Didumos69

[MOD] 42056 - Ultimately playable Porsche 911 GT3 RS

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Time to report on my last modifications to Box 1. I set myself a deadline for this: July 1st, 2016. The last modifications I made are: Rear HoG steering, a dash gear indicator and a stabilized gear rack. This time I made photo's while refactoring, so it will be a photo sequence kind of report. Again it's important to know that this MOD is built on top of the Sturdy without body MOD. I also assume you already know about the rear HoGs themselves.

EDIT (2016/07/01): I changed the position of the rear HoGs which also resulted in a slightly different routing of the rear HoG steering. See this post.

About the dash gear indicator: The original gear shifting mechanism completley relies on knob gears. This is good because they won't slip. And the actual change-over-catch-mechanism can't do without them. However, for a few weeks already I'm using a paddle-shifter-unit that operates with bevel gears instead of knob gears: I replaced the two knob gears at the bottom side of the unit with 2 12t bevel gears, aligned wit a 45 degree jumb, just like the knob gears had. And guess what, over a period of two weeks I didn't have any problem with slipping gears whatsoever. The 7x5-frame enclosing the gears prevents them from slipping. I even tried to force them to slip, but they simply didn't.

Based on this knowledge I reconfigured the lower section of the paddle-shifter-unit once again. This time to add a second output axle that drives the gear indicator. This output axle points towards the center of the car. However, on that side of the 7x5-frame a 13L liftarms was blocking the way. This liftarm is quite essential for the whole chassis structure, so I had to find a substitute for this liftarm. I solved this by attaching a liftarm to the inside of the black console-panels and by securing these panels better. The photo sequence will show how I did this.

I started off with dismantling the whole section between the D+N+R-console and the front suspension module. This includes the front HoG and the D+N+R-casing. I removed the paddle-shifter-unit as one piece. Then I replaced the axle sticking out of the front side of the D+N+R-console and I modified the way it is supported (with 2 5x3 levers):

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Next step is to add a 3x3 liftarm to the front and a 5L liftarm to support the black console-panel to the right side of the D+N+R-console:

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Then I changed the way the toggle joint and the CV-joint are supported, so I could add another 3L pin (with a 1L liftarm) to better secure the black console-panel later on:

800x450.jpg

Now I rearranged the gearing at the bottom of the paddle-shifter-unit, added the double snap and gears for the base of the gear indicator and put the unit into place. There is another - not visible - 12t bevel gear meshing with the thin 12t bevel gear inside the shifter-unit. Make sure all gears make perfect 45 degree jumbs, just like knob gears would:

800x450.jpg800x450.jpg

I added liftarms to the inside of the console-panels and some parts to hold the double snap. These structures also connect to the front suspension module (make sure all connects perfeclty, as you can see I didn't and this gave me some headaches afterwards :wink:):

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Stabilize the whole front structure with two vertically placed 4x2 liftarms:

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Now before we continue, I assume this part of the rear HoG steering to be present already, except for the CV-joint. Note that the 4x2 liftarm carrying a pin with pinhole also serves as 4th-to-1st gear block:

800x450.jpg

Next step is to insert part of the rear HoG steering axle and a 5L liftarm to support it (you can still see the pin that I didn't connect properly :wink:):

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Now we can reconstruct the D+N+R-console and the dasboard. The 12L axle used for steering needed to be divided into a 4L axle and a 8L axle, so there is space for the gear indicator axle to pass through:

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And now the gear indicator can be added (sorry, don't have an image of the result). The 3x3 liftarm can be replaced with a pin with pin hole integrated in the dashboard that is part of the body.:

800x450.jpg

And we finish off with the gearing near the gear rack and the gear rack stabilizer:

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One more thing: To make the whole shifting train operate smoothly, make sure all axles rotate without friction. Any feedback is much appreciated.

Edited by Didumos69

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Didumos this is almost a completely new car with all those mods! Maybe when I have the money I'll buy this set and apply your mods. :laugh:

Thanks. To a certain extend it is a new car, but the nice thing is, the body - Box 2 etc. - fits out-of-the-box :wink:. This is also how I'm going to present this as a Porsche dream contest entry: The looks are pretty constant over time, but what's inside evolves continuously :wink:.

