Springer build with a difference...

[Prof]

When I originally began my shovel build I planned a damped springer. To get it on the road, I extended its narrow glide front end. Later down the track, I swapped the disc brake for a twin leading shoe drum brake off a Kawasaki. Two years or so ago, Victor bought in a pair of Ford radius rods so I could finally get the front end I had planned and wished for for the last fifteen years and 140,000 miles.


Well I've been staring at those radius rods, a wheel, set of shockers and full size drawing of the set since then. the other day, Victor announced he wanted to ride his reincarnated shovel to Shovel Fest in Victoria in October. That did it. My goal is to finally have the springer done for that trip...

Over the years, I've put in a lot of time researching everything I can find on springer design. So...

#1. Damped using standard (but short shockers) because although a well designed springer isn't unduly bouncy, damping is desirable for a comfortable ride especially in the rough conditions I like to travel. Also have adjustable preload.
#2. Shockers instead of a damper on a standard springer, because I carry gear (poor mans fairing) over the headlight especially when I travel and that top set of springs bouncing up and down against the bag is not ideal. As I love the look of the classic springer, I will run a set of dummy top springs. Should look close to classic when all done.
#3. Rake of 45 degrees. This will unfortunately put me outside the 550RidikulusRool, but I've been running 45 degrees for years now and really like the handling characteristics,
#4. Trail of 8-9". I ran 7" or so for quite a while, but the handling through the twisties is much nicer with the extra.
#5. Curved rockers. These allow the pivot point to be lower than the axle which greatly improves handling and steering. When turning actually gives the effect of much less trail. Took me a long time to find this out. Length of rockers determined by axle movement. Once doesn't want the axle hitting front legs in a big bump. Another benefit of the axle/pivot difference is that the movement of the wheel acts more in line with the force of the bumps it hits = better ride and less stress on the front end.
#6. I'm with a 19" front wheel which from personal experience and research is more stable on a road bike than 21". I'd like to use a Harley wheel which has a safety rim rather than the plain 70's Jap style, but the wheel I am using dictates a 36 spoke rim so it'll have to be a jap style. Suzuki and Yamaha wheels are 36 spoke while Kawasaki, Honda, Harley and most Brit bikes use 40 spokes.
#7. Twin leader. Yes, disc brakes work better and don't fade, but I do prefer a twin leader and have had one in the past that was a real stopper. My current Kwakka brake is not as good as I would like, but kept adjusted, is quite adequate for my style of riding. However, this time I am trying one off a Suzuki Titan. I know they were good, and have heard others who had them say the same.
#8. Construction. Classic springers were welded at the top and bottom of the bottom triple tree leading to cracking at the bottom weld. My back legs (Ford radius rods) will be longitudinally welded on the inside only with a fish mouth style gusset running 6" donw the inside as well. I've hit some nasty objects on the road and would rather a bent frame and staynig upright than having the front end fold on me. Time will tell...


Setting up the Twin leader...
A drum brake on a springer, presents a problem. the brake anchor needs to attach to the back legs to prevent dive. Locked to the rocker it can twist the rocker under the pivot under hard braking... not good. However, with the brake plate anchored to the rear leg you can't tighten the axle or it locks the rockers and eventually will split the brake plate and put you over the handle bars!

Two solutions... the common Aussie 70's one of leaving the axle loose with some resulting wheel twisting or set up the backing plate to rock as the axle moves up an down. I'll of course do the latter which if one wants a lasting job takes some time and effort.

The Titan backing plate has a steel insert which first must be removed. You can see it drilled it out here and the inner piece loose. I forgot to take a pic, but I then make an alumimium bush to fit in the gap. After this I take the backing plate to an ally welder I use to fill up the speedo passage and weld in the bush...


You can see the bush here welded in. It is protrudes further in than needed and will be trimmed to allow the backing plate to have the correct clearance in the drum. The backing plate is in a four jaw chuck (what a pain this was) and the centre now bored out to a final size to take a new and larger steel liner...


Steel liner here made (blue arrow) and sitting on the partially machined brass bu sh on which the backing plate will pivot...


Steel bush pressed in with some retaining compound as it was not as tight as I would have liked...


Bronze bush is a top hat style and inserts from the inside. Rim of 'hat' will bear against the bearing. It is now tested in the wheel hub for clearance...


