Author Topic: Pilot bumper  (Read 2487 times)

hoodlum

  • Administrator
  • Hero Member
  • *****
  • Posts: 857
  • Karma: 11
    • View Profile
Pilot bumper
« on: June 12, 2005, 08:42:12 PM »
Please excuse the welding, do you see any improvements that could be made?

Moskito

  • Sr. Member
  • ****
  • Posts: 396
  • Karma: 0
    • View Profile
    • http://www.yellowdogracing.com
Pilot bumper
« Reply #1 on: June 13, 2005, 06:13:25 AM »
The bumper looks good, but the problem is that there is no damping in the system.  In other words, no shock absorbtion.  The springs will not absorb any shock, they just compress and then rebound - store the engergy on impact and then expell it as soon as they can.

You can equate the action of it all to holding your hand about an inch off the table and then smacking it with a hammer - your hand ends up getting hit by both the hammer and the table.

You have to absorb the energy, not just displace it.

You have a good idea though.  (or is it Buck's idea?  :shock:  :D  )
Moskito - Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming \'WOW-What a Ride!\'

PilotSniper

  • Sr. Member
  • ****
  • Posts: 319
  • Karma: 0
    • View Profile
Pilot bumper
« Reply #2 on: June 13, 2005, 09:06:19 AM »
Quote from: "Moskito"
You can equate the action of it all to holding your hand about an inch off the table and then smacking it with a hammer - your hand ends up getting hit by both the hammer and the table.


Yep! You're absolutely correct!!! I just tested this theory and when I got back from the hospital for the broken hand..... :mrgreen:
I started out with nothing and I still have most of it left!  :shock:

ludedude

  • Hero Member
  • *****
  • Posts: 1478
  • Karma: 0
    • View Profile
Pilot bumper
« Reply #3 on: June 13, 2005, 10:08:47 AM »
ROFLMAO....no really....


DAMN...just fell of my chair...




ROFLMAO

hoodlum

  • Administrator
  • Hero Member
  • *****
  • Posts: 857
  • Karma: 11
    • View Profile
Bumper
« Reply #4 on: June 13, 2005, 10:58:42 AM »
Do coils on truck suspensions not absorb energy, or does it take a shock absorber also?Keep in mind that I am not trying to make one that will come from a head-on without a dent or a bend. The coils are just for those minor bumps that otherwise tweek your mounts a bit. Once the springs bottom out, it becomes just as rigid as any bumper that is solid mounted. Any Ideas how to fix what you are talking about? Could mounting some small shocks help? Looked at some to begin with, but they all look too weak, thats why I went with the springs.

ludedude

  • Hero Member
  • *****
  • Posts: 1478
  • Karma: 0
    • View Profile
Pilot bumper
« Reply #5 on: June 13, 2005, 11:39:21 AM »
Quote
Do coils on truck suspensions not absorb energy, or does it take a shock absorber also?


shock absorber :)

As Skeeter posted the spring just stores and then releases it again....

I know hoser's tossed out the idea of having a tube in a tube packed with grease a long time ago....I don't like that idea as it's a one shot deal, until you stop, get out and repack the tube with grease.

So I guess you'd need a shock absorberof some type in there....the grease idea would no  doubt work....I just don't like the idea of grease flying out on impact...and having to re-load for it to be useful again. The shock absorber would be great.

Tueb in a tube for alignment and a shock(s) to abosrb the energy. See the ATVR bumper...make the horizontal tubes one inside the other to aid in aligment and restrict movement to in and out only. And mount an absorber inbetween there....now to find a short shock body that will be capable of absorbing...what....600lbs machine travelling how fast???

hoodlum

  • Administrator
  • Hero Member
  • *****
  • Posts: 857
  • Karma: 11
    • View Profile
Pilot Bumper
« Reply #6 on: June 13, 2005, 04:13:11 PM »
I looked at pictures and studied the ATVR bumper very closely before starting this project. The problem I ran into with that was the bumper needed to pivot at the bottom for movement.When it pivots, the bumper doesn't push straight in, it goes up at an angle. Anything mounted rigid would only bind up, and render itself useless.
 The other thing was the idea of two vertical tubes pointing straight back at me. The shortest shocks I could find were about 8" long. Ample length to come through the foot tub on a heavy impact. Could be very painful.
I am trying to come up with something with shockabsorbers pointing toward the center of the bumper. On impact, these would just lay over instead of coming through the foot tub.Haven't figured it out yet, but I will sooner than later.
Rooky

ludedude

  • Hero Member
  • *****
  • Posts: 1478
  • Karma: 0
    • View Profile
Pilot bumper
« Reply #7 on: June 13, 2005, 05:38:04 PM »
I think you can overcome the binding issue you speak of and still use the horizontal tubes (shock absorber)...but you'd need to build sliding mounts on the bumper end of the shock mount. As the bumper closes into the frame the mount on the bumper end can slide up to prevent binding. Nothing fancy, just a plate with the shock eye mount on it that is held under two slide retainers.

