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That’s a rough measure with an electronic angle finder at the neck the shock in your pics looks the same as mine .Work makes us disable our cellphone camara do to security I’ll use my wife’s phone tonight to take a pic of the shock.I was curious about yours because my pivot plate actually rests against the spring was thinking the shock was to much for the light front end on this bike.Looks like the top round bar rests on yours as well in the first pic but it’s hard to tell.
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Yup, I see there is contact between the OD of the spring and upper round spacer, but I have no weight on it as it is blocked up with wheels just touching the bench...
I measured the OD of the spring as 2.290", with a wire (spring coil) dia. of 0.279".
The bottom spring seat is 2.326" diameter.
The space for the upper shock mount is 0.995",while the upper shock steel mount is 0.670" wide. measured using starrett dial calipers.
The distance between upper and lower mounts is 8-5/8".
I'm thinking if the lower mount was in the 0* position, this may provide a bit more clearance between the spring and upper round spacer - I've never had it in that position.
Can you measure the overall free length of the spring when you have yours disassembled - will help with sourcing a replacement spring with measurements of spring above.
If buildin' old school choppers was easy, anyone could do it... ain't nobody said it's gonna be easy...Comment
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Have the spring with me at work it’s overall length in a free state is just .011 shy of 9.0 inch’s 8.989
2.428 od dia of spring
the coil dia is .3
id is around 1.85
using starrett dial calipersLast edited by Sds1973; 07-09-2018, 10:32 AM.Comment
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Girders and springers with an actual Shock are a nice setup, better than the uncontrolled pogo-ing on undamped forks. Springers look cool but are usually heavier than stock forks and generally ride like SH*T, So the shock sure helps.
If you take apart the shock, the damper assy theres a few tests you can do, but its obvious generally if a shock is working or not,, then there is some have different damper rates and in at least one picture it LOOKS like there is a 3 step adjuster??? What happens when the spring is removed and you try it in each of the settings?
Some shocks can be rebuilt, new seals, and clean it out and fresh oil. Depending on what oil is used might help change things. Some shocks cant be rebuilt. But seems to me you SHOULD be able to find a shock body of similar dimensions and then put your spring back on that.
Springs are a different story,, In theory, you can calculate some specs on wire dia and coil length, but in reality the only test is a compressor gauge. Been on my to-do list for a long time to make one. Seen a few commercial ones for sale but either no money at the time or too expensive but not hard to make a test station. If you feel your spring is too stiff or soft, its going to be hard to spec what you want & need without at least some form of measurement. There is several methods but generally its figured how many pounds to compress 1 inch and how many to coil bind. Might be others but thats what I recall off the top of my head.
When I order new shocks and generally thats for vintage restorations, but I do have some late model sport bikes ( Buell & Ducati) you spec the application and weights, free length eye to eye and shrouded, unshrouded etc etc. I have 8 milk crates full of used shocks, springs and bodys, and chrome and unchromed springs. Some of the springs are Tiumph/BSA external fork springs as its hard to tell the difference by looking, But I got a crap ton of this stuff.
If you knew what you wanted, I might have something but I will not make a career out of it in research and testing,, its on my to-do list testing springs and labeling them. In a pinch, you can test the springs on a bathroom scale and tape measure. (Easy to slip or launch a spring so some skill and caution needed) But Spring OD/ID, dia, free length and then compress 1 inch or whatever amount works at a defined point while looking at how many pounds to compress it.
Same with the shock specs.
To source one new, once you have the spring rates & measurements figured out as well as shock body dimensions, Jobber or wholesalers have catalogs that detail all these specs and just a matter of finding something close to what you want. A front end carries its weight differently than a rear shock, So you are correct in that your shock probably does not support a lot of weight so a safe bet would be small dirt bikes or mini bikes.
When people made this stuff, generally they pick something right out of a wholesaler catalog for componenets. Just like Hurst Airheart brakes you can buy the parts for them and some Harleys (Like a fairbanks Morse maggie) at a farm and tractor store.Comment
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The damper does have some resistance.The rust pitting on the shaft might cause some issues.The shock was originally set on the highest setting going to try it on the lowest.I assume the pivot plates should be level like a springer rocker with pivot cylinder resting on the spring feel as if it would act more like a rigid front end.Work in a machine shop was wonder if I could get the compression ratio of the spring with a press?Comment
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That shaft looks toast, if it were super rare and valuable it could be ground and industrial hard chromed and finish machined back to spec, but thats improbable here. There is a seal at the top of the body and likely its already toast, but if not it will be soon. But yes, I can look if I had specs for something similar.
Most British has between 10" and 13" inchs eye to eye free length on the bodies FYI.
