# Doing the mold for a new dirt late model.



## Pete McKay (Dec 20, 2006)

I'm going to try and document this process, it may wind up being a mess but I need to pick up a few supplies tomorrow and then I'll begin mocking up the mold for a long wheelbase dirt modified.

What I'm doing first is looking at real world cars, and the best place to start is the Prelude to The Dream at Eldora. These cars give me the general shape and features to do. While all of the cars (Ford, Chevy, Dodge and Toyota) are represented all of the bodies share the same profiles. Only the rear opera windows are different. Research plays the biggest part of the beginning of the design.




























So this is the profile the car will assume:




















The next thing I need to remember is that for most tracks the maximum width will be 1 5/16th". Since the pictures show that the tires are nearly flush with the side of the car, I'll do my mold a full 0.020 narrower than the wheels at the widest point. When vacuformed the plastic will cover the mold and make it wide enough to cover the wheels and tires perfectly, as it cools it will expand. Since the plastic will be from 0.015 to 0.010 thick I can expect at the most a 0.010 cooling expansion. 

DESIGN

OK, it's pretty much an elongated box, pointy at one end, open at the other. The tops of all of the cars I've found pictures of and watched YouTube video's of are all offset to the drivers side, the A and B posts are laid down more on the right side of the car. Mine will be no different. Where I will get creative are the strakes on the top of the tire blisters on the front of the car, and where the nose piece is attached. This will be well modeled. The hood scoop is a small deal and also easily modeled. 

The biggest hurdle will be the transition from the front end over the hood and between the front tire bulges. This entire area will be modeled then filled with epoxy, then cut to general shape with a dremel and finish sanded. If you look at how the compound curve is on Stewarts car is, it is subtle but needs to be modeled. 

OK, tomorrow I buy my gap filling super glue, some zip kicker, some 5 mnute epoxy and paper towels.....


----------



## TomH (Jan 17, 2006)

Good pick on a project. Great race Eldora was. Chilli bowl in Tulsa I will be with the midgets...hint hint for your next next project. What chassis will this latest creation fit?


----------



## Pete McKay (Dec 20, 2006)

Tom, long wheelbase, either 440X2 pan or Super G+. I may try to engineer it so it will work on either, have a long WB with a short rear end or a short wheelbase and a longer rear end. My T-Jet late model was set up the same way.










You can see the front fender strakes on the T-jet body, this actually made the front end incredibly stiff for such a small body. This body was designed before I learned how to drill holes to vacuum relief, the rear spoiler will look better on subsequent models.


----------



## ampracing99 (Jun 17, 2008)

that would be really cool, great ideah, good luck with your project, that would be a hot item to buy. shon


----------



## 1976Cordoba (Sep 20, 2000)

Dirt late models rule! :thumbsup:

Here's an Action car I converted for LWB Tyco HP7 --


----------



## Pete McKay (Dec 20, 2006)

Scratch built or resin? 

Yoshi and I have been looking through about 5 years of Circle Track magazines and online for a few hours. We're going to try something called applique relief. This is something he picked up in japan from a vacuformer there. It should work great with smooth, non-detailed molds like I make and I'll explain more once we get to that stage. 

The car will be a long wheelbase only, with guide impressions as to where to cut out for the wheels. The Bakersfield guys told me that the hardest problem for the dirt modified was figuring out where to cut for the back tires, so this one will have them indicated on the mold. The reason why we're going to do a long wheelbase car is for a couple of reason; first so that it can be swapped out on cars set up with the dirt mod body, and second because the longer wheelbase is going to accept decals better. I know, weird reason but in measuring the sides of the car between a long and short wheelbase the Patto's NASCAR decals don't fit as nicely on a short car. 

With a longer wheelbase too the car will look lower and leaner and more realistic. As far as the rivet detail I may do something with either #0 or #00 drilled relief holes for them.


----------



## noddaz (Aug 6, 1999)

*Nice thread!*

Always loved watching the modifieds at the local track...

I will keep tuned to this channel!


----------



## 1976Cordoba (Sep 20, 2000)

Pete McKay said:


> Scratch built or resin?


Die-cast metal baby :thumbsup:


----------



## gear buster (Dec 1, 2005)

Those are going to be sweet.
I started to make some scratch built ones but ran outta time for gluing..
Going to sell them?
Glad to see you back in a full swing..


