tha'ts me...measure measure measure measure measure cut/build/etc and still messed up by some margin (usualy large, some angle and distance off..I can use a T-swequare to cut along and end up with a W.
).
2008 CRF250R - QS138v3 70H - ANT - Sanyo UR18650-RX 20s20p - Votol EM260
- Thread starter bananu7
- Start date
).
It's -3C outside, so you know what it is - a perfect day for working in an unheated garage. I've 3d-printed the rear spacers and they seem to fit fine, so I have a bit more confidence with making them out of metal now. Unfortunately, I couldn't verify the fit 100% because I found another gremlin. The previous owner of the bike probably didn't have a proper swingarm nut and forced a metric one, while the original has fine thread - so now I need a new swingarm pivot too.
On the positive note, the motor seems positively rigid in the mounts, and reasonably straight. The irony is that without the swingarm rigidly in place I can't really check the chainline properly. Maybe I'll hold off with machining those until I get the new pivot...
On the battery front, things are progressing as well. I wanted to use the "duct tape cardboard to the edges" method I saw jbjork do, but at first I used wrong, thick tape, it didn't stick at all and overall made a mess of the mold, ripping some filler out. I thought i might have to scrap it, but a quick trip to the store for some cheapest, thinnest packing tape actually got me this:
I hope that the ridge formed by the cardboard will form a ridge in the final part allowing it to rest on the edge of the box.
I have to say that this form of making molds, with the filler over foam, is pretty meh overall. Maybe I have the wrong filler, but it seems like it's a never-ending job of sanding, fixing, adding more... I wish I could just CNC out a perfect shape. Maybe I'll try 3d-printing cross sections next time.
Either way, a couple more wax coats and it'll be ready for laminating, and that should allow me to progress with the internal connections.
I worked at a life size natural diorama company a few years ago, and a few (of the many) ways we minimized post layup fab work was...
-only use glass containing materials for the final part, e.g. make the base sculpt (mother mold) out of regular old clay, then coat with silver leaf (aluminum foil) and apply liberal release agent (cheap bar soap) before glass layup (laminations).
-extend all lamination edges beyond the end result, then cutoff for a clean edge without having to dust sand as much using a hard utility knife when the layup is still 'kicking' (towards end of exothermic phase of the curing process), e.g. while still pliable.
-figure out clever ways of making mother molds that maintained exterior and interior pressure on a layup, such as bladders, like an old tire inner tube pumped up. Or depending on the build, use a large contractor bag, spray inside with silicone release, and place part inside for a method of vacuum forming. In both cases the goal being minimize bubbles and maximize density of layup laminations or gel coat/filler.
I don't know the tolerance, but if your lip seat doesn't quite work on first pull, could add a bit more material along the edge of either part for improving. Maybe that's with more glass or a u-channel silicone gasket seal? Perhaps you can even rig up something that protects the other part, then with a liberal release agent base, mold this part in place to assure fit?
Your idea of 3d printing cross sections and arranging them like a fence diagram, then running a glass layup over that, is brilliant! I've done that with paper cutouts but 3d print would probably have much better tolerance control.
-only use glass containing materials for the final part, e.g. make the base sculpt (mother mold) out of regular old clay, then coat with silver leaf (aluminum foil) and apply liberal release agent (cheap bar soap) before glass layup (laminations).
-extend all lamination edges beyond the end result, then cutoff for a clean edge without having to dust sand as much using a hard utility knife when the layup is still 'kicking' (towards end of exothermic phase of the curing process), e.g. while still pliable.
-figure out clever ways of making mother molds that maintained exterior and interior pressure on a layup, such as bladders, like an old tire inner tube pumped up. Or depending on the build, use a large contractor bag, spray inside with silicone release, and place part inside for a method of vacuum forming. In both cases the goal being minimize bubbles and maximize density of layup laminations or gel coat/filler.
I don't know the tolerance, but if your lip seat doesn't quite work on first pull, could add a bit more material along the edge of either part for improving. Maybe that's with more glass or a u-channel silicone gasket seal? Perhaps you can even rig up something that protects the other part, then with a liberal release agent base, mold this part in place to assure fit?
Your idea of 3d printing cross sections and arranging them like a fence diagram, then running a glass layup over that, is brilliant! I've done that with paper cutouts but 3d print would probably have much better tolerance control.
