|
||
|
 |
|
||||||||||||||||||
|
#1
23-04-2013
|
|||
|
|||
511 Steering Geometry
So I'm doing a screw-by-screw rebuild of my 511 at the moment out of necessity rather than desire and in doing so I got to playing with the steering and wondered about options.
I'm not a geometry whiz so don't really know what maths is involved here but look at the pic below, wouldn't the left side (of the pic) labeled "Mod" be more efficient? I think the Ackerman would remain the same (no change in pivot points) only the steering rods would get shorter. Wouldn't this provide more 'direct' steering with less throw required for full lock? May require adjustments to steering Arc/Expo but that's easy enough. Can anyone far smarter than me tell me why one is better than the other? The 'mod' certainly looks more elegant...   Thoughts? 
|
|
#2
23-04-2013
|
||||
|
||||
Quote:
Just a quick thought, the mod you have done gives it a very simlar geometry to the original steering on the trf502x and tamiya modified it to give more low speed and a sharper steering response I think.........
|
|
#3
24-04-2013
|
|||
|
|||
|
Quote:
I'll try and sort out some measurements, I'm just not sure of exactly what to measure... lol!
|
|
#4
25-04-2013
|
||||
|
||||
|
Take some more pictures at both left and right full lock then it might become clear
G
__________________
Graham North http://www.atomic-carbon.co.uk https://www.facebook.com/atomiccarbon https://www.facebook.com/nortechracing 
|
|
#6
04-05-2013
|
|||
|
|||
|
Quote:
Ackerman, as I understand it, is the angle of the line drawn from the front knuckle pivot, through the front outer steering pivot to the rear axle line. This configuration does not change when moving the steering rod as I have.  I do however stand to be corrected and educated! 
|
|
#7
04-05-2013
|
||||
|
||||
|
I know what you mean, but in practice this system works quite complicated. The way the links are mounted on the inside has an effect on how much they push the steering outward or pull it inward.
I found on the systems I've drawn that moving the links to the back on the inside results in a bigger angular difference between the wheels at full steering angle, and moving the links forward a smaller difference. I'm curious to see what it does on the car, are you going to do some runs with both systems to test the differences back to back?
|
|
#9
05-05-2013
|
||||
|
||||
|
Believe it or not this has been tried before. It actually gives you less steering at both low and high speed (especially high speed). With the link on the rear of the steering bridge the outside wheel gets less lock than standard and hence less steering. This may be desirable on some cars but not on the 511. Also you may be fooled into thinking you can get this to work on a grippy track like outdoor Astro where you don't need as much steering. However what actually happens is the car turns into the corner well but as soon as you power out of the corner the inside wheel is still steering whilst the outside one is square to target. The result is a very unstable car...!
__________________
___________________________ Neil Adamson
|
|
#10
06-05-2013
|
|||
|
|||
|
Thanks for all the input and experience guys, this isn't my wheelhouse so I appreciate the insight.
The vehicle is out of commission at the moment whilst I wait for spares but I hope to take some static photos today on the hobby mat of the articulation and full range extension. I suspect as people have commented above that I'll get some type of uneven outcome. I'll share the pics here.
|
|
#12
18-05-2013
|
|||
|
|||
|
Soooo..... I recently got around to answering this question and the results are quite telling.
I ended up trying a variety of different methods to measure it all and after quite the learning experience I established the best way to reflect my findings was with wheels mounted and not tyres. Actually, to be honest the process would have been much shorter had I started with that approach. Measuring accurately (enough) without the wheels is difficult without the correct tools. I measured with the rods on either and both sides and with different stud locations and different rod lengths. The pictures below, whilst not particularly scientific, are representative of my observations under all test scenarios (except one that's irrelevant because you get no steering throw). Pay attention to the angle of the outside wheel, essentially with the rods on the back of the bridge the outside wheel angle is significantly reduced.  Here I've mirrored (and slightly shifted h/v to line it up) the red line.  My trial (and error) demonstrated to me that when connected to the front of the steering bridge (stock) the rod is forced to travel through an arc which is a (significantly) greater distance than if connected to the back of the bridge. Indeed as you can see from the pics I posted in the first post, whilst connected to the back of the bridge there's almost no arc at all. Finally, the Ackerman remains the same in either scenario but the effect is like putting a block on the inside of the steering arms so they can't travel as far in one direction. Summary: It won't work.
|
|
#13
18-05-2013
|
||||
|
||||
|
im getting a little confused what your trying to tell us what are you trying to achieve are you saying tamiyas designers have got it wrong and the steering link should be on the rear!
to make you test even you would need to change both links and plot it on the drawing board correctly and then compare your results alternatively you could run it o track and see what you prefer. stu
__________________
|
|
#14
18-05-2013
|
|||
|
|||
|
Quote:
|
|
#15
18-05-2013
|
||||
|
||||
|
ok re read still confused
I assume you understand what akerman is and what moving the inner or outer link forward or rear would do to both inside and outside wheels. is all to do with the arc of a circle.  stu
__________________
|
|
#16
18-05-2013
|
||||
|
||||
|
Here's my observations from your photos...
Using back of block - More outside wheel angle at full lock (bottom pic left side) - similar inside wheel angle at full lock (top pic left side) Using front of block - Less outside wheel angle at full lock (top pic right side) - similar inside wheel angle at full lock (bottom pic right side) Conclusion: Mounting to the back of the block results in a reduction of ackerman at full lock due to the very obvious increase in steering angle of the outside wheel. The straighter link on the outside turns that one wheel more. This is how ackerman adjustment works on RC bell-crank steering.
__________________
HE>i
|
|
#17
18-05-2013
|
|||
|
|||
|
Quote:
Quote:
 Sorry if that lead to unfair criticism!Let's try this: I concluded that using the back of the bridge is a bad idea. Tamiya got it right. Using the back of the bridge effectively reduces the possible maximum angle of the outside wheel and will significantly reduce your turn in and turning circle. The inside wheel is almost identical in most configurations. A wider arc for the inside pivot of the steering rod is desirable. The pics above are representative only, simply to show the effect. To avoid posting 12 pictures that look almost the same I used a different configuration left/right to illustrate my point (obviously not so well!  ).As for Ackerman... well I need to concede that I simply don't know enough about this to argue the point one way or the other... and I probably can't be bothered to learn enough to be convinced either way... But for sure, this is not a "mod" that my evidence suggests would be worthwhile. Apologies if I wasn't clear or conclusive in my previous post...
|
|
#18
18-05-2013
|
||||
|
||||
|
Ok I see you are trying to under stand what Ackerman does which is cool
In a very basic terms The more difference between the inside and outside wheel the car will hold a better line though the arc of a corner due to the front tyres scrubbing less and holding traction better. This can make the car feel a little more aggressive. And vice versa the more parallel the inner and outer wheels are the car will feel a little easier to drive though a corner because the front tyres will scrub more though the arc of the turn. Their are other factors that Ackerman can effect but all most drivers need to know is when the car needs to be adjusted either more Ackerman or less to achieve the best lap times. Stu
__________________
|
|
#19
18-05-2013
|
|||
|
|||
|
To be honest I've read so much on the subject that I'm a little bored of it.
What you're saying is that Ackerman (in a practical application) is not constant throughout the steering swing. This makes sense sure but I did previously believe that it could be measured at a static steering angle. If it's variable throughout the range (and I'm happy to accept it is) then I can't for the life of me imagine how you'd measure it without special equipment! My head's going to explode. I'm glad I didn't need to understand the theory to determine the answer to my quest! lol.
|
 |
|
|
Tamiya
Linear Mode
