When I graduated high school and went off to college, I also left electrathon, but last winter I was able to buy a used car from another team. However I didn't like telling people that I just bought a car and I wanted to challenge myself into building a very special one. As a mechanical engineering student I wanted something, complicated, unique, and had the opportunity for high performance. So my original idea was to just have 3 wheel steering, but that was to simple. So I decided to add front suspension to the car too. But that also was to simple, so I decided to add adjustable linkage driven suspension to the car. But that almost was to complicated for me.
In February I modeled by first 3 wheel steering proof of concept. This 3 wheel steering design would help reduce tire wear, and possibly improve handling on tight corners. However this proof of concept was WAY to simple for the real world and it lead me to find many problems. Over the next 5 months I would work on designing this car's steering and suspension. I went through over 10 different design all with flaws I wouldn't accept. Until I found a way for the steering and suspension to be more than 99.8% interdependent of each other, meaning when the car's suspension was fully compressed the steering would change only .11 degrees.
I was always a bit more of a designer than a builder so building this car is taking longer than expected.
I started off on this car by just building a box, quickly followed by the control . This box would hold the suspension and steering system for the car.
I used bushings when building all steering and suspension joints to help eliminate most slop from the car. However I ordered my metal and bushings at the same time hoping they would fit, however the piping for my rear steering was to large for the bushing, so I cut up some aluminum cans and used the thin sheets of aluminum as shims to hold the bushings. And so far it has worked great.
The suspension pivots probably took the longest of any building so far, just because the 3D models I never really accounted for mounting, just geometry, so I went through a few different mounting options before I was able to get one that worked for me.
If some of the pictures appear upside down try flipping your computer or phone screen upside down, that should fix the problem
More process is coming soon,
I plan to add a removable front end, roll bar, and all steering in the next couple days.
I was looking at your aluminum shim stock and I understand why you are taking on such a challenging (and interesting) project. You are clearly drinking way too much caffeine
From data we have collected on the Super Coupe, we use more energy going through a corner than when the vehicle is going straight at the same speed. I wonder if rear wheel steering will make the car rotate easier and lower the energy cost of going through the corner.
One warning- I vaguely remember reading about one of the Japanese car companies experimenting with rear wheel steering. I think they had the rear wheel turn outwards for tight turns but inwards for high speed sweeping turns. In a tight 180 degree turns, the drivers liked the help getting the car to rotate but in long corners, even a little rear wheel help was too much.
Nitoragro said
Aug 18, 2019
Cliff thanks for the info on the car, I never thought of having the rear wheel turn to the inside. But what is condidered high speed and low speed for them? I imagine with Electrathon the results might be a bit different, I feel that would be really easy to add that as an adjustment to the car. It would be really cool to be able to change which direction the wheel turns on the type of track. I might have to add this adjustment at Daytona and see the time differences.
Brendan_Smith said
Aug 18, 2019
Hi Ryan, Awesome idea; will be pretty illuminating if you're able to do some coast-down tests on a hill once it's built and see if/how much distance you gain against having the system disconnected! I like Jalopnik's description of the system in the Honda Prelude, as this was probably the most popular and successful mechanical-only system. I used to work for the importer and from memory the system switched to full follow-steering of about 2° at around 90km/h / 55mph, to increase precision at high speeds (less twitchy steering with larger steering wheel angles for the direction change) and was at full counter-steering of around 12° at 8km/h / 5mph (For reduced turning circle) jalopnik.com/heres-how-the-honda-prelude-4wss-four-wheel-steering-wo-1828459598
-- Edited by Brendan_Smith on Monday 19th of August 2019 02:23:41 AM
Nitoragro said
Aug 19, 2019
From my understanding of the article is the wheels didn't depend on speed, just front wheel steering angle. But I like the idea of being dependent on speed, I could make the amount of steer adjustable on the track by moving the linkage rod connected to the rear wheel to allow for more/less steer on tighter/open tracks.
And thank you for finding this article, there was 1 line in it that I thought was hilarious. "Too expensive, insufficiently practical, but totally wonderful."
Brendan_Smith said
Aug 20, 2019
I can't directly recall the mechanism, but what's shown in the article was only the tie rod adjusting mechanism, the downstream part of the system. I think it was actuated by a clutch pack biased on output shaft speed, similar to what's done to engage the rear-drive system on most AWD light SUVs these days (CRV for example).
Thought the same as I read it! Again I'm just starting out on this journey, but one of the best things about Electrathon is the sheer scope for innovation, and these vehicles are so considerably different to other classes that you just don't know until you have a try.
ProEV said
Aug 20, 2019
I have been trying to think through if there is any physical advantage to turning the rear wheel in the same direction as the front. The only thing I can see it accomplishing is slowing the rate the car pivots since the rear end crabs in the same direction the front turns. This does sound like something done for driver feel. Extra rotation is great at slow speeds but most drivers prefer a hint of understeer at high speeds. I do not see any advantage for Electrathon.