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j bjork
1 MW
I am not using duct tape, i use aluminum tape. Packing tape can work. It is a good thing it is thin, as it leaves small marks in the mold. It can sometimes swell and curl a little though.
Yes, it usually means many hours with filler and sanding
The wood board I have been using bends when the filler shrink when it is curing, leading to more filler and sanding..
I have to read again and try to understand what you mean with some of the things, but I am curious about this.
Were you able to make a clay mold covered with aluminum foil and get good finish?
I have tried taping models to not have to paint them, but the finish in the mold I make usually doesn't turn out very good then.
I've been binge-watching videos from Easy Composites myself to find out all possible ways to make those parts. One particular one that might be relevant is this one:
In short, a regular styrofoam plug is simply wrapped in release film (I was wondering if regular food cling film would work
) and the wet layup done over that. Quick, easy, perfect for one-offs or quicker molds? Perhaps worth a try.I have many more parts to make - a new airbox and some fairings. I was hoping by the time I get around to them I'll learn actual mould making, and make them in CF + epoxy. There's another technique here that Easy Composites have shown on their channel, which is vacuum bagging with regular clothes storage bags and a shop vac. That costs a fraction of a vacuum pump and a professional system, yet still (supposedly) yields good results. With wet layup apparently a perforated foil should be used instead of regular peel ply, to reduce the amount of resin pressed out into the breather. My bags are already en-route to me, and I'm waiting to pull a trigger on an order from them to get the more expensive components.
In the meantime I'm focusing on the essentials though, which is getting the battery sealed and the motor solidly in the frame.
Thanks for the response, BTW. I was planning on making the lip be oversized and then either put in a flat seal, something like this:
Or just to slather it with "bathroom-grade" silicone. The latter would seal well and still allow for disassembly if absolutely required - I hope to never have to do that, after all.
Oh, and since I'm writing an update; I've been doing some work on the Votol protocol as well - watch my GH repo for details on that. I'm working on getting button inputs and different display modes as I'm writing this.
Yes, though the quality of the final part when using this method is sensitive to the mould complexity, as well as how cleanly the foil was burnished onto the clay. Sometimes it was rather difficult to remove the cured part from the mould, either waiting too long in the cure or insufficient release agent on the surfaces. I actually only recall using that method on interior moulds, meaning nuance tolerance was more forgiving for our purposes.
Excellent repurpose of those vacuum clothes storage bags you ordered, just don't forget to use liberal release agent! Should increase structural integrity if the prep work is there, as well as make for less post production to the final part. Looking forward to seeing your testing of that method
I'd imagine the multiple seal tongues will give good ingress protection. Though as you mention, if no regular service is needed some good old silicone slather would work too. Maybe the silicone-ii (2) I think it's called? It's the non acetic acid cure type, so as to avoid any vapors trapped inside that might cause corrosion.
The day is far from over, but I needed to take a coffee break. How do you like my new oven?
This time i managed to get a heating fan fully inside (yes, yes I know it's not supposed to be covered. Read on.) I sat next to it for an hour and observed the temperatures. Unfortunately even on lowest setting it overshoots horribly, reaching air temps of over 40C. That's not good for polyester, so I had to resort to coming back to it every now and then and manually controlling the temperature.
I found cheap thermostat modules with a relay and a remote thermistor, so that's going to be the next upgrade. I'll likely build a proper insulated box as well to reduce energy consumption and improve stability. It's actually not too bad with such an "oven", the added benefit is that it severely reduces the smell.
The tape detached from the form in multiple places, so I don't have high hopes for this part. Well, I guess that's the learning process.
On the motor mounts front, I tried everything with my new axle and it all tightens down quite well. The issue is that with the wheel tightened and everything in place I can't help but think I'm actually about 3mm too much to the outside >.< All the fighting for getting as much to the outside to the possible, and I've overdone it. I still haven't made the rear spacers, so thankfully those will just be made properly, I need to shorten the front-rhs one and either add a thicker washer or remake the front-lhs one.
