The smaller the drive sprocket, the more the chain has to 'turn' on the link and the hotter it will run. (and the quicker it wears out or breaks) Reynolds Chains in the 1950's (when they were premier chain maker in the world) stated that 19t was minimum recommended for drive sprockets with an even number of teeth for driven sprockets. Saying this, Japanese manufacturers and off road bikes have been running drive sprockets as low as 11 teeth although 14 or 16 is more common (down from norm of 17t-18t in 1960's-70's) One other thing you should take into account, motorcycle hubs are not designed for lateral forces so increasing cornering ability can cause them to break, usually around the bearing rather than spoke flanges. Instead of moving axle or engine, a chain roller tensioner may be better, particularly as drive will only be one direction as CVT usually 'free wheels' rather than enables engine braking
Thanks for the advice, the duty of this car is low im not super concerned about longevity. I'm going to see what the installation stiffness of the wheels is specifically at the hub, it is where most wheels fail. Yeh the chain tensioning is not my strong suit but I still like having positive adjustment of the chain at static and then you can do the fine adjustment with a sprung chain tensioner. You sound like you've build a few cyclekarts?
@@teamjuric Actually, I haven't but been thinking about building one as I'm too old to be falling down at high speed nowadays. The wheels rarely fail on bike (C50-CB100), even when overloaded a bit but when smaller hubs are used to save weight on race bikes they crack , particularly if 'ventilated' to aid cooling. AHRMA (American Historic Racing Motorcycle Association) requires drum brakes on all pre-1974 bikes (which can fade pretty quick compared to discs). I have melted the centres out of brake pads when 'trying a bit' using organic instead of sintered pads (even if organics work much better in the wet) Hubs have a pretty easy fix though, have a shrink fit plate to support outer edge of brake drum so it can't flex, either in drum or just on edge as basically the drum brake hub is a 'U' with bearing support on lower end extended to the open end Cheap way to go racing was get a street Honda CB350 and modify things as and when you could afford it, just stripping them down to basics shed around 60 lbs (there were over 3 million CB350's made and are still pretty common for a bike that went out of production in 1973) I was a motorcycle mechanic, shop manager, instructor, etc for 50 years but unlike most I actually studied things (failed engineer, couldn't do the math, even with a slide rule, LOL) You kinda lost me with your calculations even when they were well explained (the steering/weight transfer, etc was excellent, understood things much better since I tried studying it in the 80's and again in the 90's) I've seen a lot of broken stuff over the years, some I even broke myself 😁. Always try to figure out why things broke, often I could tell customers what they did, usually shocked the hell out of them as they were 'just riding along' All for now
Thanks for the kind words. I have more videos being worked on at the moment, chassis and suspension structures. Was there any specific things you wanted to know more about?
@@teamjuric Hi, and thanks for asking. Apologies but the technical term escapes me, but how does one select front and rear spring rates to prevent unwanted oscillations? I think it's also called porpoising? Also, how critical is it to calculate roll rate? Your content is awesome. I spent over a year as an unofficial member of a Formula SAE team at a local college a few years ago. I've read every race car chassis and suspension book I can find - Adams, Aird, Costin and Phipps, Terry and Baker, Van Valkenberg and the Carrol Smith books. I also have Milliken and Milliken but it's so dense! Your content is the most detailed - and more importantly - accessible explanation of critical content that I've found. I just started cutting metal on a build that I've been preparing for/working on for many years. The base is a completely stripped '81 Bertone X1/9 body shell. What I'm doing is, think what Ferrari did with the 308 to build the 288 GTO - building a tubular chassis within the body shell and installing an Alfa twin cam + WRX transaxle in a longitudinal layout, with suspension based on a modified NA Miata geometry, preserving the inboard suspension pickups and building longer control arms to extend the OEM track from 56 in to ~60 in F/R. Similar to what Bilinski did with the front end of Midlana. Currently designing a street-specific roll cage to be build by a local speed shop after a design review, then I will fit up and tack tubing for the front and rear subframes then back to the speed shop for design review and final welding.
