Custom build in process

[ra5ax]

All,

I've been looking through the site for a little while now and thought I should share my current build few images of design and then progress.

This is based on the MX5 running gear and built from that up. a lot to do still but its slowly getting there.







Frame structure is built hopefully get a pic up tomorrow for you all.

any thoughts would be really appreciated.

Hope you enjy

[ra5ax]

images of progress

[ra5ax]

last cad drawings werent great so thought id post up these slightly amended versions this is to scale and hopefully once fully built should allow me to pull manufacture plans if there was any interest.

let me know your thoughts all criticism and compliments are always constructive.

[JG]

Very nice looking design. Will follow this with interest and great use of MX5

[ra5ax]

ill keep everything updated please perceverve the build is slow at the moment due to moving house and the winter (its currently being built outside) projected 2years to complete....

[ra5ax]

finally an update.... taken a while im afraid but i believe the chassis is almost there.

Need to work on the suspension mounts and a little more cross strengthening but let me know your thoughts.

Final body designs keep changing but now looking to cross the above model with a Mazda furia style rear end.

[IMG][/IMG]

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[IMG][/IMG]

[jmc14]

Hello Andy, I like your project. I have respect and admiration for anyone that scratch builds their dream car.

I will be interested in seeing the final frame. As it is, and from what I can see in the pictures, I am worried that it won't be very stiff, especially in torsion.

The car will be much lighter than a stock Miata so the stock shocks and springs will not work well. Since this is true, for my build, I am not using them. I am using small body coil over racing shocks. You can get them so that they are adjustable for compression and rebound. That way you can fine tune them. There is a large variety of reasonably priced springs available. The shocks that I am using are slightly less than 14 inches tall when fully extended. They have simple mounting holes with spherical bearings. They mount using a 1/2 inch bolt. This makes the upper shock mount much lower than the Miata mount and easier to construct. The front shock with spring is small enough to fit through the front upper A-frame. It can be mounted almost vertically.

The Miata engine is mounted in the front cradle. As a result it ends up being very tall. This is a challenge to get a good looking body. The Miata is close to 50/50 in weight distribution. But, when the body is removed the weight shifts to the front. This isn't ideal for handling. I prefer cars with 54% rear weight. For my build I extended the wheelbase to 95 inches and then shortened the torque arm and moved the engine rearward by about 10 inches. This lets the hood line drop quicker and shifts the weight.

When making a one of body on the cheap I use foil backed insulation foam. It is available in 4 inch thickness and in 4 by 8 foot sheets. I cut the foam board to the height required to begin sculpting. Then glue the boards together to make the width that I need. I glue them on edge. I remove the foil (before gluing) enough so that when I sand I am not going to hit it. I use a strong spray glue to glue the boards together.

The board is easily sanded and shaped. I sculpt one side of the car to the middle line. When I have the side finished I make a mark every 2 inches from front to back along the center line. I then take 1/4 inch foam board and
make a template by cutting it to match the contour. I do this every 2 inches. Then I turn the template to the other side and shape until it matches.

If you are making just 1 body you can fiberglass over the foam. (make sure that you don't use styrofoam board. The resin will eat it.) You will need to skim coat the raw fiberglass with body filler to smooth it out. When done you can remove the foam and you will have a fiberglass shell left that you can finish to paint.

If you want to make molds so that you can duplicate the body I would skim the foam with drywall mud. Sand that smooth. Then spray it with a high build primer. Sand and polish that to a great finish. Then you can make mold from the plug.

Just my 2 cents. My way is not the only way. Have fun, John

[ra5ax]

JMC14 I appreciate the input its my first build so any input is really beneficial

after looking at your frame I do think that torsionally i dont have the right amount of strength ill be working on that over the next month or so.

I posted on your thread forgetting you had replied to me so apologies there.

The car is on Bilstien racing shocks and springs sitting about 60mm lower than stock and adjustable stiffness so im hoping this will be ok.

my major issues at the moment are concerns on suspension strength but I think im going to worry about that until it hits the road no matter what strength i build into it.

regards the body process I think the Foil backed foam is the way to go. its going to be a one off just taking time at weekends and evenings its amazing how many you dont get free....

Hopefully getting some 6mm Laser plates cut from work in the next week or so which should strengthen the suspension and add some decent chassis mounting points.

Where are you based be pleased to shout you a pint or two for a bit of an exchange in knowledge and ideas

[jmc14]

Hello Andy, Looking good! I agree that we are doing a similar build and that it would be fun to get together to discus. However, I am a long way from you. I am in New York, USA.

You asked about my engine height. It is lower than stock. I extended the wheelbase on my frame to 95 inches and then moved the engine back by another 8 inches. My frame has 4.5 inches of ground clearance and my new motor mounts have the bottom of the oil pan flush with the bottom of the frame. Moving the engine back allowed me to lower the engine, provide great legroom (I have long legs), puts the shifter in the correct position as my seating position has also moved rearward, and lets me get a better balance. I'm shooting for 54% rear weight. It also allows for the bonnet to be lower an slope quicker to the front.

With your new lower shocks how much compression length is there with the frame at ride height? What is the stroke length of the shock?

Have fun.

[ra5ax]

bit of an update as the build progresses, a few images below.

Dash in (roughly needs a little more support) Pedals and steering column positioned awaiting laser cut plates to finish off, Frame complete and body work ribs started. floor to go in fairly soon but holding off as it gives me better access to all the tricky areas