I also can't stop second-guessing the sprocket height. Looking at hundreds of bike photos, it seems that the chain only gets enough clearance when the swingarm moves up under the weight. I can't do that test without getting the chassis all together, and I'm afraid that at that point I'll have to surrender and make new motor mounts that will move the rear sprocket higher. Well, can't really do much about it it seems until I test everything, and the mounts will be a straight swap if it comes to that.
This time i managed to get a heating fan fully inside (yes, yes I know it's not supposed to be covered. Read on.) I sat next to it for an hour and observed the temperatures. Unfortunately even on lowest setting it overshoots horribly, reaching air temps of over 40C. That's not good for polyester, so I had to resort to coming back to it every now and then and manually controlling the temperature.
I found cheap thermostat modules with a relay and a remote thermistor, so that's going to be the next upgrade. I'll likely build a proper insulated box as well to reduce energy consumption and improve stability. It's actually not too bad with such an "oven", the added benefit is that it severely reduces the smell.
The tape detached from the form in multiple places, so I don't have high hopes for this part. Well, I guess that's the learning process.
On the motor mounts front, I tried everything with my new axle and it all tightens down quite well. The issue is that with the wheel tightened and everything in place I can't help but think I'm actually about 3mm too much to the outside >.< All the fighting for getting as much to the outside to the possible, and I've overdone it. I still haven't made the rear spacers, so thankfully those will just be made properly, I need to shorten the front-rhs one and either add a thicker washer or remake the front-lhs one.
I also can't stop second-guessing the sprocket height. Looking at hundreds of bike photos, it seems that the chain only gets enough clearance when the swingarm moves up under the weight. I can't do that test without getting the chassis all together, and I'm afraid that at that point I'll have to surrender and make new motor mounts that will move the rear sprocket higher. Well, can't really do much about it it seems until I test everything, and the mounts will be a straight swap if it comes to that.
Doesn't look food safe ... jk.
Could you cut a hole on the top, then make a lightweight material (aluminum foil or parchment paper) that would naturally vent or exhaust to help stablize temps? Maybe that is too much fandangling and experimenting to get right for a carboard oven? Never the less, it reminds me of making tarpaulin tents for shop heater curing huge resin parts in an unheated building in the depths of a Midwest winter. Fun times!
You can rig a crude charcoal exhaust filter to help reduce the VOC smells... a smidge.
I actually do have a large spare charcoal filter i was planning to rig to this, but considering outside of the garage you can't smell absolutely anything, I don't care that much. I have ABEK1 filters in my mask now so I can't smell it even when directly next to it. I might consider adding it to the real oven if/when I get to building it. Instead of venting it, I went the opposite way and added as much insulation as I could, to help it retain heat for longer. In about 6h when it doesn't smell at all I'll just move it to my heated basement.
All in all, the model I made sucked. The good news is that I (hope I) know why it did and how to improve it the next time. Actually, I'm pretty sure I'll go for a real mold next time. Today's laminating was also much less stressful and eventful, as I already knew what to do, how to work with CSM etc. I definitely see the reason for using vacuum now, and can't wait until I get my breather, perforated peel-ply and can try vacuum bagging the next part.
As far as mechanicals... ugh. I'm now 90% sure I did put the motor too low. I did manage to set it up quite well left-to-right (setting aside the fact that the second set of spacers still wasn't enough and I'll need to machine another set), but it remains much too low. I lifted the back wheel by about 10cm from fully extended and it still didn't have a clear line to the rear sprocket.
I decided to bite the bullet and ordered a 60T aluminium sprocket from MJ. It was a bit pricy (75 eur), but really, it solves a lot of issues for me:
* better unsprung weight
* no rubbing on bottom chain guard
* better chain angle to the motor and no rubbing on top of swingarm
* much better drive ratio! look:
(wheel dia is meant to say "circumference", obviously)
14/60 is actually a better combo than 13/54, which was quite surprising. Realistically, if the larger sprocket won't move the chain enough for clearance, I'll make a new set of motor mounts and aim for 13/60.
The only downside of the new sprocket is going to be cost and longevity, but considering I'm still on my first sprocket on my EXC after 100+h, I guess I can stomach it.
They're not "cheap" but the non-clone Pymeter "power strips" are good for this sort of thing.
