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1:25th CAT 375L (Update: January 20th 2015) Options · View
brian falcone
Posted: Monday, January 07, 2008 7:21:29 PM

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looking good, thats going to be one impressive model when its done. gotta love styrene. you can build anything with that stuff. keep the updates coming. brian
Jim15
Posted: Monday, January 07, 2008 7:55:59 PM

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keeps coming along Rowan, it looks great,

Jim


RowanH
Posted: Tuesday, January 08, 2008 12:59:08 AM

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Thanks for that Randy, new CAT yellow it is. Brian, I would love to work with brass if I had the spare dollars floating about and the tools to work with it however this is my first time working with styrene and I love how versatile it is. Especially considering the cost. Thanks for the comments guys. I'll get more pictures up in a couple of hours, I'm still loving my holidays :D

Rowan.

1:25th scale CAT 375L excavator

TomCat
Posted: Tuesday, January 08, 2008 3:31:11 AM

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That is going to be awesome!Keep the pictures coming,PLEASE!!!Applause

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RowanH
Posted: Tuesday, January 08, 2008 8:29:51 AM

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Thanks Tomcat! While I am loving building it, I can't wait to see it complete in its entirety. I didn't get much work done today apart from the wooden counterweight but here are some more shots.

I sanded down the putty off the boom and cut out the built up sections for both the base of the boom and at the points where it meets the stick. I have decided not to attach these point pieces at the moment because of the way the pinion will be attached through the center.




More pictures of the built up base arms. These unfortunately aren't the best feature on the model however they are very strong and with some more putty and sanding, they will better resemble the real arms.




Pictures of the wooden mold. I was lucky to find a piece of wood lying around that already had an accurately cut bend in it. I just had to cut it down to size and sand it down a bit.






I also cut out some more frame parts for the upper structure. I can now accurately measure, space and plan out how to mount the boom and where to build up the rest of the structure.






Pictures of the partially complete model with the counterweight mold. The ruler set beside it is 25 inches long as a scale reference. The entire model stretched out as it is shown is approx 29 inches long.






I have been racking my brain about the counterweight for some time now but I have found 2 ways that I think will be best way of attempting it without building or buying a vacuum. The method I will first attempt is described as follows...

Put the balsa in a pre-heated oven 350 F; lay the plastic on top and keep an eye on it. When the plastic starts to sag, you have about one minute more.

If this method turns out to be unsuccessful, I will then try the another method as shown below.



I will be attempting these later tonight, wish my luck. I will take some pictures either way it turns out.

Rowan.

1:25th scale CAT 375L excavator

CAT 328D LCR
Posted: Tuesday, January 08, 2008 10:36:17 AM

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Great job!Applause Applause
Red
Posted: Tuesday, January 08, 2008 11:53:53 AM

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hummer13
Posted: Tuesday, January 08, 2008 2:05:39 PM

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Looks great. If you have a vacumm press you could just heat the plastic up in some hot water and put it on the mold and then press it quickly. What thickness sheet you using to mold the counter weight?
jason

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Jim15
Posted: Tuesday, January 08, 2008 7:32:28 PM

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Looks great Rowan, keep the updates coming!!! This is some true craftsmanship. Maybe you could have gone for that 1:2 scale model!!! lol, or even 1:1, lol, great job again Rowan,

Jim


Cat 966f
Posted: Tuesday, January 08, 2008 8:16:09 PM

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RowanH
Posted: Tuesday, January 08, 2008 8:56:09 PM

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Thanks guys, Jason, I did look into a Vacuum and may purchase one in the future as with more rounded machines, I can see myself needing it more and more. Almost the entire model so far has been cut from 1.5mm styrene sheeting.

I got the counterweight done last night, I'll post pics a bit later on, running out the door to go see 'I Am Legend'.

Rowan.

1:25th scale CAT 375L excavator

RowanH
Posted: Wednesday, January 09, 2008 2:14:05 AM

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Well I finally attempted, failed, attempted, failed, attempted and succeeded with the counterweight last night and I'm really pleased with the result. Firstly I decided to try the method where you place the sheet over the mold in a pre-heated oven. Unfortunately what I didn't realise (stupidly) and what was not mentioned in the original short tutorial I followed, is that heat obviously rises and in doing so, the plastic curled upwards.






I probably could have placed the mold upside down on top of the styrene sheet however I'm not sure how well this would have worked so I decided to try the other method. Here the sheet is exposed directly to a flame and then stretched over the mold as shown in the black and white diagram below. What the diagram doesn't show is that the heat gathered in the styrene sheet spreads throughout the sheet making it very difficult to hold, let alone manipulate it over the mold. After heating the plastic and placing it over the mold, I used a metal knife and some wooden skewers to try and shape the styrene but this proved to be difficult and ineffective.




