S2's Build Thread

Scott

Lifetime Supporter
(Part 2: Continuation of previous post)
GOTTA GET SOME OF THAT ONYX

The Mark Two prints with engineering nylon and Onyx. Onyx is a proprietary material that is composed of engineering nylon and chopped carbon fiber (CCF -- every cool tech has an acronym). It is more heat resistant and significantly stiffer than plain nylon. It also has a nice matte black appearance. When you combine Onyx and one of the continuous fiber strands you wind up with a really strong, good looking part.


(A part printed in Onyx on a Mark Two, not my part)

NO MOISTURE HERE
The printer comes with an air-tight dry box to hold the nylon or Onyx. It's a high-quality box from Pelican Case which, I assume, they had customized with an air-tight, push-to-connect fitting and a bracket to hold the continuous fiber spool. The continuous fiber spool appears to be 3D printed, perhaps on a Markforged. If so, you gotta love companies that eat their own dog food. When you print a part it knows the last time that you printed and it will automatically print a purge strip to consume any of the filament in the Bowden tube that may have absorbed water.

All of the filament and continuous fiber comes carefully packaged in air-tight packaging. The filament is packaged with desiccant that you're drop into the dry box.



Dry box behind the printer



The result is an end-to-end solution that produces dry nylon and a high-quality print. This is far beyond upgrading the hot end of my 3D printer.

HARDWARE
As I've already stated, if Apple were to build a 3D printer it would look the Markforged. The build quality, fit and finish are outstanding. It features a color touch screen built into base and it comes with everything that you need to begin printing.



Fits on counter






Rather than using paper as a gauge to adjust the print heads, they provide brass strips, one for nylon/Onyx and the other for the continuous strands which are set higher.
 
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Scott

Lifetime Supporter
(PART 3: Continuation of previous post)

REMOVABLE BUILD PLATFORM
The kinetic build platform is a pretty slick piece of engineering. You simply pull it out and when you drop it back in place the magnets locate it with ten-micron accuracy. This is incredibly useful because you coat the platform with Elmer's glue before every print to ensure that the part sticks. This would be more difficult to do it the bed were mounted. After trying to remove the first part I realized why the they include a steel putty knife to remove the parts. Holy crap do the parts stick. I don't think I would be able to get the parts off of the plate if it were inside of the printer -- at least not with out damaging the printer. The approach works because some of the parts that had curled bottom edges on my old printer are now perfectly flat. Elmer's glue is water soluble so a quick rinse under the faucet and a paper towel are all that are required to clean it. The only downside is that kids love this glue, so mine is going under lock and key.

A removable platform is also incredibly useful when you want to embed parts into the part being printed. For example, a nut (nylon threads aren't very durable), a stud, a RFID chip etc. With my old printer I had to carefully watch the printing process and stop it at the correct point. Keep in mind that a part can take anywhere from a few minutes to days to print depending on its size so this is actually more inconvenient than it first sounds. In addition, you need to ensure that the part is flush or below the z-axis of the layer being printed or the print head will collide with it -- not a good thing. Worst yet, unless you have Superman vision there is no way to know what layer you're on so you pretty much need to add an extraneous feature somewhere on the part that you will notice if you haven't fallen asleep.

The Mark Two's software, called Eiger, enables you pick the exact layer(s) that you'd like to pause printing. It automatically suspends printing and sends you an email notification when that layer is reached. At that point you can remove the platform, add the parts and simply drop the platform back into place. With my old printer it was somewhere between difficult and impossible to insert part. This approach makes it easy.

SOFTWARE
I wasn't sure I was going to like having the software run in the cloud. I took me only a couple of minutes to decide I liked it. All you need is Chrome and an internet connection. The printer can be hardwired or run wirelessly. I just screwed in the Wi-Fi antenna and had the connection up and running in couple of minutes. I love being able to kick off a print job from my browser without needing to download the files to a SD card or USB dongle and then monitor the progress of the job from anywhere (the Mark X has a one one-micron laser that can validate the dimensions of the part as it's being printed). I won't get into all of the features or post screen shots (they might not like that), but it's a slick web application that is clearly set up for the industrial use.

For example, you can have multiple users and every print is tracked - who, what, when, how much, etc. Do you need that in the garage? Hell yes, every time I spend $650 on toner for the family HP printer, I ask whose been printing so much... apparently it's the infamous Swartz mouse that eats all of the cookies etc. when everyone is sleeping. I know for a fact that it's a different mouse because I'm well acquainted with the one that eats the cookies and I know he doesn't waste toner LOL. I want to encourage the kids to use the printer, but I'm glad there won't be any question about who did it.

