Damper design wanted
- Thread starter Gerry
- Start date
Are they for a shock absorbsion or as additional spring rate?
Gerry
Well-Known Member
Bruce
shocks. No additional spring rate needed. Its just a thought at the moment as the design for the friction ones are not 100% in their present form. I wont know until I drive it, just trying to be a step ahead.
They will need to be very small diameter and quite long but any simple design will do.
I know the theory but wanted to ask you guys, as there is a lot of expertise in the forum
Gerry
PS Here, a shock abosrber , technically speaking is a spring. Shock absorbers are techincally called dampers. If you see what i mean *I think i got that the right way around
Gerry
Well-Known Member
Lee
Cant do that as it all has to sit inside the layout Ive got already.
I want to hide them inside the springs so that at first glance you dont see them. Coil overs would mean a whole new design. As yet I have nt tried the frictions so I dont know if they will work ok.
Gerry
one finger john
Active Member
Gosh that is pretty. Are the springs held in the pockets by compression? Is the center mount a cup affair? I'm thinking that an insert might work (a real small one), but you would still have to secure the inner portion so you would have shock action during compression and rebound. Perhaps a custom made motorcycle shock of some sort.
John
That is my thought. People do not speak highly of friction shocks but I like mine. Or maybe a small motorcycle or scooter shock minus the spring mounted inside the springs.
one finger john
Active Member
I may be wrong, but the real question here is how a hydraulic shock would be secured to the center mount. Gerry hasn't said how the springs are held in the pockets ... I just REALLY looked at the picture and saw that the springs are held in place by fitting over a collar. Should have looked closer before putting fingers to keyboard. Sorry. Still, do they slip over the collars or are they secured? I'm going quit while I'm behind.
Gerry
Well-Known Member
My fault for not explaining things.
The springs fit over a collar at the bell crank ends and in the middle and are held in place by compression. The middle is hollow so you can pass from each bell crank through the middle with no problem.
The bell cranks are already friction shocks. They have a disc of friction material between the crank and the chassis and another one between the crank and the front cone. The friction material is high grade high pressure material made and given to me by a company that makes friction material for just about everything. The sales guy said that it would cost more to raise an invoice than to just send them to me.
So I have to figure out a way of retaining tension on the front cone through the 2 friction disks for them to work, and this is where the problem is at the moment. I have looked at a spring cup washer (used in some auto transmission to maintain pressure on a clutch pack) but it means re-machining the front cones which I really dont want to do just yet.
So I thought about running a damper from each end to the middle inside the springs. Fixing at each end is not a problem but finding a damper is. I am not the kinda guys who pays big bucks for custom made parts if I think i can make them.
I just want the option of a form of damping to back up the frictions IF its needed after the car has been driven
Gerry
Gerry
Well-Known Member
Make some hydraulic shocks of a very simple design.
Many thanks for drawing.
I really need the detail for the piston. Holes and their sizes relative to the piston diameter. Also if this is oil filled what happens to the oil when the push rod is all the way in. Does it have an air gap? I am going to use these mounted horizontally so will an air gap cause problems.
I kinda know the principals for a small hole in the piston to restrict the flow through it and hence you have a damper. Its the detail I am searching for. I am very restricted for size so there is no way I can use a remote reservoir.
Thanks again
gerry
GAB
Member
I should start by saying that I have no practical experience as to whether this idea will work or not for a shock dampener. I have made a hydraulic cylinder for controlling the down feed on a horizontal band saw using the same basic construction methods and it has worked well.
The appeal of this method would be that you can size it to fit your application and use commonly available materials. It assumes that you have the means to perform the simple machine work shown. If it doesn't work, you are only out a little time and a few bucks, or quid or Euros, or whatever you fellows on that side of the pond call them.
The basic idea is to transfer fluid from one side of a piston to the other by forcing it through a small orifice (or multiple) at such a rate that it tends to resist the oscillations of a spring that it is connected with. Manufactured shocks have quite a bit of technology to accomplish this, but getting down to the basics is what you were hoping to achieve. This is just an idea that originated by that stipulation.
The body of this part is made with a piece of thin wall D.O.M. or 4130 tube. The tube should have a very smooth I.D. so that no honing is necessary. The solid end is machined from bar stock and can be configured so that a mounting can be achieved at the center point of the frame. I've shown the seal end as being threaded into the tube. A little single point threading job. The seal would need to be acquired to match the diameter of the piston rod. Apiece of drill rod would have a nice ground surface for the seal to ride on. The piston is merely a piece of bar stock that is a couple of thousandths smaller than the I.D. of the tube. A hole that is one size smaller than the piston rod diameter is drilled and a groove for an O-ring is cut on the O.D. The number and size of orifice holes is where the experimentation comes into play. Start with as few as is practical and as small as possible. I would think that the fluid would need to nearly fill the cylinder as to keep the holes submerged and the fluid being moved rather than air. Mount the unit horizontally and feel how it reacts to pushing and pulling as compared to a regular automotive shock should give some indication as to whether this idea has any merit, I would think.
