Team Juric - Lotus 25 Cyclekart Design Part 3 - Seat, Steering, Universal Joints, Brakes & Bodywork

TEAM JURIC - DESIGN PART 3 - Seat, Steering, Universal Joints, Brakes & Bodywork
In Parts 1 & 2 we looked at
Rule and Intent
Layout and Architecture
Dynamics
Power Train
Originally, I was going to look at Chassis and Suspension Structures however, the content grew such that it’s now its own video, so it’s a 4-part Trilogy!
In this video, we will be looking specifically at:
Driver controls
• Seat
• Seat Belt
• Steering
• Universal Joints
• Steering Arm Rates
• Brake System
• Braking Weight Transfer
• Braking Tyre Forces
• Braking Acceleration
• Braking Torque
• Calliper Selection
• Line Pressures
• Master Cylinder Sizing
• Pedal Ratio and Foot Forces
• Pedal Box Brake and Accelerator
Bodywork
• 2d Faceting
• Buck/Male Mold
• Female Molds
• Bogging and Sanding
• Final Parts
• Perspex Wind Deflector
I start with the seat and cockpit layout; we’ve already covered the ergonomics but having a supportive seat holding you in place is key!
The steering system is broken down into each component.
I do a deep dive into the way Universal Joints work and how they fluctuate in speed with increased angle and joint phasing. Key takeaways are to have at least two at the same internal angles and 90 deg out of phase to make them a constant velocity joint!
Next, we design the entire braking system from braking potential, and tyre grip, to the selection of rotors, callipers, line pressures, master cylinders, pedal ratios, and foot forces.
The pedal box is broken down into what is important, STIFFNESS!!
Finally, a look at how I propose to make the beautiful, laborious bodywork. I’m sure you will all enjoy future videos of me block-sanding myself into oblivion!!
We hope you enjoy!
Leave us a comment below or DM us on Instagram or Facebook @teamjuric
Part Four Stuctures and the chassis build series are in the works so stay tuned!
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[@paullayer4152]

I’m excited for part four!!

[@juscozcustoms]

a lot of planning going into this one I cant wait to see you start some fabrication I was thinking about building a Cyclekart 5 years ago but they where not very common in Australia so I decided to build a half scale lotus 7 instead.

[@teamjuric]

Thanks man, I'm so rusty with this whole thing I went back and did everything step by step from first principles. I've been fabricating the chassis, but it's been slow going with moving house and work. They're not common but there are a few people building them, would you consider building one? What motor did you use in the 7?

[@juscozcustoms]

@@teamjuric yeah there are a few now but not 5 years ago, I probably would considder building one now but I want to build my 62 mini with honda driveline and suspension before I start any more random projects. As for the "cubman" I used a 125cc 3+1 mini quad bike motor so it has 3 forward speeds and reverse its more of a microcar than a gokart as it also has full lighting and instruments as well. I have the build series on my channel if you have time.

[@teamjuric]

The mini with the Honda motor is a great combination. That's neat, I'll have a look at your vids!

[@paullayer4152]

Thanks for making this build series!!

[@teamjuric]

Thanks Paul! Appreciate your kind words. Part 4 is still in progress, I'm hoping to get some free time to finish off the pictures and start the recording! Cheers, Phil

[@paullayer4152]

@@teamjuric that’s excellent news!! Thanks Phil!!

[@teamjuric]

Is there anything else you were interested in getting some more insight into? The next vid is less specific on cyclekarts and more a general chassis theory. Or are you more interested in cyclekart specific things

[@paullayer4152]

@@teamjuric I’m really enjoying watching how you’re applying general chassis design and actual race car dynamics to cyclekart cars please keep doing your thing!! Your karts gonna be a beast for real!!

[@teamjuric]

Thanks for the feedback, unfortunately my take on cyclekarts is typically frowned upon by the majority of that community. So I'm just off to the side doing my thing, if I had the money I'd actually want to build my hillclimb/autocross car but this is the best way I can have fun

[@Apocraphtica]

Almost year has passed. Maybe overplanning is not the best thing for simple projects like cyclekart

[@teamjuric]

Yeh, been busy with work unfortunately. Glad you watched it, did you get anything out of it?

[@MrShaneSunshine]

"If you are from the US or Liberia!" 😂😂😂😂 👍🇨🇦

[@teamjuric]

😁 I'm glad someone enjoyed it!

[@MrAussieCrasher]

Great content, but I feel you have moved away from the original concept , but that just my thought . One thing i would like to know is where did you get the steering rack from, as i missed that bit of your presentation.