dhjunkie

  • Full Member
  • ***
  • Posts: 161
  • Karma: 0
    • View Profile
springy bumper
« Reply #8 on: June 13, 2005, 07:23:08 PM »
OK  here's my point of view from a car nut/hammer mechanic and general loony.  
  I have been around vehicles and fixing them for most of my life {i even get paid for it too :) }  Now the idea of an absorbing bumper is not that simple as it seems.  things to consider are, Is it going to be a one time deal or do you want it to be able to take multiple hits?  with either idea the mounts must be able to accept the force that will be supplied.  Take into consideration your typical  (old by today's standards) bumper absorber.  This absorber is basically a a shock absorber in design.  Instead of using oil and valving (like a wheel absorber) it uses either a very thick oil/grease or a silicone gel.  the silicone gel beings the more common now.  Both will take a light impact and absorb energy and then return to normal state.  But when the impact is severe it is generally DOA and stays collapsed.  Now you can substitute the gel or oil  with a solid chunk of rubber of a specified hardness.  This will absorb energy and then release it slower (not by much) than say just a strait coil spring set up.  This will also accept some larger hits without deforming too much.  
  Now comes the problem of the mounting surfaces.  The absorber mount surfaces on cars are very strong (generally boxed and reinforced (with crumple zones later on down the frame rail, but this is another topic).  You don't want your mounts too strong or it will destroy the frame somewhere else (read as domino effect on where to gusset/beef up) and then you don't want it too weak or you'll be having a bumper for high heels.  
 Now today's modern vehicles use a one time only impact cushion that literally disintegrates (it is Styrofoam) upon impact. this is great to save weight and save the vehicle, but it gets spendy to constantly replace plus it is ugly and is generally covered by a bumper cover.  They also have a corrugated abs plastic absorber. This looks like a bunch of plastic tubes stacked on end and joined together. These are better for a slightly higher impact, but also are ugly and one time impact deals.
  So there's the education on the auto bumper now  to applied ( real world) science.  to modify the existing bumper ( one in pictures with springs)  you can take a couple of the small gas pressurized shock absorbers (the ones that open up hatchbacks) and attach them to control some of the rebound dampening. But you may also want to think about repositioning the upper mounts to a less flimsy style mount, one that will resist the impact a little more.

sorry for the windy reply:)

Moskito

  • Sr. Member
  • ****
  • Posts: 396
  • Karma: 0
    • View Profile
    • http://www.yellowdogracing.com
Re: springy bumper
« Reply #9 on: June 13, 2005, 08:25:14 PM »
Quote from: "dhjunkie"
OK  here's my point of view from a car nut/hammer mechanic and general loony.  <snip>
blah, blah, blah, blah,
blah, blah, blah,
blah, blah,
blah
<snip>
sorry for the windy reply:)


Egad that was hard to read.
Must be the present state of mind.
I'm scared to try again - may pull something I need to use later...  :shock:
Moskito - Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming \'WOW-What a Ride!\'

hoodlum

  • Administrator
  • Hero Member
  • *****
  • Posts: 857
  • Karma: 11
    • View Profile
Bumper
« Reply #10 on: June 13, 2005, 11:22:43 PM »
Heeded your warnings.
Wrapped the springs in duct tape, poked a small hole in it, and forced them full of scilicone.
Hope in a few drying days I can remove the tape and have a hopefully neat looking mini shock. This should also keep my springs from blowing.
Watta u think?
Rooky

dhjunkie

  • Full Member
  • ***
  • Posts: 161
  • Karma: 0
    • View Profile
Re: springy bumper
« Reply #11 on: June 14, 2005, 06:36:33 PM »
Quote from: "Moskito"
Quote from: "dhjunkie"
OK  here's my point of view from a car nut/hammer mechanic and general loony.  <snip>
blah, blah, blah, blah,
blah, blah, blah,
blah, blah,
blah
<snip>
sorry for the windy reply:)


Egad that was hard to read.
Must be the present state of mind.
I'm scared to try again - may pull something I need to use later...  :shock:

--------------------------------------------------------------------------
LOL  I'm all over the place aren't I.  :)   I need a drink just to collect my thoughts.