mr. ed

Make a sideways view image of the car and draw an arc : with the pivot point as center and starting at the rearmost attachment point of the shock.

As the suspension travels up that moving shock end follows the arc.
The delta car had the rear shock point behind the pivot point: so the arc will go slightly up as the shock end goes forward.

On the modern cars the that shock end is in front of the pivot point so the arc is already going down and tilting further down as the shock gets compressed.

Other factors are of course concessions to make: the delta had the shock in the rear for electronics room: as such it sits over the moter and can't angle down. The speed merchant uses the inline battery configuration and has no space for lowering the foremost attachment point of the shock

Radio Active

iTrader: (2)

Ok, I've done a little sketching. So, follow up question. Is the only thing that matters here the compression of the shock as a function of pod travel, or is there also some affect to do with the shock actually travelling upward instead of downward?

YR4Dude

iTrader: (44)

^^^^^^^^^^^^^
This

I think the shock placement is more so due to simpler issues to allow for space for other components. In the older cars it was to allow more room on the chassis for the larger electronics (ie. wiper arm). In the newer cars, it was to allow room for the damper plate which was popular after the RC12L(the original 12L didn't have a shock but later versions had the shock mounted on the chassis) and more so now to allow more open access to the BL motor.

Radio Active

iTrader: (2)

Yes, this I understand. What I was driving at though, was why slope the shock with a positive gradient? Even with the rear mounted design that Delta had, they could have continued to run the shock parallel, or there was enough space to run a negative gradient at a similar angle to the Rev 7. Say they found, like I did, that running parallel produced too much exit steering, would the positive gradient solve the problem?

YR4Dude

iTrader: (44)

I think you're over analyzing the situation. Back in those days people tried many different ideas to design a 1/12. But the ideas were very basic in that it was just trying to figure a way to put shocks on a car such that it would work and provide more articulation in the suspension.

I can tell you that there wasn't so much science in setting up a pan car then as compared to now. That is not for me but maybe others can comment on that. All I remember is you try different springs, check for tweak, sauce the tires and drive the tires off the car. Maybe a little more or a little less wing and thats it.

Nowadays, I have to check ride height for both front and rear, droop for both front and rear, front camber and caster.(okay we did adjust caster then) but it seems more complex setting a pan car now than when I remember it then.

Radio Active

iTrader: (2)

Ok, so more art than science.

Reminds me of this scene from the movie Galaxy Quest.

http://www.youtube.com/watch?v=nW-NiGp1gys

mr. ed

correct: compression rate against travel, and how that rate changes while the suspension is working to get you through the curves.
Another benefit of the sloping down shock is the lower CG

LonnyJ1950

I ran that Delta car for a long time. We carefully bent the kingpins in to put in some camber. Caster was simple, it was more of a problem to prevent it from coming loose in a crash and giving you 20' or so of caster. We checked ride height, though it was difficult to change except with tire diameter, there are no ride height adjusters in the rear. You had to spend some time getting the front to work smoothly, suspension is by sliding the steering blocks up and down the kingpins. Tweak was adjusted by shimming the rear pod. We didn't worry about the angle of the shock, just about getting it to work, if you haven't built a Delta micro shock, you have no idea how frustrating it could be. BUT, if you got it right, it was a lot better than the 12i and other cars of that era. Still have mine.

azeroth

iTrader: (21)

when delta picked up the front end of the shock the which allowed to to run the thinner t bar that was available and still carry the weight of a 6 cell pack using the same shock and spring but allowed greater for side to side articulation

bakaguyjean

iTrader: (1)

I agree with what you are saying,there were some other companies that used an angled shock at the rear before it became popular,but the shock is extremely long to go over the stick pack type battery.ABC center shocks were around 7 inches long for a while.
Also there were lots of different ways of thinking about what they chassis should do. Delta was only one idea,and while i was a very popular car/company in North America it wasnt "THE" car everywhere due to the RC world just being smaller with much more local companies that did well where they were.
I think the fact that there was any kind of front bulkhead,even if it was just fiberglass to mount the shock to was more important for bodies.Bodies and tires have really been a very important tuneing item for a while.Bodies were much higher in there rear before everybody changed over to the current center shock idea.
I really think here wasnt as much brains going on but more trial and error for a very long time,of course you have to always sell new kits to make money so there is the gimic factor also.Even today it seems like lots of gimics and they all work fine with the right tires and body.
People still do good with the RC12 block front suspension and people still do good with "T" bars,very old ideas but you cant sell a bunch of kits using 30 year old parts,unless its a Mardave.

Radi0Flyer

I used to run a Trinity Reflex 10. At least you only had one shock. Try getting four of them to work on the same car!


Sean

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iTrader: (2)

Hmm, more scribbling on paper supports this. For the same up travel I get a greater compression of the negative gradient shock versus the flat mounted shock.

I'm going to plot this out properly at some point, and it will be interesting to see how progressive different geometries are, and how this correlates to handling characteristics.

Thanks everyone for taking the time to discuss these types of things with me. It's really interesting to think about how older ideas worked (and whether they should live again). But it's much harder without your expertise.

LonnyJ1950

If you really look into this you will find that as you flatten out the shock you will get to a point where the shock rate falls under further compression. If you had enough travel, the shock would actually start to extend with more suspension movement.

mr. ed

that point would be far beyond bottoming out on the floor luckily, but yes it would happen quicker on a total wrong angled shock.
A lot more info should be available from touring car and buggy tech threads: modifying the angle of the shock on the arms and towers is standard practise for them, and speaking of difficult: they almost all have 4 shocks )

InspGadgt

that was a cool car though...or the trinity ev10 the pan car with 3 of those shocks.