----------



## Pete McKay (Dec 20, 2006)

GB, more than likely after the first of the year they will be available. I've yet to even start bending plastic yet, that comes today.


----------



## Pete McKay (Dec 20, 2006)

Alright, started bending plastic today. What I do first is work up a basic shape, it usually has some curves to is on the horizontal surfaces, more to follow chassis lines than anything else. I then cut two side pieces and gule them to the top piece. Since this car will have wheel cut out impressions I cut out the tire locations on the sides, and then once I get the three pieces lined up a bit I fill those cut out areas back in.



















Mind you this is only the chassis top, the sides, a small grill piece on the front and the back in place. This process took about half an hour including curing time on the Maxi-Cure extra thick CA I use. 

On the inside I will usually put a brace midway through the car. It's more for the next process than anything else as the inside of the mold is going to be filled with 5 minute epoxy. The brace keeps the 0.020 plastic from warping from the heat of the curing.



















Essentially the plastic is forming the mold for the epoxy. Those of you familiar with resin casting could use that at this point, I use epoxy because that's what I'm familiar with. 

Once the epoxy cures, I let it have about an hour or when it's cool to the touch, I trim off all of the excess plastic and true up the mold a bit. I also grind away in areas where I need the general shape to be curved, such as the front of this car. 










Now comes a number of hours wet sanding the entire lower portion of the body. I will plain the bottom to sit flush and flat and drill a number of vacuum relieve "wells" that small holes will connect to and put a removal hook so I can pull it from the vacuformed body. I'll work towards the shape I want, especially on the nose. Right now it looks shorter than it will wind up, the applique relief process will actually give the nose and roof area a very realistic "bolted on" section look. 

Time to this stage, including curing time is about 90 minutes. I know this all looks laughably random but this is how I do it, the final result will be a nice late model suitable for HO scale racing at Eldora.


----------



## Pete McKay (Dec 20, 2006)

OK, the top was build and filled with epoxy. It will be sanded down to the height I'd like it to be. Better to start too tall than too short. 










I've also started working on the front end, getting it wide like the Eldora late models are. Also I rounded it out a bit in the lower nose. 










This shot shows how the roof line is offset to the drivers side and the lamination's that build up the lower nose. It shows the placement of the air cleaner on the hood.

OK, a few hours later and the roof line is down where I want it. I've also worked the nose and the strakes are in place and ready to be sanded. Also the rear wing is on but I think I might have to simplify it. I've also worked up an air cleaner, I wanted to see which looked better, an air cleaner or a scoop. 



















From here, more sanding and then a primer coat to look for imperfections on the mold. Sand and fill....prime, sand and fill until it's smooth. 

Time to this point is about 5 hours.


----------



## Pete McKay (Dec 20, 2006)

Got up early this morning and got right back into the saddle.

Last night I vacuformed the mold in 0.005 white styrene, this is the relief applique process that Yoshi told me about that I wanted to try. From that mold I cut the front end and roof away from the rest of the body. I cur the windows out of the roof section and trimmed up where the bolt on front end out be.



















I carefully glued the roof panel and nose in place, and thinned some Squadron Green putty with lacquer thinner and painted the edges of the roof panel with the putty. Between the glue and the putty the margins melted right into the mold and made making this part seamless easier. 



















I went to bed about midnight. Time so far, about 6 1/2 hours.

I let it all dry overnight. 

This morning about 6AM I was woke up by my daughter and couldn't get back to sleep, so off I went to sand down the putty and drill the relief holes. I carefully sanded the body, repeatedly testing how much material I was taking off the already thin applique. I got it close then did a test pop again in 0.005 white styrene. 










It looked good, a few more rough spots but a little sanding and I'll be ready for a shot in clear PETG. The relief holes are all done with a #1 bit, it's a bit bigger than the #0 and #00 I was going to use but the molding process does not show the holes. 

The body is a bit narrower than I had intended and the tires will stick out a bit more. I may try to fix that by adding a few lamination's to the sides but that also makes everything else more complicated. The only other alternative is to make an A++ draw of the car, fill that with casting material or epoxy and use it as the mold. I've done it before on some of my older molds and it could make the car up to 0.060 wider. Once I draw a few in clear I'll figure that out.

Time to this point (not including sleep), about 7 1/2 hours.


----------



## TomH (Jan 17, 2006)

Pete McKay said:


> Tom, long wheelbase, either 440X2 pan or Super G+. I may try to engineer it so it will work on either, have a long WB with a short rear end or a short wheelbase and a longer rear end. My T-Jet late model was set up the same way.
> 
> 
> 
> ...


