are so many other demands on my time I barely get time to fly let alone have some fun tweaking the MM.

 

[Justinswidebody]

Here's a few pictures of my progress...
Just have the fronts to finish now.

 

[fGene]

Justin, is there a reason for such thickness? Is the material that fragile?

 

[Justinswidebody]

Justin, is there a reason for such thickness? Is the material that fragile?

These are just quick designed prototypes to see how it all is. Then I will reduce the material down to make it less heavy.

The material where it meets the carbon is thick because that's the part of the part that's on the 3d print build plate. I'm able to print this way without supports.. but I will be reducing these areas.

 

[Justinswidebody]

Progress update...... Fronts are done!!! Tonight, I'll assemble everything and see how she flys!

 

[Justinswidebody]

Haven't test flown it yet, but here's my first prototype... I will be doing a lot of revisions soon.

 

[m80116]

Congratulations to the original poster fGene that started this thread and has done a magnificent job.

Anyway... for the feasibility of reproducing the parts I personally and humbly so think it might be possible to 3D scan and 3D print (after a good share of re-processing) the model with latest generation of resin printers (which have unprecedented accuracy), but... the way I see it, there are other parts that can easily be addressed to shave wight before you eat into the cosmetic aspect of the drone, so much easier for example to come up with lighter parts rather than going through the trouble of re-inventing the wheel, which has worked brilliantly here.

Anyway... since I see a lot expertise at work, I am catching the opportunity to ask. Is any of you 3D tuners considering a front gimbal windscreen, not completely sealed... something that could be used to minimize the cold flow of air in freezing temperatures, allow a better body compartment heat up and keep the gimbal away from frozen water droplets and a little less cold that it would otherwise be.

I am giving you a hint here: back when I started using the Mini 7 months ago Yagi/Uda boosters for the RC were unheard of. Now thanks to some 3D print file available on the Internet they sparked interest and caught on and now not only we have readily available 3D printed parts but I also saw a few days ago a branded set made with silicone and high quality copper!

I really hope somebody in the business could get to you and ask for your help to design a product because that I feel would be the only way that could bring benefit for the rest of us...until then, congrats again, and that I believe should remain as a one off to testify where passion, skill and knowledge can bring you.