Cant tell you about the pivot plates as I dont know. Several websites on frame geometry, rake, trail and all that jazz.
Your idea of using a press sounds like a great idea to me. I dont have one here yet, (On my todo list and HaborFreight has some affordable ones on sale frequently), But my wife has presses at her work,
(She works at a machine shop as well). I was thinking a Drill press which I DO have here (2 of them)
But it depends on amount of resistance. I think a press is better suited as a stiff spring would be hard to measure in a Drill press without breaking it. All anyone needs is a definable and repeatable measurement. Doesnt matter if its 1/2 Inch or an inch but find a spec that others can use against a scale.
IE: 1/2" compression = 250 lbs or something like that........
Capt Obvious here, Please be very careful compressing springs, use a safety shield or some sort of safety retention. At my old work we had presses that would go up to 30 tons. One of my coworkers pissed us off with some unsafe pranks and payback was we smashed his lunch into his metal coffee cup with the press. One very compressed wad of protein. FYI: A surprising amount of liquid comes out of a Baloney or Ham sandwich with cheese when under extreme pressure. But I saw some scary stuff when using high capacity presses.Last edited by Dougtheinternetannoyance123; 07-09-2018, 9:19 PM.Comment
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It seems as though the shock I have is not an original P&P item - different spring OD and wire diameter, the preload adjustment has round holes, not notches, there is a 'segmented' nut(three notches like a pie) on the top of the body for rebuildability - with a capital 'R' on that, but no other obvious markings or part numbers.
It doesn't look like yours can be rebuilt - no top nut on the body.
The pivot arms do not need to be level - as that would vary depending on the neck rake - but the upper and lower pivot points on the girder legs should be the same distance apart as the pivot points on the upper and lower trees to prevent any binding - so spacers may be required above/below the neck to get the same spacing between the pivot points (8-5/8").
What is your overall shock (center of eye-to-eye) length?
The preload I have is set at the softest and it rode great, never felt a need to adjust it.
Hard to tell from your photos, but was that spring a variable rate - coils closer together at one end? Need to take that into consideration when compressing it to test for spring rate. I think your idea of using a press to test it is a good one - measure pressure every half-inch until full compression, and like Doug said - be careful.
One girder I had before (not P&P) probably had a small dirtbike shock - not a variable-rate spring.
"Spring weight: Springs for coil shocks are rated using two numbers, eg 450 X 2.25. The first number is the weight (in pounds) needed to compress the spring by an inch (lighter riders needing lower-rated springs, heavier riders needing higher-rated), and the second is the travel length of the spring (in inches)." http://hub.chainreactioncycles.com/b...-buying-guide/
Might find something here:
Shock Swap Chart
with additional links in thread
If buildin' old school choppers was easy, anyone could do it... ain't nobody said it's gonna be easy...Comment
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Some more info here:
2012 Thread: Building a girder...suggestions please
..."if i should run a coil over or just a spring..."
"These high quality forks give superb road holding characteristics and are equaly suitable for classic, custom Motorcycles and Trikes.
Available in two standard widths: 6" - single shock
8" - twin shock.
Shocks are by Hagon with spring and damping rates to suit the application.
DONNIE SMITH SIGNATURE SERIES 'GIRDER' FORKS
Uses 440 IAS Progressive Suspension shock
Fork - Girder
Catalog : 1948 Chief : Fork - Girder
#785001 SHOCK ABSORBER, hydraulic, bushings included
If buildin' old school choppers was easy, anyone could do it... ain't nobody said it's gonna be easy...Comment
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The spring is is slightly small at each end .Measure from eye to eye completely extended ?or so I need to reassemble it and measure?Comment
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Just pull the shaft out to full extension and measure center of eye-to-eye, no need to reassemble.
Here is some info from Chopper Handbook on springs/shocks for girders:
Girder Shock Absorbers and Springs
In the old days Girders had a central spring, usually progressively wound, and a pair of friction shocks mounted on either side of the lower pivot points. Even back then most builders realized that the friction shocks sucked to say the least so when newer hydraulic shocks appeared on the scene they were quickly adapted.
Fortunately nowadays we've got dozens of coil-over shock combinations to choose from. Unfortunately most don't fit in between the narrow constraints of chopper forks to well since the diameter of the coils are simply to large to clear the steering neck and the fork cross-members.
A full eighty percent of all of the effort you will put into building your Girder forks will be in selecting an appropriate coil-over shock (or shocks) and then deciding on the ideal mounting points for that particular shock between the top yoke and the lower fork cross-member.
You will have to experiment with various spring rates over time until you come up with the ideal solution for your particular bike. No two bikes are alike and depending upon the location of the center of gravity for your particular ride you might need a shock with a spring rate as low as 70 pounds to as high as 300 pounds.
