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Making Tires with 3D Printed Molds

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Making Tires with 3D Printed Molds

Old 08-07-2022, 07:43 AM
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But first, lets see if I can start where it left off.
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Old 08-07-2022, 12:28 PM
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Oof, been there. Good luck on your second try.

I got my mold "seasoned" and successfully cast two tires using Vytaflex 60.




I'm completely beside myself. They glued up just fine and don't seem to have any more wobbles or vibrations than any of my other tires. They're faster around my basement track than my old red Losi x3000's, but not as fast as my green JC double dee v2's. They're about 3g lighter than a set of unmounted green bar codes I have.

Overall I would consider this an overwhelming success. I feel much more comfortable spending more time and importantly money on this.

The Vytaflex 60 is noticably firmer compound than the JC Green rubber which explains why my tires were slower around my track. Smooth-On has an additive you can mix in to your resin that softens the cured rubber. I'm going to buy that so I can experiment with different shore ratings.

Gosh, I'm so excited this has worked as well as it has! There are so many things I want to try now - different tread patterns, thinner tire carcasses lighter tires, I can even go crazy with florescent colored tires!
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Old 08-08-2022, 12:15 PM
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Originally Posted by RC10Nick
Oof, been there. Good luck on your second try.

I got my mold "seasoned" and successfully cast two tires using Vytaflex 60.




I'm completely beside myself. They glued up just fine and don't seem to have any more wobbles or vibrations than any of my other tires. They're faster around my basement track than my old red Losi x3000's, but not as fast as my green JC double dee v2's. They're about 3g lighter than a set of unmounted green bar codes I have.

Overall I would consider this an overwhelming success. I feel much more comfortable spending more time and importantly money on this.

The Vytaflex 60 is noticably firmer compound than the JC Green rubber which explains why my tires were slower around my track. Smooth-On has an additive you can mix in to your resin that softens the cured rubber. I'm going to buy that so I can experiment with different shore ratings.

Gosh, I'm so excited this has worked as well as it has! There are so many things I want to try now - different tread patterns, thinner tire carcasses lighter tires, I can even go crazy with florescent colored tires!
Those tires look really good! I might have a new project to do over the winter hahah
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Old 08-10-2022, 11:06 AM
  #34  
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A white tire - because why not? But also because I ran out of black pigment and didn't want to wait.



My Smooth-On order with the So-Flex II showed up yesterday so I went to work right away casting another tire. I mixed the So-Flex II at 10% by total resin weight into the Vytaflex 60 (30g Part A, 30g Part B, 6g So-Flex II). According to Smooth-On's tables that mixture should result in a 47A rubber. As expected, this tire feels softer and stretches more than the 60A tires. It's close enough to the JC green rubber at this point that I can't tell by hand which one is harder or softer.

Unfortunately it looks like I've run out of luck when it comes to casting these without a pressure pot. The first two tires I made do have some air bubble issues but I got lucky in that they weren't too big or in a really bad spot on the tire. This time, though, the tire is a complete loss. Fortunately I know based on my experience with the mini-b tires that a pressure pot should completely eliminate these problems so that will be the next investment.
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Old 08-10-2022, 02:02 PM
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absolutely awesome Nick!
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Old 08-12-2022, 05:41 AM
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I started working on upgrading my pressure pot setup. I ran out to harbor freight on Wednesday night to grab one of these and on Thursday I ran out to the local hardware store over my lunch break so I could pick up some brass fittings to convert it to a pressure pot for casting. There's plenty of videos on youtube showing what to do. I plan on using my small airbrush compressor since it's the only compressor I own and it's worked fine so far with my small DIY pressure pot. Unfortunately the airbrush compressor hose doesn't work with the NPT fittings I bought at the hardware store so no I have to wait until Wednesday for a special BSP to NPT fitting to show up.

In the meantime I decided to record myself running a few laps on my basement track using the first two tires I cast. Check it out!

+ YouTube Video
ERROR: If you can see this, then YouTube is down or you don't have Flash installed.
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Last edited by RC10Nick; 08-12-2022 at 06:13 AM.
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Old 08-16-2022, 12:51 AM
  #37  
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hi
Nice work. I'm trying to reproduce vintage tires I modeled in CAD (Fusion360), and my researchs brought me here...