Edited by Didumos69

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Here's a cutaway of the complete drive train (red), steer train (yellow) and shift train (green):

1280x360.jpg?a=1

Edited by Didumos69

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And here is the LXF-file showing the rear HoG steering, dash gear indicator and stabilized gear rack modifications:

1280x480.jpg?b=1

Edited by Didumos69

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I almost forgot to mention that my last refactorings made the chassis even more sturdy:

800x450.jpg?a=1

Edited by Didumos69

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I decided I want to have the rear HoGs to be positioned at the front holes in the panel above the diff instead of the rear holes. In that location they are better reachable through the rear window:

640x335.jpg

This made the rear HoGs a little more straight-forward. The 20t bevel gears at the front of the rear suspension are already locked-up by another panel that is part of Box 2. Therefore there is no need anymore for 6 half bushes and all the plumbing at the backside of the liftarms above the diff to secure the gears. The 20t bevel gears are now placed on 6L axles that run through both 13L liftarms. Between the 13L liftarms these axles are kept in place with two bushes each. Another advantage is that the HoG shifting now rotates in the same direction as the dashboard gear indicator. I also had to change the routing of the rear HoG steering, because the HoG steering axle now also rotates in the opposite direction. But this wasn't that hard. I replaced the CV-joint in the steering axle with a U-joint so I could add a 16t gear between the joint and the gear above the gear rack. A CV-joint is of course better, but the angle is so small that the sine-effect of the U-joint won't be very strong.

800x450.jpg800x450.jpg800x450.jpg800x450.jpg800x450.jpg800x450.jpg800x450.jpg800x450.jpg800x450.jpg800x450.jpg

Edited by Didumos69

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This is how frictionless it can get. In first gear, engine geared up by 300%. Overall ratio of 5:1.

Edited by Didumos69

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EDIT: I updated the front axles after finishing box 3 and 4. See this post.

Today I will report about the implementation of Ackermann steering in my playable build. In my opinion Ackermann steering is an advanced steering characteristic that is very noticeable in a playable model. When you push the Porsche without Ackermann steering, you can feel the tire scrub resistance in turns. You can also see the outer wheel making jumps to the side every few inches to overcome the lack of Ackermann-steering. Inspired by the Ackermann concept from DayWalker in the MODs and Improvements thread I designed a similar concept. I had to take into account the rear HoG steering and another important difference is that DayWalker doesn't use a gear rack and I do. In fact, I use a gear rack with stabilizing slider.

Basically, my approach boils down to turning the whole front suspension around such that the back side faces forwards and the front side faces backwards. But let me tell youI the rest of the story in terms of a photo sequence.

I started with changing the gear at the top of the PDK-unit to the other side, so the output axle rotates in the opposite direction:

800x450.jpg

Then I disconnected the front suspension module from the rest of the chassis:

800x450.jpg

I inserted the 10L slider axle and two 1L liftarms with perpendicular axles as sliders:

800x450.jpg

I assembled the composite gear rack and a connection bridge for the upper back side of the front module:

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Then I attached the gear rack to the sliders and put the connection bridge into place:

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I put together the modified wheel hub extensions. The yellow 4L levers are lowered by half a stud, but the square 4L flat plate remains in the same height. This fits inside the rims without a problem and the photo of the wheel shows this doesn't affect the looks either:

800x450.jpg800x450.jpg

After putting the new wheel hub extensions into place the front module looks like this:

800x450.jpg

Then I extended the chassis improvement I did earlier. Now I use 13L liftarms:

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And I put the front module into place. You can now see that it has been turned around:

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This yellow stabilizer makes sure the orange parts on top of the gear rack do not rotate:

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I placed all the axles and gears, also for the rear HoG steering:

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I added gear rack stoppers:

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I added the vertical liftarms:

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And finally I added the front frame:

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And it works like a charm. The angle difference is maybe hard to see, but it's there and with this setup the tire scrub resistance in turns is completely gone!:

800x450.jpg800x450.jpg

Edited by Didumos69

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The progress you're making with the ultimate playable version is just amazing. I think that version is getting as near to perfection as can be :classic:

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Is anybody planing to add power functions to this MOD? I would really love to RC controll the Porsche. I found only one link with a simple RC mod on YouTube. After all the improvements achieved so far I am confident that a RC version is possible. Unfortunately I don't have the skills and time (less of the first) to develop somthing like this ;-)

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800x450.jpg

Thanks to your floor, the difference in angle is quite obvious (to me at least). Can you assess if the line through the pivot points and steering arms indeed intersect at or near the rear differential? Since you mention no scrub, I would think so.