[@teamjuric]

Hi Paul, what aspect do you feel I have moved away from the original concept? I do try to stick to the guidelines mostly. The rack is a 420mm unit from Ali express. a.aliexpress.com/_mPNa2cO

[@jimrawnsley]

Looking at your drawing at 8:41 and listening to the commentary about introducing a little steering wheel angle, I wonder if you could dispense with the UJ's altogether, twist the rack and have a straight steering column. This is how most cyclekarts are, and I know from vehicle design this is poor due to the potential of impalement during a head on collision but this could be mitigated with a telescopic steering column. My present cyclekart has a telescopic steering column made from the tubes of a broken MTB dropper seat post collected from a scrap bin. The steering forces are low in most CK's and the rack I use I fabricated myself gives about 95mm linear movement per turn. Any lower and it would be very vague.

[@teamjuric]

You can absolutely eliminate UJ's, I just like them because they give you flexibility for any fabrication errors in the mounts. I did look at tilting the rack and it was suggested to do it in one of the design reviews I had with my mates, but for the first kart I wanted to keep the fabrication simple so I could set the rack level and not have to do a fixture to set the angle. When I'm looking to cut some weight out of it I will rotate the rack, do a straight tube and put bushings at the wheel side instead of bearings. Yeh agreed the steering forces are super low, but you can also change the feel with different steering arm lengths, castor.

[@averygoodfantasticname4206]

check out how superfastmatt did his windshield for his land speed record car

[@simonbrooke4065]

Stupid question, I'm sure, but why not just point the steering wheel axis at the rack pinion shaft and vice versa, so that in conditions of minimal distortion of the space frame there is approximately zero angle on the UJs?

[@teamjuric]

Not at all, it's a good question actually. Ideally it should be, but it's easier to fabricate them horizontally because I'm rusty. Eventually I want to simplify it to a single shaft and a bushing as the bearings and UJs are heavy.

[@NathanielSalzman]

Why does the input end of the steering rack have to be level? Why not rotate it up to point straight at the u-joint near the steering wheel? The inner tie rod joints are spherical, right?

[@teamjuric]

You don't need to make them level, you just need to keep the input and output parallel in side view so the included angles are the same. I made them level to make it easier to fabricate, it was nothing more than that. Yes the rack ends are sphericals, but it's a ball and socket type rather than a rod end type spherical.

[@whatyoudo9773]

anything worth doing....are we building a F1 car here? The big brains on brad

[@teamjuric]

It's a shame you didn't get much out of it. What kind of thing would you want to see? I'm just doing what I've done on previous cars so it's hard to gauge what enthusiasts like yourself want to see.

[@whatyoudo9773]

@@teamjuric Just way over my head i think, I would love to have your help on a similar project!

[@davidsallyshannon8468]

Sorry to trouble you Enjoying your videos Is there any competition or races for cycle karts Also the yacht fitting you mention for your pedals .,Can you please tell me what they are what brand etc

[@teamjuric]

No trouble at all! Happy to answer any questions! In America there are many events, a few in the UK, but in Australia there aren't any currently. From my understanding they don't really encourage racing or competition, it's more an artistic project as the cars are pretty dangerous... We used to use LM76 slide rails, now the Monash team use Treotham drylin T rail guide, otherwise we did use some Jib rails one year from a yacht, but they're all essentially the same. T Rail with a dovetail and a linear bearing with mounts on it and a detent for positive locking.

[@davidsallyshannon8468]

@@teamjuric Thank you Sorry but a bit high brow for me Who supplies this equipment? Any chance of some photos? Building a front engined race car where this could be used for clutch brake and accelerator pedal assembly Thanks again David

[@teamjuric]

This is the website for the linear rail. treotham.com.au/bearings/linear-technology/t-rail-guides This is some close ups of the Monash cars rails m.facebook.com/story.php?story_fbid=pfbid0FnxpiESYoCcgEwgiq3GypYGLZG2oR98Y9EEBDy7o9Gyg5fHWpkxirdFCGtvGBLP2l&id=185745901446670&mibextid=Nif5oz

[@davidsallyshannon8468]

@@teamjuric thank you much appreciated

[@teamjuric]

Any time. Also my series just uses the CycleKart as the project basis, however everything I cover can be applied to any car

[@fillman86]

so what happened with this?

[@teamjuric]

Haven't had much spare time to commit to this. Work and family take priority

[@xote316]

I want to make a cyclekart and the comments here are making me kind of sad bc i want to build something not specific to this time period. Dont mind using the engine and basic construction, but i want to make the body something of my own. This is probably the closest thing ive seen, but way more above my understanding of how to make one as far as the chassis goes. I think thats what the complaints commentary are saying also. But i think this car is cool anyway.