Now put in the mill and 3mm machined off. This allows the backing plate to sit perfectly in position and gives a broad smooth surface for the top hat to bear against reducing any tendency to wobble and to wear...


Backing plate fitted with axle. Top hat bush protrudes three mm and will bear against a bronze washer held in place by the axle spacer...


The ally welder also filled in the stock anchor slot with weld. I drill this out and insert a 3/8 UNF recoil thread for the new brake anchor...


Next step is setting up axle spacers and speedo mount on right side. It's been done but my bedtime. Tomorrow maybe...

[Prof]

So now for final set up of axle spacing. I will run a HD speedo on the right hand side. HD axles are 19mm while this axle is 15mm. So speedo needs a bush as a part of the spacing. The axle bearing is also exposed to the weather, so I need to incoporate a seal which will be an 'o' ring squeezed between the speedo and hub...


Cut and drill a couple of pieces of 25mm square tube bolt onto the axle and work out centering of wheel between rockers and make sure we have sufficient clearance between the legs and braking mechanism. Here measuring the brake plate side from centre of tyre to extended 'rocker'...


Calculations working out required spacing between legs and therefor the spacer sizes we will need. Internal measurement on a narrow glide is 130mm. For a WLA springer it is 180mm and for the DNA springers it is 190mm. My legs are 30mm wide so I compromise and and settle on an inner measurement of 140mm...


Now I can make the brake side spacer. Bottom right diagram is the final version...


Spacer machined out of stainless and installed. I experimented with an indent in the spacer to the axle plate bears directly against the stainless spacer with 1mm clearance, but I think ally against stainless will wear too quickly so will go back to original idea of a bronze washer...


Now to measure up for speedo side spacer. Measure edge of hub to wheel centre...


Calcs again...


Spacer turned on the lathe and a slot made (red arrow) with the mill to lock it into speedo (blue arrow) and prevent it from turning..


Spacer in place with a large 'O' ring installed...


After work tonight I had a bit more of a play. Set the chopper up on a jack so both tyres are both just touching the floor (ie no spring compression due to the chopper's weight. Height of steering head and rake are measured as well as distance the wheel is forwards of the steering head (605mm) from the centre of the steering head Oops Mr Plod; 55mm over the RidikulusRool!


Now set this all up on my jig. I machine up a steering head and pop in a couple of bearing cups, bearings and a headstem. This is now set up at the same angle and height as the shovel.


Close up...


Wheel set up and one of the 25mm tubes is angled down so the pivot (+) is the required 90mm below the axle


Here's the approximate location of the rear leg. Because I want to keep the same trail as I have, the leg will actually angle back slightly to the headstem angle... Ie. Rake is 44 degrees but leg is only around 40 degrees...


Next job will be to make the curved rockers and intall them. Then I'll machine up the tabs that hold the rear pivot bolts. More on that when it is done...

[Youngblood]

[Prof]

Having worked out my dimensions to achieve the rake and trail I am aiming for, I'm going to now build the rockers followed by the back legs and bottom triple tree...

Rockers...

First step is to mark out the three holes, the back two for the rear leg and front leg pivots and the front one for the axle. I am making very curved rockers to: 1. keep the axle around 60 to 80mm above the rear pivot, 2. prrovide the correct arc for the front legs as the springs compress and extend and 3. to create an eye catching sweep.

With hole centres marked out, I then run a lines that curves smoothly between and beyond the lines. This is actually a set of arcs and could be properly set up using a compass...


Next we use a washer with the correct outer diameter to mark the distance the edges will be from the holes, These are then connected in the same way as before. To get smooth curves, use your fist like a compass. I have marked the imaginary centres around which your fist swings to give a smooth curve of the pencil...


A different centre for each arc. The arcs vary in radius so the hand/pencil have to be stretched or contracted for each arc...


Tiny arc here...


Done and ready to be cut out...


Cut out with the 16mm shoulder screws sitting in place...


Shape traced onto the steel plate. Rockers are cut out of 12mm plate with an angle grinder with 1mm cutting blade. A lot of classic rockers use 10mm and some used 16mm. I think 12mm will be sufficiently stiff without looking too fat. Could also be done in stainless, but I'll get these chromed later on and save a bit on cutting and finishing effort...


Held like this to linish taking care to keep it square...


