Twin Cam frame building... Brake caliper and guard mounting

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Prof
Founder, Choppers Australia
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Joined: Sat Oct 22, 2005 3:54 pm
Location: Willunga, South Australia
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Twin Cam frame building... Brake caliper and guard mounting

Post by Prof » Fri Oct 23, 2020 10:20 pm

With the exception of painting, assembly, some polishing and wiring Garry's twin cam construction is done. So high time I caught you up on the remainder of the build.

Here's how we set up the front brake...


After market set ups can be purchased that will fit the DNA and meatballs springers. However I have often found that the spacers are not satisfactory and leverage of the brake anchor is wrong. Also, the manufacturers seem to like to poke the caliper way out in front which might advertise their product, but in my opinion as an artist does not flow with the rest of the chopper. They are fairly pricey too, usually over $500.

I prefer to use the original caliper if I can or a late model HD caliper that looks good and mounts easily. On ICV's using the original brakes also reduces hoops that have to be jumped through.

Any way, step one is to set up the springer...
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... and compress it fully so I know how close I can mount the caliper without fouling the front legs...
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Because I am also setting up the front guard, the springer needs to be fully compressed...
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Wheel needs to be centred. Both tyre and rim to springer rear leg distances are measured...
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Spacer opposite brake caliper is machined out of stainless. I prefer to mount the caliper on the left side as most photos are taken from the right hand side and the wheel looks lighter and more 'chopperish'...
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Now to make spacer a bit prettier!...
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Spacer installed. I keep the spacers fairly bulky so they provide a decent surface to press against the rocker when the axle is tightened to keep the front end as stiff as possible... the less flex(especially on long narrow springers) the better...
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Dummy spacer is made to check wheel spacing...
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Modifying a rear caliper would be an excellent solution, but unfortunately there is not enough metal at the axle end to allow for a strong mounting with the required bushing...
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Bronze bush is made in four parts... actual bearing surface here and the steel sleeve that will rock on the bush. Brass is not suitable for bushes here because unlike bronze, they wear quickly. Wealon though self lubricating is not satisfactory because it compresses when the axle is tightened...
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Washers cut from larger diameter bronze bar fit over each end of the main bush and are silver soldered...
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Next is the caliper mount to made out of 12mm steel bar. Carboard pattern first...
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Cut to approximate final shape and now to work out the mounting of the anchor...
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On the Meatballs springer, the brake anchor mount is fixed. Brake anchor should preferably be same length as the rocker so brake moves in unison with the rocker. Its angle is also very important. In the diagramme, A-X anchor position is parallel to the rocker. As the brake is applied, the front end will naturally dive. In the B-X position, brake will actually pull the front end down harder and cause excessive dive. In the C-X position dive will be reduced by the brake trying to pull the fork leg up. The amount will depend on the height of C. I add 16mm. Also a piece of threaded rod is used to join the heim joints and one lock nut used...
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Measurements marked on the caliper mount pattern (90mm to 106mm) and dimensions measured up for the shoulder screw. Screw in pic is an example...
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Caliper holes drilled with centre bit. Note the handy little adjustable stand to stop the bracket moving under drill pressure. I picked them up at a swap meet...
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Caliper centred on them and front heim joint of anchor set in place and hole marked...
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All three holes now drilled. Heim mounting hole will be thread tapped...
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Easiest way to mark the steel off the pattern is to 'colour' the steel with texta and use a thin pointed spoke to scribe a fine line...
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Measuring for length...
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Mount is cleaned up on the linshing machine. This small belt sander is also mounted to use on smaller radiuses...
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Final measurement is done with the caliper in place. Clearance is needed between the outer curve of the rotor and the caliper. This gap is imitated with a piece of 15amp electrical wire (purple in this pic)...
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Cut and curved to match sleeve OD. Note that I have also had to put a slight inward kink in the caliper mount to clear the rocker. This was done in the press, but can be done by cutting 2/3 way through, bending by hand and welding up the gap (see previous posts for this process)...
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...Then v'd for welding...
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shoulder screw is needed for the rear heim to springer leg mounting tab. A large bolt is used...
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Finished and threaded...
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Two halves of the bush...
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Final fitting of the caliper sleeve to the bush. Bush is clamped in the vice to mimic being clamped by the axle nuts. I like to leave about 1mm to 1.5mm clearance...
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Caliper mount tacked to the sleeve...
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To provide needed clearance for the front heim joint and spacer is turned up and will be bronzed in place...
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I want to keep the caliper as close to the front legs as possible, so a small relief needs to be milled. Marvin my workman for 2 months in background...
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Close up of the milled section...
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Hey! It fits! A longer bolt will be used on the front heim joint so a lock nut can be used... important on brake anchors front and back. Bolt/nut combinations need to be either lock nutted or wired or a split pin used...
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Fully welding has pulled the collar very slightly out of round, so it is blacked with texta inside and lightly sanded with the die grinder attachment until is is a nice fit...
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Checking for free play before fitting...
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Guard mounting next...
Chopit'nrideit... Prof

