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  #171  
Old 12-05-2018, 05:35 PM
Kerry Pinkerton's Avatar
Kerry Pinkerton Kerry Pinkerton is offline
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Joel, one thing that got me is the door hinge location.

I'm using some street rod hidden hinges and set them up to work and they did indeed work well. However, what bit me is the curve in the side of the body. Just like decklids, things that open OUTWARD need to have a concave flange or they will run into the outward curve in the body.

Before I had a skin on the body, the doors and A pilliar worked great. The hinges swung open to the max of the hinge which was about 90 degrees. However, once I put skins on, the door touches the side of the front fender when it is open about 60-70 degrees. Obviously this will chip the paint and dent the body because at some point I, or someone else, will allow the door to open too far.

I have two choices.

1- Come up with a stop that will keep the door from opening past a 'safe point. That would not be difficult and because the door is pretty long, a 90 degree opening is not remotely needed to get into the seat. New knees might be handy but the door opening is fine, even at 45 degrees.

2- Reshape the front edge of the door. Currently the front edge is vertical. like the following photo:

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Since I'm redoing the door back it...

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I have plenty of room and flange to lift the lip, cut the sheet metal flange and redo the flange so that it has a concave shape about 1/2". This would also eliminate the boring vertical line.

I pulled the door yesterday and will have more shop time tomorrow. I'll think about this while doing the back and make a decision. Stops would be the easiest but redoing would look better.....

You're probably smarter than me and have already figured this out but it bit me.
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  #172  
Old 12-06-2018, 11:14 AM
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heinke heinke is offline
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Quote:
Originally Posted by Kerry Pinkerton View Post
Joel, one thing that got me is the door hinge location.

I'm using some street rod hidden hinges and set them up to work and they did indeed work well. However, what bit me is the curve in the side of the body. Just like decklids, things that open OUTWARD need to have a concave flange or they will run into the outward curve in the body.

...

You're probably smarter than me and have already figured this out but it bit me.
Kerry,
Firstly, I like your new shape for rear door top corner much better. I think you're making a good choice on changing it.

Secondly, yes doors are a bitch. I spent hours and hours on my GTO doors getting them to open and close without contacting the door opening. The hinges I used had stops built in but I had to modify them anyway to stop the door from opening too far.

Thirdly, for the Miura I'm hoping to leverage GMs vast experience with door hinges and doors to cut the time and frustration. I'm going to use the C4 Corvette door hinges which have built-in stops and springs to hold the door open. The front edge on these doors opens INWARD, so hopefully I'll have less challenge with the door edge hitting the opening, cross my fingers anyway.
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  #173  
Old 12-15-2018, 01:31 PM
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heinke heinke is offline
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Post Let the station buck modeling begin!

The primary purpose of creating a 3D model for this Miura project is to create a station buck for the body. I decided to go for a stand-alone, egg crate style of buck that will be composed of multiple modules. I have limited workspace in my garage. I hope to use it judiciously by only having the buck modules assembled where Iím focusing my work at any one time and thus optimizing the available work space. The various modules are shown in different colors on this rendering.



The CAD work for designing the buck is being done by Dan Palatnik, the same person who did the CAD work on the 3D body modeling. Iím having Dan do the buck modeling as he has a lot of experience doing this and I have none. This is my first go at building a station buck. Dan started the buck modeling by first identifying where to position transverse stations.



Then he modeled the stations in detail starting at the front of the car and working rearwards.





After modeling all the stations in the front clip module, he modeled the rocker panel modules.



Thatís it for now as the holiday season is here and Dan is getting a much deserved break to celebrate. Work on the modeling the station buck will resume in the New Year.
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  #174  
Old 12-19-2018, 01:16 PM
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Post Disc Brakes

In parallel with modeling the station buck, Iíve started working on the brake system. Iíve elected to go with an aftermarket brake system made by Wilwood. Itís a high-performance brake system utilizing 13Ē rotors on all 4 wheels, 6 piston calipers, and a pedal assembly with built-in balance bar for front to rear bias adjustment on the fly. I ordered up all the pieces a while ago and now am beginning the initial assembly process.

