MAGracing Forum

Share your MAGracing with the rest of the world, get inspired and enjoy
It is currently Tue 16. Oct 2018 17:38

All times are UTC




Post new topic Reply to topic  [ 4 posts ] 
Author Message
PostPosted: Tue 29. May 2018 18:22 
Offline

Joined: Sun 13. Apr 2014 01:02
Posts: 308
Location: Sedona, AZ USA
I continue to believe that properly designed, produced, and installed plates will provide more reliable and consistent lane changes for experienced as well as newbie racers at any speed, compared to any lane change design relying only on wire. I also continue to believe that the best width of a plate is .16” (4mm) at one end and .39” (10mm) at the other, given that the diameter of the guide magnet is 4mm.

However, I now think that the best length of a plate is dependent upon the steering angle created when the operator turns the wheel on the transmitter/controller. That depends on the steering mechanism used in the car. This realization came to me after Nick Brown asked me how much steering movement I was getting with my chassis which uses an HK-5320 servo mounted between the front wheels. Martin, (aka HeliumFrog) of Magnetic Racing, uses a similar servo mounted between the front wheels.

I did more testing of the car on my track. Discovered that the car would consistently navigate a lane change to the left but would usually miss a lane change to the right. Upon examination of the car, I found that the servo arm moved farther to the left than to the right, when the servo was energized. Then I measured the steering angle created when I turned the the steering wheel to the left. It was about 8 degrees. When turned to the right it was about 4 degrees.

Using basic trigonometry, I calculated the distance between the infeed and outfeed wires needed in order to move the guide magnet 0.22” left or right, when steering angle was 8 degrees. The result of the calculation was 1.57” (40mm). For why I used 0.22” see my post on Wed 4. Jan 2017 19:12 http://magracingforum.com/viewtopic.php?f=5&p=3925#p3925

Note that Wes originally proposed a lane change plate 35mm (1.38”) long with a gap of 5mm (0.20”) between the infeed wire and plate. He suggested gaps of 2mm (0.08”) between the outfeed wires and the end of the plate. That results in a distance of 40mm (1.57”) between the ends of the infeed wire and outfeed wires which is less than the 2.20” that I receommeded. See my post on Sun 8. Jan 2017 16:06.

In the case of my track, the distance between the infeed wire and outfeed wire at the points of lane changes is usually about 2.0” Given that the calculation suggests that only 1.57” is required, I’m not surprised that my car navigates left lane changes consistently with a steering angle of 8 degrees. Note that in the case of Wes’s original car, when the steering wheel on the controller is turned left or right, a steering angle of about 15 degrees is created. With that sharp of an angle a much shorter plate, and smaller gap between infeed and outfeed wires, is needed.

I calculated the distance between the infeed and outfeed wires needed in order to move the guide magnet 0.22” left or right, when steering angle is 4 degrees. It turned out to be 3.15” (80mm). That explains why my car will usually miss right hand lane changes.

It appears to me that the minimum length required for a plate (and corresponding gap between infeed and outfeed wires) is dependent on the steering angle created when the operator turns the steering wheel. I don’t see any significant disadvantage of the plate being 10mm longer than needed.

I would like to hear from forum members who have been experimenting with a car that uses a servo mounted between the front wheels. Would also like comments from those who have been running a car sold by Martin Price of Magnetic Racing. Does the car consistently perform on left and right hand lane changes? What steering angle is created when you turn the wheel on your transmitter? Are you using lane change plates? What is the gap between infeed and outfeed wires?

I am hopeful that I will be able to design and build a chassis that uses an HK-5320 servo mounted between the front wheels which will provide a steering angle of 6 degrees both left and right. If so, such a car should work fine with plates that are 2” (51mm) long with a gap of 2.20” between the infeed and outfeed wires as I proposed Sun 8. Jan 2017. According to the calculation, 6 degrees requires at least 2.1” between infeed and outfeed wires.


Top
 Profile  
 
PostPosted: Wed 30. May 2018 07:29 
Offline

Joined: Mon 9. Nov 2015 11:49
Posts: 153
Location: Norway
Thanks Ned, this was some thorough thoughts.
I'll see what I can find from my cars.

_________________
Racing Regards

Kim K.


