Monday, October 12, 2009
Wrap around
Wild sketching for fun. In my last post I introduced my first lowracer concept, I decided to play slightly further by wrapping it with a fairing and here is a result, 'lowliner', lol. It's a little bit different than previous sketch models, it's shorter and lower, and so unready, but I was in a creative mood, it's made to look like a mean mile eater machine :D
Sunday, October 11, 2009
Lowracer concept - first appearance
'Sister-project' I would say, but to be able to make decisions, I need a good platform to test particulary driving position, which is the most critical and also unknown, how else you could ride hours unless you feel comfortable. However, these bikes are not ment to replace your livingroom sofa, but if you make a critical error in your positioning, you may not be able to pedal properly or get a good breathing. Also to driveability and manoeuvrability is very important to test, and does it have some bad habits. The design is different when it's a lowracer and not a streamliner, but at least you can have a hint of the future what's head of us. That is the meaning of the lowracer concept.
There is one thing that might look odd, it's mainly because the construction is different what it would be in a monococue streamliner, but the ground clearance is very low mainly because of the main tubing under the seat. The seating height represents the height what it would be in a monococue construction, you literally 'sit on the bottom', so that is where you need to sit in this lowracer.
Steering is something you can't deside before you have something you can fit yourself in, so that will be a matter of experimenting and it is left out at this point. Three different ways are possible, downbar, upbar or sidebar. Sidebar and 'side-steering' sounds complicated and strange.., but I feel I will give it a try :)
The height of the construction is very important, if you want to make it look like a typical lowracer, it would be much "flatter" , driver laying more in his back than sitting upwards, but streamliner is a vehicle of compromises. More upwards it means shorter lenght, better view, bigger overall height. Laying down means longer bike, low view, perhaps heavier bike. As we know now, pedal-box is the critical and most guiding issue in a liner where everything must fit inside the fairing and still make a good aerodynamics. So if you have a big pedal box like I have (big feet, long cranks), it's pointless to make a long vehicle because it also needs to be quite high. So before you think that more lower the better, maybe, but not in all cases.
Here we have a sketch of the lowracer design.
There is one thing that might look odd, it's mainly because the construction is different what it would be in a monococue streamliner, but the ground clearance is very low mainly because of the main tubing under the seat. The seating height represents the height what it would be in a monococue construction, you literally 'sit on the bottom', so that is where you need to sit in this lowracer.
Steering is something you can't deside before you have something you can fit yourself in, so that will be a matter of experimenting and it is left out at this point. Three different ways are possible, downbar, upbar or sidebar. Sidebar and 'side-steering' sounds complicated and strange.., but I feel I will give it a try :)
The height of the construction is very important, if you want to make it look like a typical lowracer, it would be much "flatter" , driver laying more in his back than sitting upwards, but streamliner is a vehicle of compromises. More upwards it means shorter lenght, better view, bigger overall height. Laying down means longer bike, low view, perhaps heavier bike. As we know now, pedal-box is the critical and most guiding issue in a liner where everything must fit inside the fairing and still make a good aerodynamics. So if you have a big pedal box like I have (big feet, long cranks), it's pointless to make a long vehicle because it also needs to be quite high. So before you think that more lower the better, maybe, but not in all cases.
Here we have a sketch of the lowracer design.
Saturday, October 10, 2009
Narrow bottom bracket
Earlier I introduced you a narrowed ISIS spindle, but now here is a narrow bottom bracket construction which uses that spindle. While narrowing spindle just about 2 centimeters, I was able to lower my Q-value down to 115mm in my crank setup i introduced some time ago.
Why narrow? The width and the height of the streamliner fairing is mostly determined by the pedal box, which is cranks, BB, and your shoes rotating in a path of your pedal stroke. If we shorten cranks and narrow our BB the pedal box comes smaller and it fits into smaller space and we can make the front section smaller in our fairing.
When narrow is good, it has its own disadvantages. If the pedals are too close to eachothers, ther's very little space for steering, and taking corners has to be with big radius, otherways you may end up rubbing your cranks with your front wheel. So again, it's a balance between the shape and the usableness.
