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Post by captainamerica on Jan 15, 2013 14:37:37 GMT -5
"I do have another question, if you are looking at the rack from the top of the vehicle, does moving it forward or back change the amount of Ackermann? I was thinking when I drew this stuff up I could change the amount of Ackermann by moving the location of the rack forward or backward in the chassis. It's been awile since I played around with this stuff, so I'm just going off memory. Does that make any sense? Thanks for your input." -Joker
The simple answer would be no, rack position front to back will not change the amount of ackermann you get by enough to make it useable. The bigger the angle is between the rack and the steering tie rods (from both the top and the front view, combined) the less motion the wheels will make for a given driver input. What you will get is less wheel motion as a whole, which you will then solve by shortening the distance from the upright castor line to the steering point. But at that point your just chasing your own tail.
So I was wrong here, After drawing a sketch in CAD and playing with it for awhile it is possible to adjust your ackermann a reasonable amount by moving the rack front and back, I learned something new today. But there are two catches, one is that if you move out of parallel you will lose some steering motion, and the other, more important one is that the angle between your tie rod and your upright needs to be acute (<90) to increase ackermann and obtuse (>90) to decrease it assuming a fixed angle at the wheel.
Which explains a strange phenomenon that I was seeing in my steering system where the inner wheel turns less then the outer, or the opposite of what I want. This is caused by the fact that my rack is forward from the upright making an obtuse angle and decreasing my ackermann. Racecars use reverse ackermann to changes the slip angle of the tires in extreme cornering so this may not be a bad thing, but understanding whats going on is huge. My solution seems to be decreasing the angle of the steering arm on the upright.
Thanks for asking that question Joker, my mind has been blown for the day, and I am still trying to understand why it works.
Pictures to come.
Also a comment to Ralf, I get what you were saying in your comment now, I couldn't tell what you were trying to say when I first read it and looked at the picture, now I get it.
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Post by captainamerica on Jan 20, 2013 22:01:11 GMT -5
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Post by captainamerica on Feb 14, 2013 2:27:31 GMT -5
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Post by captainamerica on Feb 14, 2013 2:41:51 GMT -5
February '13 I have been working on a lot of different designs; collapsible steering column, front sway bar, steering wheel quick release, gas tank, intake manifold, pedal assembly. But the most important one was the front upright/wheel bearing system which now has a solution that I might feel safe driving unlike before. I was originally using standard ball bearings, my room mate was nice enough to point out that they can't take thrust loads, so after a lot of headache I now have two tapered roller bearings with oil seals to keep the grease in, the whole system is cheaper at $70 per wheel versus $100 which is nice. I also changed to a wilwood off the shelf rotor hat to simplify the brake design, however their minimum offset is larger then i would like so it makes my spindle a bit longer then I wanted. I drew up an interesting looking intake manifold which incorporates the holes around the drivers head for anyone who was wondering why those were there. A canopy solution will render this useless but it looks good for the moment.    |
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Post by Liteway on Feb 14, 2013 12:15:04 GMT -5
Love seeing your postings Captain.
This thing looks very stout.
With all the tubing triangulation going on, couldn't you use unstressed aluminum bulkheads and save lots of weight?
This maybe a moot point if you go with an enclosed canopy, but otherwise those induction intakes will be a noise problem even with a helmet and ear plugs. I speak from experience.
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Post by DaveJ98092 on Feb 14, 2013 13:28:40 GMT -5
I agree with the sound issue. NOT trying to start a "LOUD PIPES SAVES LIVES" war but in my many years riding loud bikes and cars, the louder the noise = the shorter the trip before you get exhausted. I have done a few "Saddle Sore" 1000 mile rides and did one 1500 mile trip in 24 hours on a super quite Kawasiki LTD305. The noise wears on ya. Back in the DAZE (70'), I rode a loud 1200 Sportster. After 200 miles I was ready to take a nap break. On my current Suzuki Burgman 650 Scooter I have done 1000 miles only stopping for Gas/Food/Pi$$ing. At the end of 1000 miles I have to stop for my fellow riders as they are DONE.
In my last racecar I spent extra time and weight on using a noise reduction liner on the floor and firewall. We were alloded to run with almost open headders, a 4 inch glass pack muffler was all required. But I went the extra step to put a MagnaFlow muffler on and shoot the exhaust out the back.
