Technical PtII-Ratio of Spring weight to unsprung weight unfavorable, what helps?

It's not too far off, thread is just chasing down one of your ideas.

My buddy stopped by today and we had a discussion about this. His background is in construction and I tried to present both sides of this argument as best as I could. At the start He was fully convinced that your motor mount picture would certainly move weight back. Then I brought up the points Phil mentioned. Then we had some though experiments with 20' levers. Then we started talking about field cranes and the torque the booms put to the ground and how they actually un load the ass end of the crane. Then we started talking about torque wretches and beams and which end you might need someone to hold. Dynamic torque loads and static torque loads. How and why ladder bars work and that a cantilevered motor mount and the engines weight would create static torque.
Then he left confused lol.

I did get some scales but they are digital and giving me nothing but trouble don't seem to register anything less that 30 lbs. So I'm going to get some old fashioned non digital cheap units and try some more.

 

This is really the answer. As you've already figured out, there's only so much to be gained by removing unsprung weight and shifting sprung weight around. The thing to remember is springs are rated at 'X' lbs per inch, so for a given weight that needs to be supported, as you reduce travel the spring rate has to go up. I'd see this all the time with motorcycles where the owner wanted to lower the bike with shorter shocks and was surprised when either the bike bottomed out easily (not enough spring rate) or rode hard (enough rate to prevent bottoming). You can mitigate this somewhat with a progressive-rate spring. You can find 'new' lowering shocks for bikes for sale pretty easily... LOL.

Now, working with a leaf spring, you're probably going to have to talk to somebody who knows how to 'tune' one of those (tapered leaf? Leaf lengths?). You've got more options if using a coil-over, as it's easier to wind a progressive-rate coil. And the mounting angle will affect the shock travel, allowing you to effectively 'tune' the spring rate. But the bottom line is that with limited travel, you'll end up with a higher, stiffer spring rate compared to the same suspension with more travel.

 

I don't see how the shape of the motormount, and where it attaches to the frame, will affect anything. Awaiting the outcome of 31Vicky's tests.

 

Same here.

 

Just a simple mans thought here.
long Ladder bars and good quality rebound shocks


Not moving the engine and only moving the mounts does not move weight. Think about the weight transfer box on a tractor pull sled, only moving the weight box (engine) increases the weight on the sled.

Godspeed
MrC.

 

One thing we (my buddy and i) did agree on this afternoon was this.

800 lb motor on a 12" long mount would generate 800 ft lbs of static torque at the mount. It needs to be substantial and a very secure mount to the frame. Also that the mount will transfer that torque load into the frame rail and that will definitely do something.

What we couldn't decipher wAs what exactly that something will be or to what degree it would do it.

 

deleted post

 

Right but its where the weight is transferred onto the sled.
As the weight slides forward the tongue weight increases.

So comparing the starting to ending position and ignoring everything in between. Where's the weight transfer in the bottom sketch figuring the box is suspended off the long bars attached at the head of the trailer.

 

I have a picture on my computer at home of a rear end housing that has had holes cut in it along the length of the axle. Not that the axle itself has holes in it, but the outer tube that connects the brake assemblies to the center pumpkin. I don't know if this is a reasonable thing to do or not. I'll leave that to the experts. But it does fit your desire for low dollar ideas of combatting poor unsprung/sprung ratios. I'll attempt to remember to post the picture when I get home late tonight. It was on a front engine dragster. In that application, the frame would help support the rear end ends, so maybe they could get away with reducing the structural integrity. Also, it wouldn't have to last much more than a quarter mile. Perhaps some sort of light weight plastic dust/water cover would help on a street driven car?

 

Look at a crane -

Where the weight ? Is it under the load?
Nope it's under the front of the crane, but its also lightening up the ass end of the crane too.

 

31Vicky, I think your original thoughts about getting rid of or transferring unsprung weight to sprung are good. after you have done all that you can that way, then soften your spring rate as much as possible and get the best shocks that you can.
As far as trick engine mounts, TANNERGANG must have had a hell of an engine builder to win all those races, cause his trick motor mount didn't do shit for him! Physics 101!!!!!!!!!!

 

Just before my head hit the pillow last night I thought of the simplest and most extreme way to illustrate this scenario in a way any car guy would get. Take an engine hoist, 4 wheels and a frame like a car. Also has a adjustable cantilevered boom that reaches nearly end to end. If you were to place scales under the 2 wheels on the free end (with the hook), stand directly over the wheels, then hang off the boom (assuming your directly over the wheels), should be the same. Though if you move the boom back one notch and do it again, things change. You would have to change the physical position of the weight, not just it's mounting point.

