[WIP] Audi S3 quattro 1:12 RC - finished

[Mechbuilds]

One detail i would add is to remove the ball from the shifter and have it just an axle instead. The ball is too big and messes up the interior. Just an axle would suffice in this application in my opinion. Bonus point for axle with a stop or stud on the end. 
It looks like an easy detail to do and i would advice to at least consider it. But well done. Great work so far! Can't wait to see it finished. 

[Thirdwigg]

@T Lego I'm glad some of my ideas inspired you. Hope it fits the look you are going for.

[TechnicRCRacer]

7 hours ago, T Lego said:

 is this what you meant regarding the suspension?

Yup, you nailed it!

[T Lego]

21 hours ago, Mechbuilds said:

One detail i would add is to remove the ball from the shifter and have it just an axle instead. The ball is too big and messes up the interior. Just an axle would suffice in this application in my opinion. Bonus point for axle with a stop or stud on the end. 
It looks like an easy detail to do and i would advice to at least consider it. But well done. Great work so far! Can't wait to see it finished. 

Thanks! I agree and I will take a look.

[LEGO Train 12 Volts]

Very nice improvement for this car!

[T Lego]

Sadly I currently experiencing air leaking in my suspension system. When I pressurize the cilinders, all pressure is gone in a couple of minutes. This is the first time I am using pneumatics so I do not know what causes this problem. Does anyone have an idea how I can solve this. I am using (old) small cylinders, T-pieces, a valvse and regular silicone tubes.

Edited May 19, 2019 by T Lego

[skppo]

You have no active pump in the system right? The cylinders and valves will always leak some air as there are sliding surfaces holding pressure, it is not possible to make them absolutely air tight. I'm not sure how to solve this if there is no space for a motorized pump. If you want to use the pneumatics only as shock absorbers you need to add some springs alongside them (even elastic bands might be enough).

[T Lego]

3 minutes ago, skppo said:

You have no active pump in the system right? The cylinders and valves will always leak some air as there are sliding surfaces holding pressure, it is not possible to make them absolutely air tight. I'm not sure how to solve this if there is no space for a motorized pump. If you want to use the pneumatics only as shock absorbers you need to add some springs alongside them (even elastic bands might be enough)

Thanks! There is space for a motorized pump, but does it have to be activated at all times in order to maintain pressure?

[skppo]

Just now, T Lego said:

Thanks! There is space for a motorized pump, but does it have to be activated at all times in order to maintain pressure?

There are some nice solutions for automatic pumps using an electric switch, a cylinder and and elastic bands. These turn on automatically when pressure is low enough.

Here is an example of the idea:

Another idea:

It might be cool to have the pump on remote control instead so that one direction runs the pump and the other direction turns a valve to release pressure and slam the suspension down

 

[T Lego]

Update:
 

Sadly I've got some bad news. I have puzzeled with the pneumtic suspension for hours now, but I think I will continue this project with regular shock absorbers. @skppo I tried both of your Ideas. The Auto compressor works, but when the battery is turned of, the system obviously doens't work anymore and therefore the car will sink due to the leaks. I also tried it in combination with springs, but the hubs from the front axle will obviously pop out of the ball joints connected to the suspension arms. This happens beceause the shock absorber can only be connected to the suspension arm and in the old setup there is not a second one located above to support.

 

The wheels were also not very well connected to the axles beceause they only stick out one stud, so I also decided to use standerd three pin hubs. It required a few mods on the front, but this setup looks much better. Sadly though, using hubs created a new problem in the rear axle. It is a much bigger setup so the gearbox can not be squeezed in the same way into the rear axle. Which leaves me with two options: Increase the wheelbase by 1-2 studs or redesigning the gearbox and entire drivetrain layout. Another possibility is to use a different drivetrain setup, for instance 4x L motors and no gearbox for increased performance or something with an autocluch and brake....

If anyone has feedback or suggestions, let me know!

Edited May 27, 2019 by T Lego

[Leonardo da Bricki]

That's too bad the suspension wasn't working out. On a larger model, you could have had room for one of the air tanks, to provide constant pressure for a good while.

I am voting to increase the wheelbase by 1-2 studs. It's not a huge difference, and shouldn't affect the model noticeably. Best of luck!

[MangaNOID]

I feel the pain! 

maybe a little late but you could try thick dishwashing soap or similar put thickly over each hose connection and base of the pump (see link below) to try and isolate what might be happening.

a few minutes of air leaking is not normal in a good system...

In the excavator I'm building the main boom will stay erect for a few days and will be a good week or two before its touching the benchtop again. That is one large cylinder of course compared to the smaller ones and I did take it apart and clean and 're-grease' the internals but goes to show that it can be better than a few minutes.

a little late perhaps but were you using a small 1x6 pump? as I have cracks in most of mine that leak out air instantly. Its like a manufacturing fault or something on some pumps? Check the following out.

I put very thin superglue on mine too and it helped a lot.

 

 

Edited May 28, 2019 by MangaNOID

[Limga]

I had the same problem, when I was building MacPherson suspension with small pneumatic cylinders. Turned out that old small pneumatic cylinder was seriously leaking in certain position, like it had some micro-crack that was widening when putting in suspension. I changed all old cylinders to the new ones and the was no leak.

