Dan Woods opposed coil front suspension

If anyone plans to actually test this theory on a traditional T-bucket, please make sure you get it on video.

And yes, this is a good thread.

 

How about incorporating the friction shock in with the bellcrank. Like between the bellcrank and the frame. I designed a suspension system on my TR and the coilovers are not getting enough travel to get the dampners to work since they mounted inboard.
Gary

 

This is how I would approach the friction shock idea.

Integrate them into the pivot, and you will never know they're there.

The stiction of an oring in its bore will not be enough to do much good as far as damping goes.

Maybe a shaft wrapped in clutch lining that travels inside a tube. If you make the piston that the lining mounts to adjustable for diameter (like say those tighten in place rubber bung plugs), you'd have a very good approximation of a linear friction shock. Have to figure out some way to seal the water and grit out though, or it'll eat itself in short order .

 

I'll need a number of simple bearing pivots on the '31: there are six bell cranks in the suspension and two in the steering. What sort of bearing is recommended?

 

For all but the most heavily laden (and even them if properly designed) pivots, a simple bronze sleeve bearing that has some provision for the pressurized application of lube (a zerk type grease fitting and some kind of EP grease will be fine) should do the job nicely.

Ball and roller bearings don't like the be installed in places where the balls can't circulate (IE they never make full revolutions), because only a few balls or rollers end up bearing all the load all the time on the exact same contact points. If installed in this manner, (sometimes very rapidly) accelerated wear is the result.

Alternately, if you cannot get to the bushing to grease it, you can use a bearing material that is self lubricating (provided that it has the physical strength the bear the load you'll be applying). Materials such as UHMWPE, Delrin, or PTFE are very well suited to this kind of installation, assuming the service temperature is within their bounds.

 

Thanks, Ryan

 

Yep that works for me as well. I did mention that ball/roller/needle bearings dont like restricted movement. I have used engineering plastic in a LOT of places including my king pin bushes. For the 'internal bell cranks on my rear end I used 'oillight, which was turned and reamed to 1/2 inch. Good for restricted movement and high loads. Be warned though, they will wear in one place if they are not doing a 360 turn all the time.

Do a search on engineering plastics, there is a site I found that gives all the info you need regarding application, resistance to impact, wear rates etc. (sorry cant find the link)

One thing to note is that Teflon is very sensitive to temperature and humidity changes, so although it seems like a good idea to use it for smooth operation, it can tighten up on a running surface when the weather changes. (By experience not by hearsay)

Gerry

 

Fadt,
Have you looked into some of the older design mountain bike shocks? Years ago, I knew a guy who built a single seater autocross car using 4 of them and they worked great. All the newest ones have remote reservoirs, so they won't fit inside your springs; but the older ones weren't all like that.

 

Yep. Look at them. Told by the makers that they are not designed for the kind of loads and motion on a car. It may be something to look at more closely, though.
The shocks used these days (mono type) on the rear end of bikes,are again said by the makers not designed for the kind of motion on the front axle of a car. Its due to the frequency, which on a bike is slow compared to car. At least thats what the manufactures say. Mind you that does nt mean they wont work.
Gerry

 

Slow frequency? You need to go see what folks are hitting on their downhill rigs. MTBs of today are closer to Motocross bikes than anything. I have a couple Fox Vanilla coil overs we are using on a street bike but may steal them for my salt car.

 

Ok, Sit down, have a couple beers and 'splain it again. They invented the rubber room so Lawyers and Engineers could mumble to themselves without hurting anything or confusing the rest of us... BEER allows them to make more sense to the rest of us once they have it sorted out... LOL

Remember seeing similar horizontal spring setups on a couple early drag cars too. Best thing about these isn't that they work, it's that you can't help thinking up reasons why they shouldn't.

 

For sure they are going to tell you the shocks won't work. CYA... On that T, you have a VERY light front end, limited motion, and a relatively slow suspension frequency. Might be worth hunting a pair down to prove them wrong (or right...)

 

They are just covering their asses.Their lawyers and liability insurers would FREAK if they said yes. Trust me on this, I do commercial liability insurance for a living. Try it out.

And I STILL want to see a video of someone pushing a T-bucket to its adhesion limit to see if it understeers or oversteers at the limit! Could be better than the washing machine video that guy posted on the SBC thread...

 

If you can somehow get a pair of hydraulic lines out through the central spring seat, you could run a simple hydraulic cylinder inside each spring, plumbed to a valve block and reservoir mounted more discreetly e.g. behind or below the radiator. That way the hydraulic piston area can be the largest that'll fit inside the spring, as you won't have an annular reservoir taking up space. And both dampers can share a common reservoir.

