Long term Triumph Chopper project

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El Skitzo
Posts: 750
Joined: Wed Sep 30, 2009 6:40 pm
Location: Perth, WA

Re: Long term Triumph Chopper project

Post by El Skitzo » Thu Dec 20, 2018 11:17 am

Cheers mate, interesting.

We're hoping to have the completed roller home before Christmas, so should hopefully have some real good pics coming up...
65 Triumph Chopper (project)

El Skitzo
Posts: 750
Joined: Wed Sep 30, 2009 6:40 pm
Location: Perth, WA

Re: Long term Triumph Chopper project

Post by El Skitzo » Thu Dec 27, 2018 4:04 pm

Well the rolling chassis is home for Christmas, and I think it looks awesome!!

There's still a few minor jobs to completely finish the front end, but they can wait until next year and after an Engineer has inspected the roller and given me direction on how we achieve all the modification permits I need to apply for.

The front wheel and brakes are still undecided, and the one shown is purely for mock-up and so we can push the chassis around and take measurements.

Now that it's sitting on wheels I can confirm that we exceed the 550mm for the front end/axle by 2 inches, so lots of work to get us to the next stage.

Image

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65 Triumph Chopper (project)

Prof
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Re: Long term Triumph Chopper project

Post by Prof » Thu Dec 27, 2018 11:00 pm

Definitely tucked up in the air. Is a lovely looking girder though. Pity the pivots on the trees are set so far forwards of the headstem. A lot of girders had the bottom pivot level with the centre of the headstem with the top one forwards to keep the axle back... in the interests of sufficient trail, but also helps with Ridikulus550Rool.

In SA I believe that if an engineer can demostrate that the purpose of the R550R (supposedly to reduce strain on the neck area, although they never did state its purpose) is addressed in your modifications, it can be passed if it exceeds the 550. I guess that means some extra gusseting and reinforcement to the backbone and the engineer claiming the mods exceed strength requirements. You might be able to take that approach in WA.
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TriNortchopz
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Re: Long term Triumph Chopper project

Post by TriNortchopz » Sun Dec 30, 2018 12:18 pm

Gotta agree with you, That does look awesome! 8)
I notice that you have the P&P girder in the +10 degree rake position - is this when you are over the 'Ridicule Rule'? What if you pull in the bottom to the zero rake position? That will put the front of the bike up a bit more, but will it fit the 550ridiculerule? If so, perhaps it's just a matter of extending the front down tube, without altering the rake or the top tube, to drop the engine lower- I think we know who can help with that rather easily. :wink:

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

Re: Long term Triumph Chopper project

Post by El Skitzo » Thu Jan 24, 2019 6:06 pm

TriNortchopz wrote:
Sun Dec 30, 2018 12:18 pm
What if you pull in the bottom to the zero rake position? That will put the front of the bike up a bit more, but will it fit the 550ridiculerule? If so, perhaps it's just a matter of extending the front down tube
That's exactly what I'll be doing as the next step, setting the girder up in the zero rake position. With the girder in the +10 degree position I end up with negative trail at any rake angle that fits within the 550mm rule.

If I swap to the zero degree position I believe we can achieve positive trail even if only a couple of inches, providing we rake the frame as much as we can to put the axle near on the 550mm limit. I haven't tested this theory exactly yet, but some brief eyeballing tells me it should work.

When I get some time over the next couple of months I'll do some more exacting mockups to prove this and come up with all the exact figures I need to present to the Engineer regarding rake, trail and how much I want to stretch the frame.

I really wanted to avoid adding rake to this frame, but it looks like there's going to be no way around it in order to get this front end to work, and to have a safe and stable bike to ride.
65 Triumph Chopper (project)

Prof
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Re: Long term Triumph Chopper project

Post by Prof » Thu Jan 24, 2019 10:26 pm

A simple solution could be to turn the head stem with bottom triple tree 180 degrees which will pull the axle back (at a guess with out measuring off the photo) 5-6 inches. Then rake the steering head enough to just meet 550mm. This should give you plenty of trail... and get your chopper level. At a guess, you would still have sufficient lock... and the more the better.

If this does not work out measurement wise I would be moving the bottom rocker arm mount back on the steering head to get the correct geometry.

Get a large piece of ply or particle board and measure off your set up 1:1 and see what you will end up with. That is the simplest way.

