2008 CRF250R - QS138v3 70H - ANT - Sanyo UR18650-RX 20s20p - Votol EM260

[jkrienert]

I might have missed something ... What's the light tan material you've (?) heat formed over the frame? Whatever it is, it looks like a fun experiment and possibly novel solution.

Speaking of in place molding... you can make fantastically (almost too much) detailed molds with 100% silicone mixed ~20:1 (highly variable ratio) with acrilic paint. Clear silicone and bright color paint helps you know it's mixed. The paint is the catalyst and it will cure in about an hour. You might have to make a mother mold to support the part you'll be casting after the cure if its big in order to maintain geo. Hard part is getting the material to stick to the part once mixed. I found lightly soapy (generic blue dish soap surfactant) water 1:10 over the part to be molded breaks surface tension, and then using the same soapy water mix on your hand as a lubricant to press the loose silicone mixture like loose clay onto the part and into crevasses is important. Using a liberal amounts of silicone (cross sections thickness) helps resist my biggest encountered negative of the method, shrinking post cure.

Honestly though, I've not used this method on anything greater than a couple hundred sqr cm. It might not work as well for larger parts, but your last post gave me a convergent sense of sharing like means. It's like RTV mold making, without the benefits of pourability, yet with the benefit of being able to get the materials needed easily (my local rural dollar store sells 100% silicone for windows/bath and acrilic craft paint).

Much smaller scale and totally different application, yet some context on the results with the method. Chocolate trilobites

EDIT: hopefully this reference of the method isn't too far off topic. If so please let me know and I'll modify.

 

[amberwolf]

Speaking of in place molding... you can make fantastically (almost too much) detailed molds with 100% silicone mixed ~20:1 (highly variable ratio) with acrilic paint.

Do you mean RTV type silicone, like GE Type I acetic-acid-cure? (the water in the acrylic would help the silicone cure faster).

Or is it like GE Type II? (which I think is ammonia-methanol-cure; I don't think the water would help curing this type and might inhibit it?)

Or do you mean just using one part of a two-part platinum-cure type (platsil, like the stuff I use from Reynolds) with the acrylic providing the other part? (if so, i'm curious how that would work)

You might have to make a mother mold to support the part you'll be casting after the cure if its big in order to maintain geo.

Plaster works well for that. You can use plastic strips cut from milk jugs or shampoo bottles (HDPE) as dividers between the sections of plaster to make them easier to separate. A couple layers of paper or one of thin corrugated cardboard works too but it will bond to the plaster and make the edges messier to separate.

Hard part is getting the material to stick to the part once mixed. I found lightly soapy (generic blue dish soap surfactant) water 1:10 over the part to be molded breaks surface tension, and then using the same soapy water mix on your hand as a lubricant to press the loose silicone mixture like loose clay onto the part and into crevasses is important.

Just make sure whatever you use doesn't have any sulfur compounds in it, as that can inhibit silicone cure (definitely does for platsil, and can even for acetic-cure).

I recommend using silicone cooking spatulas like these

for application and spreading; it's usually possible to peel the cured silicone off of it and you don't have to use release agents on the spatulas (which then get mixed in to the silicone and can cause curing problems on and near the surface or anywhere else they end up).

 

[bananu7]

I might have missed something ... What's the light tan material you've (?) heat formed over the frame? Whatever it is, it looks like a fun experiment and possibly novel solution.

Calibrated sheet wax.: High Temperature Sheet Wax for Moulding - Easy Composites Not really novel at all, it's used to form a barrier but also create a consistent offset over the part. EC has presented this over 4 years ago, and I used their method:

I've made a mistake over the subframe bolt and didn't heat the wax enough, which caused it to crack. I've fixed it a bit with filleting wax, but it still caused a wavy surface. The mold is now off and fully cured, so I can try sanding it off even; i put a thick gelcoat layer so i should have plenty of thickness to work with.

 

[jkrienert]

acetic-acid-cure? (the water in the acrylic would help the silicone cure faster).

That's the type and desired reaction!

Plaster works well for that. You can use plastic strips cut from milk jugs or shampoo bottles (HDPE) as dividers between the sections of plaster to make them easier to separate.

Nice elaboration of my terse recommendation, and cleverly suggested material. You can layup burlap (or any saturated natural cloth) strips in the wet plaster for strengthening the mold.

Not really novel ...

New to me I suppose. I'd not heard of that material method before. It looks really useful, and great hearing it's already served you success. I'll definitely look into using that method on future projects.

Hope I didn't distract the thread too much.

Nice progress @bananu7 !

 

[bananu7]

Hope I didn't distract the thread too much.

No worries; I chose to go down the path of making all of those parts after the initial success of the battery box, and have been binging educational materials and soaking up all of the knowledge i can since. I have also procured a sizeable collection of mould-making and part-making supplies, so hopefully we'll soon see real carbon fiber on the CRF. So all in all I welcome all composite-related discussions here; after all, the thread from the other side of the Baltic Sea is fairly similar

So, here's the proof the bike survived:


And the mould after rough cleaning:


I really like the green gelcoat. It definitely feels like a premium product, even though it's a tooling solution. It cured into a satin (from the wax), rock-hard finish, which is very stable on its own. I want my protector to be mirror-finished, so will be polishing it to gloss anyway.

I've also been working on the oven in the meantime, as it still doesn't have a door. I've designed a hinge for it which my colleague has helpfully drawn:



It's going to be a parallelogram construction with a large hinge set made of wood. I have already cut up the material, just need to machine a set of 8 brass bushings that the hinges will slide on.

 

[jkrienert]

parallelogram

Like the type used in some astronomy mounts?

 

[bananu7]

Like the type used in some astronomy mounts?

Four-bar linkage - Wikipedia

en.wikipedia.org

 

[jkrienert]

@bananu7 good gosh - knowledge drop. Thanks for sharing this engineering method.

I was pondering this design with similar geometries, though the function is outright different.

https://www.cloudynights.com/topic/666240-diy-parallelogram-mount-designs/