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Post by captainamerica on Dec 27, 2012 0:48:03 GMT -5
November - December 2012 Took a trip to England in November, where among other things I got rocketed around the Silverstone GP circuit in a 2-seater formula car by a professional driver at 160mph+. Definitely worth the time and money as is the single seater experience where I got to drive a full race ready formula ford which can top out at 145mph on the circuit there, I was only courageous enough to get up to 125mph in the rain on the straight. First time ever being in the seat of a racecar after six years of watching them on tv and building them at the university and at home. Driving a proper open-wheel car is just as amazing as you would think it would be, could've been better had it not been pouring rain though. If anyone is interested, for ~$250 you get to drive the single seater for 40mins (20 behind a pace car, and 20 at speed). Its a better price then anything I have seen in the states. Anyway after my trip I finally got back to work on my project after a six month break. Purchased a used Acer 13x40 lathe for part fabrication, the bell crank centers and the engine mounts will be the first pieces off the bench. I redesigned my bell cranks to be 3 piece welded steel instead of single piece machined aluminum, this saves time and complexity, they are copies of what I found on the formula fords in England and are shown below. I will make the centers and then have the other two pieces waterjetted or plasma cut at a local shop. Also I added a picture of the pedals from the formula ford, they are similar to what I plan on using. The shifter has been moved to the left side to simplify the shifting linkage which is shown below. In the next month I plan to start stripping the donor bike, purchasing the penske shocks for the front end, and a getting a Miller 625 plasma cutter. Design wise I am going to be changing the front anti-roll bar setup to be simpler and not track adjustable for now. Theres lots to be done, and precious short weekends and evenings to do it in.         |
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Post by captainamerica on Dec 29, 2012 3:53:02 GMT -5
More for December I am currently on holiday in Australia, with lots of time to relax and motivation to work. So I have been adding a lot to my CAD model. Noteable changes: I added most of the bolts to check clearances of rotating pieces, the fuel line was added in from the pump to the fuel rail (with zipties because I can), new radiator cap and overflow canister, the fuel tank was changed to be easier to manufacture (no more round parts) which moved the fill port forward a couple of inches, the fuel tank also got a sight glass, I updated the bellcranks to include the real bearings from mcmaster-carr, the master cylinders were changed to built in reservoirs instead of remote ones for packaging reasons. Anyone who knows about brakes or has done brake design, does the master cylinder reservoir need to be above the calipers to work or does it not matter? Also if anyone has any ideas for how to put bearings on my anti-roll bar so its not just riding on the bolt I am open to suggestions. I am worried its going to wear into the aluminum steering rack mounts as it gets shoved side to side as well, maybe just big steel washers might work. I copied the formula ford design but I can't figure out what the piece of aluminum on either end does or how it all bolts together (previous post picture).     |
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Post by DaveJ98092 on Dec 29, 2012 17:41:48 GMT -5
NICE so far, carry on.  In answer to the reservoirs being lower that the calipers, I think that it would allow some amount of drain back without some check ball device. In all my years of fab'ing up brakes I have always remote mounted the reservoir higher. I think I remember reading Shelby had an issue on the GT40 or the Daytona Cobra but that was back in 1965ish. I'm trying to think what those Bars coming from your bellcranks forward to that bar with three adjustment holes (above the reservoirs) is for. Is that your anti-roll/sway bar? If so, is it not too short to get enough flex, causing the IFS to basically lock into non-independent? |
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Post by DaveJ98092 on Dec 29, 2012 21:58:04 GMT -5
Most of my cars thru life have been torsion bar Front suspension, Dodge Darts, Plymouth Barracudas and VW Bugs.
A sway bar/Anti-roll bar is just a Torsion bar. It connects the left side to the right. The shorter the bar, the thinner it must be or else it becomes too stiff to act. If that bar/rod is his anti-roll bar I would mount the arms as far out as possible on the bar.
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Post by captainamerica on Dec 30, 2012 3:51:28 GMT -5
The anti-roll bar is in fact that thing in front of the steering rack attached to the bell cranks. I realize that its going to need to be very thin tubing at that distance and I can actually make the attachment points as wide as the rack, but I need to do the math and figure out what tubing thickness and width will give me something reasonable. For now I am more worried about how to mount it properly. I will probably just build it the first time with whatever i have available and see what if feels like and go from there.
As of the moment the responses on the brake reservoir have no lead me to the light. Really I am just looking for a good reason to leave it the way it is because I don't know where I would locate the remotes since the anti-roll bar gets in the way above the rack.