Also, I like your build very much! There aren’t much builders who experiments with small-scale suspension that isn’t double wishbone or live axle. Motivates me to continue work on my own suspension, may be I will borrow some solutions from you:) 

[T Lego]

8 hours ago, MangaNOID said:

a little late perhaps but were you using a small 1x6 pump? as I have cracks in most of mine that leak out air instantly. Its like a manufacturing fault or something on some pumps? Check the following out.

Thanks for your comment! I do'nt think it is an issue with pneumatic pump. I connected the pump to a valve, not directly to the cylinders. When I pressurized the cylinders, I set the valve to the neutral position and there was just as much air leaking. For this reason I suppose it is not a problem with the pump.

2 hours ago, Limga said:

I had the same problem, when I was building MacPherson suspension with small pneumatic cylinders. Turned out that old small pneumatic cylinder was seriously leaking in certain position, like it had some micro-crack that was widening when putting in suspension. I changed all old cylinders to the new ones and the was no leak.

Very interesting.... I also used old cylinders, beceause they are much cheaper on BL (I still paid 20 euros for all 4). What position are you refering to? Just the vertical placement like I used?

 

2 hours ago, Limga said:

Also, I like your build very much! There aren’t much builders who experiments with small-scale suspension that isn’t double wishbone or live axle. Motivates me to continue work on my own suspension, may be I will borrow some solutions from you:) 

Thanks! It is true that there are not many new suspension ideas being shared recently. I'd love to see your suspension and I hope some of my solutions can inspire you!

[T Lego]

Update:

After a few days of of messing with the new gearbox and rear axle, I think I am on to something very decent. 

 

 

The gearbox is basically the same as before, but now it uses fewer gears to tranfer the power from to motors to the gearbox. The entire setup is also much stiffer, so that onder high loads, gears won't slip. I also conected the servo to a new, much smaller stepper which works just as good and I also made a speed indicator in the center console (you can't see it properly, beceause I have not added stickers yet). I will do some driving tests to check if the performance is acceptable, but I'll have to wait for the arrival of crucial part in order to do that.

 

 

 

If anyone has questions, feedback or suggestions, let me know!

[TechnicRCRacer]

It looks awesome! Have you tried driving it yet?

[T Lego]

On 5/31/2019 at 4:35 PM, TechnicRCRacer said:

It looks awesome! Have you tried driving it yet?

I just completed the driving test. Shifting works very smooth and the car can drive normal in every gear. Sometimes gears slip, but I only need to brace everything a bit better to solve that issue. However when I steer the car, the motors are struggeling to keep the car moving. Especially in 4th gear, when the speed changes drastically. Does anyone have an idea why this happens? I think it happens beceause there are no diffs on the axles. I didn't experience this problem in my other Audi's, but those only had RWD without diff.

Edited June 2, 2019 by T Lego

[TechnicRCRacer]

6 hours ago, T Lego said:

I think it happens beceause there are no diffs on the axles.

This is the reason.

[T Lego]

20 hours ago, TechnicRCRacer said:

This is the reason.

Yeah and it sucks. Especially since I cannot imagine this car, when keeping the same functionality and size, with diffs. There is not a single independent suspension setup that is, with these wheels, 19 sutds wide. There only is a something like a 'floating differential axle' which is narrow enough, but the overal setup is still way to big. I realy need to figure a way out to solve this...

[grego18f]

Maybe you can use a similar setup than in Gerger's GMK 6400...

Link : 

Anyway, I really like what you are doing. Keep up the good work ;)

 

 

[T Lego]

Looks awesome and thanks for sharing! Some sort of setup is what I am looking for. Unfortunately though, that setup is 2 studs too wide and even if I'd place the toggle joints two studs inwards (which also means lowering it one stud), It would still be to bulky. Especially on the front axle where I still have to incorporate the servo Motor. This axle issue gives me serious headaches....

[Thirdwigg]

It is this reason I go with the 21 studs wide for my little cars. I'm not willing to give up the diff. Maybe time to add some fender flares, and give that car some stance yo.

[T Lego]

On 6/4/2019 at 10:09 PM, Thirdwigg said:

It is this reason I go with the 21 studs wide for my little cars. I'm not willing to give up the diff.

I understand that, but I don't want to go off-scale. Even If I would make it two studs wider everything still wouldn't fit.

Edited June 8, 2019 by T Lego

[T Lego]

Hi everyone!

I made some improvements on the drivetrain and chassis and I test drove the car on some loose surface. It behaved very well and gear shifting was an absolute joy! Of course it won't turn in too smooth but I accept the overall performance.

Update:

-Improved drivetrain

- Better gear shifting (with chain)

-New DBG seats

-Adjustable seat mechanism

-Bodywork: Grill, bumper, door

 

 

Here you can see the new grill, fender and headlights.

 

 

Here is the first door design. I am very satisfied with it. It is built primarily using panels and flex axles. It can also be opened.

 

 

I also managed to place a seat mechanism in the car. The seats will move forwards and backwards by turing the black 20th gear. In my pervious audi's the seats sort of 'blend' in the interior which meant they were not realy visible. To avoid that in this car, I made them in dark bluish gray.

 

 

I'd love to know your thoughts. Suggestions for the car a as always very welcome!!!

[Jerry LEGO Creations]

I only just found out about this topic, and I wanted to say I really like your progress so far!

It is amazing how you manage to fit all those functions in an rc car this scale. Can't wait to see the finished model!