Build of IH Pumper

[Chariots of Fire]

I have a new project in mind that is based on a simple Chevy C70 fire engine that is not far from home.  But I'm going to substitute an International Loadstar cab that Dave Carey cast.  The idea behind this project is to make it a "how to" using basic techniques and tools.  The emphasis will be on clean building, careful alignment and scale.  If any of you that do occasional scratch or kit bash work have any ideas you want explored please feel free to speak up.  There will be no brass work in this build.  Strictly plastic and a bit of resin.  Here is the real truck that I will be basing the project on.

[Scott Eriksen]

We're gonna need someone to 3D print an 8.2 Detroit Diesel for that,lol !  Nice project Charles ! 

[Pete68]

Nice thread seated and following. 

[gotnitro?]

Following along! 

Love those old Chevy trucks, our local FD had a few 

[Gary Chastain]

Always willing to learn from a master, watchingg

[BK9300]

Charles, regarding the ‘how to’ aspect of your new build, you used embossed foil to replicate tread plate in your M-20 build.  If you find an opportunity to do that again here, would sure be interested to see that process - will be good to follow, regardless!

[Chariots of Fire]

3 hours ago, BK9300 said:

Charles, regarding the ‘how to’ aspect of your new build, you used embossed foil to replicate tread plate in your M-20 build.  If you find an opportunity to do that again here, would sure be interested to see that process - will be good to follow, regardless!

I'll include that, Brian.  There's plenty of treadplate on the back of the rig.  Not all has to be foil but for some areas it is perfect.

[Chariots of Fire]

Got some pics taken of some of the parts that I'm collecting for the build.  Will post one or two as soon as I can.  Have some front tires to make up for it first.

[Firebuilder]

Charles,

With the help you have given me ,I have been making molds and casting parts . Most of the parts are based from kit based pieces. It would be great to see how you make and perfect pieces to be cast from stock plastic shapes. As you are aware many of today’s fire apparatus and ambulances  have 20 plus lights on them. I am  having a Hard time making the bezels and lenses from scratch. As well with other parts I am trying to make from scratch, they look good on the bench, but when cast in resin a lot of imperfections show up. The hobby putty seems to be difficult to work with ( maybe I overwork it) and does not always adhere properly to the parts or body.Any help in these areas for  those of us  in need would be greatly appreciated! 
 

Dom

[Chariots of Fire]

3 hours ago, Firebuilder said:

Charles,

With the help you have given me ,I have been making molds and casting parts . Most of the parts are based from kit based pieces. It would be great to see how you make and perfect pieces to be cast from stock plastic shapes. As you are aware many of today’s fire apparatus and ambulances  have 20 plus lights on them. I am  having a Hard time making the bezels and lenses from scratch. As well with other parts I am trying to make from scratch, they look good on the bench, but when cast in resin a lot of imperfections show up. The hobby putty seems to be difficult to work with ( maybe I overwork it) and does not always adhere properly to the parts or body.Any help in these areas for  those of us  in need would be greatly appreciated! 
 

Dom

HI, Dom.  I have done much of the same as you; utilizing kit parts as masters.  Warning lights and bezels are not that hard to do if you have a good source for the master.  The Trumpeter ALF kit has numerous bezels and lenses that can be used that way.  Also check for things like the light bar that was with the Jeep Honcho kit.  I think there were lenses for the lights.  Even the 1/32 scale Monogram Mack CF kits can be used to effect.  If you have an extra one you might be able to cut out the tail light bezels and cast them as well as the headlights, although the latter would be small for 1/25 scale use.

Lenses are easy to cast once you have a good master to copy.  I have clear casting resin that mixes 1:1 parts A and B.  It's made by Teexpert.  Got it on Amazon.  The mold material comes from Micro-Mark and is the 1:1 Rapid Cure rubber that they sell.  It's not cheap but it picks up every detail nicely.  The clear resin seems to stay clear but it takes 24-48 hours to set completely.  Simple molds can be made by gluing the master to a flat piece of plastic or card stock and then building a wall around it with similar material.  You need to use mold release also so that the resin that you pour in does not stick to the mold.  This only works for a part that does not have an under cut.  If it does a two part mold may be the better choice.  Tires and engine parts are some of the things I have done with both a flat surface mold and a two part mold.  I will include a how-to as part of this build.

 

[Chariots of Fire]

Got a few photos of the materials that I will use in this build.  Although it will take on the look of the Chevy pumper, I'm using one of Dave Carey's IH Loadstar cabs and an AMT/Ertl ALF pumper body to start.  The IH cab is one piece except for the hood.  Included are the floorboard, dash, inside door panels, steering wheel and column, seats and running boards.  The ALF body sides are well defined and will go nicely, however the pump panel is going to be made shorter.  The long wheelbase doesn't quite cut it.  I'll also use the ALF frame although the Ford snowplow frame or even one of the Ertl International frames would work also.

This truck is not a big one and I have chosen 37" tall tires and spoke wheels.  Years ago I had a tire made and cast of the right size but it has a mud/snow tread design.  They are ok for the rear but a standard road tread is best suited for the front unless the idea is to make the rig all wheel drive.  In that case the M/S tread is good for the front as well. 

I chose to put one of the rear tires in my lathe and turn the tread pattern down.  To get it back to the right diameter I added a strip of 0.020 by 0.250 plastic strip stock to the tread area.  Then I cut grooves in the plastic while it was still on the lathe.  Not perfect but the idea is there.  Now I will have to make a mold and cast two front tires and also a couple of front rims.  I only have one right now and that will be the master for getting two more.  The mold making and casting process will be part of this build.

