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Race Car Fabrication There is a lot of cool fabriaction going on the race car industry, show us what you got.


Race Car Fabrication There is a lot of cool fabriaction going on the race car industry, show us what you got.

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  #61  
Old 03-19-2014, 12:48 PM
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LOVE my Kurt vise. That's a great upgrade.
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  #62  
Old 03-19-2014, 01:56 PM
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Originally Posted by Graham08 View Post
I'm about to start making chips fly on the Watt's link center pivot for the rear suspension.
Can't wait to see what you come up with. I've been contemplating going with a Watts or a long panhard on my Nova for both the roll-center tuning benefits and to keep the tires from rubbing under hard turns. Not a lot of people running them with leafs though and I think there is a need to match the roll centers. I just hate seeing my rear move side to side under bushing/leaf flex.

Not sure if you've seen the Fays 2 stuff. He sells the bellcrank separately if you don't want to make your own or you can get ideas from his design. http://fays2.net/ This thread has some photos: http://www.pro-touring.com/threads/8...s-installation
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Last edited by TheBandit; 03-19-2014 at 02:10 PM.
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  #63  
Old 03-19-2014, 02:21 PM
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Graham08 Graham08 is offline
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It shouldn't be real long now. I started making chips on the center pivots last night. I've seen the Fays2 stuff and it looks pretty decent, especially for the price. My center pivot is similar but a little different.

I can see where adding something to leaves would make your car corner better. It would definitely keep rear steer and scrub in check...I would lean towards a Watt's linkage just because for the usable range of travel it moves in a straight line instead of fighting the leaves to pull the rear end laterally.

I second your opinion on the Kurt vise. After actually using it a little bit, I can definitely say I should have done this a long time ago! I also tried out an inserted boring bar with aluminum specific inserts in my boring head. Easily the best surface finish I've ever done on a bored hole...amazing what using the correct tools for the job can do!
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  #64  
Old 03-28-2014, 05:23 PM
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I just finished the Watt's linkage center pivots. I'm pretty excited about how they came out. When I starting machining, I wasn't going to lighten them, just put the appropriate holes and slots in them and machine the outside profile. Partway through, I realized I could take a fair amount of weight out without too much additional work, so they ended up getting lightened up a bit.

Here's a pic after all the vise setups were done:



The Kurt vise is an awesome upgrade, BTW!

And after the rotary table work, deburring, and having the bronze bushings pressed into the center pivot:



I had a hard time making up my mind between bronze bushings and using needle bearings. The bronze won out because I was able to have a built in thrust surface by using flanged bushings, and it's just a simpler solution that works well with the adjuster I have in the works. More on that next time...
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  #65  
Old 03-28-2014, 06:15 PM
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Wow those look fantastic. How many hours do you have into those?
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  #66  
Old 03-28-2014, 08:17 PM
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Originally Posted by TheBandit View Post
Wow those look fantastic. How many hours do you have into those?
Thanks! Too many! Probably in the neighborhood of 10 hours total for the pair. It's hard to tell because I have only been able to spend an hour or so at a time in the shop recently. The lightening I did added a couple hours to the job.
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  #67  
Old 03-31-2014, 08:34 AM
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I got a fair amount of work done on the chassis side of the Watt's linkage adjuster done. I had a friend give me some parts that are used to build NASCAR truck arms, and I was able to make use of another one for this.

The serrated part of the adjuster is what I started with. Originally, this had a big mounting lug on the side that I cut off. I split a piece of 2-1/8" x 0.120" wall tube to make the ends of the pocket, and used 1/8" x 1-1/4" flat bar to make the sides.



The serrations are on a 1/4" pitch, and the slot takes a 3/4" bolt. The original application for this part is to attach the track bar to the left truck arm in a stock car.

In order to make room in the chassis for this, I had to move a tube. The tube on the right side of this picture with the dogleg in it originally made a node at the bottom of the main hoop. I spliced in a new piece so I have a 3" wide space between the main hoop and the support. It's sleeved and plug welded at the top, so the splice is stronger than the original tube.



Here is the rear view of everything tacked in place:



I welded the adjuster pocket into the rear plate on the table to minimize the amount of standing on my head required to weld it into the car.

Here's a little wider shot:



The plates are 0.090" thick 4130 sheet, spaced 1" apart. I formed a little piece to cap the top. This should be good and stiff.

Here is a pic from the front side:



I'm going to build a little access panel into the body to allow this to be adjusted easily.

