daveturnbull Posted July 30, 2011 Share Posted July 30, 2011 So, I have a possible option for a new project, but have one key point to ponder first. Ignoring the limitations of spring types & shock lengths, which gives better articulation. A frame (a-la RRC, Def, Dis1) or Watts linkage (a-la Disco 2)? Anyone got first hand experience of both? With an A frame I know the main limiting factor is the chassis end trailing arm bushes, but have no experience of a watts linkage. Quote Link to comment Share on other sites More sharing options...
ToyRoverlander Posted July 30, 2011 Share Posted July 30, 2011 A frame is far less restrictive than the watts linkage. But to be honest, if I were you I would improve front end articulation first to create a front-rear balanced suspension. Quote Link to comment Share on other sites More sharing options...
longlandy Posted July 30, 2011 Share Posted July 30, 2011 A frame is far less restrictive than the watts linkage. But to be honest, if I were you I would improve front end articulation first to create a front-rear balanced suspension. perfect answer Quote Link to comment Share on other sites More sharing options...
Anderzander Posted July 30, 2011 Share Posted July 30, 2011 Quote Link to comment Share on other sites More sharing options...
elbekko Posted July 30, 2011 Share Posted July 30, 2011 The a-frame is better. The Watts linkage on the D2 has been crappily designed. If they'd just rotated the mount a bit you could get a lot more travel out of it... I was looking at it a while ago, and just couldn't understand why they did that But yes, definitely start with improving the front. A 3-link or parallel 4-link with panhard shouldn't be that hard to fit in, the panhard would make the steering act the same (unlike a triangulated 4-link). ... I should stop reading Pirate Quote Link to comment Share on other sites More sharing options...
Anderzander Posted July 30, 2011 Share Posted July 30, 2011 Shall we post up our articulation pictures? or is that uncalled for and gratuitous? Quote Link to comment Share on other sites More sharing options...
robhybrid Posted July 30, 2011 Share Posted July 30, 2011 I have looked at this a little and as both A frame and watts linkage force the axle to articulate at the centre of the axle the design of the body soon becomes the limiting factor, where as with pan had rod you open up the door to far more articulation. I hope my picures of lego help explain better. of course there can be issues with rear steering with pan had rod but landrover use it on the front and 80 series landcruiser use it on front and rear. Quote Link to comment Share on other sites More sharing options...
western Posted July 30, 2011 Share Posted July 30, 2011 brill use of Lego technic Quote Link to comment Share on other sites More sharing options...
ToyRoverlander Posted July 31, 2011 Share Posted July 31, 2011 Shall we post up our articulation pictures? or is that uncalled for and gratuitous? I wouldn't mind... but mine is on leaf springs... got more articulation at the front than at the rear... overall articulation is ridiculous.. it hardly lifts a wheel offroad . Quote Link to comment Share on other sites More sharing options...
elbekko Posted July 31, 2011 Share Posted July 31, 2011 If we're going to post up Lego articulation pics... I'd have to disconnect the springs to get images of full articulation though That's a 4-link, for fun I put the numbers into the calculator too (they're x10 to make it work): Quote Link to comment Share on other sites More sharing options...
stuck Posted July 31, 2011 Share Posted July 31, 2011 Lego PAH, Where's my Meccano Quote Link to comment Share on other sites More sharing options...
Landy-Novice Posted July 31, 2011 Share Posted July 31, 2011 Lego PAH, Where's my Meccano Quote Link to comment Share on other sites More sharing options...
CwazyWabbit Posted July 31, 2011 Share Posted July 31, 2011 I want to see a demo with origami .... Quote Link to comment Share on other sites More sharing options...
jbs Posted July 31, 2011 Share Posted July 31, 2011 Lego PAH, Where's my Meccano It's either on the drive or in a garage somewhere Quote Link to comment Share on other sites More sharing options...