Inner small curves done on this little machine which has a flat plate so final squaring can be done...


First rocker done. Laid on the second piece of plate and marked very carefully with a scriber (pointed spoke). The slight bulge that I had originally drawn at the axle end has been trimmed a couple of mm to look better...


A couple of steps in cutting inside curves...




Both now clamped together and finished on the linisher to match exactly...


Include double checking with as square...


Holes marked on one of the rockers using the pattern...


Axle hole double checked for central...


Clamped together again and drilled in the drill press. Curved shapes hard to fix in the vice and tail at left prevents them sliding. This puts the hole to be cut well outside the vice, so a wedge (yellow arrow) is used for support...


Axle holes drilled and mounted on the wheel. To reduce twist where the axle is fixed to the rocker, I plan to weld in bosses. More on that later...


Next step is a final measure up to get make sure I get the trail I want ane then we'll make the two tabs at the bottom of the back legs that carry the shoulder bolt pivots...

[Victor]

Awesome work as ever!!

Rockers look fantastic. Really motivating me to get my linisher running.

It will be interesting to see the results of our different approaches.

For those playing at home, Prof and I are both building springers from scratch, but I started at the opposite end and doing my rockers and dropouts last.

[Prof]

Finalising critical measurements...

Reason I am beginning at bottom end is because my rear legs (well the chopper's that is) are oval shaped and will be welded on the inside to the bottom triple tree. Would be much easier if I had round legs and could do it Victor's way.

At the risk of boring many of you, I am going to go through the measurements I have made to arrive at the design I have come up with.. Purpose is to give any of you wanting to build a workable springer of your own the why's and wherefore's of the front end geometry and ha way to work out the important dimensions you will need.

I have previously set up the shovel to get approximate existing geometry, but now I am getting exact figures. There are two crucial measurements for me;
1. Trail. My existing trail seems perfect for my chopper. It is highly stable and yet just falls into the corners when I have pushing through it the twisties,
2. I want the rear rocker pivot to be much lower than the axle. My research (and some limited experience tells me that handling is much lighter if I can get at least 2" drop. Also, as previously stated, less stress applied to the forks.

So first I set up the shovel on blocks at the front to take all weight and therefor and compression off forks...


Next accurately measure the rake... 43 degrees...


Now for trail. A straight edge is run to the floor in line with the centre line of the steering head. An accurate way to do this is to measure fork offset (ie how far in front of the steering head the forks are). Take of half the diameter of the forks and trim up a piece of wood to that measurement (red arrow). Now blue arrow is where the centre meets the floor. Drop a vertical (carpenters square) from the axle (green arrow) and measure the distance. In my case it is 8½"... While I am at it, I measure up for the 550RidikulusRool... 595 which is 45mm outside the regs. However if I drop out my 3 degree raked bearing cups I get back legal if it ever comes to that...


Now for the height of the steering head from the floor which is 835mm...


Set up my test steering head and wheel to these measurements...


Figures written on the post for quick reference...


Now for rocker pivot position. Because of the drop, the axle swings back towards the chopper rather than vertically. I need to make sure it does not foul the front springer legs. So firstly, measure travel on full compresson of shockers... 65mm with a rubber buffer that needs to be installed in the shocker...


Back to the drawing board with a cardboard rocker and double check original measurements. Green arrows show unweighted positions of axle, front leg pivot and rear pivot. Red arrows show rest positions of axle and front leg pivot. Blue arrows show uppper most travel of rocker and axle. The distance from the lowest and highest front leg positions is of course the 65mm the shocker moves. This determines where the axle will end up. I have to adjust the rear pivot position to reduce the drop a little an end up with 70mm which is 20mm better than the minimum. I had wanted 90mm, but the axle would then foul the front leg...


Pivot drop shown here...


Rocker reset to final measurement. Of interest with this final arrangement due to the long rockers 500RidikulusRool is now 670mm 120mm past legal!


I am now able to set up the rear legs well almost. One other consideration. If you have been readimg my posts for a while you will know I increase steering lock with extended forks considerably over stock to allow the rider to keep a small turning circle. Case in point is that though my shovelis over a foot longer than a standard Harley, I can turn in a far tighter circle than the stock bike. This is great for manoeuvring and a bit of a show off thing as well.