All in all I really liked the software. I've have only had one crash in the browser. No data was lost and I simply had to re-click a button. No big deal. However, it's missing some features. For example:

The concentric fill algorithm doesn't wrap interior holes unless you have enough fiber rings starting from the edge to intersect the hole. For example, you have a rectangle with a hole in middle and want to reinforce the hole with five concentric rings. If you set the concentric fiber rings to five, you wind up with the picture on the left. The only way to wrap the hole is to fill the entire rectangle as shown in the picture on the right. Not a big deal, but it means that you might have to use a lot more fiber than you want to wrap an interior hole. Ideally the concentric layout algorithm would allow you to specify if you wanted to wrap interior holes and/or the perimiter.




CONDENSER BRACKETS
So back to the original point, I wanted to print some brackets for the condenser. 3D printing allowed me design an organic shape that perfectly fits the inside of the channel, provides an integral condenser/radiator spacer and to hold the condenser at a 55 degree angle.


















 

Scott

Lifetime Supporter
The Hoosier hubs arrived. As expected they are really nicely machined and very robust. The hub on the left is what came. with the kit. It's made in the USA and better than the OEM one. The only reason that I'm upgrading it is because I wanted a reluctor for traction/launch control.

The hub on the right is from Hoosier. It's a lot longer due to a bigger bearing and the reluctor, sensor and connector, but I've measured a bunch of times and there should be no issue. Also note how much thicker the flanges are; the round wheel flange is 0.5" vs. 0.3" and the rectangular upright flange is 0.46" vs. 0.32". The rectangular flange has threaded rather than clearance holes, so they'll have to be drilled. Interesting the wheel flange has holes to support both press in and screw in studs. This is possible because the flange doesn't have the three large holes the OEM flanges have (I never did figure out what those were for).

I tried to remove the uprights so that the lip mentioned in the previous post can be machined. The ball joints are stuck tight. I tried to remove the steel bar from the bottom of the upright, but I wasn't able to remove one of the bolts. I know that there are all types of tools/pullers to remove ball joints. Can someone make a recommendation?


In addition, since I'm going to remove the ball joints, I have an opportunity to upgrade them. The wiki provides some options here, but I'm wondering if anyone has any experience with them.
 

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Ken Roberts

Supporter
The large hole(s) in the wheel mounting flange is there so you can stick an extension through it to get to the four mounting bolts of the rectangular flange. I tossed the no name ball joints and bought The Moog K6136. Moog is the only brand I use for ball joints.

A typical pickle fork should work. Those hub assemblies will last a long time.

Now's a good time to replace those stacked washers at the ball joint for castle nut cotter pin alignment. I had some correct length spacers made from round bar stock cut in a lathe.
 
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Hey Scott, it's great fun following your 3D printing adventures, that's really cool stuff, I'll be pinging you for some advice at some point for a much more modest project I have in mind.

I do have a cynical question I hope you'll entertain though. I see you're essentially bolting the bottom of your radiator to the floor pan. Is that kosher? I always thought the radiator needs to be suspended using rubber mounts so it's free to expand and contract without being constrained by the chassis.
 

Scott

Lifetime Supporter
Mark,

You may have a point. I took a closer look at how the radiator is mounted. The radiator mounting flange has a rubber grommet which is made of ~0.05” rubber. From what I can tell, it’s more of a wire grommet than something designed for vibration isolation. IMO, it wouldn’t take much radial deflection to cause the thin flange to slice though the side of the grommet. My guess is that most of the value is the rubber that’s sandwiched between the radiator and chassis. It’s surely better than nothing, but I can’t imagine it doing a whole lot.

Most of the condenser brackets that I’ve see are bent metal with no apparent vibration isolation. It would be easy for me to tweak both the upper and lower brackets to have more rubber than the radiator has (and I think I will). Most of the vibration isolation parts on McMaster seem to have a durometer of 50A, so I’ll order some.

I spoke with Allan and he indicated that he isn’t aware of any issues with the early cars. They didn’t have any isolation and they already have some miles on them. I also spoke with Chuck, the guy who makes the radiators for RCR/Superlite, today about a fan shroud he’s making for me and I asked him what he thought. He’d prefer to have them mounted solid so that there are no electrolysis issues and he’s not aware of any issues with how they’re mounted.

In any event, I’m wondering what you and others have done with respect to isolating both the radiator (which has significantly more mass) and the condenser from the chassis. It would also be good to hear if anyone has had issues with how their radiator and condenser was mounted.
 
Scott, I ran through my collection of SLC hardware photos and it seems everybody has the radiator solid mounted to that front box(sorry to pick on you ;) ). I don't really use street driven cars as validation for soundness of an engineering design, specially SLCs which are driven lightly and infrequently. However the factory racer 01 car also has the radiator solid mounted to the box, so we have some race proven validation there.

I've seen one or two people get creative and try to rubber suspend the radiator, unfortunately I can't find any links. One person used an elaborate rubber mount out of an Audi I believe. Somebody else used a simple double rubber hose sleeve setup which I thought was simple and effective so I copied it for my car. Also worth a look is the QRP race car, it has a custom radiator setup but they seem to have mounted it from below using what seems to be thin sheet metal that would have some flexibility and they have air gaps between the radiator and the solid cage around it.