Hello! That sounds like a fantastic project, lots of scope to do a whole lot of fun sub projects!! I do like the x1/9, it's such a beautiful car, there is something special about the wedge style and pop up head lights that just put a smile on my face! Combine that shape and some better dynamics and a twin cam and you're going to have an absolute beast!! Id never heard of the Midlana until today, that looks super fun. For your questions about dynamics 1. Porpoising related oscillations are due to sensitive underbody aerodynamic interaction with the ground, complicated and not relevant to any of us, that term is very specific to high downforce stiffly sprung racing cars. 2. However for unwanted oscillations the very short version is, your dampers/shock absorbers do the job of absorbing, transmitting and dissipating the majority of the oscillations. 3. Slightly longer version, you will always get oscillations, but unwanted is very subjective, a passenger car doesn't want to be so stiff that you shake the fillings out of your teeth, but then a race car doesn't want floaty type oscillations that is comfortable for ride as aero platform control is so critical. So the challenge is picking what kind of behaviour you want and starting from there, RCVD does go into detail on this with good guidance on the two methods (ride frequency or travel). 4. I'll be getting into a lot more detail of roll rates in my next video that I'm currently working on, but essentially it is important. The relative roll stiffness of each axle is pretty much the main tool used to adjust the over/under/neutral steer balance of the car.
Thanks Andreas. Happy to share! Let me know if there is anything you want elaborated on, I've summarised a lot of stuff here and made some big assumptions 😂
Thanks for making these very informative and accessible videos @teamjuric ! Definitely a lot to digest here. 😅 I was wondering, I’ve seen a lot of cyclekart races that are on dirt tracks. How do you feel the tarmac based design you’re aiming for here would fare off road? Keep up the great work!
Thanks Andy. Great to hear you're enjoying it, and there is a lot to digest but feel free to reach out any time, happy to talk things through. Honestly I wouldn't have a clue how it would go on dirt. It would probably be too stiff and low, but I think the spool would definitely be decent for traction. I'll have to take it on the dirt to see what it does when I eventually finish it😂
Hi Joseph, the roll centre is the point where you can apply a lateral force and the sprung mass does not rotate. On a solid rear axle like mine, if you applied a lateral force at ground there would be a torque about the axle and rotation of the sprung mass. if you applied that lateral force at the axle centreline there would be no torque or rotation and hence is the roll centre. Thanks, Phil
That's awesome, did you machine the sprocket blank to the correct profile and then use the EDM to cut the teeth and internal key? What ratio do you use on your cart?
@@teamjuric i bought a blank 9 tooth sprocket, only 8mm pilot hole in it. So, with the EDM i cut the 16mm hole with the integrated key. I use 9 tooth on the TAV and 48 on the axle, so ratio is 1:5.33
This could nearly make me not bother to build one, whilst it might satisfy his ability to convert his very knowledgable engineering skills into practice it almost takes the fun out of wanting to make a car and discover it’s short comings for myself. I wish him well with his endeavours but as these are not ‘racing’ cars I cannot see the point evaluating the vehicle dynamics to this degree.
@metalmicky Hi Micky, the beautiful thing about this hobby is that you do what you feel comfortable with and most importantly have fun. I didn't make these videos to ruin the hobby for anyone. I appreciate your feedback and I'm sorry that it wasn't for you. This isn't for everyone, it's unfortunate that the project Ive used to document my design and build hobby is so contentious and gatekept, but don't let me be a barrier to your enjoyment. To be honest I'd much rather build a hillclimb car, but it's expensive and this is fun, so I'll keep doing the thing that I get great enjoyment from. Hopefully you have a great learning experience and we can one day have a beer and a laugh over our different ways of seeing the world.
Hi Joseph, it's a very good point, and I had another think about it. It's not ground or axle height, it's way more complex in this set up simply because it's difficult to model the kinematics, since the deflection of the axle controls the path of motion. If everything was infinitely stiff then yes absolutely on the ground, however it's not going to behave like that so I don't see the need to use it in my roll stiffness calculation. For my calcs my assumption treated the pillow block bearings as a super stiff leaf spring set up. Again it's not realistic, but given the axle will deflect at some point along the length on the cantilevered side, the RC should be at some point above the ground approximately at the centre of bending. So it won't be either, and since this was used to calculate roll stiffness, if you look at the sensitivity of the Rear RC between ground and axle height, it's about 10% shift of LLTD, not insignificant but it will be somewhere in-between. The final point is these wheels and tyres will deflect like crazy to lateral forces, the roll centre will move more from contact patch movement than deflection of the axle... I will be doing a proper roll resistance test and axle system deflection testing to actually see what the behaviour will be to get some credibility in the numbers and revise from there.