Why ISIS? ISIS-standard is a double edge sword, it's strong, and its weak. I would't blame the priciple itself, the spindle and the overall design is good with 10 tapered grooves, but the weakness lies in old shell standard which defines the space where bearings must fit in. That standard is probably 100 years old bottom bracket shell standard which is too small in diameter to fully cover modern requirements where everything must be strong and reliable. Designs and requirements have changed in these years, but the standard stays, which seems to be very odd in these modern days.
So if you wish to apply a strong thick axel, the drawback comes from the bearings. In order to fit bearings inside the shell, they need to be with very small balls, and smaller they get, weaker they are.
In this design, I did not have to go with the old bottom bracket standards, and I was able to adjust the shell size where ever i wished, thantway I maintained two different advantages: ISIS spindle, which is even thicker than the regular ISIS on it's center, and the free shell size which gives me an opportunity to use any bearing size I need.
There are many other standars for BB out there, the newest is BB30 which is a very good design with thick hollow axel and big bearings and the shell is with no threads, so the design is very simple, but for homebuilder they are problematic. If you wish to use BB30 standard in your design and narrow the spindle, you have a heavy task to modify the cranksetup because BB30 crank comes with the integrated axel and it's not removable, so you actually need to machine your crank, and what if something goes wrong..?
This design is probably the narrowest I can imagine to be usable, probably too narrow for the design..
Why narrow? The width and the height of the streamliner fairing is mostly determined by the pedal box, which is cranks, BB, and your shoes rotating in a path of your pedal stroke. If we shorten cranks and narrow our BB the pedal box comes smaller and it fits into smaller space and we can make the front section smaller in our fairing.
When narrow is good, it has its own disadvantages. If the pedals are too close to eachothers, ther's very little space for steering, and taking corners has to be with big radius, otherways you may end up rubbing your cranks with your front wheel. So again, it's a balance between the shape and the usableness.
Why ISIS? ISIS-standard is a double edge sword, it's strong, and its weak. I would't blame the priciple itself, the spindle and the overall design is good with 10 tapered grooves, but the weakness lies in old shell standard which defines the space where bearings must fit in. That standard is probably 100 years old bottom bracket shell standard which is too small in diameter to fully cover modern requirements where everything must be strong and reliable. Designs and requirements have changed in these years, but the standard stays, which seems to be very odd in these modern days.
So if you wish to apply a strong thick axel, the drawback comes from the bearings. In order to fit bearings inside the shell, they need to be with very small balls, and smaller they get, weaker they are.
In this design, I did not have to go with the old bottom bracket standards, and I was able to adjust the shell size where ever i wished, thantway I maintained two different advantages: ISIS spindle, which is even thicker than the regular ISIS on it's center, and the free shell size which gives me an opportunity to use any bearing size I need.
There are many other standars for BB out there, the newest is BB30 which is a very good design with thick hollow axel and big bearings and the shell is with no threads, so the design is very simple, but for homebuilder they are problematic. If you wish to use BB30 standard in your design and narrow the spindle, you have a heavy task to modify the cranksetup because BB30 crank comes with the integrated axel and it's not removable, so you actually need to machine your crank, and what if something goes wrong..?
This design is probably the narrowest I can imagine to be usable, probably too narrow for the design..
Friday, October 9, 2009
Mid-transmission
Mid-transmission is to lead power from the pedals into a front wheel via a double chained "gearbox", and at the same time it channels chainline from above the front wheel and again to center of the front wheel into gear cassette. Construction consists of double bearings and highly lightened aluminium gears, addition to this, bigger gear is reinforced with carbon sidepanels. All is kept smooth with no openings, with no extra cavity to keep air drag at minimum. It's a long shot, but everything is based on small things, lets say that this is the "small thing" here ;).
Weight without bolts and axel is 160 grams. If the speed range of the bike must be changed during a competition day to desired range, the bigger gear is quickly replaced by opening the 6 bolts and pulling it out by hand, no tools are required and the chainline is untouched.
It's obvious that construction takes a lot of force into itself, so it's again a balance between strenght and weight. But as the strenght and credibility is very important on a racing bike which is attended to eat miles as fast as possible and taking few nasty bumbs and hits while doing so, I wouldn't risk it for a few tens of grams. Loose spinning gear inside your closed cabin would be a unpleasant surprize..
