Stephan's SLC Build Log

[Joel K]

Hi Stephan,

Looking forward to your build thread. I live about 30 minutes from you in Millstone Township, NJ. Just east of Princeton. I’d love to be able to come by and see your SLC kit. I am trying to decide which kit car to purchase and certainly seeing an SLC would be real helpful.

Thanks,

Joel

 

[Stephan E.]

Hello Joel,

Just sent you a PM. Looking forward to meet you.

Cheers

 

[Stephan E.]

I spent some time with the new R8 shifter. I was unable to find relevant posts to show on how the Audi/Gallardo shifter console actually interferes with the tub console. I hope these pictures will give some assistance to others when they are making the decision on changing the shifter to a different model.

After I removed the Audi specific ballast from the shifter and had the remains in front of me which are actually being used, it became more clear on which parts are causing the issues.

With the gate removed the shifter fits into the tub console, tight but it goes in.
I have not figured out the height settings yet. So far so good.

To be continued...

 

[Stephan E.]

Here is where we are finding out why it does not fit. The Audi shift gate is 130mm wide and the tub console is not. I have laid out some solution but being uncertain of which way I am going. If I go with the Audi gate I have also to deal with an 60mm or 2.5" height addition to the factory shifter if left uncut. A solution could be to convert the gate using the Gallardo version which is direct bold on to the dust seal with an OD of ca. 95mm and the console being 100mm wide. It would also favor that the Gallardo version is actually leaning backwards while the Audi interior demanded a level installation hence all the adapters. Another way is to give the Audi gate a shave to bring it within 100mm. If nothing works we will be molding a new console.

The price to pay for a perfect shift experience and looks I guess. I love the design and the way it feels and that it has a dust seal and rubber bumper guides for the shift stick.

This will be interesting...

 

[Stephan E.]

Moving on to the machinical issues on integrating the factory cables to the shifter. I looked into the Audi OEM cables because I do not want to alter the shifter ball in favor of an aftermarket part. While checking on the cables and hardware being used and supplied with the factory shifter I discovered that both ends have different thread sizes. While the transmission side is using M6 x 1mm threads, the shifter side was confirmed with 1/4-28 fine thread. The fact that metric hardware was present made me remove the 10mm rod end from the gear selector and to slide it over the 10mm ball and shaft of the shifter. There is was, the rod end is large enough to carry across the ball and upper portion of the shaft and being a perfect fit without play and rattle since both are metric. I fabricated a M10 to 1/4-28 reducer to connect the cable, made sleeves, added matching washers for the cable spanners and used Teflon washers to make this a grease filled tight pack. A new M10 rod end was reordered for the gear selector. The M10 rod end has about 28 -30 degrees swivel. It travels like a hot knife through butter without hitting its limits or anything inside the shifter itself. I still have now the option to switch the Audi OEM cables if I wish to do so.

 

[Cam]

You’ll find that hot knife doesn’t slice through butter so well once you route the cables and hook it up to the transaxle. I’ve heard the factory cables have less friction.

 

[Stephan E.]

Hello Cam,

That is why I wanted the option to change them over if the shifter feel changes. I read about that fact somewhere. Of course my current experience is purely based on the fact that the transmission is not connected as of yet. Will give feedback after the transmission is in.

Cheers,
Stephan

 

[Stephan E.]

Finally, I made it to the rear brake, made brackets and converted to -3 AN. Completed line routing for the emergency brake cables and new clutch line as well. It will be hard piped to the underside of the transaxle. You can also see the beginnings of the modifications to the race tail diffuser.

 

[Stephan E.]

Back on the shifter. Used the leftover front splitter rods which I had replaced with billet versions. The hardware became handy fabricating and shifter mount that is now adjustable in three axis. Currently set off center not to come out more of what the tub console would have taken. That will give me the most space to get a decent angle to the steering wheel.

 

[Roger Reid]

Stephan. How much linear total travel do the shift cables go through. More than one and a half inch or is it less?

 

[Stephan E.]

Hello Roger,

The cables travel at different rate of length depending on their function. The cable directly connected to the shift stick has the longest travel. Just from looking at it I would say 1" inch from the neutral point forward and backwards. The reverse gear/ throw over selector is much shorter about 1 inch total.

Cheers

 

[Stephan E.]

Back to electrical today. Made the battery connections.

 

[Stephan E.]

This is about the pain in the rear end. I had a little extra on my diffuser. An extra wing which was in the way and had to be removed. It was a little bit like surgery but eventually it was done without leaving scars. I am still working on finishing the surface and rounding all edges.