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Post by kolibri on Dec 30, 2012 6:38:41 GMT -5
Hallo Captain, welcome back to the forum. Would like to be able to make this kind of CAD drawings. Good work. This is the first time I see your complete frontsuspension and steering. Maybe I'm wrong but as it looks it could be possible that you have the same problem with ackermann as Joeld (Bandit Projekt Trike side 4) and I had. The outer wheel had a bigger angel then the inner. The problem was that the steeringrack was in front of steeringarms and should be behind. Maybe you can simulate the steering with your CAD program and check out if I'm right or wrong. Have a good time in Australia. Greetings from Germany. Ralf  |
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Post by hydrojim on Dec 30, 2012 9:44:59 GMT -5
I believe kolibri is correct. I was looking at my design to and I'm also going to have the same problem. that's why I'm trying to figure out a way to mount my steering rack closer to the back of the vehicle, but in order to allow room for my legs, the tie rod ends will have to point down at a pretty steep angle. unless I mount the steering rack below my legs, but that seating position might be a little awkward with the steering shaft between my legs.
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Post by fredvv44 on Dec 30, 2012 10:49:19 GMT -5
Hallo Captain, Maybe I'm wrong but as it looks it could be possible that you have the same problem with ackermann as Joeld (Bandit Projekt Trike side 4) and I had. The outer wheel had a bigger angel then the inner. The problem was that the steeringrack was in front of steeringarms and should be behind. Maybe you can simulate the steering with your CAD program and check out if I'm right or wrong. Have a good time in Australia. Greetings from Germany. Ralf steering rack in front is not a problem and the steering arms look like they are pointed to the rear center as they should be. the tie rods pointing back is not good but can be corrected by changing the angle of the steering arms. there is not a front view so i cannot tell for sure if the tie rods are correct in the front view. they should look like this: www.circletrack.com/chassistech/ctrp_1001_bump_steer_explained/photo_02.htmlthis is where your real bump steer happens. Fred V |
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Post by kolibri on Dec 30, 2012 11:55:05 GMT -5
Hello, found a program at the net that allows to find a good ackerman condition. The problem with the program is that it is only for steeringsarms backwards. So I decided first to find a good steering with backwards steeringarms for my car. You can see this in the pic under the red line.  The blue line shows the position of my steeringrack before. There I had the problem that the outer wheel had a bigger angel than the inner. As you can see on the pic it was necessary to bring the rack back. Now I have exakt the same condition as the steeringarms where backwards. Greetings Ralf |
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Post by captainamerica on Dec 31, 2012 1:02:10 GMT -5
Right so I took some pictures to answer the steering questions for inquiring minds. I can simulate the steering and the suspension movement in my CAD program in simple sense, move it..take dimensions, move it again and so on. I have about a half of a degree of bump steer in 5" inches of suspension motion upwards from static, the reality is the dampers only have 3" in each direction so it will be even less. Technically the correct setup is as Fred pointed out above, the problem with ackermann of course is that it puts your outer steering points in the incorrect location, but as usual its all about compromise. My a-arms are so long the motion that occurs laterally when the suspension moves is very small so bump steer would be small anyway even if I designed incorrectly. To point something simple out to Kolibri and anyone else wondering, the steering rack can really be wherever you want; front or back, and top or bottom. you just have to have your upright steering attachment point on the ackermann line to make it work. So that would be towards the brake rotor in the front and away from the rotor in the back. Having it in the back is easier on upright design because you don't have to worry about hitting the rotor or getting in the way of the caliper, but then you have to have some pretty extreme angles on your steering column which can be just as bad. If you put it on the bottom front, in my case, you run your column right through the brake pedal which is usually considered not a good idea As far as I have seen my setup is correct, I am still working on sourcing better attachment points for the ends of my steering rack, I would like to go with something like the formula ford but I have yet to find a seller. I also realize that not having my steering arms parallel with the steering rack (from the top view) may cause some issues but it was the only way to get my wheel base where I wanted. I can always move it in the future with a new set of a-arms. I also altered the anti-roll bar so the tie-rod attachment points are another 1.5" apart giving me a little more give. The torsional stiffness of course still depends on the tubing wall thickness but in this case the wider the better.       The last picture here is rather complicated, but if you know your way around suspension you can understand it, the blue circles are the inboard and outboard mount points of the a-arms. It is a quick sketch I made and use to test out different setups. You can alter lots of settings and get a-arm lengths , basic camber numbers, and roll center height out. If anyone would like I copy of this and uses Solidworks just PM me and I will get it to you. |
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Post by Deleted on Dec 31, 2012 4:46:04 GMT -5
This is a great build!
