How to design parabolic leaf spring?

In summary, designing a parabolic leaf spring for a vehicle suspension requires careful consideration of various variables such as custom application, desired ride height, load capacity, desired flex, and distance between springs. Calculations involving these variables can be complex and may require a trial and error approach. It is also helpful to study existing designs, such as the ones used in the US Army's J-118 Escort Wagon, and experiment with thin and lightweight materials.
  • #1
ksachanta
3
0
hi,
can anyone please help me to design a parabolic leaf spring for vehicle suspension...
is there any software available?
 
Last edited:
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  • #2
ksachanta said:
hi,
can anyone please help me to design a parabolic leaf spring for vehicle suspension...
is there any software available?

Plz anyone can help me on this...?
 
  • #3
It's not simple matter of saying "Make it like this"
You have to consider many variables:
(a) Is this a custom application? What is your req'd, if any, eye-to-eye dimension?
(b)What is the resultant ride height you are looking for?
(c) What load must the springs carry?
(d) How much flex is required?
(e) How far apart will they be situated?

These things all make a huge difference in designing leafs. Suspension systems (even leaf springs) are not cookie cutter.
 
  • #4
Thanks for ur reply.
i want to design a parabolic spring for a heavy commercial vehicle.
the inputs are -
-- eye to eye length is ~ 1200mm to 1500 mm
-- width of leaf is taken as 70 mm or 90 mm
-- stifness required is 30 - 35 kgf/mm
-- load on each spring ranges from - 1300 kg to 1500 kg
-- flex required is about 60 - 100 mm (at laded condition)
-- camber ( free curvature of unloaded spring) is taken around 200mm
-- springs are situated at 850 mm apart.
-- Ride clearance(dist. from axle centre to chassis bottom to me maintained at 200mm

the spring to be checked for 2g load and 3.1g load (over load) conditions, where the flex will be maximum.

Here i have to decide on number of leaves required and Centre thickness & end thickness of leaves.
How could you design the parabolic profile of leaf once you got your center and end thicknesses.

Plz. help me on this .. I am unable to get exact formulas to design the spring .. suggest me some that know..

Thankyou very much .. waiting for ur reply...

Regards
Srikanth
 
  • #5
https://www.modelica.org/events/modelica2006/Proceedings/sessions/Session2d1.pdf

That might give you some insight. I've never done this as the equations aren't anything simply like
(#leaves)*(eye-to-eye)=Spring_Dimensions
There is some calculus involved. You have your variables though, so you've got that going for you.

Take a look at how some existing springs are designed. Remember, the more accurate you want your calculations (that is, the more variables up there that you want to satisfy) the more difficult they will become. My experience with stuff like this: you have to trade some of your requirements for the ones that are more pressing. Like forfeiting some flex to support your load, or some ride height to allow your flex, etc.
 
  • #6
I'm thinking that you might want to abandon your theoretical approach, and work by trial and error.

My favorite parabolic leaf springs are those aboard the US Army's J-118 Escort Wagon:

http://www.transchool.lee.army.mil/museum/transportation museum/wagons.htm

In particular, I like the scissor-spring shock absorbers of the driver's seat (a scissor-spring being, essentially, a double parabolic leaf spring with the open sides facing one another).

I would recommend experimentation with leaves as thin, and made of material as light, as possible. It might take a while, but it might make you rich!
 

1. What materials are commonly used for designing parabolic leaf springs?

The most commonly used materials for designing parabolic leaf springs are high-strength steel alloys such as SAE 5160 or 9260. Other options include composite materials such as fiberglass or carbon fiber, which offer weight savings but may not have the same durability as steel.

2. How do I determine the correct length and width for a parabolic leaf spring?

The length and width of a parabolic leaf spring are determined by the weight and load requirements of the vehicle it will be used on. Factors such as the desired ride height, suspension travel, and spring rate also play a role in determining the dimensions. It is best to consult a professional engineer or use specialized software for accurate calculations.

3. Can I install a parabolic leaf spring on any type of vehicle?

Parabolic leaf springs can be designed for a wide range of vehicles, including cars, trucks, trailers, and even some heavy-duty equipment. However, it is important to ensure that the spring is specifically designed for the weight and load requirements of your particular vehicle to ensure optimal performance and safety.

4. How do I determine the number of leaves needed for a parabolic leaf spring?

The number of leaves needed for a parabolic leaf spring is determined by the weight and load requirements of the vehicle, as well as the desired spring rate. Generally, more leaves will result in a stiffer spring with a higher load capacity, while fewer leaves will provide a softer ride with lower load capacity. Again, it is best to consult a professional engineer for accurate calculations.

5. How do I ensure proper installation and maintenance of parabolic leaf springs?

Proper installation and maintenance of parabolic leaf springs are crucial for optimal performance and safety. It is important to follow the manufacturer's instructions and torque specifications during installation. Regular inspections should also be conducted to check for any signs of wear or damage, and the springs should be replaced if necessary. Lubrication of the spring and its components is also essential for smooth operation and longevity.

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