 

[Ken Roberts]

Don't forget to re profile the backing plate for the front upper a arm rod end bracket inside the tub before you go much farther. You can see it sitting at an angle due to the weld above it. It needs to be removed and trimmed so that it will sit flat. You can see it in your battery picture post #112.

 

[Stephan E.]

Hi Ken,

Thanks so much for reminding me. I saw it when I was working in that area but totally forgot about it. Will do it right away!

 

[Stephan E.]

The diffuser is taking some more attention. I had decided not to use the factory brackets and come up with something that manages to divert high loads of down force produced by the wing into the chassis without flex, windage, rattle and losses. There is also a good chance that the diffuser will not carry the wing at all but that has not been decided yet. This posting is about the outer support of the diffuser perimeter which will eventually carry the hinge mechanism for the rear shell. I had these rods turned out of 6061-T6 again. I am always baffled on how light and strong these are. Those are only meant to help with the load of the rear shell when opening and have nothing to do with the down force handling. There are pretty too :shy:

I'll post more on the diffuser development as its progresses...

 

[Stephan E.]

The linear actuators and controllers have arrived. Ordered according to

Linear Actuators — SL-C Wiki

Thanks guys for providing this information.

 

[Cam]

The diffuser is taking some more attention. I had decided not to use the factory brackets and come up with something that manages to divert high loads of down force produced by the wing into the chassis without flex, windage, rattle and losses. There is also a good chance that the diffuser will not carry the wing at all but that has not been decided yet. This posting is about the outer support of the diffuser perimeter which will eventually carry the hinge mechanism for the rear shell. I had these rods turned out of 6061-T6 again. I am always baffled on how light and strong these are. Those are only meant to help with the load of the rear shell when opening and have nothing to do with the down force handling. There are pretty too :shy:

I'll post more on the diffuser development as its progresses...

Those rods are very nice! Using rod ends at either side means they can only take pure tension or compression; do you plan to triangulate the diffuser?

 

[Stephan E.]

Hello Cam,

Thanks for the feedback. You are correct, the rods will only compensate for a unidirectional movement, in this case downward. They are only for supporting the weight of the rear shell when opening. It is supposed to reduce or eliminate the deflection on the outer diffuser. To take the downforce of the wing it takes a little more. Here are some pictures on early ideas. This is truly work in progress. I have cut some triangular gussets leading from the attachment points running on the exterior of the diffusor to the winglets but those are not welded into their final positions yet. I still need to make sure they do not interfere with the suspension of the transaxle. A later post will show them.When placed in the correct angle, it will remove all deflection from the diffusor and direct all forces onto the attachment points. The bolts holding the diffusor in place are only M6 10.9 for now but are already incredibly strong. Eventually those will end up as M8 or M10 10.9 in the final version. I am still debating if it will require to add support rods leading from the spider or other points of the chassis to the upper section of the diffusor to add strenght. Time will tell...

 

[Cam]

That corner of the diffuser isn’t very stiff in the lateral direction. If it exerts 40#s of loading in the downward direction your strut design will exert approximately 10#s in the inward. So you will deflect that area of the diffuser before the strut takes any real load unless you box out that corner. Try pushing that corner inward with your hand, you’ll see it’s not very stiff in the lateral direction.

Try disconnecting your strut at the diffuser side and pull straight down with your fingers. You’ll find it wants to swing inward before it carries any load.

All that said, the diffuser isn’t really very stiff side to side or torsionally if you hold it by those two outer mounting points. If you’re using the factory wing mounts then your loads will be going through the two main plates the wing stanchions are attached to. The outer edges of the diffuser really should only need to be stabilized for vibration and not designed to take any real loading. That’s why the factory supplied pieces aren’t all that beefy.

While on the subject of load path - unless you really revamp how the wing’s load is carried, the rear diffuser primarily sees a moment rotating it away from the car (forgetting whatever loads are generated by the weight of the diffuser itself). So the lower attachment points will be primarily in compression and the upper in tension. I don’t think those 3 bolts in your photo will see any loading if that gussetted plate is resting on the rear chassis crossmember. If you stand on your diffuser you’ll see what I mean.

I think Howard needs to take a lesson from you! He likes to make things beefy but I think you are taking the cake. A single 1/4” grade 8 bolt can take about 2000#s of sheer load. Going to an M10 grade 8 will give you about 4000#s of shear load capability per bolt. I don’t know what wing design you’re planning to use but I believe the race wing generates about 1000#s at something north of 120mph.

Your diffuser mounts will definitely not fail!

Edit: forgot to add that the diffuser ends do have to support the rear clam if using the factory hinge.