Topic: Jakal cb550 project

[SOHC4 Cafe Racer Fan]

It also reminds me of a dirt tracker seat, but with sharper angles.

[calj737]

I have the M bars on my 550F, like them very much

They are a tad higher than super bike bars and another great choice.

The hooligan-esque posture is akin to the SuperDuke 1290/990/790 riding position. KTM (and surely every other manufacturer) did an enormous amount of ergonomic study to develop their formula for chest and shin angle alignment, heels slightly behind knee, elbow relaxed to provide the greatest comfort and control. With your heels slightly back, your feet provide the greatest steering input to the pegs, bent elbows allow weighting the grips without pressuring the wrists.

You can still/always lurch forward and hug the tank as well with an M bar or other without looking like a Praying Mantis. Hard to describe in print, but have a look at numerous websites for the new "Street" bikes and you'll see a more common posture as described above.

[Stev-o]

I'd like to see a pic of the 550F. Love the Park Racer, too.

Thanks....here's a pic of my 550F, it is a great running bike.

They are not the most comfortable bars but they look good.
Low bars put a lot of pressure on my wrists which I dont like, but it is a good riding position for short periods

[Darren Jakal]

Great info guys! I appreciate your input.

I'm going to mock up the frame with pegs and seat heights to help determine final hand position and then look for appropriate bars.

Cheers, dj

[Darren Jakal]

I'm looking into bike riding postures and what might work for me.

I like my feet under me, I know that.

So, I kind of like the older style of racer stance with feet under the body's centre of gravity with a forward tilt of the upper body at the pelvis, a C-spine and relaxed elbows.

Something like these guys.

[calj737]

Lot to like about the position. Unfortunately, it puts all the weight of your body on your tailbone. Just so you're aware- mock ups can tell you lots, but if possible, visit a few dealers and test rider some modern bikes, take pictures and measurements if their positions. Mimic what suits you after some real world experience.

[RAFster122s]

Oddly enough there is a guy who felt part of what made for a bad long distance seat was the fact you aren't holding your weight on your sit bones of the pelvis. His solution was a little unusual. It was a board with a U in the middle to eliminate pressure for that area of the man anatomy that lots of pressure on for an extended period can lead to lots of health problems and discomfort. It works quite well as it distributes the weight to your thighs/sit bones butt but, it presents a problem when approaching a stop. You have to lift up to remove the board. It needs a tether or bungie to pull it back and not let it go flying off the bike. Your legs would not reach the ground because they were being kept up by the board across the seat.
Just a bit of data...regarding seats and long distance rides.

David

[Darren Jakal]

Great advice guys.

I'm planning to pad the seat (the wooden form to make the pan is still too thick and it will be thinned out so more padding can be put in it). I'm thinking with my feet under the centre of gravity the legs can take some of the load.

And it's a commuter so I won't be doing huge long rides (in fact I'm a bit worried that my commute may not be long enough to get the engine hot enough to drive off condensation in the crankcase).

Cheers, dj

[Darren Jakal]

Still working on the seatpan pattern. Pictures show the wooden form being used to create a pattern in card stock. I'll use these patterns to make a mild steel pan.

The wood is just a form, the pan pattern is the card stock (kind of hard to see). Final seat form to be built onto the pan.

[firebane]

Great advice guys.

I'm planning to pad the seat (the wooden form to make the pan is still too thick and it will be thinned out so more padding can be put in it). I'm thinking with my feet under the centre of gravity the legs can take some of the load.

And it's a commuter so I won't be doing huge long rides (in fact I'm a bit worried that my commute may not be long enough to get the engine hot enough to drive off condensation in the crankcase).

Cheers, dj

We will just get together and go for some good rides

[Darren Jakal]

Sure thing. Let me know about drilling discs.

[Darren Jakal]

Roughed out the seat pan in 16 gauge mild steel.

Needs to be trimmed and cleaned up some more. I plan on experimenting with how the the seat and rear cowl connect and move for access.

Haven't welded in a while, but the shops new welder is not responsible for my poor technique. I'll get it back again with some more time on the machine.

Later, dj

[RAFster122s]

You apparently aren't very tall and are using rearsets... I like more room on the seat to slide back some if I want to take a different riding position...within the constraints of being able to operate the foot controls properly.

David

[Darren Jakal]

I'm six foot and this is pretty much what the stock saddle is like.

I've been checking out seating positions and will not be using rear sets. I like to hug the tank with my knees and this is pretty much where I want to be.