Because there is no offset on springers (including mine) the legs if the springer is narrow, can foul the down tubes and /or fuel tank. So I measure up the width between the rockers, subract leg diameters and then go to the shovel and see what will happen. All good. I will be able to get the same turning circle. On some frames where the down tubes are wide at the top or the tank is forwards this can be an issue. I purposely built my fuel tank back far enough to clear the forks...


The bottom of the legs need tabs to hold the rear rocker pivot. So we measure ID and OD. (a couple of inches are cut off after this pic was taken so a true ID could be measured...


Well here's the planned bottom tab. 16mm shoulder screw will be pressed into the tab with the head facing to the wheel. The tab will be machined from some 32 x25 bar. 'C' is 3D drawing of the tab showing counter bore for shoulder screw head adn section turned down to the ID of the rear leg. 'A' is a side view showing hole for shoulder screw. 'B' is an end view showing how shoulder screw fits in the tab. Depth of the turned 25mm section is 1.5 times diameter = 40mm. This is a recognised standard for any 'slugged' tube. Tab will be welded around bottom of leg and plug welded as well...


Could only get 50 x 25 bar so went to a friend's engineering shop where he has a cool saw probably 80 years old that can accurately cut the width down to 32mm I need...


Next job will be to drill and counter bore the tab and then heft up the 4 jaw chuck and turn the end. But I need to get back onto some customer's work for a few days at least.

Hope all this has been helpful adn not too confusing...

[steve]

Prof

There is a free program online that I downloaded when I did my Girder fork. It is located here https://trailsym.software.informer.com/1.1/
It can be found by googling TRAIL SYM. It has three tabs, Telescopic, girder and springer. It is basic but gives a visual and real world figures of what is happening.
The developer has a set of terms and conditions that he asks you to comply with the wording as follows; This software is distributed as freeware. Use it, enjoy it and don’t worry about the starving kids at my house. But there is a cost! If you would like a clear conscience, the next time someone is rude to you, respond with a kind word. I agree to this but must admit I have not always calmness and courtesy to do this done this. That is my fault.

I know you understand how springers work but it may help explaining to a customer what a change in one area does to things like trail.I alos have a feeling from meeting you that you would be better at the terms and conditions than me on a bad day.

Steve

[Prof]

Managed a free day recently to get some more work done on my springer what has been taunting me for weeks!

Rear leg pivots...

Blocks texta'd and marked with an odd leg caliper to find centre of hole. Centre punched and then a caliper used to mark the curve that will make a righteous looking springer look even more so!...


If you are serious about building yourself a chopper, a bench or pedestal drill and drill vice (preferably XY table) are essential for accurate work. All holes need to be centre punched and centre drilled. You will be building a chopper worth 6 grand or more so $1000 on decent tools is not much.

Also, while I am on my band wagon, "Do what you do; do well son" as the song goes. I see some horrific workmanship come into my workshop and it is easy to understand the paranoia of officialdom when it comes to modifying vehicles. Welding is particularly critical to be done properly. If you aren't sure, ask. I'll say it again, if you aren't sure ask. Learn from people who are competent and experienced. There are principles to observe in gussetting frames, tubing size and construction that are essential if you are interested in not only saving your own skin, but also anyone else who might buy your machine. Rough enough is not good enough. I'm not saying this as a supposed expert, I regularly ask advice of others who know a lot more than I do. Doing it right is more important than bluffing our way through. Anyway, sermon ended. Back to our story...

Centre drilled, then drilled to 10mm diameter...


...and then final 16mm hole. Basic curve cut with angle grinder 1mm disc...


Rounded nicely on the linisher. Hold it this way not on its side or curve will not be consistent...


Final squaring up on this little set up... a cheap little belt sander mounted permanently on its side...


Legs have some small holes drilled in them and this one will line up nicely for the plug weld. Will be drilled out to 10mm with a second hole opposite...


Now mounted in a 4 jaw chuck in the lathe; partially machined...


Machining finished to slide into the bottom of the leg...


Plug welded and shaped, then a groovy groove ground at the join to allow a suitable depth of weld...


Both legs welded...


Hole marked in the rear of the rocker using a caliper off both edges. This centres the hole...


Checked against our mockup board. Spot on Charlie...


A firmly fitting pin locates the front of the rockers. G clamped at the rear so we can drill both rockers and ensure equal distance holes in both...