While going aftermarket on a brake system gives a lot of flexibility, it also can make for some engineering challenges as this collection of parts didnít come off an assembly line in an auto plant. The first challenge I ran into is with mounting the calipers to the suspension uprights. The calipers were designed to be mounted with two 3/8Ē bolts and have only 9/16Ē between caliper mounting tabs and rotor for fastening. The suspension uprights are aluminum and given the limited space available, I canít use traditional fasteners like hex nuts behind the aluminum upright. The two milled off areas on the upright is the caliper to upright mating surface.



I could have drilled and tapped threads into the aluminum upright but I donít like this especially for a critical safety item like brakes that will be constantly going through heat/cooling cycles. The 2 fastener options I came up with are heli-coil inserts or a tee-nut. While a heli-coil would give the bolt threads something other than aluminum to grip, the heli-coil itself would still be threading into the aluminum. So better from a standpoint of serviceability in tightening/removing caliper bolts a repeated number of times but still not so good related to grip strength of threads in the aluminum.

A tee-nut gets its name because it looks like a ďTĒ in side profile. The most common use of tee-nuts is in wood where thread grip strength might be an issue and the associated fastener is typically a medium sized screw. I couldnít find a source to buy tee-nuts with a 3/8Ē bolt thread so Iíd need to machine them myself. While it would take quite a bit of time to machine tee-nuts, I felt it was worth it to end up with a superior end result for worry free brakes. A tee-nut would give me about ĹĒ length of thread in steel and a solid flange type head to sandwich the aluminum upright to the caliper.




I started with partially threaded ĹĒ stainless steel bolts. I used a lathe to drill holes into the center of the bolt head and down the shaft. The drilled hole was then threaded for 3/8Ē-24 threads using a hand tap. I then used a vertical mill to machine the bolt heads down to 1/8Ē thick so they would clear the rotor. The bolt shaft was cut off with a hack-saw and remaining shaft ground to final length on a grinding wheel. The picture above shows at various stages of machining where rearmost one is completed tee-nut with a 3/8" bolt in it. Like I said lots of machining and time to make each one and 8 tee-nuts were needed.





The rest of the assembly on the car was straight forward. I double checked the clearance and have about .030Ē between the tee-nut head and rotor surface. Not a lot but it should be enough. This brake system uses a separate cable operated caliper for parking brake. Thatís the smaller caliper in front.





More to come on brake systemÖ
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  #175  
Old 12-20-2018, 09:02 AM
kcoffield kcoffield is offline
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Quote:
Originally Posted by heinke View Post
..........The most common use of tee-nuts is in wood where thread grip strength might be an issue and the associated fastener is typically a medium sized screw. I couldnít find a source to buy tee-nuts with a 3/8Ē bolt thread so Iíd need to machine them myself. While it would take quite a bit of time to machine tee-nuts, I felt it was worth it to end up with a superior end result for worry free brakes. A tee-nut would give me about ĹĒ length of thread in steel and a solid flange type head to sandwich the aluminum upright to the caliper.
Dunno how thick the head or what the material is on the T-nuts but you may want to calculate the shear area through the head thickness and compare it with shear strength of the bolt material and load achieved when you torque the 3/8 mounting bolts. What keeps the T-nuts from spinning? Are they pressed or pinned in?

Best,
Kelly
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  #176  
Old 12-20-2018, 09:52 AM
tom walker tom walker is offline
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I noticed the T nut head thickness also, would it make more sense to start with a larger diameter bolt with threads all the way to the head and the bore and tap the mounting flange.
Tom
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  #177  
Old 12-20-2018, 11:08 AM
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Originally Posted by kcoffield View Post
Dunno how thick the head or what the material is on the T-nuts but you may want to calculate the shear area through the head thickness and compare it with shear strength of the bolt material and load achieved when you torque the 3/8 mounting bolts. What keeps the T-nuts from spinning? Are they pressed or pinned in?

