8043 - The Bucket that Never Was

[zux]

Enjoyed every steps of the v2 bucket. Didn't think it is THIS HARD to make such piece.

[Moz]

That looks pretty impressive, I can't wait to see what the molds and part look like. And thanks for the photo/build sequence and comments, I'm always interested to see the handcrafting process.

[LennyRhys]

Thanks Moz. I'm thinking hard about the mold because there is more than one way to do it, but I've spoken to somebody who has done many casts of model excavator buckets so I have a very good idea of what to do. The tricky part will be making sure all the details are reproduced without any problems, and it is therefore crucial that the mold is appropriately vented as I won't be pressure casting and I'm not able to degas the silicone or resin. I will be using a two-part mold and running the seam along the open edge of the bucket, so there should be no visible seam in the cast parts (except at the back). Will share a diagram later, as I need to draw one up for myself anyway!

At the moment I'm prepping the bucket for casting so I'm about to fill in the remaining imperfections with Milliput (excellent stuff) and once that's dry and sanded, the bucket will be ready for molding. I'm also planning to buy clay today; the clay will be used to seal the bucket to the temporary mold seam.

I realise that if this works well, I will have the option to cast the part in different colours. But black will be first!

Edited July 21, 2015 by LennyRhys2

[Out of Sight]

I was thinking vacum forming, like some R/C car body modelers do, using vacum formed lexan/polycarbonate. But I don't think it'll do well since the bucket has some fine detailing and sharp creases, not to mention the trimmings afterwards.

Anyway good luck with the casting process, it would be great if the finished product has a matte black finish, much like the original 10 x 18 bucket, however I do notice that it's made of a rather flexible plastic, similar to ABS plastic found on real car bumpers.

[Tommy Styrvoky]

Great job, i'm guessing it uses .04 in and .02 in. for thicknesses of styrene. I wonder how the nice radius was created for the edge of the bucket, as I use styrene for scratch building in some of my 1/35 Armor, but I find that a knife that doesn't have a edge to follow will skirt around. So did you use a template ? How well does it handle the stress on the teeth, did you use CA glue or a plastic cement to weld the parts together ?

[LennyRhys]

@ Out of Sight, as far as I know silicone reproduces finish, so I plan to give the styrene a coat of matte spray before making the molds. If the worst comes to the worst, the resin cast parts can easily be sprayed with matte varnish.

@ Tommy, Thanks. Most of the bucket is actually made from .06 styrene, which makes it very rigid and strong. I used .04 for some of the details like the teeth and the mounting ears.

As for the bucket curve, I just drew it freehand and traced it onto .06 styrene. To cut large curves I always use scissors because as you say the knife isn't good for this. Final smoothing of the curve is done with an emery board or sandpaper; all judgements of accuracy are made by eye and also by running a finger over the curve you can get an idea of how smooth it is. I guess it takes practice to get it just right, and I've been doing it for a few years now!

Styrene is very strong and the teeth are pretty big, approx 6mm x 4.5mm, so they won't have any trouble handling moderate stress. I use plastic cement exclusively because it's easier to work with and the bond is extremely strong if the cement is used correctly. CA is good for reinforcing seams but for actual fixing I don't like it, because it sets too fast.

[LennyRhys]

Two updates - this is moving forward a lot quicker than I anticipated!

First: I collected the silicone earlier today so I will (hopefully) be able to start pouring the first half of the mold tonight and finish up the second half of the mold in the morning. It is advised that demolding happens within 24hrs so it'd be good to have that done by tomorrow evening, after which time it is good for the silicone to sit for a while before I start pouring resin through it.

And second: I've put significant time into designing the mold and there have been some extremely helpful pointers from a number of professionals (gotta love teh interwebz), so I feel very confident that this will go smoothly.

Some further steps towards molding the part:

Milliput, used to fill in the small holes/imperfections in the styrene model and also good for sealing/reinforcing seams

Starting to create the false mold half which will receive the first pour of silicone. The aperture will be as close in size to the bucket as possible, and remaining gaps will be filled with clay.

New blades for accurate cuts. I have 50 of these because I go through them pretty fast, and in my experience they are every bit as sharp as scalpel blades but FAR stronger

Done!

Test fit before refinement...

I need to remove some material so that the teeth sit snug against this border

Teeth edge done, and also some bracing added underneath so that the sheet doesn't warp.