Wearlon (oil impregnated) bush turned up on the lathe. I don't find this stuff easy to machine accurately. Best results using a very sharp, fine tipped cutter...


Pressed into the rocker. Bush protrudes 2.5mm each side. A 3mm wearlon washer will be made for each side...


Rocker set in place. Hay man. Like that's outa sight!


Brake plate set up at angle at which it will be located so that retainer (blue line) is same angle and length as rocker centres...


Just time to work out final angle of rear legs in relation to steering head. Blue arrow shows angle of steering head. Red arrow shows parallel ruler that I use to mark the leg...


Now measure with protractor... 6 degrees less than steering head...


Now I can set up the bottom triple tree, which will be quite different to anything you have seen on a springer yet! It will be lighter than those on traditional springers, and I believe better structurally and look pretty cool into the bargain. Anyway that's for when I get some more time.

[Victor]

Great progress! It’s going to be a radical springer that’s for sure.

Coincidentally I also machined my rocker bushers today from Delrin, although I went with 1 top hat bush from the inside and a plain washer type bush on the outside. Your shouldered design is better.

[Prof]

Just thought I'd add a bit in as a result of a comment by Rod on Facebook of his experience with a springer years back.

I think they look great, especially the classic narrow springers of the 70's. But are they any good for handling? Firstly, I think that for a classic chopper, long and cruisey, they can be quite suitable. I've read from fellows with a lot of experience, that girders are potentially better than springers and can be made to handle beautifully and are also superior to telescopics.

From my research and only a little experience at this point, I believe that a properly built and tuned springer is definitely superior to a telescopic fork. A telescopic fork moves up and down at a 30 degree angle or on a chopper a 40 plus degree angle. The angle of force when the wheel hits a bump is almost at right angles to a standard telescopic... and this applies to most girders. So as the wheel hits road irregularities it is forcing the fork leg backwards not upwards... creating friction as well as most of the force trying to bend the fork leg. On a springer, the rocker can be set up to respond naturally in the direction of force created by the road irregularity. The reaction has to be much smoother and the force on the leg greatly reduced. The more rake (as in a chopper) the more angled the leg and the less sideways force it receives.

Secondly, telescopics tend to twist when braking and cornering. The solidly welded springer legs resist twisting.

Thirdly, when talking extended forks, a springer with an axle higher than the rear rocker pivot, has less flop. The lower position of the pivot also creates a power steering effect according to my research.

I am keen to put all this to practical test when my springer is built invoking all those principles. Time and trial will tell.

Regarding bought springers, both seventies and current; Some springers I've had through the workshop have had top springs which are supposed to act as dampers were so loose they'd rattle as soon as some weight was put on them. Others bottom springs so hard they don't budge when hitting bumps. A lot of guys will put a DNA springer designed for a heavy Harley on an xs650 and wonder why it isn't a pleasure to ride...

So springers generally need to be tuned to the weight of the chopper and top and bottom springs adjusted against one another to get good damping. Quality springers also have second lighter springs inside the outer springs to help reduce and harmonics that can cause pogoing.

That said, I've seen a few that work perfectly right off. One customer took his DNA with 40 odd degree rake up to 160 k and said it had perfect manners. Another bloke I know has ridden a very raked DNA springer thousands of miles.

I've ridden a seventies classic chopper a long distance and found that the long thin legs actually seemed to flex with the bumps as well. Didn't get to try this out in the twisties, but one of our members has and found it fine, keeping up with the rest of us without a lot of effort... and said it wasn't at all scary.

I'm using an oil damped set up on mine which I think will give me the best of both worlds

One other point to be aware of with springers is the fact that the axle is further forwards by about 2" reducing trail (stability and resistance to tank slapping and a highside) accordingly. On a stock rake a springer is not all that wise because the 25-30 degree rake on a stock bike gives minimal trail as it is. The springer just about halves the existing trail.

Well there's some thoughts to ponder. Hope they are helpful.

[Prof]

Been a while, but I have been putting in time here and there. Can now edit pics again so here's some more progress.

Headstem and triple tree...

Six degree kick back angle established for rear legs modified to 4 degrees because the raised axle will swing back and up on bumps increasing trail more than a normal set of rockers. Four degrees marked on legs with a protractor and legs raised at lower end to get correct angle. Arrows show angled line. Measured with a verniers sliding across the top of the ruler...