For Electrathon, wheels require the least energy to roll when pointed straight. The energy to turn the front wheels come from the driver's arms (or legs in at least one case). As the front of the vehicle turns, the energy to drag the rear wheel around comes from the kinetic energy of the car. So rear wheel steering will move that energy cost from the battery pack to the driver's arms. So that should help range but it is not clear how much.
It also feels to me like the vehicle will roll freer in the turn. My suggestion for a starting point in set up is to consider Ackerman steering geometry. When the vehicle is turning, the inside wheel is following a smaller circle than the outside wheel, so it will fight less with the outside wheel if it's steering angle is greater. The rear wheel natural arc will be smaller than the outside wheel but greater than the inside wheel, so the steering angle should be between the two.
Nitoragro said
Aug 20, 2019
I don't know what will happen if I steer the rear wheel in the same direction as the front, like a crab walk, in a fast corner. However, the people who made the 4WS on that Honda did, so I think it would be interesting to try, and VERY easy to implement. And when we race at Daytona on October we will gave up to 9 attempts, so I will have lots of opportunity to experiment.
As for efficiency, it might be less efficient, however there are some tracks where maneuverability is more important that efficiency, such as a speed race.
As for your point on ankermann angle, that is exactly what I thought originally, and that's what I modeled. That first picture I posted with the very basic car that's green and blue, that was actually my 3rd or 4th attempt at getting the ankermann geometry correct. Originally I did exactly what you said, if the front inside wheel turns 10 degree, front outside 15 degrees, the back should turn 12.5 degrees, but with a pivot arm steering system that didn't work. The rear wheel just turns to much thus messing everything up. What I found needs to happen is the rear wheel needs to turn half of the average of the front wheels, so if the front wheels are again 10 degrees and 15 degrees, the rear wheel would need to turn 6.25 degrees.
This picture shows the rear wheel steering half of the average, so you can see all the wheels share nearly the same center point.
In this picture the rear wheel turns the average of the front wheels, and you can see the rear wheel center does not line up
To adjust this I just move where the tie rod that connects to the rear wheel on the pivot arm.
<As for efficiency, it might be less efficient, however there are some tracks where maneuverability is more important that efficiency, such as a speed race.>
For electrathon, the more efficient your vehicle, the more power there is to drive the car forward. I have yet to be at an Electrathon race where I would not have benefitted from more power (ignoring the distressing tendency of parts breaking under load). Even at Daytona, since the track is built for bigger, faster cars, my guess is we will not have to slow much for the corners. Handling always matters but it might be less about how well the car turns in and more about how freely it rolls though the corner.
From your computer model, I see that my idea for amount of rear wheel steering only works if the rear wheel is in line with the front wheels (and then, I guess it is not really a rear wheel anymore). It looks like rear wheel steering angle should be less the longer the front to rear wheelbase that is used.
When I graduated high school and went off to college, I also left electrathon, but last winter I was able to buy a used car from another team. However I didn't like telling people that I just bought a car and I wanted to challenge myself into building a very special one. As a mechanical engineering student I wanted something, complicated, unique, and had the opportunity for high performance. So my original idea was to just have 3 wheel steering, but that was to simple. So I decided to add front suspension to the car too. But that also was to simple, so I decided to add adjustable linkage driven suspension to the car. But that almost was to complicated for me.
In February I modeled by first 3 wheel steering proof of concept. This 3 wheel steering design would help reduce tire wear, and possibly improve handling on tight corners. However this proof of concept was WAY to simple for the real world and it lead me to find many problems. Over the next 5 months I would work on designing this car's steering and suspension. I went through over 10 different design all with flaws I wouldn't accept. Until I found a way for the steering and suspension to be more than 99.8% interdependent of each other, meaning when the car's suspension was fully compressed the steering would change only .11 degrees.
I was always a bit more of a designer than a builder so building this car is taking longer than expected.
I started off on this car by just building a box, quickly followed by the control . This box would hold the suspension and steering system for the car.
I used bushings when building all steering and suspension joints to help eliminate most slop from the car. However I ordered my metal and bushings at the same time hoping they would fit, however the piping for my rear steering was to large for the bushing, so I cut up some aluminum cans and used the thin sheets of aluminum as shims to hold the bushings. And so far it has worked great.
The suspension pivots probably took the longest of any building so far, just because the 3D models I never really accounted for mounting, just geometry, so I went through a few different mounting options before I was able to get one that worked for me.
If some of the pictures appear upside down try flipping your computer or phone screen upside down, that should fix the problem
More process is coming soon,
I plan to add a removable front end, roll bar, and all steering in the next couple days.