I'll be watching this closely.
I just read through and may of missed it, but what are your plans with this design? Do you plan to offer kits or plans? I really like it. The body renderings look great too!
I think the open canopy will win only due to simplicity, though the fighter jet style closed canopy could be really cool.
Russell
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Post by captainamerica on Dec 31, 2012 12:18:13 GMT -5
Welcome to the site Russell, at the moment I have no plans other then to complete the first one. If its good enough the idea of producing them as a kit has crossed my mind. Its a small market but I think they could be made cheap to the point where enough people would buy them to make it profitable. The whole idea for me at the start was to create a race-car/daily driver that costs about $10k and gets decent fuel economy (30mpg would be nice). Right now I am looking at a 12-13k reality for the cost.
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Post by DaveJ98092 on Dec 31, 2012 13:43:48 GMT -5
Thanks Cap'n for updating and covering some of our questions/concerns.
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Post by captainamerica on Dec 31, 2012 18:35:22 GMT -5
Honestly I am on here all the time (3-4 times a week), I just haven't been working on my project in the last six months so I didn't have much to say. But I am always happy to discuss vehicle design with anyone.
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Post by mtntech on Dec 31, 2012 20:05:23 GMT -5
To point something simple out to Kolibri and anyone else wondering, the steering rack can really be wherever you want; front or back, and top or bottom. you just have to have your upright steering attachment point on the ackermann line to make it work. So that would be towards the brake rotor in the front and away from the rotor in the back. Having it in the back is easier on upright design because you don't have to worry about hitting the rotor or getting in the way of the caliper, but then you have to have some pretty extreme angles on your steering column which can be just as bad. Couldn't have said it better myself. Just follow the ackermann triangle rule. |
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Post by captainamerica on Dec 31, 2012 22:58:06 GMT -5
1/1/13 Happy New Year! Thanks for validating that I can actually use words to describe a mechanical system to others mtntech, I usually fail miserably at this because I can visualize things better then most people. Took some time today to update the steering rack ends with something from reality which is always a nice change. It gives a wide range of motion and its off the shelf ($100 per side) which makes my life easier. The stipulation is I have to make a small rack extension which will jump from 1/2-20 male threads to 22x1.5mm male threads.  www.pegasusautoracing.com/group.asp?GroupID=STEERRACK |
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Post by mtntech on Jan 9, 2013 0:36:33 GMT -5
You did a great job of explaining it. It was explained to me years ago the exact same way when we were designing kart frames.
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Post by captainamerica on Jan 10, 2013 12:47:01 GMT -5
So I was rereading some of my early posts, and I realized that a lot of the comments and questions other people had have disappeared. This makes my responses to those questions seem a bit out of place, anybody know why that might be happening?
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Post by DaveJ98092 on Jan 10, 2013 23:05:58 GMT -5
The person asking may have edited it or for some reason a Moderator axed them. This forum you can edit a topic months later. Most forums I visit lets you edit about 1 hour and then its up to a Mod to edit it for you.
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Post by captainamerica on Jan 15, 2013 13:01:48 GMT -5
"I think you are correct for Ackermann, but maybe not for bump steer. (I may be wrong) but if you lowered your rack in your drawing 2 inches, but left everything else the same, the Ackermann would still be correct, but wouldn’t you get pretty major bump steer? Just curious." - Joker Joker, If everything was left the same besides the movement of the rack, then yes it would be a serious problem, but you design the problem out of the system by moving the steering attachment point on the upright down as well. Just visualize the double wishbone suspension as a trapezoid (front view) with the four corners being the top and bottom suspension inboard and out board mount points. Then the steering in board (end of the rack) and out board (upright) points just need to lie on the lines that connect the top and bottom points and be relatively parallel with your a-arms.  Paint is the devil, but I have limited tools available at the moment I will add a section to my tech page about this with pictures for better understanding and link to it on here. |
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In answer to the reservoirs being lower that the calipers, I think that it would allow some amount of drain back without some check ball device. In all my years of fab'ing up brakes I have always remote mounted the reservoir higher. I think I remember reading Shelby had an issue on the GT40 or the Daytona Cobra but that was back in 1965ish. 