I've used two of the 2-outlet version for years for various temperature control tasks, they can be easily set for a wide or narrow temperature range for setpoints, and if you set the low point above the high point it works for cooling instead of heating (such as to run a fan if the temperature goes higher than a certain level). Since the 2-outlet version I use has independent setpoints and displays and alarms for each outlet, you can have one running the heater and the other running the fan, so if there is a heat excursion you can automatically run the fan to cool it quickly back down. etc.
It also has a low and high alarm point, and a sensor failure detection--any of htose triggering turns the output off for safety and beeps (though I can't really hear t he beeping anymore unless I'm right on top of it ,s ometimes not even then, because of my tinnitus).
I rewired one of them to use one relay to control neutral and the other to control hot on the outlets (instead of independent outlets), so I could use two independent sensors in different places on the same single large-surface-area heating unit, and that has worked well, too.
The temperature sensors are simple 10K 3435 NTC's, so you can build them into a project and add connectors in place of the sensors it has attached (or replace them if damaged, etc).
Just beware of clone versions; they don't always work correctly; they usually ahve really skinny ac cords and sensor wires, may have undersized relays, etc. (one version i saw reviewed somewhere when I initially researched them didn't even *have* relays, it was jumpered across the relay holes on the PCB, making it COMPLETELY USELESS AND HIGHLY DANGEROUS....I saw this same thing when researching the little tiny cheap box-controller boards too, mostly on aliexpress, some on ebay).
If you're willing to do it and have the time, you can make your own sprockets. It's kind of a PITA, but can be done with "just" a compass and hand-drill (a press would make it easier), and a set of files.
The site I originally learned from doesnt' exist anymore, but there are a lot of places with the info out there
These two pages (just skimmed right now) appear to have useful info on doing it
How To Make An Electric Scooter Chain Sprocket With Nothing But Hand Tools
Sometimes, mechanical parts can be supremely expensive, or totally unavailable. In those cases, there’s just one option — make it yourself. It was this very situation in which I found m…
BTW, for aluminum sprockets, people have even used the bottoms of large saucepans for source material. IIRC it was suggested that pans for induction stoves were thicker and machined flatter and smoother.
It's also been a material used for sprocket adapters, such as to fit a bicycle-freewheel-mounted type on the smaller bicycle ISO disc brake mount.
I don't know if any of these are thick enough for your purpose, or if it's possible to sandwich two plates together for a wider chain.
(I'm likely to use this technique to make sprockets for this: Amberwolf's Schwinn Trike Rebuild / Conversion to Heavy Cargo Hauler once I have enough of it's design decided upon to begin fabricating drivetrain parts).
It's also been a material used for sprocket adapters, such as to fit a bicycle-freewheel-mounted type on the smaller bicycle ISO disc brake mount.
I don't know if any of these are thick enough for your purpose, or if it's possible to sandwich two plates together for a wider chain.
(I'm likely to use this technique to make sprockets for this: Amberwolf's Schwinn Trike Rebuild / Conversion to Heavy Cargo Hauler once I have enough of it's design decided upon to begin fabricating drivetrain parts).
Wow, that's some creative thinking. I mean, if I wanted to make one myself, I'd likely order a laser cut flat sheet and rig up a grinding setup to put the side profile on the teeth. A lot of methods would work, I imagine... Laser, plasma, water if given enough buffer for later cleanup (to maintain accuracy). Another way would be a DIY EDM cutter, those have been getting cheaper by the day. The common factor between all of those is they retain numerical precision from CNC but don't require a stiff construction like a CNC mill, since the loads on the gantry are virtually zero.
Realistically speaking, when you count either ordering and finishing a precut stock, or doing it all yourself, a made-to-order sprocket will likely still end up cheaper...
That depends on your availble funds.
For me, I have very limited funds, so even though my time is equally limited (even moreso, usually), a DIY approach to something that can be "easily / simply" done that way is more likely to result in a completed projecct than waiting to have the money to spend on it.
For mroe complex things (like those pymeter temeprature controllers), buying is the only realistic option (sure, it's possible to diy one from some relays and an arduino or other mcu, if you know coding welle nough to write it or hack another similar project to do it...but if not...).
So what I do is usually some mix of repurposing existing or found (or really cheap) hacked bits (usualy mechanical stuff) and purchased bits (usually from thrift stores or other really cheap used sources, and these usually get hacked in some way too as the exact item I need is not usually directly available at a price I can pay).....