simonr Posted August 1, 2011 Share Posted August 1, 2011 Actually, a Watts linkage is no more or less restrictive than an A frame. The watts link is just a panhard rod replacement and it's advantage over a panhard is that the axle moves up & down in a straight line whereas with a panhard rod the axle is displaced sideways as it droops. The limiting factor (for droop anyway) on a Watts link is the length of the toggle in the middle. There are obviously practical limitations to this, but the limitation can actually act as an advantage on side slopes. The reason I say this is that it limits the amount an axle can droop. beyond that point, the axle can still articulate, but only by compressing one spring and expanding the other. With a panhard rod, you can have a situation where (on a side slope) both springs are extended, one more than the other which gives you a higher centre of gravity and also moves the GoG closer to the down hill wheel - both reducing stability. By limiting the droop more than articulation, it can also give an advantage on hill climbs / descents. On a climb, the front axle is unloaded and the springs push the axle as far away from the body as they can, which further unloads them. This can lead to reduced steering capability and more tendency to 'wheelie'. Limiting the droop, increases the pressure on the front axle and makes the vehicle more inclined to steer and less inclined to wheelie! A lot of rock-crawling trucks use a couple of little ATV winches to pull the axles up towards the body to achieve the same effect. By pulling on the middle of the axle, it can still articulate but it improves stability on side slopes and climbs. Taken to extremes, too much/free axle articulation and/or droop can be a bad thing - as I found (to my surprise) on my twist-in-the-middle buggy. It had enough articulation to lift a wheel 52" in the air but if you tried to climb a side slope diagonally, it would roll over the rear down-hill wheel on fairly gentle (30 deg) slopes that a standard LR could traverse easily. Like everything, it's a compromise - and anything taken to an extreme, though it may make one aspect of off roading better it is likely to make another worse! Si Quote Link to comment Share on other sites More sharing options...
andyb Posted August 1, 2011 Share Posted August 1, 2011 I don't have any Lego or meccano to demo this, but my mind (such that it is!) is telling me that a Watts link will not have the anti-squat characteristics of the a-frame setup. Well not that it is due to the a-frame as such. Just thought I'd add that as nobody else has mentioned it. Could be relavent to Daves project. Quote Link to comment Share on other sites More sharing options...
elbekko Posted August 1, 2011 Share Posted August 1, 2011 Actually, a Watts linkage is no more or less restrictive than an A frame. The watts link is just a panhard rod replacement and it's advantage over a panhard is that the axle moves up & down in a straight line whereas with a panhard rod the axle is displaced sideways as it droops. And for that reason I wouldn't like a Watts up front with mechanical steering, way too much bump steer. Quote Link to comment Share on other sites More sharing options...
daveturnbull Posted August 2, 2011 Author Share Posted August 2, 2011 Thanks to everyone for all the replies. Some quite interesting points there; mostly confirming my original suspicions. So I'll be sticking with an A frame setup for this project. Wilst the watts linkage does have potential, the D2 implementation of it is a bit too restrictive. @robhybrid - building LEGO suspension link models at 11pm on a saturday night... You know how to live! @cwazywabbit - origami is just no good for wading... @andyb - you should have had a boy, then you'd have LEGO to play with ;-) Quote Link to comment Share on other sites More sharing options...
CwazyWabbit Posted August 2, 2011 Share Posted August 2, 2011 Wax paper origami? Quote Link to comment Share on other sites More sharing options...
robhybrid Posted August 4, 2011 Share Posted August 4, 2011 Thanks to everyone for all the replies. Some quite interesting points there; mostly confirming my original suspicions. So I'll be sticking with an A frame setup for this project. Wilst the watts linkage does have potential, the D2 implementation of it is a bit too restrictive. @robhybrid - building LEGO suspension link models at 11pm on a saturday night... You know how to live! @cwazywabbit - origami is just no good for wading... @andyb - you should have had a boy, then you'd have LEGO to play with ;-) Actually the pictures were taken nearly 8 months ago when I was looking at ideas for building my slow up to 30mph rock crawling style winch challenge capable buggy, I am still undecided and have a huge collection of parts in the workshop. For my application I like the idea of reverse A with pan had rod and some form of axle limiting system. Quote Link to comment Share on other sites More sharing options...
bishbosh Posted August 8, 2011 Share Posted August 8, 2011 20 posts in and not one comment on that duvet cover????? My coat? Why thank you! Quote Link to comment Share on other sites More sharing options...
discomikey Posted August 8, 2011 Share Posted August 8, 2011 im amased that he could use colour coordianated pieces of lego, in my house it would have looked like elmo the elephant Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.