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

31V, If you have a flat rear spring you basically have a solid bar and no spring. The deflection is only in the bending of the stack under severe load which will give you a buckboard ride. To get another perspective look at your transverse spring as a leaf spring action and how it works.

 

Or maybe there was another change he didn't recall or think to mention. A change that really made the difference attributed to the engine mounts?

Then again, moving the engine mount attachment point back does increase cantilever & therefore flexibility of the forward frame a bit. That maybe has the effect of improving front suspension response under the particular circumstances involved.

Back on topic, this brings up another thought: a flexy frame has the same effect as decreasing sprung weight, regarding suspension response. Making the frame stiffer would effectively make the car "feel" heavier to the suspension. Ride quality would improve if it could be stiffened considering that you'll also add weight.

But adding weight isn't something a sane hotrodder does without very good reasons. Stiffening the frame qualifies as a good one.

 

Well Dick I'm not so sure of that,
There's plenty of paralleled spring applications that run flat, some are even reverse arch when the weight of the car settles in, then add payload and they get even more in that direction. It becomes a solid bar when it bottoms on the hangers or pulls 180 on the shackles.

Surely I'm not the first to run this spring, the hangers are spaced correctly, the shackles are correct dimensions and there's plenty of discussion on them.

But it's not completely flat, its nearly flat about 1" plus arch and the shackles at 45 *.
As that arch flattens and the eye to eye grows, the shackles will go towards 90* and not bind with the hangers. As the suspension moves further the spring will/should reverse its arch and the eye to eye will will get smaller as the spring reverses. the shackles go back towards the 45* position and this can go till the shackles reach 0 or 180. Ironically this is also 3-1/2" or more of suspension travel and never bind the shackles. I'm not sure 3-1/2" suspension travel on a higher arch transverse mount spring is possible with only 1-1/2" c/c shackles.

Getting the spring rate correct so that the spring moves thruout its allowable range of motion is the critical thing right?

 

If you'd have left all that bondo on it the ratio would have been much better.

 

Yeah, I was thinking the same thing. Lol
Maybe I can get 5 cases of mud and carry it in the trunk

 

Yes you are correct on the spring rate aspect but you are limiting your travel with only 1" of compression and then the spring goes stiff as the stack compresses. Remember that a long leaf spring only has a couple leafs not 11 stacked so the spring is bowing back upon over load, your hits a brick wall with all those leafs. It is almost like running a severely progressive spring where the overload requires a higher load rating, here you dont have additional load you need travel to make the spring function. Backing up a bit there are no set ratios but your sprung weight to unsprung weight ratio should be computed out in the 3-4 :1 range ratio for a leaf spring.

 

31Vicky, Here is an example of a Free Body Diagram for the pictures you drew. All 3 have the same reactions at the supports because the loads or better stated (where the loads occur) are the same. What would be different would be the reactions or stresses WITHIN the structure.

Think of the frame as a roof truss. Throw a given load on the roof and the walls will see some load. Now cut an internal truss support. That wall load remains the same REGARDLESS of how many internal beams you may remove. However when you remove those internal beams what you will change is the loading on each and every remaining beam - however the wall load will be unchanged.

The interaction "concert" is very elaborate. I won't pretend to understand all of it.

Now do I say this to disprove previous posts - no absolutely not. I tend to lean with the idea that the different structures have different stiffness and THAT may very well result in tangible improvements.

 

Well,it's been suggested to turn the shocks upside down.Without switching to lighter components, there is not much you can do to reduce the unsprung weight and the only way to improve the ratio of unsprung vs sprung weight is to increase the weight of the car which is kind of undesirable,playing with the spring stiffness messes up your travel clearances.So apart from shaving a couple of pounds of unsprung weight there is not a lot of options left if the car is built. I ran into this problem with my 27 rpu with a desoto hemi up front and a ladder bar, buggy spring 8" ford rear, I had 31" michelin radials mounted on steelies and lowered the tire pressure to 16 psi, that gave me quite an improved ride. P.S. this was an interesting thread to read.

 

Thanks hemi !
The truss analogy made it click really well.

Still a bit confused though,
This is a real experience so bear with me.
Concrete slab with a 8" hole in it about 1/3 to one end. Stick a spud bar thru that hole and I can lift any side or corner by applying weight to the end of the bar. With it being 1/3 to one end is harder to raise the short end by pushing over the long end but it happens. And pushing over the short end is trying to move more concrete but it happens.

Did I loose you ?
Am I wrong in trying to apply that "saw it with my own eyes" weight transfer to this motor mounts thought experiment? The slab would be the frame. The hole would be the frame mount connection, The bar would be the motor mounts, and the weight would be the engine. So maybe the weight can't be shifted rearward slightly on a chassis, but why can I shift enough weight to move the slab.