For me, I have very limited funds, so even though my time is equally limited (even moreso, usually), a DIY approach to something that can be "easily / simply" done that way is more likely to result in a completed projecct than waiting to have the money to spend on it.
For mroe complex things (like those pymeter temeprature controllers), buying is the only realistic option (sure, it's possible to diy one from some relays and an arduino or other mcu, if you know coding welle nough to write it or hack another similar project to do it...but if not...).
So what I do is usually some mix of repurposing existing or found (or really cheap) hacked bits (usualy mechanical stuff) and purchased bits (usually from thrift stores or other really cheap used sources, and these usually get hacked in some way too as the exact item I need is not usually directly available at a price I can pay).....
I get it, but when you start looking at even tools needed to work with aluminium efficiently, those tools will cost a lot themselves. And it's often the case that when working with suboptimal stock the tooling needs are even bigger because it's not straight etc.
Either way... I pulled the thing out of the thing:
Only took a bit of persuasion, really.
The foam cracked when I pulled on it a bit too hard, but the plug almost survived this time. Now, you might be wondering why the heck does it all look like that.
In the last second attempts, I added some packing tape on top of the form surface. I only covered half of it as an experiment. It's decidedly much shinier, but the folds in the haphazardly laid tape left a log of creases. In comparison, the waxed filler is flatter but also rougher. A lot of the filler stuck to the gelcoat and had to be be manually scraped. All in all, as I said, there's been definite issues in my form making, and I am now quite sure that the filler desperately needs paint or gelcoat before waxing to really get a nice surface, but there might still be potential with cling film or other types of wrap, such as peel ply.
I also experimented with tape on the final part. This was mostly to pull the edges inwards, as they were just hanging by gravity. They flared up outwards too much and I was afraid they would make the part too wide at the base, so I just added tape to pull them closer. Here I've already cut the part, but I think it actually did a reasonable job. It was also obvious that in the areas where I pulled the tape across the laminate, it compressed it, pushing excess resin out like a vacuum bag would.
So yeah, definitely seeing the case for vacuum bagging wet layup parts, but the importance of a good form can't be overstated.
After all the effort, it fit... Meh. Barely.
Since I did a lot of experimentation with techniques I wasn't sure about, I'm not surprised some didn't turn out great. The ridge where it was supposed to rest on the edge formed partially - great in some places and not at all in others. Since the outer perimeter wasn't well defined, that meant the lid doesn't really want to sit flat
I see three options in my future:
* Declare victory, trim as much protruding excess as possible, mate with silicone and hope the seat pressure won't dislodge it.
* Declare partial victory, retreat, and try to use this part as a mold for a smaller actual final cover that would fit better
* Declare defeat and start over.
The main issue is that I think I did myself in by not creating a 90 degree mating flange on the box itself. That would mean closing it sooooo much easier with tons of tolerance. The way things are now, I think it's going to be really hard to make the part fit better with this idea.
That being said, I think I can stack the odds in my favor. If I made the cover be the exact copy of the shape of the box at the bottom, I could make them mate like a butt-joint. That itself isn't enough, but if I then glued or otherwise attached a strip of material, I could form the mating ridge, either internal or external. The other alternative is to, before gelcoating the plug, add an evenly rolled strip of plasticine to make a ridge that's actually precise and doesn't have the problems of taped cardboard.
The history will remember my battles only as a road towards the campaign victory, so while I mull over all that on my upcoming ski trip next week, let me know what you think and if you have some ideas for me.
Either way... I pulled the thing out of the thing:
Only took a bit of persuasion, really.
The foam cracked when I pulled on it a bit too hard, but the plug almost survived this time. Now, you might be wondering why the heck does it all look like that.
In the last second attempts, I added some packing tape on top of the form surface. I only covered half of it as an experiment. It's decidedly much shinier, but the folds in the haphazardly laid tape left a log of creases. In comparison, the waxed filler is flatter but also rougher. A lot of the filler stuck to the gelcoat and had to be be manually scraped. All in all, as I said, there's been definite issues in my form making, and I am now quite sure that the filler desperately needs paint or gelcoat before waxing to really get a nice surface, but there might still be potential with cling film or other types of wrap, such as peel ply.
