Ideas to improve the motor mount of Dusty
12.4.18 at 08:23 #31101apocalypsedudeParticipant
Ideas to improve the motor mount of Dusty
As reported here, the motor mount of my Dusty failed as so many others did before.
I’m really pissed at the moment, for several reasons:
1. The failure has been reported many times and it wasn’t considered in the update of the plane
2. 3Dlab assumes that it works as long as the motor mount is annealed and glued in well. Not true, at least mine did fail even if I proceeded like suggested.
3. I’m annoyed of myself, too. I should have known better.
I doubt that there will be another update of Dusty and I have either do an improvement myself or leave it on the ground.
But there is one problem. I build Dusty mainly for my children. They love Dusty and my little daughter even cried when it crashed. She wanted to know if Dusty goes to heaven now…
I promised her, that Dusty is not dead and he will fly again!
But just rebuilding it without any motor mount modifications will not work.
So I’m asking for ideas how to improve it.
I really like the mounting method of the small Spitfire for example. A massive block is screwed form the outside to a stable fitting inside of the fuselage.
That’s what I would prefer for Dusty, too.
I have tried to modify the part myself, but my CAD skills are not good enough to realize it.
Is there anybody who is able to do it?
Or are there other ideas how to secure the motor to the fuselage?
Any suggestions are welcome!
Thank you guys in advance!16.4.18 at 07:13 #31326Burton HookerParticipant
Personally I glue the block in for the Spitfire MK XVI. In some of my earlier planes when I was still working on getting better layer bonding I found that one of the most likely places for the layers to split was where the holes get drilled for the motor mounts.17.4.18 at 20:46 #31458
I’m really sorry for your disappointment, but we’ve seen some actual inflight videos of Pawnees already, so this is the proof the design works for some of us without issues.
For example: https://www.youtube.com/watch?v=YmM-c4-TlDY
But to your problem… I’ve seen your front part failed not on the glued joint, but most likely the layers of the nose part didn’t hold up. There has been a community motor mount by Rob Johnson available in Facebook Group: https://www.facebook.com/groups/400505486960463/files/ that could a bit better spread the forces to more layers at once.
Also you could print the front part reinforced with 2 perimeters without the need to alter the mesh, but sacrificing some weight. Or you can at least increase the filament flow.
This 6S setup is really powerful, so if your layer adhesion or flow is not very optimal, the whole front part could fail.
Hope you get your Dusty flying soon.18.4.18 at 07:07 #31476apocalypsedudeParticipant
thanks for your comment and the link. I’m already working on another solution. Looks promising so far, but it’s not finished yet.
I know that there are people out there, who flew/fly Dusty successfully. But I also know that there are way too much people who were not able to fly Dusty due to known issues.
So, if your standard is….let’s say 50% success rate…..well….
I know you can do it better, since you released some really fantastic and well designed aircrafts. Don’t let one model ruin the reputation you earned with hard work before!
Back to my Dusty:
I also thought that the layer bonding is the root cause of the crash, but in fact the layers bond together very strong and not better or worse than on my other printed planes.
I’m pretty sure, that the reason for the fail is the design of the firewall/motor mount itself. It’s on the edge of working/failing and only small irregularities can turn the switch from work to fail.
BTW: I run it on 4S only, though the motor has a higher KV rating. Compared to the recommended 6S setup, there is a little less thrust with my setup.18.4.18 at 21:32 #31515
I already bench tested the 6S setup to full throttle with the updated spinner and standard nose printed from factories, but I have to admit, it really is on the edge of possibilities, and I was a bit scared when doing this. There’s some real deal thrust produced by this setup.
I believe increasing the perimeter count for whole fuselage1 and from 59th mm to the top of the fuselage8 part, and possibly using the Rob Johnsons mount should be vastly enough to sort this out for anybody. According to Simplify3D it’s around 20g weight increase.