Now if I cast the part like this, there will be a seam running over that top section of the bucket. I plan to mold this with clay which will hide the seam.

So that's it for now. I still have a lot more work to do before I can pour silicone, but that's what holidays are for! Didn't expect to put quite so much work and prep into this, but it'll be worth it for a good quality part.

[RohanBeckett]

awesome work! always great fun watching a worklog like this!

and it sorta makes me miss my plastic kit modelling days, when I was younger...

[LennyRhys]

Thanks!

I didn't manage to pour the mold last night because I was waiting for varnish to dry. Sadly, the varnish was still tacky this morning so I angrily removed it with sandpaper. That's the last time I use that varnish!!

Back to business. I started padding out the template with Newplast, and I also filled in the mounting holes just enough so that I could still know where to drill when the cast part is removed. Newplast is great stuff but oh my, is it messy!

Registration keys for the mold halves - what else would I use on a project like this?!

The box that will contain the two halves of the silicone mold is very simple. It's made from 6mm MDF sheet and I secured it in place with hot glue. Hot glue is ideal in this situation because it's very strong but can also be removed very easily, which I will have to do after the first half of the mold cures.

I've also gone round the bucket with Newplast to seal any small gaps, and that was a very laborious process. I'm not looking forward to cleaning that off when the time comes to pour the second half!

Adding vents and pour gate. Using straw vents is conveniet because it will help prolong mold life by shielding the silicone from the casting material.

I have used ten vents in total, which direct material (and stray air bubbles) away from high points or intersections in the bucket form.

Here's the silicone after being mixed with catalyst. I left it to sit for a few minutes so that the air bubbles would rise to the top. I calculated a volume of 1.3L which worked out at just over 1.5kg of silicone for the first half of the mold, so I'm glad I got 5Kg as I'll likely need most of it.

And here's the mold box after pouring in the top half. There are a number of pouring techniques which help to minimise trapped air in the silicone, and I used the "high pour" method. I poured the silicone in at one corner and kept it really slow and stringy. It takes quite a long time for the silicone to conform to the shape of the box and its contents, but it's worth it in the long run. It may seem intuitive to pour directly onto the part, but this is a very bad idea as it will just introduce more air into the silicone that will likely ruin the mold.

I checked it recently and it's been curing for almost 2 hours now, and it looks really good on top with hardly any air bubbles. I'll be pouring the second half of the silicone tonight and will update this thread either then or in the morning. Fingers crossed that the rest of this project progresses without a hitch. Now I need to buy some resin and get casting!

[TheNextLegoDesinger]

nicely done anny progress?

[LennyRhys]

Yes, progress indeed! The molds are finished and I'm about ready to keel over... it was A LOT of work and I'm so glad that it's done (at least for now). I have 2KG of black polyurethane resin on order and I plan to start casting in the next few days. I still need to clean the molds properly before the first use, but other than that they are pretty much ready to go.

When the first half of the mold cured I had to flip it over and remove the styrene and clay to prepare for pouring the second half. As you can see, there's a lot of clay there and it's really sticky and difficult to clean off, so this took considerable time. It was important to pack the bucket firmly otherwise it might move and the mould would be spoiled... a potentially expensive mistake!

I took a lot of care around the detail parts, especially the teeth. There will be a seam line here but it should be easy to conceal. The pigment in the clay is very strong and transferred onto the part and onto the mold, but I did clean the actual clay out of the mold.

And here it is after pouring the second half, with vents and main fill port removed. These holes will be filled with straws to protect the mold from resin, hopefully extending its life somewhat.

I brushed the first half with Vaseline to prevent the two halves sticking together (silicone bonds to silicone, and it WILL NOT come apart!). The capability of the silicone is shown here as it actually molded the texture of the brushed Vaseline. LOL. You can also see how clean the detail of the teeth is in the last image. I'm really excited for the first resin cast... fingers crossed!

[Bob De Quatre]

I'm absolutely not interested in 8043, I do'nt even know what model it is... But it's great to see in detail how you can achieve to mold a part like that, extremely interesting topic. Hope you'll get the result you are awaiting

[Victor Imaginator]

Great topic, looks like pure magic)

[higgins91]

great job !

and the result looks realy good !

how many hours did you spend on it ?