I also experimented with tape on the final part. This was mostly to pull the edges inwards, as they were just hanging by gravity. They flared up outwards too much and I was afraid they would make the part too wide at the base, so I just added tape to pull them closer. Here I've already cut the part, but I think it actually did a reasonable job. It was also obvious that in the areas where I pulled the tape across the laminate, it compressed it, pushing excess resin out like a vacuum bag would.
So yeah, definitely seeing the case for vacuum bagging wet layup parts, but the importance of a good form can't be overstated.
After all the effort, it fit... Meh. Barely.
Since I did a lot of experimentation with techniques I wasn't sure about, I'm not surprised some didn't turn out great. The ridge where it was supposed to rest on the edge formed partially - great in some places and not at all in others. Since the outer perimeter wasn't well defined, that meant the lid doesn't really want to sit flat
I see three options in my future:
* Declare victory, trim as much protruding excess as possible, mate with silicone and hope the seat pressure won't dislodge it.
* Declare partial victory, retreat, and try to use this part as a mold for a smaller actual final cover that would fit better
* Declare defeat and start over.
The main issue is that I think I did myself in by not creating a 90 degree mating flange on the box itself. That would mean closing it sooooo much easier with tons of tolerance. The way things are now, I think it's going to be really hard to make the part fit better with this idea.
That being said, I think I can stack the odds in my favor. If I made the cover be the exact copy of the shape of the box at the bottom, I could make them mate like a butt-joint. That itself isn't enough, but if I then glued or otherwise attached a strip of material, I could form the mating ridge, either internal or external. The other alternative is to, before gelcoating the plug, add an evenly rolled strip of plasticine to make a ridge that's actually precise and doesn't have the problems of taped cardboard.
The history will remember my battles only as a road towards the campaign victory, so while I mull over all that on my upcoming ski trip next week, let me know what you think and if you have some ideas for me.
I'm way too impatient, so spoiler alert, new form is in the making:
This time I'm going to be shaping it directly on the box to make the sliding angle and the interface match as closely as possible. Note that the box isn't cut at 90 degrees, which means that the cover slides on at an angle not perpendicular to the bottom surface.
Things that I'm going to try to do differently this time:
* aforementioned shaping directly on the box (i simply used hot glue to secure it).
* the ridge will be formed to the _inside_ of the part, relying only on stiff foam for a precise edge.
* I'll use the polyester filler again. Now, fun fact:
This is what happened to the old form. All of those areas have been thoroughly covered with acrylic filler - and that didn't stop the resin vapors to eat into and dissolve the foam underneath. It's a slight miracle that the filler actually held its shape well enough during layup. I observed no such damage with polyester filler.
Now, apparently polyester filler actually isn't a great material for release from polyester resin on top. It should be covered with gelcoat, but I think I'll try polishing it and spray-painting this time. I really only need a thin layer, which might be hard with the thick filler I have, but I hope that with this part being much smaller I'll be able to smooth it out enough to make sanding passable. I'm still a bit tempted to try out cling film for mold release, though...
I think in the long run, using a different kind of foam and applying gelcoat directly on top of it could be just the right balance of effort vs release.
This time I'm going to be shaping it directly on the box to make the sliding angle and the interface match as closely as possible. Note that the box isn't cut at 90 degrees, which means that the cover slides on at an angle not perpendicular to the bottom surface.
Things that I'm going to try to do differently this time:
* aforementioned shaping directly on the box (i simply used hot glue to secure it).
* the ridge will be formed to the _inside_ of the part, relying only on stiff foam for a precise edge.
* I'll use the polyester filler again. Now, fun fact:
This is what happened to the old form. All of those areas have been thoroughly covered with acrylic filler - and that didn't stop the resin vapors to eat into and dissolve the foam underneath. It's a slight miracle that the filler actually held its shape well enough during layup. I observed no such damage with polyester filler.
Now, apparently polyester filler actually isn't a great material for release from polyester resin on top. It should be covered with gelcoat, but I think I'll try polishing it and spray-painting this time. I really only need a thin layer, which might be hard with the thick filler I have, but I hope that with this part being much smaller I'll be able to smooth it out enough to make sanding passable. I'm still a bit tempted to try out cling film for mold release, though...
