Yea, sorry. Similar ride height and increased spring rate.
Yea, sorry. Similar ride height and increased spring rate.
tuna55 wrote: Does anyone have any thoughts regarding an "optimal" angle for the dampers? It seems to me as if you'd want 1:1 motion ratio, so, straight up and down as ideal. Now, I can't get that because my dampers would be crazy-short. If I move both upper brackets and buy 7" drop dampers (shortest I can find), I can decrease the angle of inclination from 35 degrees to 18ish. I think that's worth it, what say ye?
I am still trying to source used leaf spring packs.
This damper angle is going to become an issue. If I mount the dampers such that they have a near 1:1 motion ratio, they need 9-10 inches of travel and have a compressed length of 6.5", so that's pretty impossible. It seems given a fixed height above the mount of 14", I almost have to lay them down back where they were originally (35 degrees) to get the compressed/extended lengths to match anything off-the-shelf as far as dampers. If I lean them over 20 degrees, we're talking compressed 10.3" and extended 19.65, which is still not really possible.
Any ideas?
their position was probably defined by off-the-shelf extended and compressed lengths. easiest solution will be to put 'em back where they were.
AngryCorvair wrote: their position was probably defined by off-the-shelf extended and compressed lengths. easiest solution will be to put 'em back where they were.
But by this math the absolute shortest available dampers (7") are barely short enough for the stock location at the stock ride height!!
These, intended for a 1-2" drop, are too long by 1" to be used in a sock ride height!
http://www.summitracing.com/parts/wst-55805/overview/year/1972/make/gmc/model/c15-c1500-pickup
Perhaps I need to measure when it's not really really late at night.
You need to check out this board.
http://67-72chevytrucks.com/vboard/index.php
It's a very active board and they are always customizing these trucks. BTW I just bought a 72 1 ton wrecker and am trying to decide how I can customize it and still use it as a wrecker when needed.
Cotton wrote: You need to check out this board. http://67-72chevytrucks.com/vboard/index.php It's a very active board and they are always customizing these trucks. BTW I just bought a 72 1 ton wrecker and am trying to decide how I can customize it and still use it as a wrecker when needed.
I have - I am a member. I was a paying member, but I dropped that. I have never heard of anyone there sciencing our the damper length, though, or flipping the upper bracket for correcting geometry, this place is better for that sort of thing.
In reply to tuna55:
You have a lot more experience over there than me then. I just found it after buying the wrecker and thought "this will be a great resource". Of course, I don't plan to do anything too crazy with mine since I still want to move cars with it.
Cotton wrote: In reply to tuna55: You have a lot more experience over there than me then. I just found it after buying the wrecker and thought "this will be a great resource". Of course, I don't plan to do anything too crazy with mine since I still want to move cars with it.
It's a great place (although be careful about asking questions on the paint forum) but nowhere on the internet is it safe to ask "How can I flip this bracket and adapt this thing and ..." without getting the "doesn't xyz sell drop springs for that?" as the answer. GRM wins when it comes to creativity. If I want to look for ideas, rust repair stuff, specific vendor pieces for bolt-ons, that board rocks.
I wonder if dampers are not sized for the full range of travel. Their "collapsed" length is longer than their "travel" length, which leads me to believe it's possible that they just expect you to not use the entire travel all of the time. Am I crazy?
their lengths are given as mount-to-mount, so the collapsed length has to be longer than their travel length.
Another copy and paste from the build thread:
Now, I measured a bunch of damper related stuff. John is making me some brackets which will enable me to drop the current lower mount by about 4-5". I want to make the dampers more vertical, and I can EASILY do that by flipping the upper mounts side to side, gaining me 3" inboard towards the axle.
I did some calcs. I want you all to check these over. If they are right, then there is no way to get a damper on this truck, ever, not even with stock geometry. The range of motion required by the suspension is too great. It cannot be right. I presume the 'extended length' means 'the damper will break if you stretch it farther than this'.
The shortest damper I can find on summit with a decent range is this
http://www.summitracing.com/parts/djm-1800/overview/year/1972/make/gmc/model/c15-c1500-pickup
And even the range is too small for any of those scenarios other than the stock setup. The stock setup on Summit calls for a damper from something like 12-13.5 at max compression to 18.5ish at max extension. I cannot believe that this is the only way to set these things up. I am guessing that you don't size the damper for full compression, since the travel length is a good bit shorter, it may just not control the truck well in that range? If that's the case, I need to discover how much extra room I have on the compression stroke so that I can select something now.
Any ideas?
If you really wanted to go nut-so, you could use a bell crank and then lay the shock horizontal. Then you could use whatever damper you wanted.
Appleseed wrote: If you really wanted to go nut-so, you could use a bell crank and then lay the shock horizontal. Then you could use whatever damper you wanted.
Well that really would offer no advantage over laying them down at an extreme angle. It's just mechanical advantage in a different plane, adding friction and stressed components in the mix for little gain.
I'd be very surprised if you EVER encountered a situation where you used 9-10" of shock absorber travel. Unless you're planning on recreating Bullitt, I doubt you'll need more than a couple of inches of shock travel in either direction from the neutral position.
I'd say get the brackets tacked in where you think you want them, buy a selection of generic, no-name shocks from your FLAPS, install, jump on bumper to check travel, remove, return to store if you're not happy with them (or once you've figured out what size of brand name shock you want to order).
JohnInKansas wrote: I'd be very surprised if you EVER encountered a situation where you used 9-10" of shock absorber travel.
This is what I am expecting, too. I already have some new Monroe cheapies intended for the truck at stock everything.