Prof
Founder, Choppers Australia
Posts: 6012
Joined: Sat Oct 22, 2005 3:54 pm
Location: Willunga, South Australia
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Re: Twin Cam frame building... Brake caliper and guard mounting

Post by Prof » Sun Oct 25, 2020 12:19 pm

Front guard...

Front clearance on a springer is critical. If it is mounted to close to the wheel when the springer is fully compressed (as in hitting a pothole or spoon drain), the wheel jams and the rider is instantly airborne with often painful or catastrophic results on landing! There's a good chance the front legs will also be badly bent if the guard is attached to them.

The ONLY safe way to be sure this won't happen is to fully compress the springer with G clamp and then add 1/2" clearance. Here the springer compressed. Ruler shown here because I measured the difference in uncompressed and fully compressed for interest...
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For front and rear guard clearance I use a piece of 620 chain. This amount of clearance is absolute minimum because different brand tyres differ slightly in diameter, Tyres expand at speed when hot and allowance for any inner mounted bracket (in this case) or protruding bolts. Next step is centering wheel. See previous post for centering proceedure...
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Right spacer...
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Left side brake caliper mounting. Now wheel centred...
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There are a number of mounting options with Meatballs and DNA springers... You can purchase clamp on guard mounting systems (front leg). You can mount the guard directly off the front axle as in the next two pics and described here, viewtopic.php?f=60&t=8538...
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However, we are mounting Garry's off the front legs using nutcerts and our own manufactured brackets.

Step one is to remove the stock guard's bracket by grinding off the rivets. The area around the holes is now flattened gently so our new brackets with fit firmly with no chance of looseness over time...
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Chain placed on wheel and guard set in approximate place...
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Pattern for bracket is made with some light aluminium. Ally holds its shape better than cardboard and can be bent and hold position...
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Marked on 5mm thick mild steel bar. Garry wants everything chromed rather than stainless otherwise I would do this in stainless...
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Measuring hole locations...
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Transferring to the steel...
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Different sized washers can be used to create even curves...
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Brackets cut out, clamped together, centre drilled and then drilled to suit 1/4" bolts. Because it is impossible to drill holes in steel to absolute accuracy in the small workshop and gurads are not perfectly shaped, I always drill larger than the intended bolt; in this case 1/4" = 6.3mm so I drill 7mm holes. This allows for some tweaking on final mounting. If you think about it, change of 1mm between two holes 60mm apart becomes 15 or so mm at the end of the guard...
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aluminium pattern now checked for bend accuracy and...
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The bend location marked on the bracket. Use of a parallelogram keeps the bend parallel to the mounting holes, otherwise the guard will skew. Allowance for the thickness of the metal has to be calculated into the equation, which can be difficult...
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This neat bender is available on line for a reasonable price and will bend up to 5mm mild steel if you have a large strong vice...
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Brackets bent and tested. I didn't get them quite right and had to restraighten them and move the bends out another 3mm...
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Brackets now clamped to front legs and the G clamp compressing the springer undone. This is the gap that will be visible...
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Legs and brackets marked for drilling...
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Bottom hole in bracket only drilled...
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Front legs measured to ensure holes on each side are same distance from axle. Otherwise guard would cant to one side...
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Holes for nutcerts drilled in the front legs and 1/4" nutcerts crimped in. It would be nice to go t o 5/16, but that would require too large a hole in the legs. Before final assembly, areas around nutcerts will be sealed with clear so the front legs don't rust where the chrome has pierced...
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Here are two nutcert sets. One on the left is easiest to use in most cases, because the handpiece gives plenty of leverage. However in this case with the legs of the springer close together, the left one won't fit and the right side set has to be used...
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Close up of an installed nutcert. You can buy them in Metric Coarse and UNC. I would like UNF and Metric fine, but not available...
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Springer now fully recompressed with the G clamp. Bottom bolts now used to mount the guard brackets and guard. Clearances checked front and rear ends of guard and for side to side. Texta now used to mark the brackets as they correctly line up with the tyre so the top mounting holes can be drilled in the mounts...
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Paper is used to accurately transfer position of top holes. Metal is centre punched through the paper...
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Brackets mounted and marked along the edges of the legs for final shaping...
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Because the nutcert has a slight lip, I will counterbore the brackets so they set against the legs rather than just locating on the thin lips of the nutcerts...
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Counterbored using a standard drill bit whose tip has been reshaped with the angle grinder and then reground. In this pic you can see how the bracket is centred for the next counter bore. I use same size drill bit (upside down) as the hole to locate the bracket. Then I can put in the counterboring bit...
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Counter bored and reshaped and ready for fitting...
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Guard mounted and clamp released for final time...
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This guard is to be painted. If it was to be chromed this job would be finished. However, if we pull the bolts tight over the paint it will be at best crinkled and at worst, cracked off. Solution is a pair of thin covers under the bolts. Measurement made and total length calculated...
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Cut out of 2mm material...
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Installed...
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Last job on front end is the axle. Axle supplied has a pair of dome nuts. We need to lock on in place turn it into a 'bolt head'. High strength thread locker used and the nut screwed on tightly. Then drilled for a 3.5mm roll pin. 3.5 is the drill size. The roll pin is slightly bigger in diameter and crushed slightly as it is tapped in... Ends are ground off and will also be sealed with clear...
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Job done for a neat and tidy front guard mounting. Need to make a headlight mount and that will be next...