Once we got this tested and if we don’t find any better solution, this will probably go official including the factories.24.7.18 at 09:00 #35775martin.formanekParticipant
I have made this02.8.18 at 22:37 #36308
See the updated files, the motor mount has been altered along with the front part of fuselage, so there are screws for added safety. I also suggest using the aluminium cross that is part of the motor to further reinforce the motor mount. Sometimes it could break when the prop hits the ground on taxiing and the cross helps to distribute the torque.10.8.18 at 23:09 #36671
Hey, Guys – I had the same issues that many have had with the Dusty motor mount. But there were other problems that became known as well.
1. the CG needed much nose weight in order to balance
2. the large spinner was hard to balance and prone to vibration
3. Cooling for the motor was blocked by the spinner
4. Heat from the motor was a concern, being transferred directly to the mount
5. Motor mount glued in tension only, no shear connections.
My Dusty ejected the entire motor assembly, luckily after landing on the first flight – I needed a better solution.
Below are pictures of a modeled alternative. This allows the motor to be moved forward quite a bit, better CG. Allows you to use the X brace with the motor, isolating the heat from the print. The spinner has been more than halved, reducing inertia and balancing problems. Gives a small cooling inlet. The plane looks the same in the air, still has the appearance of the large spinner. Attached are the files if you are able to use them.
(In this and below thread)
All the best, Don10.8.18 at 23:11 #3667711.8.18 at 16:04 #36688
Nice work on the design! Will these modifications work on the original Dusty as well as the new update?
-Mike11.8.18 at 17:05 #36689
Hey, Mike. I can’t be sure what has been changed on the Dusty, I haven’t downloaded any changes from 3DLP since the original files. My guess is that it will. The webs on the back of the new motor mount will “clock” into the webs on the nose and by using an adhesive such as epoxy, will give quite a bit of shear strength to each.
I see that you are a moderator – perhaps you can tell me how to make the STL files available to the forum. When I try to upload an STL, “those types of files are not permitted for security reasons.” When I pack them in a zip file, “file is empty.”
I was able to have success with packing them in a 7zip file, but that may not be as convenient for some to unpack.
I’m a moderator on the “Water Rocket” forum – but I haven’t figured this problem out yet.
All the best, Don11.8.18 at 19:37 #36698
I have the original version and it’s been a hanger queen since I read all of the motor mount issues. I was thinking about making a slurry of epoxy to coat the interior of the nose but never got around to it. I’ll give your conversion a shot and let you know how it worked.
As for the U/L’s you need to zip up the files, they only allow .ZIP and .JPG file extensions. Most people have tools to unpack the ZIP files.
BTW- are we going to see the B-25 up here on the 3DLabGang site anytime soon? I did the Corsair F2G modifications and the P&W Radial, so far it’s working O.K. The hard part is doing the documentations and making sure you don’t miss anything or you’ll be answering a million questions.
-Mike11.8.18 at 20:59 #36700
Hey, Mike – yes, let me know how it works for you. I was able to get the files uploaded in a 7z file – I guess you found it.
I’ve had good luck printing spinners using this method – even a custom set for the P38 – I’ll upload them to another thread.
B-25? If someone said they were working on it, it wasn’t me that I can remember. Was working on a C-17, but that is a very long term project.
Found that my Dusty airframe was splitting at the joints just under the battery access, re-glue and added some uni-directional carbon rich bracing (Popsicle sticks) along both interior sides with epoxy. Out to flying field tonight to test.
All the best, Don12.8.18 at 04:59 #36704
Ah! Must be a different Don…here is the B-25 I was talking about. Thought it was you because of the CAD work you did on the mount.
https://www.rcgroups.com/forums/showpost.php?p=40060053&postcount=10515.8.18 at 21:56 #36797
the updated Dusty has all the issues solved. Spinner is strong enough, and the motor mount holds well. Also the landing gear has been addressed. It’s good to reinforce the motor mount with aluminium cross included with the motor to prevent damage in case the prop strikes the ground on taxiing.
I appreciate the work, but probably no need to reinvent anything here. Just download the updates.
Still I crashed Dusty on hard landing, as it’s a bit above my flying skills. Broke almost everything other than the things causing problems in first version 🙂
It’s a great attraction for kids however 🙂
Looking forward to another Gang projects!
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