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Lightweight carbon fibre dual 8" 18/36V BUILD

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Category: General
Forum Name: 12v Powered Systems
Forum Description: From Mini-rigs to ICE, all your low voltage audio needs here...
URL: https://forum.speakerplans.com/forum_posts.asp?TID=99352
Printed Date: 16 September 2019 at 7:43am
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Topic: Lightweight carbon fibre dual 8" 18/36V BUILD
Posted By: Keivn.Pawlus
Subject: Lightweight carbon fibre dual 8" 18/36V BUILD
Date Posted: 30 September 2017 at 9:43pm
Hello!  

I always found the problem with my battery-powered speakers is that they are to heavy and therefore barely get used. This time I will build one light-weight in carbon fibre.

http://forumbilder.se/G9KCU/20170930-142346 -

http://forumbilder.se/G9KCU/20170930-154539 -
http://forumbilder.se/G9KCU/20170930-180734 -
http://forumbilder.se/G9KCU/20170930-203641 -

I have some old Philips 8" drivers that I know sounds good in a sealed cabinet in this size. I will cut two holes for the tweeter also, but im not sure witsch tweeter yet. Or if anyone could recommend some sensitive 8" I¨ll be very happy to hear about it (maybe neodym?)  :) 

I¨m going to make a slot for two 18v 5ah Makita batteries on the back. The speaker will be powered with a TA2020 for now, and in the future maybe some 36v amplifier. But I need to do some more research on 36v amplifiers first. I must connect some diodes in serie with the battery to get the voltage down to something like 14v so I dont fry the TA2020, maybe not the most efficient solution.

First I build a template that I will make a mould of, so I can make it of carbon fibre later. I¨m aware that carbon does¨t have the best acoustic properties(similar to metal) , but if it will be light and used I¨m happy.

Lots and lots of sanding... OuchLOL



Replies:
Posted By: bitSmasher
Date Posted: 01 October 2017 at 1:46am
Nice concept- just yesterday I resolved myself to try an 18v powered TPA3116 using a Ryobi battery... need to hunt down old/broken tools to repurpose for the battery socket

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"Battery Acid Sound System" blog hopefully happening in 2017


Posted By: Hemisphere
Date Posted: 01 October 2017 at 7:40pm
Have I missed something in the images? I can see a square of something that looks like carbon fibre but the rest seems like wood. Or is it foamcore?

Edit: Oh, I see. it's a mould is it?

How are you planning to do the walls? Most of the fibreglass and carbon fibre cabinets I've seen recently have had an XPS foam core with a thin skin of glass or carbon on the surface. That gives the best strength to weight ratio and is also the cheapest way to do it. It's a challenge to get the structure looking neat in the end but the one I built sounds great and is light as a feather. Something like 9kg loaded with 2x12 and a CD+Horn.


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Phase 1: Post on Speakerplans
Phase 2: ?????
Phase 3: https://www.youtube.com/watch?v=3zc4bGkU05o" rel="nofollow - Profit!


Posted By: Keivn.Pawlus
Date Posted: 01 October 2017 at 9:23pm
Thanks, this is the first time I work with carbon. So I hope it goes well 

I think i will mill some rails for the battery out of some plastic. Do you know how long you could run the  TPA3116 with your Ryobi battery? 


Posted By: Keivn.Pawlus
Date Posted: 01 October 2017 at 9:29pm
Originally posted by Hemisphere Hemisphere wrote:

Have I missed something in the images? I can see a square of something that looks like carbon fibre but the rest seems like wood. Or is it foamcore?

Edit: Oh, I see. it's a mould is it?

How are you planning to do the walls? Most of the fibreglass and carbon fibre cabinets I've seen recently have had an XPS foam core with a thin skin of glass or carbon on the surface. That gives the best strength to weight ratio and is also the cheapest way to do it. It's a challenge to get the structure looking neat in the end but the one I built sounds great and is light as a feather. Something like 9kg loaded with 2x12 and a CD+Horn.

What you see is a mix of kevlar and carbon fibre. I have not started yet with the carbon fibre part, now I just build the mould. 

Wow, 9kg is neat Wink I will make the walls with 3-4 layers of carbon, then I will have 10mm foam and end up with a couple of layers on the inside.

I have decided to go with the Eighteensound 8NMB420 & Beyma CP 12/N now


Posted By: Keivn.Pawlus
Date Posted: 14 October 2017 at 10:28pm
Today I was finished with the "original" and I have now started to make a mould out of this in glassfibre.