By this stage I was getting rather frustrated and wasting quite a bit of styrene so finally I decided to do it my own way. Armed wearing a pair of oven mits, I again applied the styrene over the stove top flame waiting for it to sag, indicating it was ready to be shaped. I would then place it over the mold and using simply force with the oven mits I pressed, curled and formed it over the mold. It was almost like needing bread and because I was wearing the soft oven mits, I didn't leave any marks or fingerprints on the soft surface. This was by far the most effective way of shaping the piece.






There were obviously overhang and some crimped edges from the rounding however nothing a sharp knife and a file couldn't fix up.






I have decided to leave the wood mold in the counterweight so I can cut out the plate for the CAT logo as well as drill the hole for the mounting bolts as shown below.




I think that I have figured out a rather clever way of building the center pivot ring that I will show later on but today I'm going to work on the back of the raised engine cover that mimics the curved design of the counterweight. I will also spend some more time on the counterweight and figure out how to mount it.

Rowan.

1:25th scale CAT 375L excavator

Red
Posted: Wednesday, January 09, 2008 2:18:35 AM

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Great job. You could have casted the counterweight in resin instead, that way you could have put weights in the mold to add some weight to it. Also, if you casted it it would be a much easier process and very quick.

Red

redscustomscalemodels.com

RowanH
Posted: Wednesday, January 09, 2008 2:21:56 AM

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^ I never even thought of that Red, definitely something I will consider next time! Thanks for heads up, I especially like the idea of adding actual weight to it.

Rowan.

1:25th scale CAT 375L excavator

Eric Pioszak
Posted: Wednesday, January 09, 2008 7:11:21 AM

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Rowan,

That looks pretty good, especially for a first try. one thing you might try is using a larger sheet of plastic, that way the edges of the plastic that get warped are further away from the desired part.

i don't know if you've ever seen this book but it's a great reference for such work:
http://www.ares-server.com/Ares/Ares.asp?MerchantID=RET01229&Action=Catalog&Type=Product&ID=80868

an investment in a Vacuum pump is actually very useful, I've owned one for about 2 years now, and it is indispensable for making rubber molds. my total system with vacuum pump and degassing chamber cost about $400, but it removes a majority of the air from the liquid rubber, especially where there are undercuts in the mold that would normally trap air bubbles.

Eric

Eric W. Pioszak, Operating Engineers Local 701, Portland, Oregon

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caucasianaasian
Posted: Wednesday, January 09, 2008 7:19:49 AM

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Rowan,
That is going to be a masterpiece mate!!!!
Cheers,
Craig

The Caucasianaasian

Tor Kjetil
Posted: Wednesday, January 09, 2008 1:06:35 PM

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Fantastic workApplause Applause

Tor Kjetil

Paul R
Posted: Wednesday, January 09, 2008 1:29:14 PM

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That will be very impressive when it is done!

Paul R
RowanH
Posted: Thursday, January 10, 2008 3:23:45 AM

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Thanks again guys, glad to see so many people enjoying the thread. Eric, I will definitely be using larger sheets next time and thanks for the book link, I will definitely be getting my hands on a copy, looks like interesting reading Smiley

Well I thought that I had enough styrene sheeting to build the model 2 times over but it actually happened, I run out. I may head into the inner city tomorrow to purchase some more sheets from my local hobby store while I wait for my ebay order however it is currently 42 degrees Celsius (108 Fahrenheit) and is forecast for the same tomorrow. It's really too hot to be doing anything other than spending time in a pool or at the beach.

I got some more work done last night on the side and the inner structure of the carbody. I got the central steps built up and some other small pieces glued in. From here on, I think I'm going to avoid gluing any more new pieces on as it will be more difficult to get a quality paint finish all over. They will remain removable.










This following series of shots shows how the carbody builds up at the moment.

















I really didn't know how I was going to build the swing ring while making it strong and functional. Built up styrene with metal plating was looking like my best bet however I think that I have found a better option. Using the lid from this tin (attached to the bottom of the upper structure) and a sawn off piece from the base of the tin corrected to the undercarriage (cut across the line as indicated). I can recreate the swing ring without too much hassle. I will still have to reinforce the whole ring but the entire machine will be able to rotate left to right while withstanding the weight of the model without rocking forward or backwards.




I still need to work on a lot more of the carbody structure as well as in and around the boom mounting points, the swing ring motor etc however it's slowly taking shape. With work starting back for me next Monday, they updates will still be coming but not as frequently as over the past couple weeks. Thanks again for looking.

Rowan.

1:25th scale CAT 375L excavator

Red
Posted: Thursday, January 10, 2008 3:27:39 AM

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Great job, I can see it coming together already. By the way it's -2 celsius where I live.Teeth Whatever

Red

redscustomscalemodels.com

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