(this is the complete Tokyo Marui tire collection in CAD).
I initially thought about MJF Rubber like printing, but the cost estimation are maing this completely unrealistic, and further, I believe the shore would be too high for actual usage (maybe for shelfers this would work). In other words, I started to search about molding, found your videos, and then this forum entry.
I'm scratching my head on the way to mould those complex tires, knowing I have absolutely no experience in casting. Your videos were already great indications, and I'm considering 40A to 60A as shore target.

The issues I can think of are:
  • what is the proper wall thickness to consider for the tires depending on the shore?
  • Mould orientation : I understand the resin should enter on the bottom side and get to the upper side, and I should manage vents on the top of my mould.
  • Should I add vents or air cavity for each of the spikes? And if I'm doing this what about the unmoulding?
  • Center mould : how the cured flexible resin is elastic : is this elastic enough so the center can be extracted in one single part? If I don't take any consideration for the elasticity of the resin, I calculated that the center mould should be made with 3 floor of 8 parts each and a center key to hold that up: probably not optimal
I would be very interested by your feedback on those few question f you can take a few minutes

Thanks,
Marc
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Last edited by silvertriple; 08-16-2022 at 02:41 AM.
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Old 08-16-2022, 05:06 AM
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Hi Marc, nice looking models! To answer your questions:

Tire/Wall Thickness - so far I have been basing my designs on existing tires. I took some old worn out tires, cut them up, and took measurements of all the parameters I needed to make a model. So far I haven't had any issues with tire failures, though I'm only in the early stages of larger 1/10 tires and I'm only running a 17.5 motor. The softer 47A white tire I cast is still pretty tough despite its lower shore rating - I tried my best to rip it by hand and couldn't so I think at this point if you replicate an existing tire you shouldn't have any issues with material failures. For reference, my 1/10 tire carcass is designed to be 1.75mm thick and my 1/16 tires are 1.3mm thick.

Treads/spikes - I personally don't think adding vents to every tread/spike is the answer. I tried to think about how real tire manufacturers prevent air bubbles in their treads and the best I could come up with is the injection molding processes they use are likely at such high pressure that any air bubbles get crushed into nothing and eliminates the problem. The closest we can get to that kind of process is putting the mold into a pressure pot to cure, and that's what I've been doing with my small 1/16 tires. It has so far worked really well - I get no air bubbles in the treads doing that. Without the pressure pot all of my tread pins have air bubbles. I'd say it's a critical piece of equipment for making treaded tires. However I have yet to do it with a 1/10 tire as I don't have a large enough pressure pot set up yet, but I will in a few days.

Center mold - so far the cured rubber has been stretchy enough that I have no problems de-molding the tires from the single piece mold center.

I hope this clears up things for you. Let me know if you have any other questions and I'll be happy to do my best answering them. Good luck!
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Old 08-16-2022, 05:35 AM
  #39  
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Hi Nick,

Thanks for this valuable piece of knowledge you share, this will be useful for me :-). I'm not exactly new at 3D printing (my profile on thingiverse is silvertriple), but casting will be for sure totally new experience for me, so your hints are very valuable!.
Thinking about this for a few weeks, I've done a lot of searchs and so far, this thread and the videos you shard on youtube are probably the most encouraging elements I had seen in my journey.

Initially I started to work on Marui Big Bear tires, but it appear they are too big to do tries (I've been up to a point where I designed a full set of moulds for halve parts, I believe the rim size may be too small to extract the center mould part). And I would have no clue on gluing the halves together...



Ultimately, I decided to start with smaller tires...

And to react to your comments about air bubbles, talking about pressured injection, I've done some search as well, and identified one maker in France doing a manual injection press (you can search for Holipress from Holimaker), but the price of the equipment is still out of reach for most of DYIers... I've contacted them to understand if one of their press was available in one Fablab nearby my place so I can do my own experiments. I also identified resins from Formlabs (Resin10K) that is pitched to work with high temps for moulding (more than 100 parts with temps of injected material below 250C and 10 parts for material injected above 250C). I do not have a resin printer yet, but I may have finally to consider this anyway...