@@teamjuric Hi Phil. I've been rethinking it too, and came to pretty much the same conclusions, though I'm not as fluent in the language of suspension. Thanks for being open minded. I learned a lot from your first two videos and I'm sure third will be as good.
Hi Phil. I had another think too, and I think the dynamics of the situation overrule me .The load transfer in a corner will be high. and the roll lever will be from the ground to CG height. With rear weight bias, no diff and not much front roll stiffness this means a strong tendency to oversteer. looking at it this way I think the rear roll center should be considered to be at CG height. I would think you'd need a very stiff front anti roll bar to balance the front and rear grip.@@teamjuric
Its funny, the more degrees of freedom you remove the more difficult it is to predict... This is another complex issue which I'm hoping to elaborate on in the next video. In my initial suspension rate calculation I assumed an infinitely stiff chassis, but given how stiff the suspension rates are, the chassis won't be stiff enough to maintain that level of fidelity required. What that results in, is the chassis acts as a torsional spring in series to the suspension springs and reduces the stiffness of the overall roll rate, and this isn't easy to predict what suspension spring changes will do to the balance/roll stiffness distribution. In short so many unknowns especially tyres, I need to build it, design in adjustment, do bench testing and then dynamic validation. It's going to be a fun process but a long one!!
The smaller the drive sprocket, the more the chain has to 'turn' on the link and the hotter it will run. (and the quicker it wears out or breaks)
Reynolds Chains in the 1950's (when they were premier chain maker in the world) stated that 19t was minimum recommended for drive sprockets with an even number of teeth for driven sprockets.
Saying this, Japanese manufacturers and off road bikes have been running drive sprockets as low as 11 teeth although 14 or 16 is more common (down from norm of 17t-18t in 1960's-70's)
One other thing you should take into account, motorcycle hubs are not designed for lateral forces so increasing cornering ability can cause them to break, usually around the bearing rather than spoke flanges.
Instead of moving axle or engine, a chain roller tensioner may be better, particularly as drive will only be one direction as CVT usually 'free wheels' rather than enables engine braking
Thanks for the advice, the duty of this car is low im not super concerned about longevity.
I'm going to see what the installation stiffness of the wheels is specifically at the hub, it is where most wheels fail.
Yeh the chain tensioning is not my strong suit but I still like having positive adjustment of the chain at static and then you can do the fine adjustment with a sprung chain tensioner.
You sound like you've build a few cyclekarts?
@@teamjuric Actually, I haven't but been thinking about building one as I'm too old to be falling down at high speed nowadays.
The wheels rarely fail on bike (C50-CB100), even when overloaded a bit but when smaller hubs are used to save weight on race bikes they crack , particularly if 'ventilated' to aid cooling.
AHRMA (American Historic Racing Motorcycle Association) requires drum brakes on all pre-1974 bikes (which can fade pretty quick compared to discs). I have melted the centres out of brake pads when 'trying a bit' using organic instead of sintered pads (even if organics work much better in the wet)
Hubs have a pretty easy fix though, have a shrink fit plate to support outer edge of brake drum so it can't flex, either in drum or just on edge as basically the drum brake hub is a 'U' with bearing support on lower end extended to the open end
Cheap way to go racing was get a street Honda CB350 and modify things as and when you could afford it, just stripping them down to basics shed around 60 lbs (there were over 3 million CB350's made and are still pretty common for a bike that went out of production in 1973)
I was a motorcycle mechanic, shop manager, instructor, etc for 50 years but unlike most I actually studied things (failed engineer, couldn't do the math, even with a slide rule, LOL) You kinda lost me with your calculations even when they were well explained (the steering/weight transfer, etc was excellent, understood things much better since I tried studying it in the 80's and again in the 90's)
I've seen a lot of broken stuff over the years, some I even broke myself 😁.
Always try to figure out why things broke, often I could tell customers what they did, usually shocked the hell out of them as they were 'just riding along'
All for now
amazing content. thanks for sharing.
Thanks for the kind words. I have more videos being worked on at the moment, chassis and suspension structures. Was there any specific things you wanted to know more about?