If you got time explain that it would be great.
We should get together sometime.

 

Here's one of those hack pics LS and A likes to see.
Demonstrating the bar thru the concrete slab.
There is a bit of overlap in my doodle, but top doodle is pushing over short end and bottom pic is pushing over long end.

I know very well that if I take a long enough bar to go under the front crossmember and over the rear, I can stand this chassis on end.

 

kinda my thought about some weight being ahead of the king pin.

 

31Vicky, "Wrong" for applying what you see - unlikely. What can happen is drawing the wrong conclusions based on assumptions mixed with limited observations. Been guilty of that myself more than I would like to admit.

So IF I understand your question I see it like this - see pic. However to make things easier (for me and hopefully you) to understand I treated your pushing as a "moment" (since we are pivoting the cement which basically means it's a torque - this lets me rotate the force (90 degrees) and apply it so I have a simple Free Body Diagram again. So if you can make that leap the rest I think will make perfect sense.

Remember TORQUE can be thought of in ANY direction. Torque a bolt to 100ft/lbs - doesn't matter if the torque wrench is oriented at 12:00, 6:00, 3:00, 9:00 or anywhere in between.

Now for me to see the "motor" side might take a bit. Call me a slow learner....


EDIT: I see I missed the 8" hole part, but the explanation is the same regardless.
I am surprised we haven't met already - have we ever talked at any of the Thompson Gasser reunion???

 

I don't think we've met, but I bet we have walked past each other once or twice.

So lets work up to this in steps.
Ok so using torque figures and methods of calculating-
What happens if we put 900 lbs on a 12 bar in the concrete slab ?

Then make the slab 10 feet long - What happens then?

Not sure exactly how to read your sketches. But I'm sure it will start clicking like a baseball card in the spokes

 

Correct - any aircraft owners on here will do this regularly to confirm their W&B is correct for safe flight, it matters not, how the weight is mounted to the frame, just where it is located on the longitudenal axis.

 

My thoughts would lead me to throw a set of scales under each wheel and get some baseline figures to work with(you may not have a problem) only one set of scales are required although you will need three pieces of wood the same thickness as the scales to keep the car level while doing the weighing (one per wheel) so as to get reliable readings.
In saying this I would give some thought as others have to said moving the gas tank and battery behind the rear axel so as to balance that hemi up front. I'm interested to hear what the corner weights are as is. cheers - Colly!

 

You Do not understand them very well! As You could not be more wrong with what you are saying!....What Tannergang is saying here is correct. The weight is transfered using leverage. I will make it simpler for you. Go in your bathroom and stand on your scale, then lean out sideways as much as you can without falling and watch the needle move. I been around a stock car or 2 myself..

 

Incorrect - don't matter how you attach the weight(engine)to the frame the weight (Mass?) is still located where its located, Mr gravity does not care how complex your engine mount all he see's is a mass trying to relocate to the centre of the earth.
Its your springs, tyres etc job to stop that happening.
Spring rates shocks and inertia all determine how comfy (or not) the ride will be. cheers - Colly

 

This is not the concept!!.....You are only measuring the overall weight here of the levered end, Your brick is acting as a hinge, Nothing more. You need to Do it with 2 scales (One at each end) I tell you what you do, Go talk to someone who has operated a boom tow truck for about 10 years. Try telling him that transfering weight using leverage makes no diffrence.....

 

Sorry - I typed up a long reply to your post, but then it dawned on me that nothing I can say will sway your train of thought. I personally side with physics and science and will leave others to their own personal views, perhaps this is one of those threads to which everyone brings their own personal view. so while all is civil and at peace I will take my leave. cheers colly

 

Let's not make this one of "those" threads,
Breaking the civility and peace gets threads deleted.

 

Good point, I deleted my last 2 post because I really could care less how you mount your engine, As it is not going to make my car perform any better or go any faster....LOL. I will tell you one thing Tannergang was trying to help you, And gave you some good advice IMO. But looks like we have a bunch of experts on here who think a 62 year old racer Don't know his ass from a hole in the ground. I wonder what they are experts of? And what their Racing experience is??.....Anyhow goodluck with your build....

 

wall, i would think any experiment tried, without motion of the mass, is useless. Tannergang's said he used this in a race car and saw results. i am just trying to learn here, my mind tells me not moving the weight, no matter how it is mounted, would not change any thing. i could picture the weights momentum, in a corner or braking using leverage, but i would think some of the weight has to be on the other side of the fulcrum. is this why this works?

 

Some times the application of science changes things, how its applied or thought about. Maybe the wrong application of the right science- maybe the wrong science to the right application. Maybe the right science in a different application.