Legs blocked up...


Bottom triple tree is different to anything I have seen on a springer. All the stresses on the rear leg are focussed at the bottom join between leg and triple tree. There is also significant side stress on the legs when cornering. So, I am spreadng the stress over a wide area with the vertical gusset and only welding on the inside of the leg.

A weld always reduces strength on the edge of the weld so this way the weakness (though slight) is only on part of the leg not all the the way around. It is for this same reason that when you weld brackets to your frame tubes you try to weld longitudinally not across the tube.

I will use 10mm angle for the bottom tree...


Rear legs are Ford radius rods and a bit thinner than I would like, though my engineer says they will be more than adequate. Being a cautious sort of bloke I am going to opt for a bit more safety, particularly because I get off the blacktop a lot. A side plate will be welded in to cover the inside of each leg to increase leg thickness where triple tree is welded in. Two 3mm x 50mm plates are cut...


... and shaped to once again spread the stresspoint...


One curved side cut and traced to other plate and vice versa...


Cutting. Piece of angle and G clamp essential for accurate and easy cutting...


Plates cut and legs marked. Aluminium pattern also made for triple tree...


Curved to match the leg profile. Watch out at swap meets for these hammers... very handy...


Plates are drilled for plug welding to increase contact area. Tacked on one side...


Can now apply some heat to conform them exactly to the leg profile...


Can now be fully welded...


Triple tree is angled 4 degrees so an idea of final shape is worked out. Square keeps the triple tree pattern at correct angle...


Marking out triple tree. Dust plate provides diameter of bottom of steering head...


This bender former provides an ideal shape for the triple tree gusset...


Cutting out...


Finishing on linisher...


Then shaping to match the leg profile...


Legs need to be parallel and hole for head stem needs to be centre. Takes time to get it right...


Hole for headstem needs to be square so once mounted in the drill vice a ruler and verniers is used to get triple tree perfectly square...


Drilled and fitted...


Headstem machined up out of 30mm stock. Areas where bearings sit are carefully machined to be a close slide fit. Shaft is left slightly larger because the headstem will be bolted top and bottom to make bearing replacement easier. Thread is 7/8 UNEF (finer than UNF)...


A 20mm block will be welded into the bottom of the triple tree make the headstem mounting stronger. Here being threaded before being cut to size...


Flats are cut into the headstem to make it easier to tighten and loosen the headstem in the bottom triple tree. Here done in the mill, but can be down with an angle grinder as well...


Mounted up. An acorn nut will act as a lock nut...


Back to the springer. Headstem needs to be square to the legs so a centre line is set up...


Lined up. Notice the slight angle the triple tree had to be shaped to fit the 4 degree angle...


Ready to tack weld...


Spring hanger...

Spring hanger is next. Built out of 12mm flat bar. An aluminium patten is cut out and the two shockers set up in their positions...


I could have used the standard top shocker mount, but want this to look closer to a traditional springer. So I will be adding a set of upper springs that will be both for looks and will retain the shocker. Texta drawing shows 'the plan'...


Shocker shaft will screw into the bottom of this top hat. Curve was to allow for the minor oscillating movement of the front legs due to the rockers describing an arc. But I will remachine this flat and add in a oilite button. Thinner shaft of this top hat has enough thread to mount a long rod that will retain the top springs. The thinner shaft fits through the spring hanger...


Spring hanger drawn up...


Marking out the steel plate...


Punch mark become a centre for compass to mark headstem clearance curve...


This bit of scrap the right diameter for the front curve. Notice that curves are marked in first and then straight lines ruled up to them. This gives a great looking bracket...


At this point, Victor rolled up with his freshly chrome plated springer to make up a few more bits that are hard to do on his little lathe...


Hole saw used where possible. Needs very slow speed and plenty of lubrication...


When using large drill bits to drill, I start with a small bit because the centre 20 percent of a drill is rather flat and easily wanders...


Top hats fit with a little clearance. Chamfer has been added to bottom of hanger to allow the button to rock slightly...


Spring hanger in place. This also is only attached to inside of legs. Makes for a tidier job methinks...

[Prof]

Front legs...