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Post by stretchmobileski on Feb 15, 2013 22:40:11 GMT -5
 Yours are much nicer than mine. However, I bet I have you beat on the price. Nice machinery, too bad about the problems. Once you get them worked out you'll be sittin' pretty. I do have friends with much nicer equipment. These are so I can do simple things quickly and not have to run to my buddies shop for everything. |
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Post by captainamerica on Feb 16, 2013 0:02:31 GMT -5
It is true I could use aluminum bulkheads and body panels, but this is a first run through on the chassis and I am trying to keep it simple, riveting in all those panels would be a pain i think. I opt to simplicity over weight at the moment because the idea is to have a total weight over 900 lbs so that when I put the canopy on I don't need a helmet (CA vehicle code). There is also a new chassis design in the works for my second version if I get that far, its my fifth revision and it should make manufacturing easier, but I really need a fab table to do it correctly, currently the whole thing is best effort with calipers and tape measures.
I haven't had the time to do anything with the new chuck or test it, that's for next weekend, but the old chuck you could visibly see the part wobble, I have used three jaws before and this was the worst I had ever seen. I can handle .003" off, and I have a 4 jaw to do the closer stuff.
I hadn't really thought about the intake noise, I'll keep that in mind, this was just a mock up to fill space really. I don't expect the exhaust noise to be a huge problem considering its the stock exhaust off the bike, which has to meet the vehicle code standards.
That shop in the picture actually has both an old sheldon lathe and a mini mill owned by the building owner, they are both in disrepair, needing new belts and a lot of clean up, the sheldon didn't have a foot brake and its power switch is on the far side of the chuck neither of which I was a fan of.
As far as cutting all the tubing, I always started with the tubing notcher. But yes some of the angles are too extreme for it, I actually measured the angle ticks on the notcher and marked on three more to take me out to 75 degrees at max instead of 60 which helps a lot but I have to be more careful with how fast I cut at those angles. I clean all my cuts and welds up with flapper wheels, they are far superior to grinding wheels in my opinion.
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Post by mtntech on Feb 17, 2013 12:36:27 GMT -5
Nice progress. What size is your tubing?
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Post by captainamerica on Feb 17, 2013 13:50:10 GMT -5
The front chassis plate is now tacked onto the car and the steering rack is there. I also got around to purchasing the 1-14 thread die i needed to finish the engine mount tubes with lock nuts, turns out .065 is going to be to thin so I am stepping that up to .095 or .120 depending on what the OD of mount bolts allow. The gauge cluster panel and cover are cut and bent and now need to be fitted to the frame. I also cannibalized the GSXR gas tank for the pump flange and the fill flange, even though I had flushed the tank with water there was definitely some hesitation on my part the first time I hit it with the plasma cutter. The first cut and bent gas tank came in, to heavy and incorrectly designed by me but it will act as a good mock up article for the future one made of thinner stainless steel and TIG welded at a shop.
All the tubing on the chassis is 1-1.5"x0.065-0.095 depending on how structurally important I thought they were. A-arms, push rods, and steering tie rods are 3/4"x0.120
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Post by fredvv44 on Feb 17, 2013 20:53:59 GMT -5
"I do have another question, if you are looking at the rack from the top of the vehicle, does moving it forward or back change the amount of Ackermann? I was thinking when I drew this stuff up I could change the amount of Ackermann by moving the location of the rack forward or backward in the chassis. It's been awile since I played around with this stuff, so I'm just going off memory. Does that make any sense? Thanks for your input." -Joker The simple answer would be no, rack position front to back will not change the amount of ackermann you get by enough to make it useable. The bigger the angle is between the rack and the steering tie rods (from both the top and the front view, combined) the less motion the wheels will make for a given driver input. What you will get is less wheel motion as a whole, which you will then solve by shortening the distance from the upright castor line to the steering point. But at that point your just chasing your own tail. So I was wrong here, After drawing a sketch in CAD and playing with it for awhile it is possible to adjust your ackermann a reasonable amount by moving the rack front and back, I learned something new today. But there are two catches, one is that if you move out of parallel you will lose some steering motion, and the other, more important one is that the angle between your tie rod and your upright needs to be acute (<90) to increase ackermann and obtuse (>90) to decrease it assuming