Ryan,
I was looking at your aluminum shim stock and I understand why you are taking on such a challenging (and interesting) project. You are clearly drinking way too much caffeine
From data we have collected on the Super Coupe, we use more energy going through a corner than when the vehicle is going straight at the same speed. I wonder if rear wheel steering will make the car rotate easier and lower the energy cost of going through the corner.
One warning- I vaguely remember reading about one of the Japanese car companies experimenting with rear wheel steering. I think they had the rear wheel turn outwards for tight turns but inwards for high speed sweeping turns. In a tight 180 degree turns, the drivers liked the help getting the car to rotate but in long corners, even a little rear wheel help was too much.
Hi Ryan,
Awesome idea; will be pretty illuminating if you're able to do some coast-down tests on a hill once it's built and see if/how much distance you gain against having the system disconnected!
I like Jalopnik's description of the system in the Honda Prelude, as this was probably the most popular and successful mechanical-only system. I used to work for the importer and from memory the system switched to full follow-steering of about 2° at around 90km/h / 55mph, to increase precision at high speeds (less twitchy steering with larger steering wheel angles for the direction change) and was at full counter-steering of around 12° at 8km/h / 5mph (For reduced turning circle)
jalopnik.com/heres-how-the-honda-prelude-4wss-four-wheel-steering-wo-1828459598
-- Edited by Brendan_Smith on Monday 19th of August 2019 02:23:41 AM
And thank you for finding this article, there was 1 line in it that I thought was hilarious. "Too expensive, insufficiently practical, but totally wonderful."
Thought the same as I read it! Again I'm just starting out on this journey, but one of the best things about Electrathon is the sheer scope for innovation, and these vehicles are so considerably different to other classes that you just don't know until you have a try.
I have been trying to think through if there is any physical advantage to turning the rear wheel in the same direction as the front. The only thing I can see it accomplishing is slowing the rate the car pivots since the rear end crabs in the same direction the front turns. This does sound like something done for driver feel. Extra rotation is great at slow speeds but most drivers prefer a hint of understeer at high speeds. I do not see any advantage for Electrathon.
For Electrathon, wheels require the least energy to roll when pointed straight. The energy to turn the front wheels come from the driver's arms (or legs in at least one case). As the front of the vehicle turns, the energy to drag the rear wheel around comes from the kinetic energy of the car. So rear wheel steering will move that energy cost from the battery pack to the driver's arms. So that should help range but it is not clear how much.
It also feels to me like the vehicle will roll freer in the turn. My suggestion for a starting point in set up is to consider Ackerman steering geometry. When the vehicle is turning, the inside wheel is following a smaller circle than the outside wheel, so it will fight less with the outside wheel if it's steering angle is greater. The rear wheel natural arc will be smaller than the outside wheel but greater than the inside wheel, so the steering angle should be between the two.
I don't know what will happen if I steer the rear wheel in the same direction as the front, like a crab walk, in a fast corner. However, the people who made the 4WS on that Honda did, so I think it would be interesting to try, and VERY easy to implement. And when we race at Daytona on October we will gave up to 9 attempts, so I will have lots of opportunity to experiment.
As for efficiency, it might be less efficient, however there are some tracks where maneuverability is more important that efficiency, such as a speed race.
As for your point on ankermann angle, that is exactly what I thought originally, and that's what I modeled. That first picture I posted with the very basic car that's green and blue, that was actually my 3rd or 4th attempt at getting the ankermann geometry correct. Originally I did exactly what you said, if the front inside wheel turns 10 degree, front outside 15 degrees, the back should turn 12.5 degrees, but with a pivot arm steering system that didn't work. The rear wheel just turns to much thus messing everything up. What I found needs to happen is the rear wheel needs to turn half of the average of the front wheels, so if the front wheels are again 10 degrees and 15 degrees, the rear wheel would need to turn 6.25 degrees.
This picture shows the rear wheel steering half of the average, so you can see all the wheels share nearly the same center point.
In this picture the rear wheel turns the average of the front wheels, and you can see the rear wheel center does not line up
To adjust this I just move where the tie rod that connects to the rear wheel on the pivot arm.
<As for efficiency, it might be less efficient, however there are some tracks where maneuverability is more important that efficiency, such as a speed race.>
For electrathon, the more efficient your vehicle, the more power there is to drive the car forward. I have yet to be at an Electrathon race where I would not have benefitted from more power (ignoring the distressing tendency of parts breaking under load). Even at Daytona, since the track is built for bigger, faster cars, my guess is we will not have to slow much for the corners. Handling always matters but it might be less about how well the car turns in and more about how freely it rolls though the corner.
From your computer model, I see that my idea for amount of rear wheel steering only works if the rear wheel is in line with the front wheels (and then, I guess it is not really a rear wheel anymore
). It looks like rear wheel steering angle should be less the longer the front to rear wheelbase that is used.