[@teamjuric]

Hi Joshy-Z, The thing I like about cyclekarts is that they're a great balance of cost, complexity and design freedom to make something really fun to build and drive! I've also found most people in the community are curious and very supportive I don't get too caught up in people's opinions on what is "real" and isn't (I'm more curious as to why they feel a particular way), just do your thing, fun is subjective, build something you enjoy. What body were you thinking of doing? With respect to the explanations, I'm documenting my process, it can be overwhelming but I try to lay it out in a more typical design process that a race car follows, but this doesn't need to be followed. You follow the process that makes sense to you. I guess because I go from first principles, hopefully for some who has a car with heavy steering, or has a really touchy brake pedal, can use these explanations to understand how to get to the bottom of it, maybe... I'm happy to talk through anything if you're interested. Thanks for your kind words too! Cheers, Phil

[@xote316]

@teamjuric I want to build something that is a hybrid of a modern F1 car and the cars from the postwar era. No wings or serious aero, but basically a high nose car with a traditional by cyclekart standards rear. There wouldn't be wings or anything like that, but there might be some flow dynamics I would want to come from the floor I intended on building. I'm not good at the calculations of CFD, I just want to drive something I would actually like to see. I thought cyclekarts would be the way, but I guess there is some gatekeeping here, and it's disappointing. I just feel like if you can build it, you should be able to race it. These guys don't really even race, they just have fun. I don't understand why they have these limitations on who should be allowed to if you show up for the same reasons. There is no prize money. Cyclekarts should be building your fantasy car at economical prices. I'm not Adrian Newey.

[@teamjuric]

That would be mega!!! I love the idea of mixing old and new, super cool idea. I think the gatekeeping is the minority, there would be some events to avoid but I'm sure the majority would be keen for something like what you're proposing. There is probably some reluctance due to the dickhe@d factor with people taking these things too far with competing as these cars are super freaking dangerous, but as long as it's clear it's not just about performance or trying to win some imaginary competition they are generally cool. Call it a cyclekart, do your thing, I cannot wait to see it!!

[@DJustmusicMusic]

Hey, thought i'd give my perspective on some stuff as I've worked on the vehicle dynamics of a formula student car before. You go into a lot of detail about the velocity change in U joints and trying to reduce the angle of the steering shaft but I think you're making it too complicated for yourself. Usually in automotive applications, 2 double u joints are used meaning the output will be a constant velocity at any angle and thus the wheel and rack won't have to be aligned to the same plane. This is also why the angle of your steering wheel in your car can be adjusted. The benefit here is that you don't need to be as precise during manufacturing because aligning a u joint at 90 degrees at such a long distance is pretty difficult and your chassis will never be as straight as you've drawn up in CAD. Not sure how far along you are in the design but I think using 2 double u joints would give you a lot more freedom for mounting the rack and wheel. Also, a double u shouldn't be that expensive compared to a single u. Wish you good luck with the rest of the project, looks like a lot of fun!

[@teamjuric]

Hi Chris, totally agree with using double UJ's there are so many benefits to using them if you can. Unfortunately in cyclekarts and other applications I've seen, there are steering kits off the shelf that have the Cardan shaft arrangment shown in my video and are very widely used. Given that these kits are the "norm" it's better to explain how to get the best out of them. This is by no means perfect and I will have sloppiness in the steering (it won't just be from the angles and phasing, these kits are pretty poo quality) but right now it's something I'm happy to live with to get the car moving. Once I finish the first car, I have a list of things I want to improve on for the next build and this was one of them, just like any good race car :D Thanks for the feedback, really appreciate it. I'm assuming you were at Delft? Phil J

[@DJustmusicMusic]

@teamjuric yeah, better to get the car moving first of course. As engineers, we're all guilty of spending too much time on a design sometimes :) (and nit-picking designs of others....) Will you also be making videos on the building process besides the shorts or is that some time away? Also, I did indeed study in Delft but worked on the car of a different university. Hope to work on the car of Delft during my masters though!

[@teamjuric]

We all are guilty of it, but it's ok because we are all curious and its a good thing! I am filming all of the build and I have lots of content, but I have young kids and full time job so its hard to find time to edit it all together without it being a big pile of poo... Fingers crossed for you, I saw a video of a sub-3 second acceleration event which just blew my mind!!