 

best I could find; NOT a normal front suspension, and not a steady state skidpad course....

http://www.youtube.com/watch?v=0YyHAPVhT7M&feature=related

 

ew.......

 

Hmm. Yea, push, push WHOOOPS OVERSTEER! Id rather see the transition at speed on a road course! Could wake you up!

 

Somebody needs to teach the silly bugger how to turn an actual donut.

Ugly car to boot, so the guy fails on many levels.

 

Hi
Been looking at mini motor dirt bikes. They have small rear damper and they are cheap as well. Thought I might try them and see how it goes.
Gerry

 

man thats a cool setup.

 

If you can somehow get a pair of hydraulic lines out through the central spring seat, you could run a simple hydraulic cylinder inside each spring, plumbed to a valve block and rese.....

Interesting idea and very do-able. At the moment I just want to keep it as simple and clean as I can
Gerry

 

Gerry, do you have any close up pics of your T? It has great proportions!

Steve

 

Would having a different rated spring inside of the larger one, that osculated at a different rate, be as effective as a shock? Especially in a very limited movement situation like that? Isn't that one of the benefits of dual valve springs... they control valve float through differing oscillation?

 

Yep there are more pics but they are on another T specific Forum
Gerry

 

The object is to keep the ratio between the two levers on the bell crank as close to 1:1 as possible, right?

If you lengthen the arm that attaches to the spring, it wouldn't look right. The springs and shocks would stick up in the air.

That leaves the other side of the lever. So, how about moving the pivot point of bell crank outward, closer to the ends of the axle, thereby shortening the long arm?

If the shocks are too short, lengthen either the mount between them or lengthen the shock absorber shaft - as in the crude picture below. I prefer lengthening the shaft. It just looks lighter and cleaner to me.

Also, I would only slot one of the bell cranks. The other would act as a panhard bar to locate the axle laterally.

 

The limitation on the horizontal arm is the amount of travel one needs to accommodate. The shorter the arm, the greater the angular movement at any given suspension travel: and it reaches an absolute limit at 90° in both directions. That is a, say, 2" arm allows one only 4" overall travel from full bump to full droop, which might not be enough, and which might too easily induce an over-centre situation.

I don't know what is generally acceptable in these sorts of applications, but I would not want the sweep of such an arm to come near to 180°. I'd think about 120° to be an absolute limit, and try to aim for 90° in general use. A 2" arm will give a mere 3.46" of travel at 120°, an a tiny 2.83" at 90°. I'd say one would want at least about 6" of travel for real-world road use.

The above considers the arms simply, and the situation becomes more complex when one considers the slotted end. The shorter the arm, the greater the ratio of the required slot length to the arm length. In any event this arrangement exhibits a variance in mechanical advantage such that the greatest effective spring rate is seen with the arm in the horizontal position. That is, one has falling-rate geometry, which is not ideal, and the effect is exascerbated as the slot length increases in relation to the arm length.

And using one arm as an effective Panhard rod not only leaves one with a Panhard rod only 2" long (to stick to my example), and consequently a relatively great lateral motion in bump/droop, it doubles the required slot length on the other side: and that means constant-rate springing on one side and seriously rapid falling-rate geometry on the other!

It was good thinking, wsdad: the question needed to be asked. That it turns out to be a dead end doesn't mean that we don't learn something going there and back

 

Ned Ludd: "The limitation on the horizontal arm is the amount of travel one needs to accommodate..."

I just had another thought. Instead of putting a shock absorber inside the spring coil, let's imagine we have a hydraulic cylinder, as someone mentioned earlier. It is as large around as space permits. Now let's run some hydraulic lines to a narrower, longer cylinder (ie: the real shock absorber) hidden away somewhere that provides plenty of space for it (perhaps inside the frame rails).

We have created a hydraulic lever which gives back the travel the shock absorber needs to operate without shortening the actual lever on the bell crank.

In fact, we could simply leave the metal springs out altogether and just use the hydraulic cylinders - pressurizing the hidden cylinders so they become air springs.

Would that be too Rube Goldberg?

"...one has falling-rate geometry, which is not ideal..."

That's true. But I wonder if it's enough to matter in real-world driving?

"And using one arm as an effective Panhard rod not only leaves one with a Panhard rod only 2" long..."

Yeah, you're right. That idea wasn't thought through so well.

"...it turns out to be a dead end doesn't mean that we don't learn something going there and back "

I like the way you think!

 

Gerry if your laying the shocks over you need gas not oil.

 

Does anybody have a detailed diagram, including the type of shocks to use and the dimensions of the levers, axle mounts, etc........

From a tried, tested and true setup, so we can all see it and put some of the debate to rest.

I'm very interested and curious to see myself, but it's almost falling into the realm of boringnes. Too much reading!!