I have also done some milling for the battery rails.


http://postimg.org/image/10d81lqlzf/ -

http://postimg.org/image/9h7ml98657/ -

http://postimg.org/image/874pexr9ez/ -

http://postimg.org/image/5fvn6v4xnf/ -

http://postimg.org/image/1sdc56js63/ -


Posted By: SouthwestCNC
Date Posted: 14 October 2017 at 10:39pm
Nice work! looks like your going to need to get your head inside it to lay it up


Posted By: Keivn.Pawlus
Date Posted: 14 October 2017 at 10:55pm
Originally posted by SouthwestCNC SouthwestCNC wrote:

Nice work! looks like your going to need to get your head inside it to lay it up

Thanks, yes probablyLOL  If it looks possible I think I will try with vacuum injection for an easier lay up


Posted By: Keivn.Pawlus
Date Posted: 15 October 2017 at 2:03pm
Now I've come this far. 

http://postimg.org/image/1s6ppv1fyz/ -

http://postimg.org/image/1vqbnkvszf/ -

http://postimg.org/image/35t8twfi0r/ -



Posted By: snowflake
Date Posted: 15 October 2017 at 2:22pm
weight for weight, is a carbon fibre panel actually any stiffer than a wooden one? the main advantage of carbon fibre is that you can easily make curved shapes that are inherently rigid. you can also do this by laminating thin ply but with fibreglass you can curve in two dimensions at once.


Posted By: davey t
Date Posted: 23 October 2017 at 1:17pm
exactly.. if you want to save weight and increase rigidity, you should make a sphere/cylinder/hemisphere etc. Or at least use curved panels. What you've made will require lots of bracing

Good work though... good work


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Minirig portable soundsystem movement


Posted By: Hemisphere
Date Posted: 29 October 2017 at 6:09pm
I notice you mention 10mm foam and 3/4 layers of carbon - you might want to reconsider this for future builds.

The science of layered glass/carbon and foam composite structures is that the rigidity is mostly determined by the thickness of the foam. I saw a chart which illustrated this once and it's a steep exponential curve. 20mm is several times stronger than 10mm despite costing and weighing almost the same. You could save a layer or two of carbon or comfortably substitute cheaper and easier to work with glass by using more substantial foam.

Also you probably want it to have as many layers inside as out or the panel flex will be uneven. 3 in 3 out would certainly be preferable to 2 in 4 out.

-------------
Phase 1: Post on Speakerplans
Phase 2: ?????
Phase 3: https://www.youtube.com/watch?v=3zc4bGkU05o" rel="nofollow - Profit!


Posted By: Keivn.Pawlus
Date Posted: 29 October 2017 at 8:16pm
Originally posted by Hemisphere Hemisphere wrote:

I notice you mention 10mm foam and 3/4 layers of carbon - you might want to reconsider this for future builds.

The science of layered glass/carbon and foam composite structures is that the rigidity is mostly determined by the thickness of the foam. I saw a chart which illustrated this once and it's a steep exponential curve. 20mm is several times stronger than 10mm despite costing and weighing almost the same. You could save a layer or two of carbon or comfortably substitute cheaper and easier to work with glass by using more substantial foam.

Also you probably want it to have as many layers inside as out or the panel flex will be uneven. 3 in 3 out would certainly be preferable to 2 in 4 out.

Thanks for the tip. When you say it, I think I have read it somewear also. 




Posted By: Keivn.Pawlus
Date Posted: 29 October 2017 at 8:27pm
Some problems did occur when i tried to release the mould. It was completely impossible to release.
I think the main reason for this was the shape of the mould, I ended up scrapping the whole project and started from the beginning again.

https://postimg.org/image/15myuztusr/ -

https://postimg.org/image/6klhdfaah7/ -

This time I will try with a 4-piece split mould instead of a 2-piece split. Also a different release agent this time. 

Thank you for all the comments so farSmile


Posted By: Hemisphere
Date Posted: 29 October 2017 at 9:57pm
Have you considered revising the design to a more simple hand layup with flat panels? There are some very well documented foam core builds on the TalkBass forums - the ZacLite builds especially, although many of the images are now dead links

People on diyaudio talk about foam core builds quite a bit as well but I didn't see any comprehensive documenting of the builds and theory behind it as on TalkBass.