On my car I added a few washers to the horizontal rods to spread out the radiator box so it doesn't land lock the radiator. I have about 1/4" air gap on either side now. I also used that double hose trick. The radiator mount holes were ground out so that the thinner rubber hose goes through it and there is no metal on metal contact.
 

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I've had two radiator core failures on my SLC due to insufficient isolation of the radiator from the chassis. Pics of my new rubber mounting system for the end tanks included. I've now done 10,000kms with this setup including time on the track, without issue.
IMG_3100.jpgIMG_3098.jpgradiator mounting.jpg

Shroud design (1st pic is pre fan holes being cut) and fans mounted in case anyones interested.
IMG_3103.jpgIMG_3104.jpgIMG_3105.jpg
 
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Scott

Lifetime Supporter
Mark, I think this is the link to the approach you copied. Certainly gives more isolation than the grommets.
http://www.gt40s.com/forum/slc-clubhouse/41384-radiator-mount.html

Stu, thanks for posting your experience. I had been looking at a bunch of mounts from McMaster:
https://www.mcmaster.com/#vibration-damping-sandwich-mounts/=15k5k57
But I couldn't figure out how to make them fit because I was thinking horizontal. Your brackets allow vertical mounting, problem solved. Do you know what the specs are for the rubber? If I go that route, there are lots of options...

I'm also working with someone to build a shroud.
 
Stu, thanks for posting your experience. I had been looking at a bunch of mounts from McMaster:
https://www.mcmaster.com/#vibration-damping-sandwich-mounts/=15k5k57
But I couldn't figure out how to make them fit because I was thinking horizontal. Your brackets allow vertical mounting, problem solved. Do you know what the specs are for the rubber? If I go that route, there are lots of options...
I'm also working with someone to build a shroud.
Scott
The 9376K48 is similar to the metric M8 ones I'm using.

Also a quick correction to post #110. My radiator core failure was MAINLY caused by an installation issue with the end tanks in relation to the core, as the core heater expanded it was coming into contact with the end tanks and over time this destroyed the core. The new bracket mounting system was additional security for the lack of flex/isolation.
 
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Scott

Lifetime Supporter
Thanks Mark/Stu/Ken, I'm going to do some thinking about my approach to the radiator/condenser mounting.

I took the uprights and hubs to a local machine shop and they came out great. As you can see in the first picture a large rotary table was used to remove the lip on the upright that was preventing the hub from being mounted. A very small chamfer was also added to the opening so that the flange would sit flat. The four threaded holes in the rectangular flange were also drilled to make them clearance holes. The machinist said it was as tough as any metal he's ever drilled.






The housing that bolts to the upright has an electroless nickel finish that should hold up well to the elements. They didn't use nickel on the wheel flange because it would have changed the dimensions on the bearing surfaces and masking was prohibitively expensive. It's a chromemoly forging and won't flash rust like a mild steel part does. I'll just apply some Boeshield T-9 to both surfaces.

I also confirmed that there are 47 teeth on the reluctor... the primary reason for upgrading the hubs.
 
Mark

In your post thread #109 is a picture of the Blue Mistress. Raced in 25 hr for 3 yrs.

The radiator is mounted at the top sides with one 1/4" bolt on each side with a rubber pad sandwiched in between. The bottom of the radiator has a rubber edge mounted and just sits on the bottom aluminum pan.

So to say it is mounted solid is not exactly true.

:)
 
Thanks for clarifying that Don! That was the best picture I had and I tried my best at guessing how it was setup.

I think we all appreciate the work you've done on that car, it serves as a great test mule for identifying the strengths and weaknesses of the platform given the stresses it's been put through.
 

Scott

Lifetime Supporter
Scott...

That is f'ing awesome.
Preston, thanks, it’s been a lot of fun learning.

Allan mentioned that you also had the removable side impact bars. I designed some end caps to cover the connectors when the bars are out. They look great when printed in Onyx (tough nylon with chopped carbon fiber) and since I print them with a 10% fill density they weigh next to nothing. If you’re interested in a set, PM me your address and I’ll print some for you.
 
Wow! Amazing AND quick learning on 3D printing considering you've never done it prior to this. I know 2D CAD, but just now learning 3D for personal use. I'm in the same boat as you as far as 3D printing and being able to be used for SLC items. I'm envious you beat me to it, lol. Keep up the good work!
 

Scott

Lifetime Supporter
Del,

The jump from 2D to 3D isn’t so bad if you’re modeling solids (as opposed to surfaces). With most packages you draw a 2D sketch and then extrude it to create a 3D shape. Then you pick a plane on that shape and draw a 2D sketch on it and then do one of the following: extrude, extrude cut, revolve, revolve cut or loft. And you just repeat that process until you’re done.
 
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