I think in the long run, using a different kind of foam and applying gelcoat directly on top of it could be just the right balance of effort vs release.
Oh, and I think the proper foam for this, i.e. not something ridiculously expensive for model making and not XPS/styrofoam/styrodur, is actually called PUR/PIR foam (which, AFAICT, is expanded polyurethane). It's used as building insulation material and has all the right properties; the only choice that matters is the density - lower (~40) shapes easier, higher (90+) is stiffer and gives better surface and stability.
It should accept any filler and even polyester gelcoat directly on top.
It should accept any filler and even polyester gelcoat directly on top.
While it might not be appropriate for everything, I've used green PartAll PVA mold release for all of my casting endeavors with various resins, silicones, etc. I bought a gallon jug probably 30 years ago and am still using it these days; still works just like it did originally.
It's green, and uses some form of alcohol as a solvent to suspend a waxy coating until it evaporates and settles the coating on the surface. Most of the plastic surfaces I've used as molds required multiple coats because really smooth surfaces tend to bead up the PVA to some degree. Airbrushing is the "best" method, but I've used brushes and even just poured it on some mold surfaces (like plaster) and let it dry and recoat as needed.
This is the same stuff I use, though my jug label looks different because it's so much older.
Sometimes mold release isn't needed: once on a project in the 90s where I changed my mind on what I was going to cast the mold with, before I coated the plaster positive mold with PVA, then decided I was going to vacuform it instead of making a silicone negative mold (to then use to make a resin positive item). Ended up good enough to just use the vacuform *as* the item, if not as sharply detailed, and the styrene didn't stick to the plaster. Surprisingly I still have one pic of some of the results (you can see some charring on the plaster where I used a handheld torch to preheat it to help the vacuforming process; these days I'd've just stuck it in the oven first for a couple hours).
It's green, and uses some form of alcohol as a solvent to suspend a waxy coating until it evaporates and settles the coating on the surface. Most of the plastic surfaces I've used as molds required multiple coats because really smooth surfaces tend to bead up the PVA to some degree. Airbrushing is the "best" method, but I've used brushes and even just poured it on some mold surfaces (like plaster) and let it dry and recoat as needed.
This is the same stuff I use, though my jug label looks different because it's so much older.
Sometimes mold release isn't needed: once on a project in the 90s where I changed my mind on what I was going to cast the mold with, before I coated the plaster positive mold with PVA, then decided I was going to vacuform it instead of making a silicone negative mold (to then use to make a resin positive item). Ended up good enough to just use the vacuform *as* the item, if not as sharply detailed, and the styrene didn't stick to the plaster. Surprisingly I still have one pic of some of the results (you can see some charring on the plaster where I used a handheld torch to preheat it to help the vacuforming process; these days I'd've just stuck it in the oven first for a couple hours).
FWIW, I often use plaster for making molds (both negative and positive) because it's easy to carve detail into while it's curing after it's solidified but is still wet.
For large items I'll usually make a layered cardboard core, like a catscratcher is made, cuz the plaster sticks to that pretty well and the cb can deform with the plaster as it shrinks or expands in the various processes so it doesn't shatter the mold.
These days I am molding silicone parts with the process, rather than resin, but it worked for those too; with the partall it doesn't stick to the parts for either type of mold (the silicone will usualy come off even without the partall, but you end up with the bubbles as texturing on the silicone, whcih is useful for grips and grip covers but not so much for things you need a smooth surface on ) .
Disadvantage of plaster is that any detail on there will wear off after enough casts are made from it, but the advantage is that if you don't care that the size is sligntly different you can just recarve it back in... Or you can cast a whole new mold from the first piece you cast from it, if you don't use that part for anything.
Oh, and plaster is very heavy, and fragile, so...don't drop ur molds.
For large items I'll usually make a layered cardboard core, like a catscratcher is made, cuz the plaster sticks to that pretty well and the cb can deform with the plaster as it shrinks or expands in the various processes so it doesn't shatter the mold.
These days I am molding silicone parts with the process, rather than resin, but it worked for those too; with the partall it doesn't stick to the parts for either type of mold (the silicone will usualy come off even without the partall, but you end up with the bubbles as texturing on the silicone, whcih is useful for grips and grip covers but not so much for things you need a smooth surface on
) .Disadvantage of plaster is that any detail on there will wear off after enough casts are made from it, but the advantage is that if you don't care that the size is sligntly different you can just recarve it back in... Or you can cast a whole new mold from the first piece you cast from it, if you don't use that part for anything.
