Poll

Sadly, I am colour deficient, and useless at making decisions upon colour choices. What colour should the BSA be in your opinion? (I withold the right for my wife to veto any of your choices) :-)

Black with red upholstry
1 (12.5%)
Cream sides, green bonnet and boot with black upholstry
2 (25%)
Dogsc0#k red (sorry, apparently it is a thing so my decorator colleague says) and black
0 (0%)
British Racing Green + black upholstry
3 (37.5%)
Cream and navy upholstry
2 (25%)

Total Members Voted: 8

Author Topic: BSA 3 wheeler.  (Read 5681 times)

Jimr1999

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Re: BSA 3 wheeler.
« Reply #45 on: 09 Apr 22, 02:25 pm »
Sorting out the front end today for a couple of hours and thinking about brake lines.
Do I go flexible or rigid?
The pit bike caliper came with a cylinder attached for a rear foot break on a bike, Obviously this is not long enough. I can get up to a 2m flexible braided hose but would this lose too much in efficiency and make things spongy?
Will the cylinder reservoir built in be sufficient or is it better to put in a remote reservoir?

Steering will be my next thing after, or at the same time as that as I wait for a few bits.

The space to get in and out - 27" top of dash/ bodywork to back works for me and my 6'4" frame, the knees just clear the dash and the width of the thing makes getting in and out do-able without too many acrobatics... It could almost seat two little uns!

Off for some relaxation now - and maybe a beer.
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dunworkin

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Re: BSA 3 wheeler.
« Reply #46 on: 09 Apr 22, 06:14 pm »
Love the use of "found objects " in your springs, some might call it "art "

Jimr1999

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Re: BSA 3 wheeler.
« Reply #47 on: 09 Apr 22, 06:26 pm »
If your definition of art is anything that makes you feel, I think most cyclekarts are probably art 😁
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RhysN

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Re: BSA 3 wheeler.
« Reply #48 on: 10 Apr 22, 08:06 am »
Jim, braided lines will be fine.
We must avoid torturing our brains with false problems, it occupies but it can annoy. In jest!

Jimr1999

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Re: BSA 3 wheeler.
« Reply #49 on: 10 Apr 22, 08:16 am »
Thanks again Rhys, this will simplify things a bit
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Adrian

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Re: BSA 3 wheeler.
« Reply #50 on: 10 Apr 22, 11:22 pm »
Really good thread Jim, interesting ideas on a good inspiration car.
The brakes are important as several of us will testify!
A few things are essential to understand.
Brakes work by converting kinetic energy into heat energy and then dissipating that heat faster than the friction of the pad against the disc can produce it, no matter how hard you press the pedal.

Assuming your brakes are hydraulically operated, when you put your foot on the brake you are pressurising the fluid in the master cylinder which in turn pushes the master cylinder piston outwards, moving fluid through the pipework, pushing the brake pads into contact with the brake disc. The harder you press, the higher the pressure and more friction is created which is instantly turned into heat and stored in the disc.
When you lift your foot off the brake, the pressure behind the piston in the brake caliper drops to zero and the brake pads are pulled back, away from the pads by the piston seal (which actually grips the piston slightly in order to do so). The friction drops to zero.
Now the disc can start to dissipate the stored heat and cool down, ready for the next brake application.
Lesson over so back to your point about building a system……..
The volume of the pressurised fluid displaced by the piston in the Master Cylinder must match the volume of fluid required for the Brake Caliper to move it’s piston far enough to push the pads against the disc. 
If the master cylinder is too big, the pedal movement will be very small and may be small enough to overcome the return action of the piston seal. This will cause the brake pads to constantly rub on the disc, warming it up. More importantly perhaps, you will have very little in the way of ‘feel’ or ‘feedback’ during braking and the disc will already be warmer.
If the master cylinder is too small, the brake pedal travel will be too long and the brakes will feel very spongy. Possibly, the volume in the master cylinder may be less than the volume required to move the brake pads far enough so the brakes don’t work at all!
Getting the balance right is the trick.
I have always bought a brake 'set' of Master Cylinder and Caliper (from Gemini) to ensure all is well from the start.
Make no mistake, brakes work a lot harder than you might think.
In the past, one of our members built a CycleKart which he fitted with Mountain Bike disc brakes. This seemed a good, cheap option which worked well until one day, it was going fast into a hairpin. 
Several corners had already been taken by then and the disc was no doubt very hot.
When the brake was pressed hard the disc instantly heated up to a temperature that it’s low mass could neither store for long enough or dissipate it's heat fast enough. The brake stopped working almost instantly with the result that the Cyclekart crashed heavily into the banking. The driver suffered an injury which he is still suffering from.
The crash was wrongly assumed to be ‘driver error’.
At the next meeting a 'guest' driver had an almost identical crash and was very lucky to get away un-harmed. The driver this time however had had a lot of experience driving race cars and he recognised the problem as 'brake fade'.  The small disc and was overwhelmed by the demand placed on it.
The brakes were changed for go-kart brakes and the problem went away.
My advice is to use only Go-Kart brakes, hydraulic or mechanical. (Other suppliers are available) ;>) .
I agree that ordinary flexible pipes are fine. (I use stainless steel braided pipes because I like the look of them).