The front tire is on the left, a blank rear in the center and the proposed rear rims on the right.  The front rim will be cast separate from the tire.  More to come. 

[Chariots of Fire]

Next up is to get the molds made for the tires and wheels.  I cut some cardboard into pieces large enough to leave a 1/4" gap between the tire and inside face of the mold box.  Same for the wheel.  The pieces are put together using a hot glue gun and a mark was made inside the tire mold box where I want the first pour to go.

A wheel mold needs three pours of mold rubber.  The first is to fill the bottom of the box up to the line and let it cure.  The next pour will include the wheel.  The wheel master is inserted into the box after a thin layer of mold rubber is poured on top of the first pour.  The rubber needs to coat the bottom surface of the tire completely and sit flat on the mold rubber.  Very carefully pour the rest of the liquid rubber around the tire master on the outside only.  Do this a little at a time, keeping the tire securely in place so this pour does not get inside the center hole of the tire.  Weight it down with a paint bottle or similar weight until this second pour is cured.  The second pour is continued until it just rises to the top of the tire but does not spill over onto the sidewall.  Once this is done let it cure completely.  

The mold boxes are ready for the first pour.  Note the marks on the two plastic cups.  The mold rubber is mixed in 1:1 parts A and B.  I mark one cup, insert it inside the second cup to mark it taking into account the thickness of the cup bottom.  Use the lines on the cups as a guide for equal amounts of each.

The first pours are done and need to cure.  When that is done the second pour for the tire and wheel can be done.  For the wheel I'll cast it face down.  I cut out a circle of masking tape and put it inside the back of the wheel.  This will keep the mold rubber from filling the inside of the wheel when it is put into the mold.  The tape will be taken out after the second pour is cured.

[BK9300]

It sure would help for me to acquire this skill - great info, Charles - good idea for a build thread!

[Chariots of Fire]

The mold is almost ready for the second pour.  The base mold rubber is setting up.  In this photo is the cast resin tire that I added the straight tread pattern to.  Beside it is one of the rear tires.  The masking tape inside the front wheel will trap the mold rubber underneath.

The second pour has been completed.  Note that the mold rubber is brought to the top of the tire.  There is a little bit of spillover onto the sidewall in one place but after the rubber is cured, that can be cut away.  Trying to clean it before the rubbers sets only makes a mess.  To the right is the front wheel set in the second pour.  It is brought up to but not over the outside flange.  When both of these are fully cured two things need to be done.  First is to cut some notches in the edges of the rubber.  The purpose is to provide some points of alignment for the two mold halves once they are finished.  Second is to spray the entire inside of the mold box including the master with mold release.  If this is not done the top rubber mold will stick to the bottom one and the master will be sealed inside.  It's hard to see but the center of the tire is free of rubber for most of its depth.  This will also provide alignment and eliminate a lot of the flash that you see on kit tires or the two halves not being centered all around.

[gotnitro?]

So appreciative of you  doing this " how to" especially the mold making part! I've been wanting to try these techniques 

Keep up the great info

[GLMFAA1]

Like Yoda to Luke: thank you for the instructions.

greg

[Bronzekeg]

great work by you as usual.

[Pete68]

On 12/30/2024 at 4:29 PM, Chariots of Fire said:

The mold rubber

Nice choice Charles I’ve used that for years when I use to cast and always had good luck when I casted my 1/87 scale cab masters. 
 

Truck is going to look great thanks for sharing. 

[Warren D]

Great tutorial, just what I need!  Do you need to spray the master part with mold release before you do the 2nd pour (the one that fills the box outside of the tire in your example)?  Or do you only need the mold release prior to your third pour?

[Chariots of Fire]

Hi, Warren.  No, the only mold release needed is between the second and last pour.  The master comes away from the mold without any issues.  The second pour adheres to the first one as it should.   Will post some new photos in the next session.

[gotnitro?]

What brand mold release do you recommend 

[Warren D]

On 12/29/2024 at 11:18 PM, Chariots of Fire said:

Hi, Warren.  No, the only mold release needed is between the second and last pour.  The master comes away from the mold without any issues.  The second pour adheres to the first one as it should.   Will post some new photos in the next session.

Thanks, looking forward to the rest of this tutorial!

Edited January 2 by Warren D

[Chariots of Fire]

7 hours ago, gotnitro? said:

What brand mold release do you recommend 

I use the spray that Micro-Mark sells.

[Chariots of Fire]

The mold results are in.  Now it will be back to the frame, get some springs and set the location of the cab on the frame.  The tire mold is complete and the wheel mold is setting up.  I use communion cups for the casting resin.  You only need small amounts for most parts so they are ideal.  You can see in the photo below that very little flash is around the tire.

Here's the mold for the engine from the IH Scout.  It fits well with the Loadstar.

Tires and wheels are now done.

Here's a look at what I'm after.   The ALF body is about the right height but the Loadstar cab needs to drop down.  IT's not 4WH drive so it should sit lower on the frame.  Right now there are just temporary pieces of plastic holding it up.  The tires that were cast are painted with Tamiya TS-82 rubber black.  Best stuff yet that I have found for getting that rubbery look.

Thinking of a companion piece for this Reo Gold Comet color wise.

[Warren D]

I don't see any holes to pour the resin.  Am I correct that, at least for the parts you show, you fill the lower mold with resin and squish out the excess when you put the top on?  Before Jeff asks, I'll ask, what molding resin do you use?  (If I had to guess, I'd say something from Micro-mark)