a fixed angle at the wheel. Which explains a strange phenomenon that I was seeing in my steering system where the inner wheel turns less then the outer, or the opposite of what I want. This is caused by the fact that my rack is forward from the upright making an obtuse angle and decreasing my ackermann. Racecars use reverse ackermann to changes the slip angle of the tires in extreme cornering so this may not be a bad thing, but understanding whats going on is huge. My solution seems to be decreasing the angle of the steering arm on the upright. Thanks for asking that question Joker, my mind has been blown for the day, and I am still trying to understand why it works. Pictures to come. Also a comment to Ralf, I get what you were saying in your comment now, I couldn't tell what you were trying to say when I first read it and looked at the picture, now I get it. here is an excellent article on this subject. it explains what happens when you move the rack in every direction. (srx660) This link has changed so i am putting in the newest link from woodward stering. woodwardsteering.com/PDF/tech%20section%20guide.pdfdownload the article "basic rack and pinion tech" it's free. Fred V |
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Post by captainamerica on Feb 18, 2013 1:29:40 GMT -5
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Post by stretchmobileski on Feb 18, 2013 11:31:39 GMT -5
I don't know if you are aware of these nifty little tilt steering units. Makes your steering set up much more convenient. Available in left or right release, raw, powder coated and chrome. Sandrail suppliers for under $100.  |
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Post by captainamerica on Feb 18, 2013 17:23:20 GMT -5
Its a decent design, but I am not sure how I would fit that into my setup. I built the steering system to be at the "right" height and angle, which I found out last night is slightly too low for me to see the top of the tachometer. Such is life with an 11" steering wheel.
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Post by captainamerica on Mar 2, 2013 1:25:02 GMT -5
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Post by hydrojim on Mar 3, 2013 11:22:55 GMT -5
Really liking how this is turning out. Have you thought about trying a different size or style steering wheel?
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Post by captainamerica on Mar 4, 2013 1:02:46 GMT -5
There was a lengthy discussion about the options for the steering wheel, at the moment the best one is using a yoke type with the top cut out so that at least when you're going straight the top of the tach is visible. I got my first parts off the new lathe finally, still working on the proper feeds and speeds needed to get a nice surface finish but I did pretty well I think. The rear shock is now mounted and I have both swing arm mounts ready to go, one is tack welded the other just needs to be, and then I am going to mount the rear wheel. I was surprised how well my simple jig worked for making the swing arm mounts, I didn't have time to take a picture of it today but it will be up later this week. I also spent a lot of last week upgrading my design to include the new wheel bearing design and new a-arm design. Next up is the pedal box which has been on the back burner to long. I ordered and received all the rocker bearings, main wheel bearings and seals, and the steering column bearings. Another small thing to note, the engine mount design was changed to incorporate one piece clamps instead of 1-14 lock nuts. Its simpler and the threads that I tried to cut for the initial design look like crap.     Question out to the forum, has anyone used paddle/button shifters to replace shift lever and linkage? I found some decent all electric ones in Europe that run about $700 with two buttons on the steering wheel and can even be linked to an auto ignition kill during shifts to allow for clutch less up-shifting. I don't think there is room in my cockpit for the shifter and I didn't want one to begin with so I am looking for an alternative. www.kliktronic.co.uk/home.htmwww.flatshifter.com/ |
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Post by captainamerica on Mar 6, 2013 17:45:21 GMT -5
The swing arm has been mounted successfully, one wheel down, two to go.
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Post by Liteway on Mar 6, 2013 19:49:21 GMT -5
Lookin' good Captain. Love to watch your progress.
What's up with the thick steel hood over the instruments?
Couldn't find some boiler plate somewhere?
How did you bend that stuff anyway? I screwed up my 40 dollar Harbor Freight sheet bender on .080 aluminum. They said .050 was the limit but I didn't believe them.
Careful with that beautiful but fuzzy MOMO. Sooner or later you'll forget you have grease on your hands.
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Post by captainamerica on Mar 7, 2013 22:45:45 GMT -5
Haha I have a good friend who works at an industrial metal shop. I like the feeling of rigidity in my parts and you use that to hop in an out of the vehicle. Beyond that I bought a sheet of 12 gauge to use for the body panels and the gauge cluster pieces just got put on that as well.
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