Over the years I've become pretty suspicious about published spring rates from various shock manufacturers so take anything you get from spec-sheets with a grain of salt. For example one popular mountain bike shock supplier has a unit with a so-called 180 pound spring rate but if you look at the little .25 diameter coils that are almost 2" on center vertically compared to the much beefier Koni with .375 diameter wire stock at 1 inch on center for the same published rate you just have to wonder who's closer to the fact of the matter.
We bought a very narrow shock from Italy that was rated at 150 pounds with 3.5" of travel all in a package that was only 1.75" in diameter but when we received it the real rate was more like 8 pounds since we could easily compress it to full bind with just body weight alone.
I'm sorry to say it but as to shock selection you're completely on your own as we've bought and tried several dozens of units from various makers and to date I'm still not completely satisfied that we've found a starting point that we can recommend.
For those wanting to experiment we want to remind readers that spring rate is expressed in the terms of X pounds needed to compress the spring at its unloaded (free) height by one inch in length. For example if we have a spring with a rate of 100 pounds it will take a weight of 100 pounds to compress it one inch in length or height and a weight of 200 pounds to compress it two inches in length or height and so fourth. If we have a spring that is 10 inches long having a rate of 100lbs./in. with no weight on it and we put it in a set of forks bearing 200 pounds of the bikes weight it will compress two inches under static load leaving only eight more inches to use for real suspension.
Unfortunately however very few springs have nearly this much effective range before they bind, or reach the point where the coils stack up against one another and in effect become a solid mass. In shock salesman terms this is the coil bind position or point of maximum compression. Keep in mind however that springs stretch as well as compress so what we're looking for, ideally, is a spring that will compress around 1" when the front weight of the bike is on it (about 2/5th the bike total weight actually) but still gives us around 2.5" more compression before binding. Such a spring will also stretch 2.5� (probably significantly more) at full extension. In other words we�re looking for a spring with fairly small diameter coils having a rate of around 200 pounds that has at least 2.5" of compression room before the bind point for a light chopper.
Don't bother looking at car coil-overs for possible Girder springs since they are usually far too large in overall diameter to fit between the forks and the steering stem. Instead look at small coil-overs for ATV's, golf-carts, motor scooters (Vespa), mountain-bikes and rear shock units for small displacement imported swing-arm bikes. Right now one of the old rear coil-over shocks on my Honda 750 is looking pretty good but it's really about one inch to long for what I really want.
(Upon daily inspection however it seems to be shrinking in anticipation of the inevitable moment of experimentation).
For those who want specifics before they start a design project we've found that coil-over shocks having an overall (fully extended) length approaching 11.5" are a good starting point. At load condition these units typically are near 10" in length and shorten to around 8.0" at maximum compression giving you about 3.5" of effective range of motion. You can fit almost anything you find however by playing around with the location and angles of the shock mounting tabs so don't be discouraged if you can't find the ultimate unit for your particular application right from the start. Sooner or later you'll stumble across a unit that'll be perfect.
Keep in mind that girder shocks can take of advantage of unequal valve rates and that you need more dampening on the extension stroke than on the compression stroke for a smoother perceived ride. This is just the opposite of what you'd normally expect. Always keep in mind that the spring is really doing the suspension work and that the shock is just dampening the spring, which seems to be a hard fact for many Americans to grasp after fifty years of brainwashing about shocks.
If buildin' old school choppers was easy, anyone could do it... ain't nobody said it's gonna be easy...Comment
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I plan to fab a girder soon and as such I have been looking at many shock packages. Of course as someone said earlier, every application is different, so I haven't a clue what I will need or use. The links below are but a few of the ones that I have looked at, there are literally hundreds to choose from. My advantage will be that I can change mounting points to some extent and this will allow me a bit of flexibility.
In your case you need to find a replacement that pretty much mimics the original in attachment configuration, physical size, spring rate and damping. My approach in your situation would be to identify those that would physically fit in the forks, then buy and try, and if they don't have the right action resale them on ebay or picclick or wherever, or even swap meets if you have those in your locale, play cutthroat if needed, keep looking until you get that perfect fit.
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Appreciate all the help and info looks like it will take some experimentation to find the right shock for the job .Those Hagon shocks are nice but really pricey.Im definitely thinking the current shock is too much for the light front end on this bike.The presses at work only measure in tonage so with a bathroom scale like described above in conjunction with the press will probably give me a good idea of what the current shock rating is .Comment
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I’ll post my results might help someone else that runs into the same problem.Comment
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An original ad for the P&P girder:
If buildin' old school choppers was easy, anyone could do it... ain't nobody said it's gonna be easy...Comment
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Anyone have an axle for a dual shock P+P?Comment
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