Image

When you put weight on the chopper remember that the forks and therefore axle will move forwards as the frame sinks an inch under the weight. A customer has found a girder for his XS and the spring on it does not move more than a few mm when he takes the chopper off the jack. He needs to get a lighter spring made. If the chopper does not drop an inch under the bikes weight, it will be way too harsh a ride.

Not sure what trail you have ridden with, but my shovel (heavy bike) runs about 9" I think and that is perfect for the bike. Paul's 550 trail is an inch or so more and also beautiful to ride. Steering is a bit heavy when wheeling the chopper around the shed but I can ride no hands down to 25mph and pull up at the lights with one hand on the pullbacks. What I am saying don't be afraid of trail... gives you a self steering bike and very relaxing to ride, beautiful in the corners too.
Chopit'nrideit... Prof

El Skitzo
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Re: Long term Triumph Chopper project

Post by El Skitzo » Sat Feb 02, 2019 10:02 pm

I finally had some time to play in the shed today, and got stuck into the front end.

After realising that with the front end bolted together in the +10 degrees rake position I was going to be well over the 550mm ADR rule (50mm too much), and end up with negative trail, I stripped the front end apart and put it back together in the 0 degrees rake position.

You can see below visually just how much of a difference this makes. +10 degrees on the left, and 0 degrees on the right.

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Once I put the front end back in the frame, as expected the front axle did come a fair way back towards the neck, plus this pushed the front of the bike up even higher and therefore increased the effective rake at the neck. But visually it still looks great to me.

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So what is the end result? Bloody good news!!!

The horizontal distance between the front axle and a line dropped from the centre of the neck, now measures exactly 550mm, which is bang on the legal limit. The trail is now positive and comes in at 3", which is well within recommended guidelines for a bike like this.

So as you see it sitting below, the roller now meets legal limits, and should have acceptable safe handling and low and higher speeds. The concept of fitting this front end to this bike has now in mind been proven, so I'm stoked!!

Image
65 Triumph Chopper (project)

TriNortchopz
Posts: 67
Joined: Sat Feb 24, 2018 5:41 pm
Location: Haines Junction,Yukon, Canada
Interests: Choppers, nature, learning more about choppers

Re: Long term Triumph Chopper project

Post by TriNortchopz » Sun Feb 03, 2019 2:19 am

That looks great in the zero-rake position! Good to hear it meets the silly regs too. Been thinking about an option for your machine...well a couple more; one could be as I mentioned before - leave the frame neck where it is - no change in rake and still tied to the backbone as original, and just stretch the front single frame downtube to get the engine lower to the ground, which will help with center of gravity issues. Another option to lower it, is to find a shock which is an inch or so shorter...and another I looked at is to re-position the axle to to the holes intended for the brake stays - keep the top of those holes in the same place and enlarge them to 5/8" lower (offset from existing holes); looks like it would lower the front end about 2 inches and not require any welding to modify that - just slip the legs off, back to the machine shop and boom, 20 minutes later, done; however, this will require a few fancy spacers to fit against the flat of the plates and relieved to fit around the round sections - but doable... but then you will still need a brake mount location...perhaps that could be a weld-on tab at the back of one leg...or one of the 'former' axle holes.

Prof
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Re: Long term Triumph Chopper project

Post by Prof » Sun Feb 03, 2019 3:30 pm

to keep a straight line from steering head to rear axle, you could lengthen both the front down tube and the seat post. Remember that once there is weight on the bike and the girder arms move upwards they will also push the axle outwards. Getting there though.
Chopit'nrideit... Prof

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

Re: Long term Triumph Chopper project

Post by El Skitzo » Mon Feb 04, 2019 10:53 am

Thanks guys, and you're both pretty much on the money with where I want to go to next.

The position of the neck in terms of height from the ground and the angle of rake will need to remain pretty much where it is, or maybe a degree or so less rake just to make sure we absolutely 100% do come in just under 550mm. But the plan is to chop the frame, to extend the down tube and the seat post/backbone.

Obviously consulting with an Engineer and obtaining modification permits are needed from the Transport department, but I feel so happy that a proof of concept is coming together at last.
65 Triumph Chopper (project)

Prof
Founder, Choppers Australia
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Re: Long term Triumph Chopper project

Post by Prof » Tue Feb 05, 2019 9:06 am

Those Triumph frames are way over engineered, which is why they out handled jap bikes and made the jappers look like their frames were made of spaghetti!!
Chopit'nrideit... Prof

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