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Springer build with a difference...

Posted: Mon Aug 06, 2018 12:01 am
by 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.
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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 10". I ran 8" for quite a while, but the handling through the twisties is much nicer with the extra 2"
#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'll use a Harley wheel which has a safety rim rather than the plain 70's Jap style.
#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...
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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...
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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...
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Steel liner here made (blue arrow) and sitting on the partially machined brass bu sh on which the backing plate will pivot...
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Steel bush pressed in with some retaining compound as it was not as tight as I would have liked...
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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...
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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...
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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...
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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...
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Next step is setting up axle spacers and speedo mount on right side. It's been done but my bedtime. Tomorrow maybe...

Re: Springer build with a difference...

Posted: Thu Aug 09, 2018 12:36 am
by 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...
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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'...
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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...
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Now I can make the brake side spacer. Bottom right diagram is the final version...
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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...
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Now to measure up for speedo side spacer. Measure edge of hub to wheel centre...
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Calcs again...
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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..
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Spacer in place with a large 'O' ring installed...
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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!
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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.
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Close up...
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Wheel set up and one of the 25mm tubes is angled down so the pivot (+) is the required 90mm below the axle
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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...
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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...

Re: Springer build with a difference...

Posted: Thu Aug 09, 2018 11:02 pm
by Youngblood
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Re: Springer build with a difference...

Posted: Mon Sep 24, 2018 10:02 pm
by 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...
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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...
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A different centre for each arc. The arcs vary in radius so the hand/pencil have to be stretched or contracted for each arc...
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Tiny arc here...
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Done and ready to be cut out...
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Cut out with the 16mm shoulder screws sitting in place...
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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...
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Held like this to linish taking care to keep it square...
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Inner small curves done on this little machine which has a flat plate so final squaring can be done...
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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...
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A couple of steps in cutting inside curves...
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Both now clamped together and finished on the linisher to match exactly...
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Include double checking with as square...
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Holes marked on one of the rockers using the pattern...
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Axle hole double checked for central...
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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...
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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...
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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...

Re: Springer build with a difference...

Posted: Tue Sep 25, 2018 7:59 pm
by 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.

Re: Springer build with a difference...

Posted: Tue Sep 25, 2018 10:11 pm
by 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...
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Next accurately measure the rake... 43 degrees...
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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...
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Now for the height of the steering head from the floor which is 835mm...
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Set up my test steering head and wheel to these measurements...
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Figures written on the post for quick reference...
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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...
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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...
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Pivot drop shown here...
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Rocker reset to final measurement. Of interest with this final arrangement due to the long rockers 500RidikulusRool is now 670mm 120mm past legal!
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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...
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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...
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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...
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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...
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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...

Re: Springer build with a difference...

Posted: Wed Sep 26, 2018 5:56 pm
by 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