My BTTF Inspired Bag V2 Page 4

Damn, that sucks losing 5kg of rubber.
Yep, there was a sigificant amount of swearing. And here is the picture. This was full the lowest part of the wall, then it oozed out on the left.

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Hi, any news about price or when are you starting to deliver ?

Not really. The new mold has fixed the issues I was having from the last mold. So I am starting to make end caps now.

The body is being a right PITA but I am getting there.

I still need more silicone to make more parts.

I am also experimenting with adding fibre glass to the parts. This makes the parts lighter and stronger.
 
I think I have got the bugs out of the end cap mold. This part came out near perfect and almost no flashing to trim.
Just need 59 more just like that. https://uploads.tapatalk-cdn.com/20171222/b4eff8fbdf355049bbd0ade7374d38f8.jpg

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Finally decided to do more work on this today.

I realized that I really hate making mold walls, so given this part was round, I just used a big bucket.

This is the part needed to hold the body in shape and to allow it to be attached to the end cap.
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Finally decided to do more work on this today.

I realized that I really hate making mold walls, so given this part was round, I just used a big bucket.

This is the part needed to hold the body in shape and to allow it to be attached to the end cap. https://uploads.tapatalk-cdn.com/20180201/896b3fe9d3a426b4d5e6689d23873f34.jpghttps://uploads.tapatalk-cdn.com/20180201/13c0afd107009f53429a6d276183c199.jpghttps://uploads.tapatalk-cdn.com/20180201/a36fbc47dbef073e843ab3907280b570.jpg

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So yesterday was hot, like 35 degrees C. The silicone I use is normally 6 hour cure time and when it is hot like yesterday, it can cure in half that time.

Today however was cool to cold and rainy, so the cure time was extended to almost 10 hours for this part.

Another mold done and another step closer to the end result.
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What is the main tube going to be made of?

The same black epoxy resin but I am currently experimenting with fibre glass woven matting to keep the weight down and up the tensile strength. The part I made two days ago is extremely light and won't crack like earlier test parts have done.
 
This project has been taking ages because it seems that for every step forward, something forces me to rethink and start again.

Today I went back to a guy I would consider very knowledgeable about all things fibre glass. What I like about this guy is he wants to know what I want to do so he can work out what would be the best course of action and not just sell me product.

I have been working on the body of this bag for a while and am getting stronger and lighters parts. The other day I made a part that was ultra light, but it flexed. I had wondered if rotating the woven mat to say 45 degrees in one layer would help. Well today he listened to what I had done and then showed me this product. See image.

This is a woven mat that is more like a hybrid between chopped strand and woven mat and then is stitched to prevent freying. Notice the grain runs at 45 degrees to the stitching. So he told me that if I make my first layer from the woven mat as normal, then add a layer of this, then a 3rd layer using the woven matting, that I will get strong and light weight parts.

We also spoke about adding chopped mat strands to the cast parts which will also reduce the amount of resin bring used and also lighten those parts as well as making them strong.

Progress at last.
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So I am doing a test run on the body using this new fibre glass mat.

Not sure how this is going to turn out as I really can't fibre glass for sh1t.

Given I now have the new spacer mold done, I was thinking about going back to 1.4mm polypropylene. PP is a slippery plastic, light and can take a knock. It can also be transformed. Also whist most glues won't stick to it, the epoxy I am using does.

Stay tuned...
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I know you've been wanting to produce a bag that can live up to the beatings of daily use, but do you think people will want to do that? I might just be speaking for myself, but I'm going to keep mine on display only. Just a thought if you're beating yourself up (bad pun) about getting the material right.
 
I know you've been wanting to produce a bag that can live up to the beatings of daily use, but do you think people will want to do that? I might just be speaking for myself, but I'm going to keep mine on display only. Just a thought if you're beating yourself up (bad pun) about getting the material right.
I understand where you are coming from, but I just want to make something better than a cardboard tube.

My early version PVC pipe is just too heavy and so I am now testing thermoforming polypropylene.

First test looks promising.
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Female tool for the vacuum form. I won't be vacuum forming, rather thermoforming. Hopefully I will find the correct silicone sheet. I don't want to vacuum form where the plastic is stretched. The method I want to use allows precut parts to be formed and therefore each part remains the same thickness as it was prior to heating. Traditional vacuum forming stretches the plastic making it thin.

I am using the largest diameter rolled aluminum part and a mix of sand and epoxy to back it up. I still need to fill the back all the way up. I decided to half fill each side to see how much resin I need and not to over do it in case of thermal shock that can crack epoxy.

Epoxy sticks to itself really good so there is no issue of the part breaking later on. Also it will fuse to the MDF and probably will never break away from the form either.

The neat part about building tools this way is that they can stack. Male tools (bucks) have to be stored away so they don't get damaged.

This diameter is the correct one for the lids. To make smaller diameter parts like the body, I have rubber insert sheets that can lay inside to reduce the size by a known amount.

I am hoping that I can make a buck of the handle recess that can sit inside of the main form. Then the handle recess can be part of the lid and not glued on later.
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And this how you make a vacuum forming tool. This is an 3mm aluminum skin backed up with epoxy and sand in an MDF form. The aluminum helps disapate heat and the epoxy and sand mix is pretty like concrete without the weight. I could have used hydrocal I suppose but expoy sets up in hours not days.

I was thinking that there needs to be two small holes drilled at 45 degrees at the very edge of the aluminium. As it stands, under suction greater than 6"Hg, MDF is porus so vent holed are not needed given I will be using my vacuum pump, not some shop vacuum cleaner to make my vacuum pulls.

Still have not found a silicone sheet and I have heard the 1m square I need is going to cost me about $300, so I might just be better off pouring my own, about 5mm thick. Even though the form is 800mm square, I need a metre so I have rubber to wrap around the frame and that is secured by aluminum angle, some tee nuts and, well I still need to think more on that.

The top plate of the vacuum chamber is 6mm steel and the tool sits just below that. So silicone mat should make a good seal.
For those that don't know, the sheet provides the seal and stretches over, or into in my case, the tool helping form the heated plastic. This way the plastic is not stretched and made thinner. It also reduced waste as the parts can be precut and don't need trimming later on.

Also looking at gas for heating.
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