 

^^^ That's what I was wondering if the mount would want to pick up on the back end. I will be watching this one got me scratching my head.
One option but not cheap? to get gun drilled axles.

 

And as AGO and probably others said, soft springs and travel do wonders for light cars. My old room mate and his buddy had nearly carbon copy T buckets and one rode dreamy and hooked up all the power you could throw at it, the other anything but. The other had coil overs that about topped out static.

 

Yeah, I get that one for sure - it's easy peazy.

Lets try this .
Same hoist with an engine + Trans on it. Front is under hook and rear is under mast. Assume any chain does not swing.

Test one- engine hanging very nose heavy Trans tail up.
Come along from Trans tail to rear wheels. Get up on come along enough to level the Trans. Does that transfer weight amongst the 4 scales?

Test 2 engine hanging tail heavy nose up.
Come along from nose to front wheels enough to level.
Does that transfer weight?

Test 3 same as 2
Come along from nose to rear wheels
Does that transfer weight?

 

The weight is being shifted slightly so yes.

 

Is this the concept?

 

I think what some are trying to say is that under certain dynamic conditions, mounting points or some changes in suspension geometry can make a difference in how things react. But under static conditions, I'd say they don't. So accelerating/braking/cornering may change, but hitting a pothole at a steady speed will get the same reaction regardless of those changes. That's over-simplified but the gist of it....

 

Nobody has an opinion here ?

 

Haha, Glad to know I'm not the only one that was thinking of a way to prove it would change nothing. Nice job!

 

The traditional fix would be to put 200lbs. of stuff in the trunk!

 

I'm thinking it is more like this.
And if I use a 10:1 scale ill be working with 80 lbs and a 12" rail.

1/2 scale would be 400 lbs on a 56" rail.

 

Did you see post 5

 

Interesting discussion. So if I build my motor mounts off the rear bumper but keep the motor up front than I will have a wheelstander. Just being funny. I will conceded the cane does carry the weight on it nose instead of under the load itself but how far back do you think you can move the mounts 2 inches 3? Will that amount of transfer be worth the effort.

Godspeed
MrC.

 

My calculation and tape measure say I can get every bit of 18" back with the same effort as 2-3". I can get almost 24 if I really change a bunch of shit, that might not be worth it.

Maybe it's a goose chase

 

I still believe weight/gravity are loading the wheels the same but there is one heck of a torsional load at the frame from the offset mounts. To further clarify my hoist theory, it had mostly to do with where "you" are and the fact that "you" are mounted at two opposite ends of the frame and nothing to do with angles or height. About as relative and dramatic a demonstration as I could come up with. Things would be different if not supported in 4 corners and instead just under the frame mounting point but that would be a unicycle.

With the pull sled weight is again moving off center and the crane is just a single scenario and would be the same outcome if you mounted it off the front bumper. You are way overthinking things, get back to what you do best and melt some metal together. There's a neglected Model A still sneering at you waiting for it's place in line.

 

What are looking to do w/ this car, this dictates the setup....just a streeter, race ?.........I just used scales to get the data I needed to make my decision for engine location......and my choice happens to fall within the 10 % max. gasser rule..if a rule states the max. is X, that does not mean X is the best location.......You need to know why you chose to make a change..........just like weight transfer is an action-reaction........what are you doing to control the reaction ect....Just moving the battery from the front of the car to the truck does wonders, all the little things add up...and light will alway's be faster...I wish I knew more ....but will be learning all the way to the end.....scale that sucker and set up the balace you want, with you sitting in the car......Littleman

 

Yes, as drawn - your crane is falling over. Free Body Diagram. Summation of moments from any given point must equal zero - or - it's moving.

 

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I'm sorry I caused so much trouble trying to give a little advice to try and help a fellow HAMBER....my diagram of the motor mount was an exaggerated drawing to show what I was talking about...just moving a little could help him.....I wasn't talking about making the mounts run back 5 feet or to the bumper as people have laughingly talked about........You guys spend more time trying to prove someone wrong than you do trying to help.......and for the good engine man...I had one of the best in the country....didn't cost me a dime and he delivered them over 800 miles....I am very proud of what I've accomplished in my lifetime...I also have learned a valuable lesson on here.....you CANNOT help people for the nah sayers climbing in to try and make you look like a fool.....I don't have to prove anything to anyone.......It just makes me feel good to try and help someone........I will NOT POST any more suggestions on here to help anyone else...I'll do it privately......YOU GUYS HAVE SUCCEEDED IN RUNNING ANOTHER OLD GUY OFF...........CONGRATULATIONS!

 

Ohhhh, you know how to get somebody motivated