The next step is the serrated mating piece for this adjuster, which will also include a short shaft for the Watt's linkage pivot to ride on. More on that soon...
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  #68  
Old 04-09-2014, 08:09 AM
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I finished up the rest of the pieces to attach the Watt's linkage to the chassis last night. Here's everything lined up:



They stack up in order from left to right. Second from left is the inner pivot/serrated adjuster. The business end looks like this:



I cut the serrations using a 0.060" corner radius end mill, with the head of the milling machine tilted over 45 degrees. The shaft is 0.002" smaller in diameter than bushings in the center pivot, and about 0.010" longer than the outside dimension of the bushings. This allows the whole assembly to be torqued and not bind the center pivot up.

The washers and inner pivot are made out of 4140 HT.

Here's everything stacked up, ready to bolt on:



All bolted up!



It will go all the way down on the adjuster with the bottom of the center pivot just above the bottom of the frame. This is a good thing because bottoming the frame out is a fact of life with 2" of static ride height.

Next up are some links to actually make this a Watt's linkage, and the stuff they attach to on the rear end.


Last edited by Graham08; 04-09-2014 at 08:14 AM.
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  #69  
Old 04-09-2014, 12:12 PM
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Badass

I haven't had much time to think through this, but what is the effect of having the Watts pivot mounted off center? Are the axle pivots also going to be off center with equal length connecting rods?
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Last edited by TheBandit; 04-09-2014 at 12:57 PM.
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  #70  
Old 04-09-2014, 12:32 PM
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Badass
I second what Clint said!
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  #71  
Old 04-09-2014, 01:28 PM
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Originally Posted by TheBandit View Post
Badass

I haven't had much time to think through this, but what is the effect of having the Watts pivot mounted off center? Are the axle pivots also going to be off center with equal length connecting rods?
Thanks! It's only badass if it actually works on the track.

The offset Watt's linkage mounting not a big deal. For the most part, the vertical loads from the links being non-level during travel cancel each other out. It's not like a Panhard rod where you start to get significant jacking forces when it's not level. This is the biggest effect that an asymmetric mounting would cause: asymmetric wheel loads due to the jacking force being applied somewhere other than the center of the axle. This can be a tuning tool with a Panhard rod on ovals, which makes the Watt's linkage a compromise because you lose the ability to manipulate the jacking force. The other side of the coin is because the Watt's linkage provides linear motion over a large range, it doesn't bind the torque tube, which should be better for grip.

The reason for it being offset in the first place is because sprint cars use an open tube axle. The axle itself is exposed and must be supported on the ends with bearing carriers ("birdcages"). This limits possible mounting locations on the rear end to either the quick change center section or the birdcages. The links will be equal length, with the lower one mounted to the left side of the center section (it will go underneath to get to the left side), and the upper link mounted to the right birdcage.

I have a fair amount of work ahead of me to get to that point. I have to make the birdcages, the mounting bracket on the center section, and the links themselves.

As they say, when one plans to think outside the box, one should also plan on being lonely!
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  #72  
Old 04-19-2014, 08:23 AM
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My dad an I were both fortunate enough to have yesterday off of work, so we spent the day working in the shop! He came over and we took a slight detour from making suspension parts to put the back of the frame back together.

The original plan for the car was for rear torsion bars, as discussed earlier in this thread. A few years have passed, and my experiences in that time have led me to believe that coil-overs are the way to go, which led to the rear clip being cut off the car to get rid of the weight of the torsion tubes, and rearrange some things to be a better fit for the coils. Plus, my skills as both a designer and fabricator have improved in that time, so there were some things I just wanted to change.

Here is the overall result of our day's work:



Basically everything behind the rear hoop was done in a day, with the exception of the lower main frame rails and the rear crossmember.

Here's a rear 3/4 view:



The rear clip is pretty much done with the exception of shock mounts.

I wound up having to put a bend in the top tube running from the back of the cage down to the rear crossmember because I pushed the node back where the rear shocks attach to the car. It makes some room for the LR which was needed because of the geometry change, and cleans up the attachment of the RR tower to the car. I have some streamline tubing on hand to make the RR tower...stay tuned for that!

I finally got to use my Baileigh TN-250 for the purpose I had envisioned when I got it: bent tube gussets!



The TN-250 really simplifies the process of making these things. Once we got the angle of bend and notch angle sorted, these fit super tight without a bunch of grinding.

Here those gussets are being used to stiffen up an area that's impossible to triangulate properly:



This is because the fuel tank goes in this space. We have to run a "standard, sprint car appearing tail" according to the rules, which means there ends up being a big hole in the frame to accommodate it (and the rear end). If I had unlimited funds, I would make a custom tank (and have the bladder made for it: $$$) that is more conducive to triangulating the frame, and build a "standard, sprint car appearing" cover for it. Maybe on version 2...

