Marui Big Bear tires - let's CAD :)

[Dadio]

Your absolutely right to go this direction with tires , 3d printed tires will always look wrong with current tech or be the wrong type of material , the best results I've seen were resin but from my own resin printer experience the material is still not good for tires .
Resin printing the moulds might be a good idea .

[silvertriple]

After yesterday's various discussions I had with different people, I reviewed the mold.

First, I modified the centering cone.


The idea is to put the compound in the exernal mould, and then add the centering part inside, ideally with pressure.


No change in the principle to assemble the two halves after removal of the center parts of the moulds


After that I rethought the FDM printing topic. Main issue to print something without support is to remove all overhangs or to reduce them under a certain threeshold. I thought about printing the tires in halves, and to glue them after wards. I integrated the sleeves and used them to remove most of the overhangs of the side wall. I believe Chevron could print easily, as long as the mid plane of the tire is the printing bed. I have created the files for the two sides...




Still thinking about possible improvements (have many ideas flowing to my mind currently )

[silvertriple]

Someone sent me this video
https://www.youtube.com/watch?v=JMbaM7q9YaQ

I may need to rethink my mould to allow injection the way it is presnted in this video. For this I believe I must close the mould, and have some holes at the top level to allow the end of the process.
The injection hole must go thru the cone, and the cone would be a separate part, or 2 parts, fixed by the central part...

Need to think about it, but is looks like it is possible to do something

[Dadio]

I've watched a load of similar videos and they all use vacuum pumps , I keep thinking I really need one .

[silvertriple]

I've watched a load of similar videos and they all use vacuum pumps , I keep thinking I really need one .

Sorry if I reminded you this

[silvertriple]

Those tires are running in my brain the whole night... On one side, I can see there is a lot of people awaiting for this.

First action this morning was to contact the guy from the video to get some details on how he was avoiding air to be captured in the his tire mould. There should be a way.. I also contacted a small company here in France. they are doing some vintage tires for 1/8. They are in holidays currently, they messaged me back they thank me for the message and they would contact me as soon as they are back from vacations... I believe they are not far, so I could eventually visit them to get more information on how to proceed and eventually more.

For those reasons, I decided to hold on the publications of the files on Thingiverse for the time being:
- I want to get the things right. It means getting additional feedback and informations from experienced people in the matter, even if it is for DYI mode
- if I can find an opportunity to have people doing tires for us, that would be super great news

At the end, be patient, my goal is still to provide a solution or a set of solutions for Big Bear fans...

[silvertriple]

Quick update. I'll put the Big Bear tire on the side for the moment. I need to do some testing. For this, I'll need a smaller tire. The main reason for this is that the Big Bear tire is big and that may lead to lot of spoiled material and desillusions even before having it right. I choose to work on another tire, smaller, and which I need for 2 cars. I have already the model done, added some lettering, and will proceed to build a mould, so I can experiment at some point.

I have a vacuum machine somewhere. I will have to find some pipes, accessories, silicon and pigments and to order some resin prints once the model is done... It put the Big Bear tire on hold for some times, but I'll come back on this later on.

[Dadio]

Mark , I have a resin printer , if it would help I could print a split tire that could be used to make a mould , my printer is too small to make the mould but a regular tire should fit , just a thought , you may have someone more local .

[silvertriple]

Mark , I have a resin printer , if it would help I could print a split tire that could be used to make a mould , my printer is too small to make the mould but a regular tire should fit , just a thought , you may have someone more local .

I take note of this. But when saying I'm thinking about a smaller tire, I'm exploring the model of the Shogun tire. I have the CAD model, I added lettering on it already, and i'm trying to work out a mold for it, their is multiple difficulties I can envision ;
1. the injection path : this needs to go thru the mold assembly plans as it requires to be easy to unmould. I'm thinking top center to bottom ring in 3 or 4 injection points in the bottom ring, assuming the mould would be fit flat with the tire flat in it.
2. internals : the center mould needs to be done in a way that it is removable from the center. to be clear I have no idea how much what I'm going to mould is flexible so I need to find a way to get this easy to remove. I'm thinking about a puzzle. I need to find a way to get this properly positioned (centered) and the parts being attached together when we mount the mould and easy to detach and remove once we have pourred the tire in...
3. I was thinking about priting the mould in resin in mutiple parts, so we can put release agent on top of all the parts so the pourred material is easy to detach... and since there is a few things to order, it would take time to get there in any case. In the meantime, I may simply order resin stl prints online...

I like challenges, but I think my brain is melting now . And what I need right now is actually my brain more than anything . Maybe that is the right time to pull on of the kits under my desk and to build it.

If you have any ideas, they are always valuable and will fuel my own, so don't hesitate to chime in

[Dadio]

Mark nobody here would dream of stopping you build another kit , its primary behaviour

[silvertriple]

Mark nobody here would dream of stopping you build another kit , its primary behaviour

Did something else, as I could not decide which build to start . And since we have a new car at home, I went for a ride. Not sure how much cells the battery have, but the Peugeot e208 GT is like a kart
Once back I review the Big Bear tire half moulds to include a 3 parts central injector... I'll show some pics later on . Moulding tire half parts is quite easy, in fact. There is one thing which I was not able to solve yet : how to make a center mould for a complete tire. It does need to be in multiple parts so it can be removable, and that's tricky...

[silvertriple]

As I said, Yesterday, I refreshed the melting brain and the cooling had some effect again...
I did reworked the mould


I designed a 3 parts center piece that serves the purpose of the injection, and allows to spread the injected material into the ring.



And this morning, while finalising this, I was thinking again to the next problem : assembly of the two halves.
For this, I believe the best way is to extend the surface where there is contact between the two parts is the way to go. and as well, I thought there could be a way to make it in order to ease the assembly.


I decided to remove a ring of a millimeter thickness and few millimeter deep and add it on the other side. I required to make the side mold rather différent...

After some work, I have completed a mould for each side.



Now that looks cool already. I'll add some marking on each distinct part to allow this to work and avoid user mistakes.

And over the last two days, I contacted many people to get feedback and to see if there is opportunities to use those tires CAD model to decline real tires, in a very vintage way... With all those bottles I launched around, maybe one will have an idea to do something about this... I'll publish the files by early September the latest: I need to do some research first on the material to use, and will include this. THat means time without CAD, without building and just research... Time will come

[Frankentruck]

One thing to determine is if the tire material requires a higher temperature that the mold can handle.

[silvertriple]

One thing to determine is if the tire material requires a higher temperature that the mold can handle.

i've done some research for this: Formlabs pitch their Resin10K has being having a heat deflection temp around 220°C, and they announced in their webinar about injection molding it is suitable to build more than 100+ parts with materials injected under 250°C. And i was initially thinking about DYI injection, so no heating but curing time... Overal, that even open more possibilities than what I had initially in mind...

[silvertriple]

Update the design to make sure each part is properly marked with the useful information...



There is 2 elements still in my todo list for this CAD design:
- include tolerances for assembly. At this stage there is none in the design. Normally, to get the assembly air tight, one should used fine sand paper to make it nice and smooth. But I may want to add a tenth of millimeter between all assembly plans so it's not required.
- I want to inludes some elements to ease mold separation.

During this last night, it was a bit hold, I have a bad sleep, a lot of thoughts again, and I may have an idea on how to proceed for a smaller tire to get it injected in once... Need to work in CAD for that... See you in NInja/Coors/Shogun thread