@@teamjuric Hi, and thanks for asking. Apologies but the technical term escapes me, but how does one select front and rear spring rates to prevent unwanted oscillations? I think it's also called porpoising? Also, how critical is it to calculate roll rate?
Your content is awesome. I spent over a year as an unofficial member of a Formula SAE team at a local college a few years ago. I've read every race car chassis and suspension book I can find - Adams, Aird, Costin and Phipps, Terry and Baker, Van Valkenberg and the Carrol Smith books. I also have Milliken and Milliken but it's so dense! Your content is the most detailed - and more importantly - accessible explanation of critical content that I've found.
I just started cutting metal on a build that I've been preparing for/working on for many years. The base is a completely stripped '81 Bertone X1/9 body shell. What I'm doing is, think what Ferrari did with the 308 to build the 288 GTO - building a tubular chassis within the body shell and installing an Alfa twin cam + WRX transaxle in a longitudinal layout, with suspension based on a modified NA Miata geometry, preserving the inboard suspension pickups and building longer control arms to extend the OEM track from 56 in to ~60 in F/R. Similar to what Bilinski did with the front end of Midlana. Currently designing a street-specific roll cage to be build by a local speed shop after a design review, then I will fit up and tack tubing for the front and rear subframes then back to the speed shop for design review and final welding.
Hello! That sounds like a fantastic project, lots of scope to do a whole lot of fun sub projects!! I do like the x1/9, it's such a beautiful car, there is something special about the wedge style and pop up head lights that just put a smile on my face! Combine that shape and some better dynamics and a twin cam and you're going to have an absolute beast!!
Id never heard of the Midlana until today, that looks super fun.
For your questions about dynamics
1. Porpoising related oscillations are due to sensitive underbody aerodynamic interaction with the ground, complicated and not relevant to any of us, that term is very specific to high downforce stiffly sprung racing cars.
2. However for unwanted oscillations the very short version is, your dampers/shock absorbers do the job of absorbing, transmitting and dissipating the majority of the oscillations.
3. Slightly longer version, you will always get oscillations, but unwanted is very subjective, a passenger car doesn't want to be so stiff that you shake the fillings out of your teeth, but then a race car doesn't want floaty type oscillations that is comfortable for ride as aero platform control is so critical. So the challenge is picking what kind of behaviour you want and starting from there, RCVD does go into detail on this with good guidance on the two methods (ride frequency or travel).
4. I'll be getting into a lot more detail of roll rates in my next video that I'm currently working on, but essentially it is important. The relative roll stiffness of each axle is pretty much the main tool used to adjust the over/under/neutral steer balance of the car.
Aside from that your video is very interesting and informative. Thanks.
Glad you liked it! keep asking questions, be curious!!
Thanks again Phil., and keep up the good work. Looking forward to new installments, and I"ll try not to go off half cocked again
All good man, ask the worst thing to happen is we both learn something 😜
Beautiful explanation. Thank You mate!!!
Thanks Andreas. Happy to share! Let me know if there is anything you want elaborated on, I've summarised a lot of stuff here and made some big assumptions 😂
@@teamjuric i want to build my own cyclecar with engineering analysis. I loved your channel for that particular condition! Thanks again!
@@andresbernal9851 great to hear it! Looking forward to seeing your car!
Thanks for making these very informative and accessible videos @teamjuric ! Definitely a lot to digest here. 😅
I was wondering, I’ve seen a lot of cyclekart races that are on dirt tracks. How do you feel the tarmac based design you’re aiming for here would fare off road?
Keep up the great work!
Thanks Andy. Great to hear you're enjoying it, and there is a lot to digest but feel free to reach out any time, happy to talk things through.
Honestly I wouldn't have a clue how it would go on dirt. It would probably be too stiff and low, but I think the spool would definitely be decent for traction. I'll have to take it on the dirt to see what it does when I eventually finish it😂
I'm thinking that if there's no rear suspension the rear roll center is on the ground.
Hi Joseph, the roll centre is the point where you can apply a lateral force and the sprung mass does not rotate. On a solid rear axle like mine, if you applied a lateral force at ground there would be a torque about the axle and rotation of the sprung mass. if you applied that lateral force at the axle centreline there would be no torque or rotation and hence is the roll centre.