Next step in this springer build are the front legs. As you have seen in the previous post, I am using some short shockers with the bottom rings removed and new tops made. Attaching these to the front legs has taken a fair bit of thought over the years I have been designing this springer...


I am trying to create a light look to the springer and also keep the weight down, so have settled on a pair of slotted rings joined in the centre by a pair of bars that pull down with allen bolts.

Here the rings have been machined and slotted. The drawing under them is full scale so I can set them up at the correct distance apart...


Here 3mm slots done with an angle grinder...


Checked to make sure of clearance when pulled down; plenty...


Two 3/8 Socket Head Cap Screws (Allen bolts) would be ideal but with a 70mm centre on the clamps there is not enough room, so one 1/2" Socket Head Cap Screw will have to do. An important consideration is strength. I am using 30 x 12 bar. Will the weld area be sufficient? Yes. More than adequate I think. Will the 1/2" bolt holes weaken the bars to much. Again, more than adequate...


An easy way to measure 'centre to centre' is to measure matching sides. Centre to centre needs to be 70mm...


We can now measure the required length of two inner bars...


Here marked ready for cutting. Angled cut is to allow for full weld penetration seeing as we can only weld from one side...


Cut and checked. Angled cuts need to be greater....


Bars are marked and drilled firstly with a centre drill then 7mm bit followed by 11.5mm bit needed for 1/2"UNF thread. I always use fine threads in steel and stainless because they can be pulled up tighter and are less prone to loosening under vibration. You need to use coarse threads in aluminium to reduce the likelyhood of threads stripping in the soft aluminium...


Allen bolt head is machined to 17.5mm to allow a counter bore of 18mm...


Drilled to 12.5mm and then counterbored. Blue arrow points to an ordinary drill bit with its point removed (flat end now) for this purpose...


Prior to welding I make up a pair of 3mm spacers...


Here installed to keep the parts in alighnment and then a final check that we still have a 70mm centre...


Quickly tack welded on all 8 corners to prevent warping and pulling...


Shocker mount completed except for some final touching up of low spots...


Another view...


When building one off parts you can make mistakes especially if there are days between making a part it is easy to miss a process or get a measurement wrong. Don't get discouraged. It is part of the process. Below is the first shocker mount I made... 20mm to wide. How did I make it 90 between centres in stead of 70, I'll never know, but it happened. The exercise was beneficial, because I decided so much of the grooves would be hidden they would not work visually and I realised I need a big V on one side of each bar not a pair of small v's for welding.

Just take setbacks like this as a test of patience and a learning experience...measure twice (three times for me!) cut once!


Now I can finally make the front legs... and my springer is getting close to ready for a test fit. Yippee! Been a lot of years in the planning.

[Prof]

Time for making the front legs. I am using 22mm OD x 5mm wall hydraulic tube. Wall thickness is a bit of over kill, but used because I want a slight bend near the rockers and a major bend at the spring base and wanted plenty of strength and wall thickness for welding in the tube. DOM would be more acceptable, but having built successful front legs from 22mm x 2mm wall tube, I am sure the hydraulic tube though less rigid than DOM will still be fine.

I want the legs to run parallel to the centre line of the tapered back legs so set them up to be parallel to the flat base on which they are sitting...


Now centre the springs. They have been centred with a string line, but this is a double check. Set square on the base allows me to get an accurate outer edge on the curved tube so an accurate measurement can be made with the steel rule...


Measure length of tube needed for front legs...


Top curve of leg tube bent in the bender...


Easy way to get a parallel cut on the tube...


Red arrow shows uncut tube. Closest tube is cut...


Legs positioned. Distance between them measured...


Top measurement made. Back legs are wider at the top than at the rockers, so final measurement made so front legs match the rear...


Both tubes now held in a piece of angle iron and cut to new required length...


Polished and ready for welding. Pieces of steel plate and flooring used to centre legs fore and aft on the spring mounts. Red arrow shows large pieces of plate used to keep the curve levelled. Yellow arrow shows steel plate used as a lower spacer. there can't be a bend at the join; legs and springs need to be in a perfect plane. This takes about 20 minutes of measuring and checking...


Welded and laid in place...


You will remember from a previous post that the shocker springs are held in place by these top hats which screw onto the shafts and butt up against the spring plate. Because there will be a slight oscilating motionof the front lefs as the rockers move up and down I machine up some wearlon buttons that locate in chamfers in the bottom of the spring plate...