I'll give update when I progress on this...
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Old 08-19-2022, 02:29 AM
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Yesterday, i met the people of Loisirs Creation RC. They are a very small french company, and they put on the market vintage 1/8 buggy tires for 50mm wheels last year. They are doing things with a real passion, and they are really nice people, and I spent the day with them to discuss my ideas and learn about making tires (you can find their products on ebay : loisirscreations2009).

The discussion again confirmed some of the things I had in mind: I need to rework my moulds to get this done with urethane resin... And from the discussion I learned some tricks about how the real mould is done and how the the tires are done with a injection press. I won't have access to this, but from both this and the discussion and the discussion in this thread, I know how to move forward...
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Old 08-19-2022, 04:16 AM
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Wow, that's a great opportunity! I'd love to be able to pick the brain of someone who does this kind of stuff for a living. Any tips or info you picked up that you could share?
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Old 08-19-2022, 04:55 AM
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Had a chance to see how the mould is done and how the rubber flow goes : the rubber goes by the top and there is a flange of rubber around the ring when the tire is unmoulded: that flange is used for capture of the aire and also to ease the unmoulding : there is inside the core of the mould a one way tube that is used to send compressed air into the tire to remove it from the core. On the principle it is quite easy. The pressure from the injection press is quite high. But with urethane resin, this should work as well with a bit of pressure. They suggested to heat the resin to ease the flow as well.
That was a great day with them. They also looked at what i'm doing and they get some ideas they never thought about... Not sure it will drive to something at their end, but for me, that was a very nice learning day...

And to be honest, when I contacted them, I did not even thought it could be that helpful: many people doing this as business won't explain or show what they are doing, let alone listen from some random guy contacting them with some ideas he want to explore and the request to meet them to learn something...
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Old 08-22-2022, 03:05 PM
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SUCCESS!



It's been a minute since my last progress update. Brass fittings... man I hate those things. Without getting into the weeds of my struggles with fittings and the follies of trying to connect a rinky dinky airbrush compressor to industrial equipment, I finally managed to get everything to work. I now have a working pressure pot big enough for 1/10 tires. Here's the setup. The small airbrush compressor takes a few minutes to get the pot up to 30psi, but it works!



And obviously I bought a new pigment to play with. I settled on blue because I thought that would work best with my cars and my paintjobs and I was inspired by the Losi Spec Racer tires. I love the way it pops against neon yellow!



The tire has only very minor air bubbles in one spot on the mounting bead, but nowhere else. All treads are fully formed with no air bubbles, and the internal webbing looks great, too. I was so excited to make a tire last night I forgot to use the So-Flex, so this is straight Vytaflex 60A rubber.

As for what's next, I'm going to cast two more tires to try to use on an outdoor dirt track. I'll also want to modify the design and print out a new mold. I want to make some quality of life improvements to the mold and the tire OD is too big by about 5mm. I didn't account for the insert stretching out the rubber when I first designed the tire carcass so the finished tire is about 4mm too big compared to my JC double dee's.
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Old 08-22-2022, 03:48 PM
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That blue is giving me flash backs of the Losi Spec class tires from like 1993..LOL
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Old 08-26-2022, 07:00 PM
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Another update tonight:



I now have two blue ~40A tires. I glued them up and gave them a test spin on my basement track. I think I can safely say they grip more than anything else I've ran on bare concrete including the JC green DDv2's. However, they're a bit squirmy due to the tall profile, and they also balloon slightly more than the JC's.

I wanted to make these tires a little softer than the white tire I made previously. The white tire continued to cure over a few days and now feels slightly firmer than the JC green compound. I mixed these tires up using the same 60g of Vytaflex 60 but with 9.7g of the So-Flex II. According to the simple linear regression I calculated using the 4 data points Smooth-On provided, that should result in approximately a 40A shore rating. This is definitely bordering on too soft. I can tear off individual tread pins by hand and the increased ballooning I've noticed may be a problem with mod motors. I'll give them a few more days and see if they cure any further, and going to a lower tire profile with a closed cell insert may help as well.

Also, and this might not come across too well in the picture, but the tires are two very slightly different shades of blue. I thought this might be an issue and turned out I was right, though it's easy enough to prevent in the future.
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