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Old 12-08-2017, 03:40 PM
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It is a low profile servo. Have you like.. measured the CoG with the servo upright vs laid down? With a bellcrank system or whatever you add weight high up anyway..


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Old 12-09-2017, 04:40 AM
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Thanks guys!
@Mats: No I haven't done the CoG comparison. A standing servo will definitely lift the whole construction in comparison.

As we speak of it: Today I build a mock up of the earlier mentioned Ackermann solution via long steering arms. Moving the ballstud 18mm more outside in front of the tire makes a huge difference in the Ackermann angle. Like this it matches the angles of my T4.

Before I entertain you with pictures I need help: Around 60mm long turnbuckles are needed for this construction. Preferably in Tamiya blue or black. I couldn't find ones in this size. Any suggestion is appreciated!





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Old 12-09-2017, 06:40 AM
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That will not last long in an impact. Unless flexible on impact so the loads go into the rim. I guess a one or two piece steering hub could do it.

It is ok to chase ideas but a simple one while you tinker is ok too. Standing up is not a big handicap if done right. You do not get the screws on the top etc.

If the ideal wheel angles is purely down to the length of the links you can run shorter arms on the wheelhub and put the link on the inside of the wheel like a regular car.

As for rubbing the wheel you make it bent so it goes around the wheel rim when turned inn. Can the link go as far in as shown on the outside?
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Old 12-09-2017, 06:50 AM
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Do you have access to TLR or AE offroad buggy parts? They would have the turnbuckles you're looking for.
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Old 12-09-2017, 07:48 AM
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After the geometry test with the acrylic sheet parts was good, I produced 2.5mm carbon parts. These are attached at the steering arm in the normal thread and an added hole near the center. With aluminium screws it again looks nice:





The turnbuckle is still a problem. Amain has some fitting ones, I now have to check if I can buy them here in Europe. If all fails Xrays XB2 has 55mm turnbuckles. A little bit too short, but could work...

@Mats: Luckily no rubbing. I will recheck the standing servo later next week.
@30tooth: Thanks, I will check later.
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Old 12-09-2017, 01:21 PM
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Looks real good!
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Old 12-09-2017, 02:18 PM
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Originally Posted by wtcc View Post
Before I entertain you with pictures I need help: Around 60mm long turnbuckles are needed for this construction. Preferably in Tamiya blue or black. I couldn't find ones in this size. Any suggestion is appreciated!
3Racing make Titanium turnbuckles in those sort of lengths but they are all silver coloured - but if no other option is forthcoming
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Old 12-09-2017, 03:37 PM
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I finally found 3x60mm turnbuckles in Tamiya blue from MST in a danish shop for drift cars

Tomorrow I am driving indoor again. I hope for a smooth steering. Another focus will be on the spring rate. My box of springs including rates between AE foam springs and Tamiya bright red (which should be 6-7lb/in) will accompany me tomorrow.

Last edited by wtcc; 12-09-2017 at 04:01 PM.
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Old 12-10-2017, 01:02 PM
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I am back from another interesting day.
This time I could drive together with our ETS gang and like this see all weak spots. First of all I experimented with spring rates. I ended up with the springs from the Tamiya Tuned spring set for Touring Cars. These springs are very soft. The hardest spring equals Xray 2.3. The softest rate is approximately 6-7lb/in. These are in the rear. The medium hard yellow springs are in front. The soft springs in the rear also helped with the steering. The steering was very smooth today. It also took away the grip roll tendency. The car was easy to drive, I had not one accident. But the rear was much too stuck. During the day I reduced the rear toe in several steps from 2* to 0*. Zero toe was good, but not good enough. Next time I will also reduce camber, maybe use a anti roll bar.
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Old 12-10-2017, 04:06 PM
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Maybe increase the spring rate in the rear and even go to toe out. This is what is done in real life fwd racecars to loosen up the rear.
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Old 12-11-2017, 12:46 AM
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Originally Posted by wtcc View Post
But the rear was much too stuck. During the day I reduced the rear toe in several steps from 2* to 0*. Zero toe was good, but not good enough. Next time I will also reduce camber, maybe use a anti roll bar.
I think rear ARB may be way to go. Even real FWD cars lift inner rear wheel in corner to get weight to outside front wheel.
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Old 12-11-2017, 03:35 AM
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Just finding out about this thread today... this car is shockingly beautiful, and I admire your devotion to permanently improving it

One question - why keep a servo saver? Especially when you have the FWD torque on the wheels. Have you tried a solid arm at all? Possibly with some trick extra-part pivot to keep the same ackermann

Gruss!
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Old 12-11-2017, 04:13 AM
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Originally Posted by heretic View Post
Great job wtcc! How is your bumpsteer? The more I look at your servo saver, the more I wonder if you couldn't get rid of it altogether. With the steering turnbuckles anchored so far from the center of the servo, it seems possible that the servo saver is going to become too soft. Plus, using a solid servo arm would maybe allow you to lower the pickup points by 2 or 3mm, thus putting the steering turnbuckles closer to horizontal. Car looks stunning in any case.
Late to the party again, Paul.
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Old 12-11-2017, 05:29 AM
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Originally Posted by heretic View Post
Late to the party again, Paul.



Hey at least looks like it could be a sensible idea no matter what... unless we're both wrong, of course, which isn't beyond the real of possibilities

But, yeah, I'd get rid of that SS... the trick is, if the OP's car ackermann is optimal-ish by now, a single pivot point would whack the geometry off. This means a dual-point servo arm, or an extra bit of pivoting kit (a tiny bit of cwf for instance) to partly mitigate it.

How about just making it solid? a beefy tie-wrap tightened around the spring can do the job in a few seconds to already give you a feel of what driving without that likely springy link feels, and is easily reversible

(I always drove with a hudy "extra stiff" SS up until a couple of years ago on all my touring cars, be they xray or others... then I switched to a solid arm in the middle of a race day once as I was looking for a tiny bit more steering - I never went back as the car was very different, and much better.... and I haven't broken any servo either. SS do "open" during normal driving, not just when crashing)
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Old 12-11-2017, 06:38 AM
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So much details... I am lucky to have you around. Servoposition and servo arm are in my focus now.

Edit: I played around with the servo position and found no positive effect on Ackermann. Package wise a 1/12 sized servo brings no benefit because in one dimension its size is greater than of a normal low profile one.

Having a standing servo seems to have a positive effect on bumpsteer, but would need a new complicated mount. Right now I am not motivated to build one.

The solid servo arm is easy to do as I found an old Xray arm which was too short for the T4 and now will serve as base element for a carbon plate.

Last edited by wtcc; 12-11-2017 at 10:08 AM.
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