The issue is this, when I jack the truck up, I really don't want to support the rear end by the damper, right?
When it hits the bumpstops (which has happened before, hauling loads that I shouldn't have), I don't want the damper to be the new bumpstop, right?
So, if they tell me the extended length is X, does that mean that if I pull it X+0.25" that the damper will break? If they tell me that the compressed length is Y, at Y-0.25", will anything bad happen? At least for the latter circumstance, I suspect not. Since the travel position is always smaller, I am assuming that the damper can physically be in that position (meaning shorter than the listed compressed length) but it will wear faster, or not control as well, which is fine. Obviously the extended length is more critical.
I want to test this using my Monrow cheapies tonight. Per this chart
http://www.monroe.com/assets/downloads/english/08_MountingLengthSheet.pdf
My 31000 series dampers should have a 19.5 extended length, a 12" compressed length and a travel length of 7.5. I can then see if there is margin built in. Those numbers are very similar to what I have seen on the internet for other dampers, and according to my calcs, the Monroes are too long by 3" ish at their shortest position, so they have already been used into their 'shorter than compressed length' previously without ill effects. I'll check to see what the max extension length is this evening.
tuna55 wrote: The issue is this, when I jack the truck up, I really don't want to support the rear end by the damper, right? When it hits the bumpstops (which has happened before, hauling loads that I shouldn't have), I don't want the damper to be the new bumpstop, right?
Correct on both counts, by my understanding of it.
So... make the changes to the leaves including any ride height changes, tentatively install shock mounts, measure distance between shock eyes at full droop, and the distance between the eyes at neutral minus the distance between the bumpstop and the (frame?) at neutral position (which should be the shock length when the truck is loaded to the bumpstops). Armed with those dimensions, see if there's a shock that has the required specifications. If not, see if you can relocate the mounting points to make one of the available shocks meet your requirements.
Or have you done that and that's where 9-10" came from?
JohnInKansas wrote:tuna55 wrote: The issue is this, when I jack the truck up, I really don't want to support the rear end by the damper, right? When it hits the bumpstops (which has happened before, hauling loads that I shouldn't have), I don't want the damper to be the new bumpstop, right?Correct on both counts, by my understanding of it. So... make the changes to the leaves including any ride height changes, tentatively install shock mounts, measure distance between shock eyes at full droop, and the distance between the eyes at neutral *minus* the distance between the bumpstop and the (frame?) at neutral position (which should be the shock length when the truck is loaded to the bumpstops). Armed with those dimensions, see if there's a shock that has the required specifications. If not, see if you can relocate the mounting points to make one of the available shocks meet your requirements. Or have you done that and that's where 9-10" came from?
Yeah, that snapshot from Excel is exactly that. It's everything that you described, but it asks for a damper that doesn't exist. Even in the stock location and ride height it asks for a damper which doesn't exist, so there is something else at work here which I am not privy too.
Ah piss. Can't see Photobucket at work.
Think I'll sit down and shut up now. Sorry bout that.
Okay, how much bed space would you sacrifice if you punched holes in the bed floor/wheel arch to accommodate the upper shock mounts, assuming you use the shortest available shocks with the travel you need, mounted vertically?
JohnInKansas wrote: Okay, how much bed space would you sacrifice if you punched holes in the bed floor/wheel arch to accommodate the upper shock mounts, assuming you use the shortest available shocks with the travel you need, mounted vertically?
yeah, OK, no. You're driveshaft safety loop idea was good, and your inspiration to have me start on this mess again rocked, but that idea sucks.
Plus, the dampers travel is too short, regardless of starting and stopping points. You'll see this more when yo can look at that screen grab.
Actually, hang on. I think I can E-mail it to you...
I see a big problem. The third set of data when I added "dropping the truck 2"" I removed 2" from the compression side. Since I am not moving the mount or the bump stop for this step, it is wrong, and the compressed length is calculated wrong for the last two scenarios. it should be 12.7 and 11.2, and now I can find dampers to fit!
OK folks, I am going to order dampers from DJM suspensions. They have a relatively long range damper available for a reasonable price. I spoke with the tech guy and it seems like a good choice.
Where do you guys recommend buying individual leaf spring leaves? I have called locally and found $40 per leaf to be typical, is there an online resource?
Did you think about adding a leaf and flipping the axle? I've got brand new springs on the F150. I had them add 1 leaf and it raised the rear probably around 2 inches. If you calculate it out, you could add springs and lower it. Maybe I'm late, but this is first I've seen of your thread.
For a custom set of springs, it was around $200 a set were locally made. These guys made the springs on Bigfoot 5. the real big one.
N Sperlo wrote: Did you think about adding a leaf and flipping the axle? I've got brand new springs on the F150. I had them add 1 leaf and it raised the rear probably around 2 inches. If you calculate it out, you could add springs and lower it. Maybe I'm late, but this is first I've seen of your thread. For a custom set of springs, it was around $200 a set were locally made. These guys made the springs on Bigfoot 5. the real big one.
We talked about it, but I decided against it. The idea here was to add one leaf upside down to lower it as well as moving the front spring bracket. I want the rear to be stiffer, so that extra leaf will help. I wanted top keep it looking sorta stock, so not flipping is OK with me.
The leafs (leaves?) are 2 1/4, not 2 1/2, so they are harder to find.
They'll have the springs, just need the vin. They'll have to ship or I'll pickm up and ship them to you if you end up needing new leaves, but these guys can fab something up in one day or probably send you whatever leaf you need if you want to go that direction. Just give them a call. I'd bet on them having what you need.
http://www.saintlouisspring.com/
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