[@jeffschlosser3146]

That’s not a cycle kart that’s just your project kart interesting as it maybe good luck with that. I won’t be back

[@teamjuric]

Hi Jeff, what aspects do you feel don't meet the CycleKart intent? I'm getting lots of feedback that it's not a cyclekart, but when I ask what specifically is the problem no one can articulate their position, so I'm feeling pretty confused by the commentary.

[@theosalt1]

Your two graphs for the 35 degree universals at about 10.59 minutes seem to have the same labels. I think that the left graph should be labeled 0 degrees phase.😟

[@teamjuric]

You are absolutely spot on, the left graph should be 0 deg! I'll try to figure out how to fix it up!

[@jimrawnsley]

Hey @teamjuric. For my next cyclekart, I am looking at a similar set up to the one you have in CAD there. Your work is thorough, and I appreciate the time and attention you are giving to this project. Two questions. 1. Your rack orientation looks with the pinion uppermost and the steering arms forward looks to give counter steering (left goes right, right goes left) am I missing anything? 2 Are you going for anti Ackerman with the angle of the steering arms?

[@teamjuric]

Hi Jim, you are spot on, in my haste and I'll claim my lack of match fitness I put the steering in upside down and only picked it up after it was all test fit on the car a month ago! It's all fixed up and the correct way up now. For Ackerman, I dont have tyre data to really tune the dynamic toe with plus it's not really something that I think has a huge influence on these cars to be honest, it just so happens I have anti Ackerman but it's just the way it landed.

[@jimrawnsley]

@@teamjuric Yes, I hear that Ackerman is pretty irrelevant on CK's . Depending on who you listen to, positive, anti or non existent are all equal or better than the others so take your advice from anyone with a pinch of salt. Much better to concentrate on bump steer elimination if you can, that does happen with some designs I have seen. As Ackerman seems to make little difference, I try to include it in my designs where I can as it cannot hurt.

[@teamjuric]

It doesn't hurt to have some Ackermann, but its influence is overstated. Bump steer is an interesting one, on the leaf-sprung front ends I don't know how stiff they are and how much travel they get, but on mine based on the part 2 video, the spring rates I've set are really stiff and I'm expecting very little travel, 1-2mm max so bump steer doesn't shouldn't really be too much of a concern. Also, bump steer isn't always a bad thing. Toe-in bump steer under braking is good as it provides braking stability...

[@jeffallen3382]

What ever happened with this project?

[@teamjuric]

Unfortunately I haven't had any spare time for the past year to dedicate to this. It's trickling along in the background, the next design video just needs time to clean up and record, and the build videos scare me having to go through all the footage 🤣 Have these been useful? The feedback has been mixed so far? Are you building a cycle kart or do you have a proper project?

[@jeffallen3382]

@@teamjuric I just found out about cyclekart. I had never heard of it before and it looks interesting. I joined 2 Facebook groups last night and will be looking more into this.

[@teamjuric]

Ah I see, my stuff is not the norm and frowned upon by the cycle kart mafia

[@jeffallen3382]

@@teamjuric "Mafia"?

[@jeffallen3382]

​​@@teamjuricI see my reply is not showing for some reason. To answer your question, I just found out about cyclekarts just recently. If I make one I'd like to do a design similar to your Lotus 25 here. But I'm not finding many people are doing any post war designs. I would also like to maybe even do a monocoque body design similar to how Chapman built his F1 cars that revolutionized F1 racing. Are "post war" designs frowned upon in the cyclekart world? I wouldn't mind doing a pre war design but my 1st choice would be post war F1/Indy cars.

[@trout4bait549]

Anyone that can actually understand your explanation of u-joints, doesn't need you to explain u-joints to them. LOL This is way too technical for the "built out of junk" intent of cyclekarts, for me... and, I have to wonder why if you were willing to step away from the intent - right from the get-go - by using a tribute car outside of the timeline parameters - why not use this as an opportunity to explore a late model open wheel class, which falls closer to your recipe, anyways? The motorcycle wheels could be swapped out for 13" trailer tires (highway speed rated) on a set of wide and a set of narrower rims, tread patterns could be found that would be suitable to specific surfaces, and the 8hp (301cc) clone motors used, real 4 wheel brakes, limited slip rear axles, safety considerations, etc... a long ways from a legends car, but a much more serious racer than a cyclekart. Much like this video series, it's just food for thought. ;)

[@teamjuric]

I'm happy with my project, it's the right cost and complexity for now. I'm getting back into the groove of the design and build. Ideally I want to then go back and build the hillclimb car, but it's too expensive for me right now so I'll stick to my Lotus... With respect to the UJs explanation, I had someone explain it to me when I was younger so maybe this will help someone else...