Oh, and plaster is very heavy, and fragile, so...don't drop ur molds.
For negative molds I'm planning to either keep using my current GFRP setup, or invest in some low-shrink tooling resin. EasyComposites have this great uni-mould system that forms a complete solution that produces forms compatible with all resins; after the airbox, I hope to make the side panels with CF and epoxy, so I need something compatible with that.
EDIT: also, for CF I really need to step up my mold making game, because the raw material cost is so high, I can't just "try and see". That's why I hope to make the airbox with better technology - positive foam mold, negative GF mold, then GF inside but vacuum bagged. If all goes well, I'll just replace the GF with CF for the side panels.
Plaster sounds interesting; I can imagine that clay could also work quite well for the positive mold if handled delicately. Ideal material would be easy to work both additively and subtractively, and then finish up to gloss with minimum dust during sanding. I like using foam because it's lightweight (easy to handle and easy to glue into large shapes), can be shaped with a knife and is reasonably inexpensive. I totally want to try out combining it with a 3D printed skeleton at some point too.
As far as release agents, the last part was (in addition to tape) covered in dedicated mold release wax and an extra layer of PVA on top. The first box was inverted order, so PVA was applied first, then 7 layers of wax on that. I also have some liquid wax I've been meaning to try out.
EDIT: also, for CF I really need to step up my mold making game, because the raw material cost is so high, I can't just "try and see". That's why I hope to make the airbox with better technology - positive foam mold, negative GF mold, then GF inside but vacuum bagged. If all goes well, I'll just replace the GF with CF for the side panels.
Plaster sounds interesting; I can imagine that clay could also work quite well for the positive mold if handled delicately. Ideal material would be easy to work both additively and subtractively, and then finish up to gloss with minimum dust during sanding. I like using foam because it's lightweight (easy to handle and easy to glue into large shapes), can be shaped with a knife and is reasonably inexpensive. I totally want to try out combining it with a 3D printed skeleton at some point too.
As far as release agents, the last part was (in addition to tape) covered in dedicated mold release wax and an extra layer of PVA on top. The first box was inverted order, so PVA was applied first, then 7 layers of wax on that. I also have some liquid wax I've been meaning to try out.
A-DamW
1 kW
Yes, you have the right idea.
Polystyrene foam is a thermoplastic, and most common solvents will dissolve it.
Polyurethane foam is a two part thermoset, which is an irreversible chemical process, and most common solvents will not dissolve it.
Source: I sprayed PU foam for 20+ years in a building/thin shell dome profession:
Just make sure what the specific clay you use contains--sometimes clays can contain compounds that inhibit curing of what's being molded.
I made that mistake once using a non-hardening modelling clay for a temporary mold for a platsil experiment...even with pva completely covering the clay, it prevented any of the platsil from curing at all, ever. Turns out the sulfur commonly in these types of clays does that....
I had another problem later with the regular sculpting clay (that you can dry and kiln) causing a similar problem with plain old clear (PE?) resin, though only right at the surface instead of the whole depth. :/
Cory Wong's Meditation, strictly a guitar pieceAnd it doesn't even have WearEver stamped on it.
BTW: What's the score?
I tried it on - it's still a bit smaller than 51T@520, but I wasn't able to find more than 60T anyway and it would make it a fully custom order. 60 sits close enough that the bottom guard seems completely fine, is indeed very lightweight and it buys me a bit more clearance, to the point where I think I'm going to try and see what happens, and only move the motor up if I see excessive slider wear.
In the meantime after having been gone for a week, my main PC drive died (nvme this time). This time I have restored I think everything from the various backups, so the PC is back up and running already, which is very necessary for CAD and the electronic bits. What are the odds, though...
I also did some work on the new positive model for the top cover. I have ordered better filler, spray on epoxy primer for the final coat, a more accurate scale and the aforementioned temperature controller, all of which should get to me today. I should be able to do all the remaining prep on Thursday and another laminating job on Friday and Saturday, if everything goes to plan.
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