Like Tree172Likes

wtcc's FF project

Reply

Old 11-29-2017, 01:20 PM
  #76  
Tech Master
iTrader: (11)
 
b20btec's Avatar
 
Join Date: Oct 2011
Location: Sugar Land
Posts: 1,152
Trader Rating: 11 (100%+)
Default

Thanks for making a "BOM" list! Good news is I got some of those parts laying around and can substitute with something else.
wtcc likes this.
b20btec is offline  
Reply With Quote
Old 11-30-2017, 06:50 AM
  #77  
Tech Master
 
patorz31's Avatar
 
Join Date: Nov 2007
Location: Edmonton Ab
Posts: 1,472
Default

The old Custom Works Dominator dirt oval car had the servo in front of the blukhead. Their solution is pictured below.



They have bellcranks mounted vertically. Might be something to consider.
wtcc likes this.
patorz31 is offline  
Reply With Quote
Old 11-30-2017, 07:38 AM
  #78  
Tech Master
 
heretic's Avatar
 
Join Date: Aug 2006
Location: europe
Posts: 1,110
Default

Originally Posted by wtcc View Post
Thank you all

@heretic: The Ackermann is still f***** up. I adress it later with additional cfk plates on the steering hub. That is why my bumpsteer is set like this I will take a look at the softness of the saver next time. Until now I haven't focussed on this subject. This is the T4 x-hard servosaver. Maybe it is strong enough for my lw car? I will check Which solid servo arm in an at least equal length can you recommend?
Motor: Aluminium for life Seriously: I use aluminium screws on my F1 and 4wd cars and somehow haven't had bad experiences with it.
Sorry wtcc, forgot to answer. Maybe you can use something like this?

http://cmchobbies.co.za/shop/image/c...a1-600x600.jpg

Originally Posted by wtcc View Post
Maybe I was just lucky...
You know what they say... "smart people have all the luck".
wtcc likes this.
heretic is offline  
Reply With Quote
Old 11-30-2017, 10:58 AM
  #79  
Tech Master
Thread Starter
iTrader: (1)
 
wtcc's Avatar
 
Join Date: Jul 2010
Location: Germany
Posts: 1,475
Trader Rating: 1 (100%+)
Default

Awesome! Thanks for this cool input.
I will look how to implement this for my FF.
wtcc is offline  
Reply With Quote
Old 11-30-2017, 03:24 PM
  #80  
Tech Elite
iTrader: (1)
 
Join Date: Sep 2010
Location: My house.
Posts: 3,500
Trader Rating: 1 (100%+)
Default

Originally Posted by wtcc View Post
Awesome! Thanks for this cool input.
I will look how to implement this for my FF.
If all else fails consider a linear rack
30Tooth is offline  
Reply With Quote
Old 11-30-2017, 11:47 PM
  #81  
Tech Regular
 
Join Date: Sep 2011
Location: Czech republic
Posts: 259
Default

Originally Posted by patorz31 View Post
They have bellcranks mounted vertically. Might be something to consider.
Problem with vertical belcranks is, that they will always make some bump steer, because of height change in inner link mounts.

What about ABC Gambado solution? It might work. Or you can mount low-profile servo vertically, it shouldn't affect CG that much.
Papi is offline  
Reply With Quote
Old 12-01-2017, 04:03 AM
  #82  
Tech Rookie
 
Join Date: Sep 2012
Posts: 11
Default

I like the direct steering arrangement! Less moving parts and less slop. As discussed eariler, bumpsteer can be minimized by making the arms horisontal. You could add shims to raise the outer ends of the steering arms higher.
A long servo arm can be a good thing. The height difference between center and full lock is smaller when the arm is long. A longer arm also makes the steering faster (but weaker).

A possible way to adjust ackermann would be shimming the whole servo forward/backward.
thomsva is offline  
Reply With Quote
Old 12-01-2017, 08:29 AM
  #83  
Tech Master
 
patorz31's Avatar
 
Join Date: Nov 2007
Location: Edmonton Ab
Posts: 1,472
Default

Weaker should not be a problem. With a front steer system the force needed to turn the tires is less. There was a big debate on this in full scale circle track racing years ago when no one wanted to run power steering. The best way it was explained to me was " It's easier to pull a stick on the ground then push it..."
Makes sense there will be less force needed to pull the loaded outside front in the turn then to push it against the force of the turn.