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Jimr1999

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Re: BSA 3 wheeler.
« Reply #51 on: 11 Apr 22, 06:46 am »
Thanks Adrien, :)
A little to show my logic so far, any pointers are welcome if people feel I am missing something.
The rear disc is a vented pit bike 210mm one of a good thickness and I would imagine it is an order of magnitude greater in thermal mass than any mountain bike set up I have come across and weighs a lot more. It is a starting point I hope will do the job. I have experienced brake fade in discs in cars (Volvo 340 after a lot of fast hills around the lakes), E bikes and, terrifyingly, on a tandem descending a long hill. (More terrifying for me as the stoker was pleasantly unaware of the potential for disaster)  :)
It is not pleasant and always a product of under-design of the disc - caliper for the end use.
 I only have the one wheel to brake at the back, which has a smaller radius than the fronts but a wider tyre and I estimate a similar contact patch.
 I see that a lot of cyclekarts are one wheel power and one wheel braking. as I am a tadpole trike, this should at least be symmetrical in a straight line.
The caliper is a rear pit bike caliper that is already attached to a master cylinder and a short braided line. It is designed as a rear brake for a motorbike up to 125cc and I am running it on a 10mm oversize disc (Pit bike front 210mm disc to biggest pit bike rear caliper available 200mm. the rotor clears the caliper pins and the contact patch of the pads is within the disc surface). The cylinder should be a match, as it came attached, I just need to get the leverage ratio correct at the pedal. I aim for similar to the pit bike to start with.
My questions above relate to the loss of efficacy of a semi flexible system related to a more rigid system and if I need to have a remote cylinder - I still ponder this one as it may be awkward to check the levels when the box is complete.
I intend to test things out slowly at first, I am sure things will need tweaking a lot when I get rolling.

Your comments welcome as always
« Last Edit: 11 Apr 22, 07:08 am by Jimr1999 »
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StefanN

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Re: BSA 3 wheeler.
« Reply #52 on: 11 Apr 22, 08:15 am »
Hi Jim,
I’ve written a guide to brake system design which you can find in the technical section.    There’s lots of factors, including pedal length, pedal ratio, master cylinder and calliper piston areas, swept volumes, disc diameter, pad design, wheel diameter, weight, number of wheels and braked wheels, cooling etc.   Happy to talk through your design if that’s helpful.

David F-R

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Re: BSA 3 wheeler.
« Reply #53 on: 11 Apr 22, 08:56 am »
Hi Jim,
I’ve written a guide to brake system design which you can find in the technical section.    There’s lots of factors, including pedal length, pedal ratio, master cylinder and calliper piston areas, swept volumes, disc diameter, pad design, wheel diameter, weight, number of wheels and braked wheels, cooling etc.   Happy to talk through your design if that’s helpful.
I'm many miles away from this stage Stefan but I'll start reading. Thanks.
There is clearly more to brakes on cks than locos.
I'm not quite as green as I'm cabbage sounding.

Jimr1999

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Re: BSA 3 wheeler.
« Reply #54 on: 11 Apr 22, 10:28 am »
Hi Jim,
I’ve written a guide to brake system design which you can find in the technical section.    There’s lots of factors, including pedal length, pedal ratio, master cylinder and calliper piston areas, swept volumes, disc diameter, pad design, wheel diameter, weight, number of wheels and braked wheels, cooling etc.   Happy to talk through your design if that’s helpful.
Thanks Stephan, if you would PM me a contact I would be most grateful for this 😁
... You can lead a horse to water, but a pencil must be lead.

Adrian

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Re: BSA 3 wheeler.
« Reply #55 on: 11 Apr 22, 11:44 am »
You'll find Stefans 'Beginners Guide to Brake Dancing' is at the top of the builders blog section in the Technical Section. It is very good.
I thought  you were more of a woody guy than a metal guy hence the lecture, sorry.
You clearly know what I mean. I would have a remote reservoir. Lots of motorbikes have reservoirs on the brake lever??????
Have a nice day.
:>)
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Jimr1999

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Re: BSA 3 wheeler.
« Reply #56 on: 11 Apr 22, 12:23 pm »
You'll find Stefans 'Beginners Guide to Brake Dancing' is at the top of the builders blog section in the Technical Section. It is very good.
I thought  you were more of a woody guy than a metal guy hence the lecture, sorry.
You clearly know what I mean. I would have a remote reservoir. Lots of motorbikes have reservoirs on the brake lever??????
Have a nice day.
:>)
[/quoteThanks again for this Adrien, and I really do like the two way conversations these problems bring up, I think about too much in isolation up here in Cumbria. Always welcome pointers, and am always worried I have missed the obvious. No need for any apologies 👍
... You can lead a horse to water, but a pencil must be lead.

Jimr1999

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Re: BSA 3 wheeler.
« Reply #57 on: 11 Apr 22, 03:50 pm »
Today I have been mostly shaping curvy bits.
... You can lead a horse to water, but a pencil must be lead.

Adrian

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Re: BSA 3 wheeler.
« Reply #58 on: 11 Apr 22, 09:08 pm »
Wish I was shaping some curvy bits.
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Jimr1999

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Re: BSA 3 wheeler.
« Reply #59 on: 12 Apr 22, 02:25 pm »
Mind -bending day of compound angles into curves, but the engine has clearance and the tail is as near an equilateral gothic arch as makes no difference.
Engine mount marking out next while glue sets.
... You can lead a horse to water, but a pencil must be lead.