Then some jobs to do on the frame before final welding including the side stand and exhaust mounts...
Chopit'nrideit... Prof

El Skitzo
Posts: 819
Joined: Wed Sep 30, 2009 6:40 pm
Location: Perth, WA

Re: Twin Cam frame building... Brake caliper and guard mounting

Post by El Skitzo » Tue Oct 27, 2020 12:00 pm

There's no easy way to mount a fender or a brake caliper with a springer, and you've really shown how much thought, design and engineering is required to make it work well AND look good. Well done!
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Prof
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Posts: 6012
Joined: Sat Oct 22, 2005 3:54 pm
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Re: Twin Cam frame building... Brake caliper and guard mounting

Post by Prof » Tue Oct 27, 2020 9:43 pm

Thanks mate. A question has been raised about drilling the front legs for nutcerts. I am confident that the size hole will not be an issue, but will be asking the owners to keep a check on the area. Any sign of cracking and I will weld in threaded bungs and rechrome the legs. I would certainly go no larger with those holes.
Chopit'nrideit... Prof

Prof
Founder, Choppers Australia
Posts: 6012
Joined: Sat Oct 22, 2005 3:54 pm
Location: Willunga, South Australia
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Re: Twin Cam frame building... Brake caliper and guard mounting

Post by Prof » Fri Oct 30, 2020 9:07 pm

Headlight and mounting...

Garry has chosen a Bates style 5 3/4" headlight, simple and elegant and a good light with a decent reflector.

Some 'super cool' 70's and current headlights may look 'outasight', but many are of no use to a serious rider. One not uncommon 70's fad was to use a couple of volksy reversing lights to 'keep it legal', but they put out about as much useable light as a candle lantern on an old buggy!

Similarly some fancy modern lights can be just as useless. Lights with grills or vertical bars not only lose light, but also are invisible from almost every angle but straight ahead. If you ride at night and want to see and be seen forget them.

Twin rectangular driving lights scream 70's classic chopper, but need to be chosen with care. Some ran only 35W globes which are totally inadequate in this day and age either out on the road or in traffic. Their dull light is lost amidst a carpet of super bright modern car headlights. A car enthusiast in Adelaide manufactures high power globes to suit these fittings.

Another potential problem with twin round or rectangular spot lights is the one used for low beam. Yes low beam is both a legal requirement and just plain good manners towards oncoming drivers. Low beam can be effectively achieved with a clear fog light lens, but these are not common, most being yellow. If buying a new set, Hella do a matching set of driving and clear fog. Lucas also did the same set up in the 70's, but a set these days is very expensive...

Anyway, back to Garry's light...