Last edited by patorz31; 12-01-2017 at 08:42 AM.
patorz31 is offline  
Reply With Quote
Old 12-01-2017, 10:39 AM
  #84  
Tech Regular
 
Join Date: Sep 2011
Location: Czech republic
Posts: 259
Default

Originally Posted by thomsva View Post
I like the direct steering arrangement! Less moving parts and less slop. As discussed eariler, bumpsteer can be minimized by making the arms horisontal. You could add shims to raise the outer ends of the steering arms higher.
A long servo arm can be a good thing. The height difference between center and full lock is smaller when the arm is long. A longer arm also makes the steering faster (but weaker).
But single arm also pull steering rods closer together, as it rotates. Although it can be reduced by making it longer, it's still not as good as double steering arms.

Also, with steering arms rotating around vertical axle, not only will reduce height change, but also introduce front/rear movement of centre, which can be used to tune ackermann more precisely without change in bump steer. Which is needed, as in case of front steering you need angled steering rods at straight and parallel (perpendicular to longitudinal axle of car) in full lock

Last edited by Papi; 12-01-2017 at 10:51 AM.
Papi is offline  
Reply With Quote
Old 12-01-2017, 12:33 PM
  #85  
Tech Regular
 
Join Date: Jul 2009
Posts: 499
Default

If it works, it works. Compare lap times first. Then the design if your behind.
MatsNorway is offline  
Reply With Quote
Old 12-01-2017, 12:38 PM
  #86  
Tech Master
Thread Starter
iTrader: (1)
 
wtcc's Avatar
 
Join Date: Jul 2010
Location: Germany
Posts: 1,475
Trader Rating: 1 (100%+)
Default

I really appreciate this discussion.
Looking at this from the available space between gear box and bumper a 1/12 sized servo would be perfect. But the height should be lower. Are there low profile 1/12 servos?



Tomorrow is shakedown day. I soldered the motor cables, added a flat sensor cable and changed the colorful steering servo cable with a black one. The plastic rocker arms were replaced by the beautiful blue aluminium ones. The M410ULT is also ready. With color, sticker and wing it weights in at 68g. Now the whole car is down to 1014g

wtcc is offline  
Reply With Quote
Old 12-02-2017, 10:48 AM
  #87  
Tech Master
Thread Starter
iTrader: (1)
 
wtcc's Avatar
 
Join Date: Jul 2010
Location: Germany
Posts: 1,475
Trader Rating: 1 (100%+)
Default



Back from a successful first trainingsday with the KR-MF chassis.
All new prototype parts hold up very well. I was a little afraid that the new "gearbox" would cause trouble, because of its reduced stiffness in comparison to aluminium, but no it did a fantastic job holding all gears at perfect distance. The 10.5t motor was too much for this small high grip indoor circuit. I reduced its power to 70% to achieve a nice balance between speed and front-tire-killing. The body helped a lot to reduce roll. Yet, in some situations using half the curb let to a barrel roll move which always was landed perfectly on all four tires. I am sure my springs are to hard. I started with 2.5-2.8 in front and the car didn't look good on track. The switch to 2.3-2.6 was much better, but I think even softer would be better. Something like 11lbs springs should do a better job.
Apart from this typical lw-car-problem everything was smooth. Again I had not even a loose screw.


FF cars are funny:
G-rem, thomsva and JoJo1241 like this.
wtcc is offline  
Reply With Quote
Old 12-03-2017, 12:42 PM
  #88  
Tech Master
iTrader: (1)
 
Airwave's Avatar
 
Join Date: Jul 2007
Posts: 1,031
Trader Rating: 1 (100%+)
Default

Honestly I wouldn't be a Tamiya engineer looking at this picture... I don't know what I would be feeling at this moment lol

Do you plan to do something for the rear rocker? They don't seem to work in a proper plane...
Airwave is offline  
Reply With Quote
Old 12-03-2017, 02:02 PM
  #89  
Tech Master
Thread Starter
iTrader: (1)
 
wtcc's Avatar
 
Join Date: Jul 2010
Location: Germany
Posts: 1,475
Trader Rating: 1 (100%+)
Default

I know the angles look suboptimal, but fact is that they work properly. The rear of the car is stuck. Right now I ran 2.6 springs, which is quite hard for the light rear and two degrees of toe in.
What would you recommend me to do? Should I build angled bases for the arms?
wtcc is offline  
Reply With Quote
Old 12-04-2017, 02:15 PM
  #90  
Tech Master
iTrader: (1)
 
Airwave's Avatar
 
Join Date: Jul 2007
Posts: 1,031
Trader Rating: 1 (100%+)
Default

If it is working... That's just the last point you get make better.

If by stuck you mean that the rear wheels are glued to the asphalt, I think you can go for less toe, or try to transfer your inboard toe to outboard toe. The behaviour can be different but it can also make the rear slide a little...
Airwave is offline  
Reply With Quote

Thread Tools
Search this Thread

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service