(I never understood why those lines have to intersect there, but never bothered to do the math either... :blush: )

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I like all these improvements. And will definitely apply them all.

I also think there should be mods like "adjustable camber" or "coilovers" version, all mods like the tuners do on cars :laugh: Maybe sway bars, "lower" springs, wider body kits, lower bumpers......

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Thanks to your floor, the difference in angle is quite obvious (to me at least). Can you assess if the line through the pivot points and steering arms indeed intersect at or near the rear differential? Since you mention no scrub, I would think so.

(I never understood why those lines have to intersect there, but never bothered to do the math either... :blush: )

I know what theory you are referring to. A quick sketch shows me that these lines intersect way in front of the diff. However, the substantial slack in standard Lego wheel hubs give the wheels some range of freedom to find their own line - with the least friction. Apparently - given my observations regarding tire scrub - the range of freedom with this Ackermann setup includes the ideal line and the range of feeedom with the out-of-the-box setup does not.

So, from a theoretical perspective this is not ideal, but from a practical - or playable - perspective it is.

EDIT: The line through the pivot point and steering axis makes 2 studs backwards for each single stud inwards. So it would arrive at the midline of the car 22 studs behind the front axles. That is 17 studs in front of the center of the diff.

Edited by Didumos69

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Actually, it isn't far off at all. I remember an image made by Tommy Styrkovy for where the mounting points had to be for the steering rack to achieve Ackermann

27434878342_be608be66d.jpg

Like this image, moving it inward one stud as DayWalker and you did is pretty spot on.

@Ludo, can't really explain it words, but perhaps this image helps:

488px-Ackermann_turning.svg.png

Basically the stuff has to line up in a bigger circle for no tyre scrub.

Edited by Appie

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Thank you Didumos69 for this work!

You're welcome!

I like all these improvements. And will definitely apply them all.

I also think there should be mods like "adjustable camber" or "coilovers" version, all mods like the tuners do on cars :laugh: Maybe sway bars, "lower" springs, wider body kits, lower bumpers......

I also like to see active camber, but for one stud suspension travel I don't think it's worth the effort. Another issue is that the appr. 6 stud wide tires like to be flat on the road. This would even more be an issue when you would implement caster angle.

Is anybody planing to add power functions to this MOD? I would really love to RC controll the Porsche. I found only one link with a simple RC mod on YouTube. After all the improvements achieved so far I am confident that a RC version is possible. Unfortunately I don't have the skills and time (less of the first) to develop somthing like this ;-)

Not me, that's for sure. But the car would be a perfect target for it. I've seen a video, but I didn't like the battery box being on the passenger seat. There's lots of space throughout the vehicle. I would remove the gearbox to make space for the battery box(es). That would also be a nice position to get the center of gravity right and with a removable body you should be able to reach the batteries easily.

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So I implemented a few of your modification including the 90 degree limiter, and I cannot recommend doing it after you have already built the entire set :tongue:. It was a real chore to get back to where I had to add the limiter. I may just rebuild box 1 in its entirety when I have the time and implement all the great modifications that have been made.

I did have to add another rubber band to the limiter for it to actually stay at 90 degree intervals. Otherwise it would stay at 45 degrees. But that may be because I was not exactly gentile when building the thing :sceptic:

On another note, and I may have to ask this in the mods and improvements thread as well, but has anyone thought about making the front wheels higher. The clearance is really, really terrible when the body is attached. So much so that you can barely compress the front shocks at all. I may try it myself, but then again, time is my most limiting factor, as well as skill at this point.

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So I implemented a few of your modification including the 90 degree limiter, and I cannot recommend doing it after you have already built the entire set :tongue:. It was a real chore to get back to where I had to add the limiter. I may just rebuild box 1 in its entirety when I have the time and implement all the great modifications that have been made.

I did have to add another rubber band to the limiter for it to actually stay at 90 degree intervals. Otherwise it would stay at 45 degrees. But that may be because I was not exactly gentile when building the thing :sceptic:

On another note, and I may have to ask this in the mods and improvements thread as well, but has anyone thought about making the front wheels higher. The clearance is really, really terrible when the body is attached. So much so that you can barely compress the front shocks at all. I may try it myself, but then again, time is my most limiting factor, as well as skill at this point.

Great that you have taken the time to try! I agree that it will be more easy to apply most mods while building from scratch. That's why I'm planning to provide a BI for the 'Minimal version' in terms of an errata-sheet with references to the original building steps and a parts list. However, the 90 degree limiter should be doable without taking the chassis apart. Simply pull out the axles with the orange paddles, then remove the 3L liftarms inside the H-frame and put the limiter into place part by part. and finally insert the (different) axles.