I used 25mm foam and 2 layers of 185gsm glass on each side (plus a bit extra here and there and some bracing inside). Feels solid as a decent wooden cab to me and does the job on the sound, haven't measured it or a/b with a wooden equivalent though. That's woven roving of course not CSM. Ideally you can get an even tighter knit weave of glass cloth, e-glass it may be called. The tighter the weave the better and it'll always be way cheaper than carbon.

The process was messy and laborious and the finish tricky, but the guys on TalkBass did a much better job with similar results.

-------------
Phase 1: Post on Speakerplans
Phase 2: ?????
Phase 3: https://www.youtube.com/watch?v=3zc4bGkU05o" rel="nofollow - Profit!


Posted By: Hemisphere
Date Posted: 29 October 2017 at 10:16pm
Did you use mould release wax on the mould or something else to aid release? I'm not sure if this is a silly question or not as I know nothing about glass moulding

-------------
Phase 1: Post on Speakerplans
Phase 2: ?????
Phase 3: https://www.youtube.com/watch?v=3zc4bGkU05o" rel="nofollow - Profit!


Posted By: SouthwestCNC
Date Posted: 29 October 2017 at 10:24pm
Originally posted by Keivn.Pawlus Keivn.Pawlus wrote:

Some problems did occur when i tried to release the mould. It was completely impossible to release.
I think the main reason for this was the shape of the mould, I ended up scrapping the whole project and started from the beginning again.

https://postimg.org/image/15myuztusr/ - </a>

https://postimg.org/image/6klhdfaah7/ - </a>

This time I will try with a 4-piece split mould instead of a 2-piece split. Also a different release agent this time. 

Thank you for all the comments so farSmile



What product are you using to finish your mould in? A strene based product requires a week minimum to stop leaching before you try taking a pull from it. 10 coats of semi permanent release works a charm on new moulds. And compressed air and blower is your friend when it comes to release it.


Posted By: Keivn.Pawlus
Date Posted: 20 November 2017 at 7:56pm
Originally posted by Hemisphere Hemisphere wrote:

Did you use mould release wax on the mould or something else to aid release? I'm not sure if this is a silly question or not as I know nothing about glass moulding

Yes, the first time I used one coat PVA release agent. And I had to scrap it, it was impossible to remove.
I think the problem was caused by the shape of the mould and also the surface finish. So i'm not saying its a bad release but it didn't work for me.

Second time i used 6 coats of easycomposites Easy-Lease. It came of very easy Tongue The second time I also build an 4-piece split mould


Posted By: Keivn.Pawlus
Date Posted: 20 November 2017 at 7:58pm
Originally posted by SouthwestCNC SouthwestCNC wrote:

Originally posted by Keivn.Pawlus Keivn.Pawlus wrote:

Some problems did occur when i tried to release the mould. It was completely impossible to release.
I think the main reason for this was the shape of the mould, I ended up scrapping the whole project and started from the beginning again.

https://postimg.org/image/15myuztusr/ - </a>

https://postimg.org/image/6klhdfaah7/ - </a>

This time I will try with a 4-piece split mould instead of a 2-piece split. Also a different release agent this time. 

Thank you for all the comments so farSmile



What product are you using to finish your mould in? A strene based product requires a week minimum to stop leaching before you try taking a pull from it. 10 coats of semi permanent release works a charm on new moulds. And compressed air and blower is your friend when it comes to release it.

I used the complete"Uni-Mould Making System" from Easycomposites. Everything worked very well


Posted By: Keivn.Pawlus
Date Posted: 20 November 2017 at 8:01pm
This is the second attempt, everything has worked so far. Now I have some polishing to do before I can start with the carbon fibre.

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https://postimg.org/image/mmd0k3a8n/" rel="nofollow">

https://postimg.org/image/ba0f2attz/" rel="nofollow">

https://postimg.org/image/5ylihluwn/" rel="nofollow">

https://postimg.org/image/nbvswgxxj/" rel="nofollow">

https://postimg.org/image/592q599sn/" rel="nofollow">



Posted By: Keivn.Pawlus
Date Posted: 01 August 2019 at 7:28pm
After two years I¨m almost finished. This project had taken far more time than I first though.
I also learned that carbon fibre is very hard work with. Right now ïm waiting on two coils that I have ordered and hopefully I will have them tomorrow. Then i can build the crossover








Posted By: Keivn.Pawlus
Date Posted: 12 August 2019 at 8:06pm

The only thing left now is the grill.






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