Thanks,
Phil
I made 9 tooth sprocket for #428 chain for the TAV with wire EDM. This way the key is part of the procket.
That's awesome, did you machine the sprocket blank to the correct profile and then use the EDM to cut the teeth and internal key? What ratio do you use on your cart?
@@teamjuric i bought a blank 9 tooth sprocket, only 8mm pilot hole in it. So, with the EDM i cut the 16mm hole with the integrated key. I use 9 tooth on the TAV and 48 on the axle, so ratio is 1:5.33
Where did you get the blanks from? I'm keen to make one for myself
Bro applying Formula 1 physics to adult go carts...😕
I'm just applying engineering to my project.
This could nearly make me not bother to build one, whilst it might satisfy his ability to convert his very knowledgable engineering skills into practice it almost takes the fun out of wanting to make a car and discover it’s short comings for myself. I wish him well with his endeavours but as these are not ‘racing’ cars I cannot see the point evaluating the vehicle dynamics to this degree.
@metalmicky Hi Micky, the beautiful thing about this hobby is that you do what you feel comfortable with and most importantly have fun. I didn't make these videos to ruin the hobby for anyone.
I appreciate your feedback and I'm sorry that it wasn't for you. This isn't for everyone, it's unfortunate that the project Ive used to document my design and build hobby is so contentious and gatekept, but don't let me be a barrier to your enjoyment.
To be honest I'd much rather build a hillclimb car, but it's expensive and this is fun, so I'll keep doing the thing that I get great enjoyment from.
Hopefully you have a great learning experience and we can one day have a beer and a laugh over our different ways of seeing the world.
I wish you would sleep on it Phil. I'm sorry to be a pest but I stand my ground.
Hi Joseph, it's a very good point, and I had another think about it. It's not ground or axle height, it's way more complex in this set up simply because it's difficult to model the kinematics, since the deflection of the axle controls the path of motion.
If everything was infinitely stiff then yes absolutely on the ground, however it's not going to behave like that so I don't see the need to use it in my roll stiffness calculation.
For my calcs my assumption treated the pillow block bearings as a super stiff leaf spring set up. Again it's not realistic, but given the axle will deflect at some point along the length on the cantilevered side, the RC should be at some point above the ground approximately at the centre of bending.
So it won't be either, and since this was used to calculate roll stiffness, if you look at the sensitivity of the Rear RC between ground and axle height, it's about 10% shift of LLTD, not insignificant but it will be somewhere in-between.
The final point is these wheels and tyres will deflect like crazy to lateral forces, the roll centre will move more from contact patch movement than deflection of the axle...
I will be doing a proper roll resistance test and axle system deflection testing to actually see what the behaviour will be to get some credibility in the numbers and revise from there.
@@teamjuric Hi Phil. I've been rethinking it too, and came to pretty much the same conclusions, though I'm not as fluent in the language of suspension. Thanks for being open minded. I learned a lot from your first two videos and I'm sure third will be as good.
Hi Phil. I had another think too, and I think the dynamics of the situation overrule me .The load transfer in a corner will be high. and the roll lever will be from the ground to CG height. With rear weight bias, no diff and not much front roll stiffness this means a strong tendency to oversteer. looking at it this way I think the rear roll center should be considered to be at CG height. I would think you'd need a very stiff front anti roll bar to balance the front and rear grip.@@teamjuric
Its funny, the more degrees of freedom you remove the more difficult it is to predict...
This is another complex issue which I'm hoping to elaborate on in the next video. In my initial suspension rate calculation I assumed an infinitely stiff chassis, but given how stiff the suspension rates are, the chassis won't be stiff enough to maintain that level of fidelity required.
What that results in, is the chassis acts as a torsional spring in series to the suspension springs and reduces the stiffness of the overall roll rate, and this isn't easy to predict what suspension spring changes will do to the balance/roll stiffness distribution.
In short so many unknowns especially tyres, I need to build it, design in adjustment, do bench testing and then dynamic validation. It's going to be a fun process but a long one!!
500 cc Honda for extra uhm, excitement 👍🦘🇦🇺
What I'd love to do for some excitement is to get a 4 cylinder cbr250 engine, spin that sucker up to 15k rpm!