[Karle]

Your project comes at a great time for me. I've ordered the parts I need to build the 8043 and would like to order one of your buckets.

[LennyRhys]

Thanks folks.

I hope to get organised asap for selling this part but there are a few things I need to do first. I think it'd be better to sell it as a modification kit with all the required parts complete as a set, because set 8043 doesn't have some of the parts that will be required to appropriately fit the bucket with intentional functionality.

I don't know how many hours I've put into this, but more than one 14 hour day for sure!

[LennyRhys]

I decided to build a mock-up of the 8043 stick and it turns out I have all the parts that I need (at least to make it representational for the purpose of scale and proportion).

I spent some time experimenting with different linkages and it turns out that the greatest (and most realistic) range of movement can be achieved by having 4L liftarms placed 1 hole apart on the stick and bucket. Like I said before, there are MANY ways to mount this bucket, but I think that this is the one I'll settle for.

Here's an example of range of movement using the prototype bucket and some rushed phone pics! I'm not sure what kind of force the linear actuators can exert, but this is definitely sturdy enough to do some digging.

[Alasdair Ryan]

I have messed around with silicon rubber and resin in the past too,I actually cast some parts for my die-cast model collection.

When I made a cast of a bucket I found out that the ears of the bucket tended to get deformed due to the rubber closing in on its self,which made them weak compared to the rest of the bucket.

Edited July 24, 2015 by Alasdair Ryan

[LennyRhys]

When silicone rubber cures it won't change shape unless there's something acting on it (if thin enough it will flex under its own weight). This is why box molds have so much excess above/below and to the sides of the part - in the case of my mold halves, there's about 1 inch of solid rubber in every direction beyond the internal shape. I have no concerns about the resin parts breaking or deforming... my only worry at this stage is whether or not the part will look good when it comes out of the mold!

Seeing how much work (and money ) goes into resin casting I don't think it's something I'd do often, but it has been a lot of fun.

[kieran]

I really hope this works for you,man huge amount of time must have gone in, do you have any idea how long the mood wil last, how many casts I mean?

[LennyRhys]

Thanks kieran.

It's hard to say how many casts I will get from this mold because of the variables. I could get upwards of 30 casts because of the low volume of the bucket (about 40ml), but the mold might start to deteriorate after 20 casts, so I just have to wait and see. I'd really like to get as many as possible, naturally, and if there is sufficient demand for the bucket, then I'll make another mold (possibly with higher grade silicone called "platinum cure" which can cost well over £100 for 5KG) and in theory that will allow me to cast a higher volume of parts before the mold gives up.

Waiting for the resin to arrive is a test in itself, but to be honest it's probably good to be having a break from this because it'll get pretty intense again this coming week. I've been looking on bricklink for the parts that I'd need to make kits that I can ship out with each bucket, so hopefully I'll get that organised soon!

[gevans12]

I'd definitely be interested in buying one!

Have you considered making other sized buckets like narrower trenching buckets or the wider style grading/loading loading bucket?

I think they would be excellent additions and would be interested in them certainly

[Dafgek81]

Love to see a wheelloader bucket without the teeth TLG has on them.

And slightly wider than the on on the 8265 loader, the bucket is to narrow, it should be slightly wider than the loader itself.

[Karle]

I want one. I have plenty of beams and other parts to mount the bucket so I don't think you need to worry about providing extra parts.

[LennyRhys]

Thanks guys. I'd be able to make other buckets no problem. but I don't think it would be cost-effective to mold and cast them because TLG already has a selection of loader buckets available.

My main reason for building the backhoe bucket is that it has been 23 years since TLG produced a new backhoe bucket (2950, released in 1992 with Pneumatic Excavator set 8837). The bucket was not included in a set again until eleven years after its initial release, where it was featured in set 8455 - the only time it was ever molded in yellow.

I have to say that I'm still REALLY surprised that TLG didn't create a new mold for set 8043, given how much an appropriate bucket would improve the model's look and functionality.

@Karle, I think that initially I will be shipping the bucket with a conversion kit, purely because it keeps things simple for people who want to make one purchase to put the bucket on their excavator (even though it's more work for me).

Something occurred to me earlier today: with the money I've spent on this project, I could have bought a Mercedes Arocs set. Maybe once I've sold several buckets, that's what I'll do!!