In the 'Minimal version' MODs that I summarized in the OP of this thread I thought I mentioned that it would be best to apply 2 silicon bands around the 90 degree limiter. Or did you even need 3? And did you remove the friction-generating 8T gears in the shift train? When it comes to shifting gears, it's very important that you follow all of the 6 steps summarized here. I you would need 3 silicon bands, then there is probably some friction somewhere in the shift train. Make sure all individual axles rotate without friction.

I did not look into the clearance yet.

Edited by Didumos69

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On another note, and I may have to ask this in the mods and improvements thread as well, but has anyone thought about making the front wheels higher. The clearance is really, really terrible when the body is attached. So much so that you can barely compress the front shocks at all. I may try it myself, but then again, time is my most limiting factor, as well as skill at this point.

This might be a quick fix for the front clearance. It won't work without body, as the rims rub the suspension arms, but it might be okay with body:

2016-07-05%2023.31.35.jpg

800x450.jpg

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EDIT: With this stopper it will also work without the body. Also fits with the body:

800x450.jpg

Edited by Didumos69

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Great that you have taken the time to try! I agree that it will be more easy to apply most mods while building from scratch. That's why I'm planning to provide a BI for the 'Minimal version' in terms of an errata-sheet for the original BI with references to the original building steps and including a parts list. However, the 90 degree limiter should be doable without taking the chassis apart. Simply pull out the axles with the orange paddles, then remove the 3L liftarms inside the H-frame and put the limiter into place part by part. and finally insert the (different) axles.

In the 'Minimal version' MODs that I summarized in the OP of this thread I thought I mentioned that it would be best to apply 2 silicon bands around the 90 degree limiter. Or did you even need 3? And did you remove the friction-generating 8T gears in the shift train?

I did not look into the clearance yet.

To clarify, your goal will be to make instructions for the minimal mods, and a list of extra necessary parts to make them?

Also, will that be a goal for the ultimately playable version?

Would love to do just 1 bricklink purchase :grin:

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To clarify, your goal will be to make instructions for the minimal mods, and a list of extra necessary parts to make them?

Also, will that be a goal for the ultimately playable version?

Would love to do just 1 bricklink purchase :grin:

Yes it concerns the Minimal version, errata and parts list.

I have to be a bit more careful with promises about the ultimately playable version, I'm affraid the modifications are to big to write them down in a errata-sheet. But I will certainly be sharing a parts list and a LXF-file showing all MODs in terms of groups for box 1 and 2.

Edited by Didumos69

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@Ludo, can't really explain it words, but perhaps this image helps:

488px-Ackermann_turning.svg.png

Basically the stuff has to line up in a bigger circle for no tyre scrub.

I'm familiar with that image. I'm confused however how that image relates to the first one (where the lines intersect in the center of the rear axle). When the wheels are pointing straight, the yellow dot (centre of turning circle) is somewhere at infinity... I once started with the math, but quickly ran out of paper :grin:

Maybe this is not the right topic to discuss this. Sorry Didumos!

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I'm familiar with that image. I'm confused however how that image relates to the first one (where the lines intersect in the center of the rear axle). When the wheels are pointing straight, the yellow dot (centre of turning circle) is somewhere at infinity... I once started with the math, but quickly ran out of paper :grin:

Maybe this is not the right topic to discuss this. Sorry Didumos!

EDIT: Now that I re-read your post i think I'm still not taking away your confusion. I think you should see it like a tangent, it doesn't exist for a 90 degree angle. In other words the image with lines coming together in a shared center point doesn't apply to wheels that line up straight.

No problem.

The image Appie showed is indeed confusing. It shows the ideal lines and not the lines you get when you use a 1L pivot offset with a pivot that lays 2L behind the steering axis.

This is the geometry that me and DayWalker are using, I hope this takes away the confusion. Measurements are from heart to heart:

960x375.jpg

Like I said, substantial slack in standard Lego wheel hubs give the wheels some range of freedom to find their own line - with the least friction. Apparently - given my observations regarding tire scrub - the range of freedom with this Ackermann setup includes the ideal line and the range of feeedom with the out-of-the-box setup does not.

So, from a theoretical perspective this is not ideal, but from a practical - or playable - perspective it is good enough.

Edited by Didumos69

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