Yellow arrow shows one of them...


Shocker needs a cushioning rubber for when it bottoms out on the potholes specially manufactured and protected by our road builders. Why they are protected when they are not an endangered species I'm not sure, but anyway! I keep any rubber bits I find and now go through my collection for some suitable donor pieces (yellow arrows)...


Die grinder is used to counter bore for the lock nuts...


Shockers, top hats and extensions all bolted up. Closest rubber shown in final position. I have also made the final top spring retailers. They screw into the 10 x 1.25 threads set up for the shocker shafts. The top dome nut and locknut (and springs) are replacement items for standard DNA style springers. Their threads are 1/2" UNF...


The front legs have to be cut to final length and as all has been measured at the rest position (bike's weight on the springer) this is double checked on our mock up and rocker marked...


But first I want to pull up the springs into position and make the final bits up top. Two locators for the bottoms of the springs are machined from aluminium...


I am expecting the top springs to hold the shockers in position, so they need to be compressed heavily. Ya can't do that by hand buddy! So we will compress them in the vice. Here measuring length needed...


Spring compressed in vice and tied with wire. Be careful to centre your spring in the vice so it doesn't come flying out at you and break your teeth of take out an eye. Wire also has a tendency to slide to the side and the spring bend like a banana, but a bit of care and it does the trick...


Springs now compressed enough to screw on the top nuts. Springs hold the shocker firmly in place as I'd hoped...


Now with all that in place I measure up the front legs' centres at rest and full extension...


Leg is marked with springer at full extension. Measurement taken so we can make sure there will be no clearance issues...


Bottom pivots have been drawn up and cut out ready for machining. That's for the next post when they are completed...

[Prof]

Bottom pivots for front legs...

Bottom pivots will run the same M16 shoulder screws as the rear legs. Could go back to M12, but will simplify rebushing if it is needed. Pivots are 24mm x 20mm cut out of 50x20 bar. One end will be machinedto 16mm to be a neat fit inside the legs...


Marked out. Scriber came from a swap meet and I use it for straight lines but prefer a sharpened spoke for curves...


50mm bar cut to length. Now needs to be spit in two (dotted line). To hold it in the bandsaw vice I tack weld it to the remaining piece of bar. Forgot a pic in the saw. Sorry...


Two pieces clamped in drill press. Strange you say? Aha! Vee haf tricks up de sleeve! Clamping them lengthways gives the best chance of keeping the drill hole perpendicular. Vices always have a little play in the moving jaw, that lifts slightly under pressure. Won't affect the hole doing it this way...


Marked for machining the cylindrical section. The length of this is 1.5 times the diameter plus a bit. 1.5 x being standard engineering practice...


Four jaw chuck installed for this bit... and its a heavy bugger too!. The end of the piece has been marked and centre punched so I can get it centred in the chuck using a dead centre as my guide...


Both pieces machined. I have put a slight radius in the cut for strength. For welding, the rest will be chamfered on the linishing wheel...


Curves around the holes marked with an odd leg caliper... very handy swap meet purchase...


Chamfered ready for welding. Piece of tube was cut off one leg to get the correct diameter for the cylindrical section...


Legs now need a slight bend close to the bottom. This is not the best practice as the leg will want to flex at this point, but I think material is strong enough to withstand that. Reason for the bend is to keep the front legs parallel to the back legs at the rest position. I originally designed the rockers (and the front leg hole position) intending to have the rear leg pivots set back 20mm, but ended up doing them straight. Better alternative would be to make a new set of rockers with the hole back a bit, but time is of the essence at present, so I will see how this goes. Fingers crossed.

Here in bender being squared up...


Legs bent and reinstalled measuring the final length...


About to be cut with angle grinder. I use a pipe cutter to mark the cut so I can keep it square...


Cut and pivots installed. Need to make up some bushes out of wearlon. Legs will then be drilled for plug welding and tacked. I won't fully weld them until the springer has been test fitted with the weight of the bike...


Next job the top clamp (triple tree)Cardboard pattern made to get some measurements...


Have to stop for a while now as customers are waiting for their jobs to be done. Back soon however...

[Victor]

Incredible! Shaping out to be a truly unique fork with a lot of hidden tricks !!!