Thanks for comments, though.

Darren

[palepainter]

I like the way the front of tail sections transitions into back of tank.

[Darren Jakal]

Hey thanks palepainter, btw I’m following your build and it is beautiful, such nice work you get to see here at sohc/4.

Anyway, I’ve concluded that the seat pan is critical to getting other details of my build right.

Not only will this pan support the seat and rider (I’m going to try to suspend a leather saddle on the pan) but it sets up the transition conditions between the tank and seat and the seat and the rear cowl. It can also help re-enforce a horizontal line formed by the lower edge of the tank that I want to carry on towards the back of the bike. I really like some of the frame details and want them to be part of the overall composition.

Work in progress, but time will tell.

Later, dj

[Darren Jakal]

Working out the seat profile.

dj

[Darren Jakal]

I spent some time tweaking the fit of the seat pan. I've found that while the real critical frame geometries are pretty good (swing arm mounts, head set angles, etc) some of the other welded parts are not so spot on.

The semi circular piece that forms the tank hold-down is off square by a couple of mm. I thought I had a twist in the pan but after much tweaking I discovered a slight high spot on the horse shoe shaped piece that he seat sits on. Banged that down and the pan sits pretty good now.

The cowl is a mock-up out of thin aluminium and I have some more details to work out, but things are moving along.

Cheers, Darren

[Darren Jakal]

The bike was missing side panels and the headlight bucket was bashed up and the seat was not to my liking so I figured this low budget build could include some low budget styling.

I'm going to try and make some kind of fairing and have started to sketch it up on the front end. I've decided I want this bike to be along the lines of the scramble suit in Philip K Dick's book "A Scanner Darkly" where the narcs have suits that project all human forms as a kind of disguise. In this case I'm going to go with as much raw aluminum finish (polished and bead blasted) as I can and with a hint of chrome and zinc plating in hopes that the finish will reflect its surroundings (it should look blueish when reflecting the sky or greenish when reflecting foliage). I'm going to leave it a little beat up and dirty as I kind of think that a bike should be just a little bit dirty in the right places.

Having fun as always, Darren

[Bootsey]

I'm digging the direction you're taking with this, the seat & side covers should look the part. Look forward to seeing what you come up with for the fairing.

[Darren Jakal]

Hey thanks Bootsey.

I'm using this project to try all kinds of things and I just had to check out your build (how is that going, love to see it?). This is where I discovered peanut oil to clean up rubber and plastic!

Fantastic!

Thanks again

[Bootsey]

Hey thanks Bootsey.

I'm using this project to try all kinds of things and I just had to check out your build (how is that going, love to see it?). This is where I discovered peanut oil to clean up rubber and plastic!

Fantastic!

Thanks again

Glad there was some info of worth in my rambles
I've been tinkering away slowly, not much worthy of an update sadly, life keeps getting in the way. Hopefully get some paint down whilst the weather is good.

How exactly did you form those side covers you've got now? Are you planning on using those as a template to follow and shape them out of aluminium?

[Darren Jakal]

Hey Bootsie, thanks for the update!

The side panels are vacuum formed styrene and they are just for show and to check out some ideas. I will eventually try to make them out of aluminium and I'm investigating flow-forming right now as a potential method for making them. My plan is to make some new moulds for this.

I've been working on another form for the seat. I made it out of wood as I want to use it in the vacuum former (some experiments with petg) and the vacuum bag (for experimenting with vacuum bagging leather), so I want it robust.

I still need to work it some more as it is still a bit fat. I went at it with the bandsaw, the sawzall, planes and spoke shave, horizontal belt sander and more. Wood makes good moulds but it is easy to go to far (I need to make at least one patch already) so I will take it slow and fit it often before I'm ready to pull some forms.

Later, dj

[firebane]

If you made left and right side covers you could definitely sell them in fact if you did I would buy a set

[Darren Jakal]

Hey thanks firebane,

I will make both sides and because of the way I do things I would be able to do small runs. But I tell you, once I have made enough for myself I really don't have much interest in making more (I like to create form and not so much reproduce it).

But we can talk about it when you see the finished product. I'll have forms and pulling some extra vacuum positives is pretty easy (maybe out of ABS), but I don't know what it's going to be like to form them in aluminium yet (a reversed form is used in flow-forming, but easy to make a positive to use in the vacuum former).

How goes the ride? You lucked out with the F model. I'd take a resto 550F in a second.

Later, dj