One teeny-weeny detail must take into account, how close to the gear you will go during your pedaling is still unknown, I would mind hitting my feet into high rpm razorblade ;). This will go around about 4+ times per second at 80 rpm cadence and it's as close as few centimeters away from you!
Picture is a projection from two different sides of one unit and it does not include axel, bolts or any other attachement elements.
Weight without bolts and axel is 160 grams. If the speed range of the bike must be changed during a competition day to desired range, the bigger gear is quickly replaced by opening the 6 bolts and pulling it out by hand, no tools are required and the chainline is untouched.
It's obvious that construction takes a lot of force into itself, so it's again a balance between strenght and weight. But as the strenght and credibility is very important on a racing bike which is attended to eat miles as fast as possible and taking few nasty bumbs and hits while doing so, I wouldn't risk it for a few tens of grams. Loose spinning gear inside your closed cabin would be a unpleasant surprize..
One teeny-weeny detail must take into account, how close to the gear you will go during your pedaling is still unknown, I would mind hitting my feet into high rpm razorblade ;). This will go around about 4+ times per second at 80 rpm cadence and it's as close as few centimeters away from you!
Picture is a projection from two different sides of one unit and it does not include axel, bolts or any other attachement elements.
Monday, October 5, 2009
Narrow Spindle
Came up the idea that I need a narrow Q-factor cranks and since there are no real options on the market, I went with designing my own. No cutting existing spindles, no welding joints, it's totally new one! This time with ISIS type of splined spindle. With this I'm able to lower my Q-factor down to 115mm with FSA AERO TT cranks which again helps me to narrow my liner. At this point I skip custom crank designing and stick with the ready made ones, but perhaps in the future, (ideas allready bouncing around in my head).. The new spindle is only made shorter while keeping the rest as standard, other parts comes from commercially available BB. Spindle is supposed to be done from titanium alloy (wooo!) and is milled to precision ;), M15 crank bolts would add the weight-wheenie points, but I'd rather stay on the safe side and keep M12 bolts as a standard, nothing beats the strenght! Spindle alone weights 100 grams, and this could be the first narrow ISIS bottom bracket in the world.
Sunday, October 4, 2009
Chains and ratios
Time to think what speed I wish to ride on TT, that's why I need to calculate gear ratios. I think that 50km/h is very good top speed, and to make some calculations I end up doing Exel sheet of graphical diagram of how the speed will vary in different ratios. Wheel size, cadense, and all gear teeth's can be added and put into diagram.
A picture how I will put my chain go thru into front wheel is here.
Here we can see a diagram with a candence of 80 rpm. Gear ratios are 12-27, main ring is 44T to keept it small. Still I have to figure out does my feet bang into derailleur, then I have to go with my plan-b.
Speed increment is very linear as they usually are, which is very good. Speed starts from 20km/h to be able to start from launch wheels and topping to 50km/h. Hopefully I need to change gears to suit better to 60km/h ;-)
A picture how I will put my chain go thru into front wheel is here.
Here we can see a diagram with a candence of 80 rpm. Gear ratios are 12-27, main ring is 44T to keept it small. Still I have to figure out does my feet bang into derailleur, then I have to go with my plan-b.
Speed increment is very linear as they usually are, which is very good. Speed starts from 20km/h to be able to start from launch wheels and topping to 50km/h. Hopefully I need to change gears to suit better to 60km/h ;-)
Saturday, October 3, 2009
More shapes !
New fairing sketch is here ! after some brainstorm :D, I went with cranks down to 110mm Q-factor, thatway I managed to narrow the pedal box few centimeters. I also went to 170mm cranks which I'v tested on my road bike 8 years ago. That also made it more narrow and also lower. Lenght also was cut to 260cm because of the rear wheel was moved towards. Front section is also a bit lower to make better view. Iteration will happen in few days again when I get more ideas and get some ideas of the parts I will need. Also tilt angle was increased to 40 degrees to get the corners !
Measurements are:
lenght: 260cm, 102"
height without canopy: 73cm, 29"
width: 49cm, 19"
Measurements are:
lenght: 260cm, 102"
height without canopy: 73cm, 29"
width: 49cm, 19"
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