I'm not going to pretend to know everything, but I do understand most of the things I've done and seen.

Here's what I know,
leverage moves things.
In order to move things you must shift the weight to something or someplace else or with enough force. "Give me a long enough lever and I can move the earth"

This concept is all about leverages,
Leverages and force "appear" to defy gravity. I'm sure everyone on this site has seen this at least once, just look at a gasser leave the line and plant the rear bumper on the ground. That front end has appeared to have over came the science of it doesn't matter where the weights attached and will continue to do it until the force stops. There's plenty of levers and leverage at work to do this. The engines rotational force "torque" is multiplied by the Trans gear, that multiplied torque is further multiplied again by the rear end gears, then that force is transferred to the tires. If the tires don't move, the force is transferred back to the rear end housing, then to the ladder bars and all that weight gets transferred and up it goes. Lots of torque, lots of multiplication, lots of transfer, and it doesn't matter how this weight is attached, but it damn sure gets transferred.

A 12" bar with 800 lbs on it, generates a force of 800 ft lbs torque.
Applying that force to the chassis is going to change something.

 

Some times the application of science changes things, how its applied or thought about. Maybe the wrong application of the right science- maybe the wrong science to the right application. Maybe the right science in a different application.

I'm not going to pretend to know everything, but I do understand most of the things I've done and seen.

Here's what I know,
leverage moves things.
In order to move things you must shift the weight to something or someplace else or with enough force. "Give me a long enough lever and I can move the earth"

This concept is all about leverages,
Leverages and force "appear" to defy gravity. I'm sure everyone on this site has seen this at least once, just look at a gasser leave the line and plant the rear bumper on the ground. That front end has appeared to have over came the science of it doesn't matter where the weights attached and will continue to do it until the force stops. There's plenty of levers and leverage at work to do this. The engines rotational force "torque" is multiplied by the Trans gear, that multiplied torque is further multiplied again by the rear end gears, then that force is transferred to the tires. If the tires don't move, the force is transferred back to the rear end housing, then to the ladder bars and all that weight gets transferred and up it goes. Lots of torque, lots of multiplication, lots of transfer, and it doesn't matter how this weight is attached, but it damn sure gets transferred.

A 12" bar with 800 lbs on it, generates a force of 800 ft lbs torque.
Applying that force to the chassis is going to change something.

 

Wish I had a second shipping scale but in my best Chong voice...hey man are you guy's ready to have your minds blown? Take the image of the angled offset motor mount, then weld a stringer from the frame straight in to the motor. Doubt the front of the car is going to instantly get heavier.

 

Hmm, a scale at each end... The reading on the scale did not change, the weight of the assembly did not change, but the weight on the brick would be different? That's magic! I tell you what you do, go run that by a boom truck operator.

 

The argument is that changing a mount from 1 (below) to 2 will change weight distribution. Let's say you do that and you put scales under each end. Then you simply lay a brace across as in 3, not bolts. Is the weight distribution going to change? Of course not. Now bolt the brace in. Any change? Now you saw the angled piece in half. Any change?

 

31 Vicky I m sorry for reading this incorrectly but as the conversation goes are you trying to determine the weight transfer front to rear on acceleration? If you are this is a rocket science project. This would be based upon the traction surface, the tire compound, the tire radius and air pressure, the gear ratio torque, bracket length and the length and angle of the radius rods. Statically all you can do is figure out a guestimate answer because of the variables. So If your comps find that you are able to lift say 400lbs you then have to compute the mass center of gravity and determine how far that 400lb lift moves the CG rearward or forward for weight transfer. After that a 400lb lift might only change the weight distribution by 75lbs because the CG only moved a couple inches.

 

It's not magic, but a car has suspension on both the front and the rear, in otherwords spring load distrbution. Your scale acts as suspension as that is really what it is measuring is pressure (weight) Your little make shift model has only got suspension on one end. Therefore all the suspended weight is on one end. If you had another scale on the other end acting as suspenison like a car. (both front and back) they would be spliting the weight and where the pressure was applied (motor mounts) would change as you moved it. Don't take my word for it! Try it for yourself! I mean you went through all the trouble of making a model Wrong to try and prove your right. put suspenison on both ends of the frame and prove me wrong!...I think if you do You are going to learn something, As far as a boom operator, I was in the Tow business for 4 years and did a lot of winch outs in the winter time. I was trying to drag a pickup out of a ditch on slick pavment. With my boom at say 45 degrees my truck would slide, but with the boom at about 30 degrees it still tryed to slide but not as bad and was moving the truck out of the ditch more than moving my truck backwards. Same amount of weight just applyed with diffren't leverage.

 

Here you go. I'd really like to hear the answers to post #147, from anyone.