Great job. If that is painted from the inside on the T-Jet body, would velcro then be used to attach it to the chassis, or would posts be somehow attached to the paint?


----------



## Pete McKay (Dec 20, 2006)

Tom this one was mounted on a Cobra Clip, which is what the body was designed to fit. I still have that mold, it will be revised soon and bodies made available this spring.


----------



## roadrner (Jul 21, 1999)

Great pix! Keep them coming. :thumbsup::thumbsup: rr


----------



## Pete McKay (Dec 20, 2006)

OK, going to wrap this one up for a few days.



















This is my test mule. It is NOT a prototypical paint scheme or a show car, this is what I'll run laps with to see where the mold might need some changes made. It was pretty much a hack job cutting it out, I will need to cut a few more to see exactly where I need to cut to make it work better. I think this is a bit lower than I will have my own cars lay down. 

Overall I'm happy with the design although the front end does look a bit heavy now. The window recesses worked out great, shape is fine as well. The thicker peel and stick decals don't work on the curves as well as waterslide would but I'll have to order some to see.


----------



## Pete McKay (Dec 20, 2006)

*Some pairisons*

New late model vs. new dirt modified:



















New late model vs. Lifelike CoT:










Car looks more imposing than it is. It's the same height as the dirt modified, the rear over hang is the same length and of course the front is longer.


----------



## gear buster (Dec 1, 2005)

Looks great Pete. You can almost smell the dust thats going to be kicked up by that baby..


----------



## resinmonger (Mar 5, 2008)

I love the smell of dirt in the evening. It smells like victory.


----------



## Pete McKay (Dec 20, 2006)

This is the first "show car", painted it with narrower posts and cut it to ride a bit higher. Wheel cut outs are still problematic because it's hard to cut recessed areas. I may be filling them in soon. 










This car is going to Coach's auction for February I believe.


----------



## slotcarman12078 (Oct 3, 2008)

*She Looks sweet, Pete!!!*

I hear ya Russ!! I don't know what they run in them cars now, but deep in my memory banks I can still smell the dirt, rubber and that 104+ rocket fuel they used to burn in them.. That latest model sends me back there... mid straight, about 5th row. Still close enough to get hit by the flying chunks of rubber!!! Awesome!!! It's been 19 years!! Dayum, I need to go to some races this year!!!

UtherJoe


----------



## Pete McKay (Dec 20, 2006)

Dirt late models run at Hanford about 45 minutes south of Fresno. While not as fast as the 440 sprinters they offer more close racing. I used to sit in the turn 1 bleechers until a WoO show where during qualifying I got my beer filled with flying chunks of clay. When we go now we sit in the Lithia Ford box just above the fence level on the starting line. 

Version 2 of the car is underway, same mold being used but it's a different look already. I have v1 saved in casting resin but I think v2 is going to be the one that will be more popular. No pics yet, Yoshi and Sarah have my new camera in Dizzyland for the next couple of days.


----------



## Pete McKay (Dec 20, 2006)

OK, got my camera back and took some pics of the v.2 mold today.










The car is another 0.030 wider, the tire cut outs are covered and the rear wing and roof line have been widened. I sanded off the applique nose and roof line details, once I get a couple of test shots done I'll decide if I'll redo that feature or leave it smooth. If I leave it smooth the painter can decided where the window lines go, just as on the dirt modified. 

The hood scoop replaces the air cleaner, the impression between the front fenders is deeper and the front is slightly re-profiled. In widening the roof line I kept the offset on the right side. The area where ahead of the front wheel wells is a smooth transition to the nose as well. Without the wheel wells indicated the driver can decide how far forward or back to mount it as well. Rules will be written into our rule book to govern that.

I lost track of time but I think we're up to about 11 hours now.


----------



## ampracing99 (Jun 17, 2008)

*wow*

wow, great job Pete, do you sell these bodies? i might be interested, very nice work, shon:thumbsup:


----------



## Pete McKay (Dec 20, 2006)

Shon, I will after the new year. They more than likely will be $3 (plus shipping) cut and painted in a single solid color. Shipping will be ablout $2 and that will cover 1 to 20 cars. Over $20...might be a bit more. Wait until I get it prototypes and on a chassis before you decide. I'll be doing that between Christmas and New years.


----------