Another view of one of those gussets:



And finally, a gusset in the bottom rear corner of the frame. Just trying to stiffen things up a bit, plus they just look cool!



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  #73  
Old 04-23-2014, 10:19 AM
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Those look great. Did it take a lot of trial and error to figure out the bend and notch angles or is there a straightforward way to set it up? I see you did both 90 degree and <90 degree corners - would be interested to know the process you used to get the notches right.
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Last edited by TheBandit; 04-23-2014 at 10:24 AM.
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  #74  
Old 04-23-2014, 11:27 AM
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Thanks Clint!

The setup for this is actually surprisingly rigid. The only real issue I had was if the two notches got too close together to where the front and rear jaws in the vise weren't gripping tube the whole way around. In that case, it didn't take much to knock the piece out of alignment because there wasn't a good grip.

We actually did the acute angle first. I don't know if it was beginner's luck or what, but those didn't take much to get right. I guessed at a 60 degree bend, and had to iterate a bit on the notch angle, but the piece that was the first attempt ended up getting used.

I'm not going to lie, the 90 degree corners kicked my ass. I think it's because there has to be a short flat at the ends, which makes it really sensitive to where the tube gets clamped in the notcher in addition to the notch angle. I wound up bending the tube 45 degrees, then checking the angle of the notcher to the flat section to ensure it was 22.5 degrees to get reliable results. I made some scrap, but once I got the first one, I was able to repeat the process and get the second one right on the first attempt.

I think if I was using a 5.5" bend radius instead of a 4.5" it would not have been so tricky, because the length of the bend would be longer, and it would push the bend out from the corner without having to have a short straight section.

Thanks for watching. I've had to take a couple days away from this because I traded some labor for some parts and need to hold up my end of that deal, but I'll be back on it pretty soon. I have the Watt's linkage attachment to the center section of the rear end designed and have started making some pieces for that.

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  #75  
Old 04-23-2014, 01:12 PM
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Great build. I don't know why I missed all the machined parts until now, but I really like it. I know how much time you must have in them, including all the time spent figure out how to make them.
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  #76  
Old 04-24-2014, 09:25 AM
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Thanks Mike! I just found your thread about your Buick. Awesome work there!

There's way too much time in this thing at this point...and still a bunch more to go. But, it's the only way to get what I've envisioned in my head for way too long now.

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  #77  
Old 05-15-2014, 07:54 AM
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I finally got back on this project. I traded some labor for a magneto, so we have a spare. In retrospect, I would have probably been further ahead to just buy a mag, but it is what it is.

I am continuing to make rear suspension parts with the links that make up the Watt's linkage. The right side is really straightforward, but the left requires a bend to go under the center section of the rear end and have adequate clearance for adjustment and droop travel. This means the diameter and wall thickness both have to go up to preserve strength and stiffness.

Another thing that played into the design is I wanted to use a spherical bearing in one end so I wouldn't be loading a rod end in bending. If any of you guys ever did Formula SAE, you know this is one of Carroll Smith's (RIP) cardinal sins. I was given a bunch of 3/4" sphericals, so I figured I better use some of them up.

I had originally planned to just weld a uniball cup in the end of the tube and wrap it with strap, but then I saw these things from Armada Engineering:



Unfortunately, they don't make them for 3/4" sphericals, so I decided to make my own.

I started with 2" 1018 bar stock. Since the sizes are way overkill, 1018 will be more than adequately strong. Here is the first one after doing all the straight turning:



And after turning the radii on one end:



Here is what they look like after round 1 of lathe work (sorta like a trailer hitch ball):



Next it was over to the mill to machine flats on either side:



I got one side done before it was time to quit for the night. I'm hoping McMaster-Carr delivers a ball end mill today so I can do a radius transition from the flat to the shank, then this thing gets bored for the bearing and a snap ring groove cut.
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  #78  
Old 05-15-2014, 11:54 AM
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really cool build
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  #79  
Old 05-16-2014, 07:31 AM
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I was able to finish up spherical housing #1 last night!

After milling the flat sides and the transition to the shank, I roughed in the hole for the spherical bearing with a 1" drill. This gave me something to indicate on in the lathe. I'm using a Super Spacer here to hold the part...these are really sweet because you can index easily and repeatably in 15 degree increments.



Next it was back over to the lathe to finish the bore and cut the snap ring groove:



The finished part!



I think I'm going to make the link up before finishing the second one of these guys to make sure there are absolutely no issues. I'm going to get this rear suspension done yet...
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  #80  
Old 05-16-2014, 09:37 AM
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Very cool Graham!
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