You can purchase a cheap reflector for the Bates (same as 5 3/4 car four head light set ups) at most auto shops, but they have a poor beam and reflectors dull fairly quickly. I only use Narva which gives a great beam and lasts a long time. Hella is fine too but more expensive.
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However, Australian reflector mounting lugs (red arrows) do not match the American Bates light. American reflectors send the low beam to the right and Australian reflectors swing it to the left. Remedying this situation requires an angle grinder (and a steady hand)...
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Two cutouts in the Bates ring, need to be widenened and deepened slightly and a new one cut...
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Firstly mark the vertical position...
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Two (red) cutouts need to be widened. New one needs to be cut at blue arrow. Now reflector is vertical and will not spin in the headlight bucket...
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Garry requested an eyebrow. This clips in under the headlight rim...
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Headlight assembled...
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Mounting...

Headlight is mounted using the centre hole in the spring hanger. The two lugs on the outside were for mounting the stock 7" headlight bracket which was a big lump of pressed steel.

Some chopper jocks with narrow springers will mount their headlights on the cross bar of the front legs. This means the light bounces with the bumps which shortens globe life and cracks headlight buckets. Because the hole is not threaded, the bracket is threaded and fits under the spring hanger...
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Garry's mount is a bit artier than the one pictured above with a point that curves downwards...
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Bracket is set up so that headlight mounts horizontally. This allows it to be aligned for night riding with a slight cant to the right to keep the beam in the centre of the road though you are riding to the left of centre. Blue arrow shows the position of the spring hanger. Green arrow shows bolt location. Upward pointing tab stops the bracket moving to right of left and is a close fit to the front edge of the spring hanger...
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Headlight mounted. Garry is not into camping, so headlight is mounted fairly high. If you will be travelling and camping, it is handy to mount an bag or sleeping bag (poor man's fairing) above the light in front of the bars, so the light would then be mounted lower. The lower mount also makes the bike look longer and sleeker and if you have an illegally long front end helps hide the length!

Well, somehow I'd just finished typing this up and lost it all and had to do it all again, so this is al you'll get tonight. Sidestand and exhaust mounting next...
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Chopit'nrideit... Prof

El Skitzo
Posts: 819
Joined: Wed Sep 30, 2009 6:40 pm
Location: Perth, WA

Re: Twin Cam frame building... Brake caliper and guard mounting

Post by El Skitzo » Mon Nov 02, 2020 10:24 am

Nice mounting bracket, cleverly done!
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Prof
Founder, Choppers Australia
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Re: Twin Cam frame building... Brake caliper and guard mounting

Post by Prof » Tue Dec 29, 2020 10:16 pm

Polishing brake calipers...

Garry wants lots of shine on his chopper, so many parts have gone to chrome platers. The brake calipers however, I will polish as it is too easy for mating surfaces and cylinders for pistons to be adversely affected by the plating and polishing process.

HD brake calipers are painted with black crinkle paint. First step then is to use paint stripper to remove the paint...
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As you can see from this photo of the rear caliper the casting is very rough (purposely)...
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This along with casting marks and slight misalignment between the two parts of each caliper, is taken off with the linishing belt...
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... a mini sander...
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... and a die grinder using metal cutting bits and these little sanding rolls...
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The raised sausage shape is also ground down using an angle grinder and then sanded and polished smooth. This not only creates a nice shiny area, but also makes it infinitely easier to keep clean and polished...
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A couple of different width polishing wheels are used on the larger surfaces and the hard to get at spots...
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Finally polished on the rag wheel. Different cutting compounds (block shape) are required for these tasks...
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Finished. Close inspection will show sharp edges have been rounded for ease of cleaning...
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Rear caliper gets the same treatment. As with the front caliper, 12 point bolts are replaced with stainless button heads for better looks and ease of cleaning and polishing. A couple are shortened to block the banjo hole and bleed screw while we are polishing...
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Removing the casting dimples...
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Area behind banjo has a very sharp edge due to machining making it very hard to clean...
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This is rounded off with die grinder...
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Rear caliper finished...
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Polishing completed...
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Some of the tools used; die grinder uses steel cutters and these sanding rolls. Other tool can use a variety of sanding and polishing discs. Right disc is one of two different grit sanding discs I use. For polishing I use a brown, maroon and blue disc...
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7.3 hours work from beginning to end. These are not just polished to look cool, but reshaped for both looks and easy cleaning. Just another thing on Garry's bike that will stand out as different to any other machine out there.
Chopit'nrideit... Prof

El Skitzo
Posts: 819
Joined: Wed Sep 30, 2009 6:40 pm
Location: Perth, WA

Re: Twin Cam frame building... Brake caliper and guard mounting

Post by El Skitzo » Tue Jan 05, 2021 10:40 am

Wow those calipers turned out AMAZING, well done!!
'65 Triumph Chopper (project)
'64 Triumph Chopper (project)

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