The drawing was sized with a 1" x .065" tube that is 5" long with a 3/8" piston rod turned down to 5/16" and threaded for a lock nut. The piston is 7/8" diameter that is turned down to .868" and is 1/2" long. The O-ring is 3/32" x 25/32". Each end piece is made from 1" cold rolled bar stock. The holes in the piston are 1/16 " at 3 places for a starting point.
I don't know if this has any value or not. It started out as just an idea and remains that way at this point. Should this seem worthwhile to pursue on your part, I would be happy to help in any way that I can.
The appeal of this method would be that you can size it to fit your application and use commonly available materials. It assumes that you have the means to perform the simple machine work shown. If it doesn't work, you are only out a little time and a few bucks, or quid or Euros, or whatever you fellows on that side of the pond call them.
The basic idea is to transfer fluid from one side of a piston to the other by forcing it through a small orifice (or multiple) at such a rate that it tends to resist the oscillations of a spring that it is connected with. Manufactured shocks have quite a bit of technology to accomplish this, but getting down to the basics is what you were hoping to achieve. This is just an idea that originated by that stipulation.
The body of this part is made with a piece of thin wall D.O.M. or 4130 tube. The tube should have a very smooth I.D. so that no honing is necessary. The solid end is machined from bar stock and can be configured so that a mounting can be achieved at the center point of the frame. I've shown the seal end as being threaded into the tube. A little single point threading job. The seal would need to be acquired to match the diameter of the piston rod. Apiece of drill rod would have a nice ground surface for the seal to ride on. The piston is merely a piece of bar stock that is a couple of thousandths smaller than the I.D. of the tube. A hole that is one size smaller than the piston rod diameter is drilled and a groove for an O-ring is cut on the O.D. The number and size of orifice holes is where the experimentation comes into play. Start with as few as is practical and as small as possible. I would think that the fluid would need to nearly fill the cylinder as to keep the holes submerged and the fluid being moved rather than air. Mount the unit horizontally and feel how it reacts to pushing and pulling as compared to a regular automotive shock should give some indication as to whether this idea has any merit, I would think.
The drawing was sized with a 1" x .065" tube that is 5" long with a 3/8" piston rod turned down to 5/16" and threaded for a lock nut. The piston is 7/8" diameter that is turned down to .868" and is 1/2" long. The O-ring is 3/32" x 25/32". Each end piece is made from 1" cold rolled bar stock. The holes in the piston are 1/16 " at 3 places for a starting point.
I don't know if this has any value or not. It started out as just an idea and remains that way at this point. Should this seem worthwhile to pursue on your part, I would be happy to help in any way that I can.
Gerry
Well-Known Member
Thanks for such detail. Nothing seems to be a problem except the displacement caused by the push rod going in to and out of the cylinder. If i leave an air gap, which would be all along the top of the cylinder (when its mounter horizontally) will this affect the damping. I have wondered about using a couple of low force gas ram, like they use on trunk lids etc. What do you think?
Gerry
Admittedly, I haven't read all the posts.... I'm practicing to get into politics.
How about a couple of hydraulic shocks from a motor bike - small diameters, lots of choices, chrome.....
Hydraulic shocks should be able to be mounted in about any attitude.
The gas filled rams or gas springs as I call'em are many times only providing dampeming in one direction as in bonnet and boot applications.
How about a couple of hydraulic shocks from a motor bike - small diameters, lots of choices, chrome.....
Hydraulic shocks should be able to be mounted in about any attitude.
The gas filled rams or gas springs as I call'em are many times only providing dampeming in one direction as in bonnet and boot applications.
Gerry
Well-Known Member
Now that looks like a great idea. Cheap to make and try out. I was thinking along the line of a sincle cylinder with a piston at each end so your idea is spot on. Just wondering about a reaction from one to the other. What do you think will happen if the axle moves up in one and both pistons need to move together.?
Thanks again
gerry
rooster57
Member
I think the air volume will always be enough to dampen the spring bounce. Both pistons need a hole drilled in them to limit the air escaping and of course the lid on each end needs a hole too . Start small.
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