Best,
Kelly
The head on the tee-nut is 1/8" thick. I couldn't go any thicker and have the needed clearance to rotor surface (only have .028" clearance now). I will be glueing the tee-nuts to the upright with the same methacrylate glue that was used to bond all the chassis parts together. This should spread the strain/pull when bolts are torqued into tee-nuts over the surface of the tee-nut and not just on the head. The glue will keep them from spinning when torqued but I will also have a thin 3/4" wrench on them as well.

Quote:
Originally Posted by tom walker View Post
I noticed the T nut head thickness also, would it make more sense to start with a larger diameter bolt with threads all the way to the head and the bore and tap the mounting flange.
Tom
I did think about having tee-nuts with an exterior thread and screwing them into the upright. I decided against it as there's not enough aluminum around the outside edge of the upright to work with. The Wilwood calipers have a fairly short mounting tab and this limits/constrains the space on upright for fasteners.

Thanks for the questions and ideas guys! I think the tee-nuts I have will work fine but I will be keeping an eye on them once the car mechanical shake down starts to make sure.
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  #178  
Old 12-20-2018, 05:07 PM
Charlie Myres Charlie Myres is offline
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I wonder about using stainless steel for the fasteners; it is not high-tensile and may be too weak for the job,

Cheers Charlie
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  #179  
Old 12-21-2018, 11:24 AM
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I wonder about using stainless steel for the fasteners; it is not high-tensile and may be too weak for the job,

Cheers Charlie
Good point Charlie. Yes, the stainless steel bolts I used as base stock don't have the same tensile strength as a steel bolt does. I chose stainless steel to avoid the rust and corrosion that might occur on the bare steel after machining took the plating off.

Here's the thought process I went through. The calipers have 6 pistons and thus should have equal amounts of clamping pressure on each side of the rotor. Given that, the caliper mounting bolts should have a much greater amount of shear force against them than tension force. The shear force will go against the 3/8" bolt and not against the tee-nut. The tee-nut should only have the amount of tension against it that's applied during assembly torquing. I don't think the caliper bolts will need to be torqued to an extreme as the whole caliper and upright assembly (both aluminum) will tighten up from heat expansion as braking heats them.

So I felt the lower tensile strength of stainless steel would be adequate and I could avoid having a bunch of rusted up fasteners. I do have a backup plan for how to mount the calipers but it felt like over-engineering and I don't want to go there unless what I've done actually has an issue.
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  #180  
Old 12-30-2018, 02:57 PM
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Post Radiator coolant tubes

Iíve switched focus again from brake system to coolant lines. A great thing about a project at this early stage is that if you hit an issue with one area, thereís plenty of other areas where progress can be made. Iíve decided to connect the radiator openings to the main under chassis coolant tubes with 1 ĹĒ purpose routed, bent aluminum tubes. I am making these from mandrel bent Al 6061 tube and welding them together. I did some preliminary design and ordered up the mandrel bends and silicon hose adapters/couplers I thought were needed.

I started fabrication with the bottom tube as I needed to establish its position so the upper tube could be routed around it. Both these tubes need to be routed to clear the spare tire.



One each of 120 degree, 45 degree and 60 degree bends and 2 welds were needed to complete this tube. All in all, fairly straight forward. The upper tube is more complicated as it needs to be routed over the rack & pinion but still under the spare tire. A 180 degree bend cut in the middle and repositioned gives the needed jog for this. A hose clamp temporarily holds the joint for mockup purposes.



I then started from the other end to determine what type of bend was needed for the middle. For the middle tube area, I need a bend thatís between 15 to 20 degrees. Of course, I donít have one of these and it took an Internet search to find a source. I found a source for an 18 degree bend and now have it on order.



I need to have an air bleed valve at the topmost part above the radiator so I made a bung and welded it on at the top of the top tube.



Iím now at a hold state to finish these coolant tubes until the last tube bend arrives.
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