Top
 Profile  
 
PostPosted: Wed 30. May 2018 14:35 
Offline

Joined: Fri 21. Dec 2012 17:37
Posts: 310
Forgive me for mentioning this Ned but are you using the steering trim and rate/throw controls on your tx/controller? I find that these are the major improvement over our original controller. I have 3 cars, all tuned to one tx at present and each time I run one, the first thing is to trim the car to run straight (each car is different). There is an area approx. 12" x 50" in the middle of the track where I do this. If the car still doesn't take all the l/cs, it may need a further tweak.
Re. the degrees of movement on the servo arm, these are changed by the rate dial. I prefer more rather than less as this gives greater turning lock for manoevering 'off the wire'. However. I accept that too much movement on the servo magnet can produce less pull on the steering arm'
I still have one car with the forward servo and two with mid mounted ones. Still not sure which is best but car No 4 will be mid mounted.
Re. l/c plates, I have tried differing sizes and shapes on my new track but still favour the 4mm x 35 size. My theory for the max. width of 4mm is that, firstly it works well and secondly, the car will definately take one or the other wires. If the out wires are spaced further apart, I think the steering magnet could go in between them. On faster sections of track, some further encouragement may be required and I usually just cut a little off the 'in' wire using a small carborundum saw (see photo)
Photo is of one l/c on my new track which is working well with the 4 + 35 + 4mm gaps. Occasionally the 'in' and 'out' wires are not perfectly aligned. Check with a straight edge and tweak slightly if necessary.


Attachments:
DSCF0585 (640x446).jpg
DSCF0585 (640x446).jpg [ 190.34 KiB | Viewed 672 times ]
Top
 Profile  
 
PostPosted: Thu 31. May 2018 02:18 
Offline

Joined: Sun 13. Apr 2014 01:02
Posts: 308
Location: Sedona, AZ USA
Thanks for the feedback Wes. I had adjusted the trim and rate/throw controls on my tx/controller so that the car would track straight without any steering input and with the rotation of the servo arm left and right set to maximum. Your comment got me thinking. What if I adjusted the trim so that it would track slightly to the right (on a table top or smooth floor) with no steering input? After doing that, I discovered that with the turning of the wheel on the transmitter, the steering angle would go to about +5 degrees (left) to -5 degrees (right). For the definition of steering angle I’m using see
http://street.umn.edu/VehControl/javahelp/HTML/Definition_of_Vehicle_Heading_and_Steeing_Angle.htm

Then I tried the car on my track. To my surprise, the car ran much better. As before, it consistently executed left lane changes and usually navigated the right lane changes successfully. A big improvement. In the process of troubleshooting the problem, I discovered that the slot in the tie rod for the pin attached to the end of the guide arm was just a little too wide. (0.007” too big to be exact.) That slop allowed the steering angle to change about 1 degree without any movement in the guide arm.

My newest version of chassis kit CK8 will eliminate that slop. It also will locate the servo about 0.030” to the right. I discovered that the servo was off set too far to the left in the prior version. I’ll also raise the servo higher which will require a longer servo arm to hold the magnet. The end of the longer arm will swing farther left and right, which should increase the steering angle when the wheel on the transmitter is turned. With those changes I’m confident that the chassis will perform well on my track, and most existing magracing tracks.

Concerning l/c plates, I’ve decided now that there is no advantage to having the l/c plate 0.39” wide at one end. I’m planning to go with a plate that is 4mm wide at one end and 8mm (0.31”) wide at the other end. Ideally for a plate of that shape, the 4mm diameter guide magnet would shift 4mm left (for a left hand l/c) or right (for a right hand l/c) while traveling above the l/c plate. Assuming a 5 degree steering angle, that requires the distance between the infeed and outfeed wires to be at least 1.58”. For safekeeping I plan to make future l/c plates 2” long with very little gap between the end of the l/c and the infeed and outfeed wires. I also plan to have a space of 4mm between adjacent outfeed wires. I don’t see how a 4mm diameter magnet could shoot a gap of 4mm (.16”) between adjacent outfeed wires. But as Wes pointed out, perhaps the guide magnet could pass between the outfeed wires if they were .22” apart as I proposed yesterday.

As I understand Wes’s comment, he is using rectangular l/c plates that measure 4mm x 35mm with 4mm gaps between ends of the l/c plate and the infeed and outfeed wires. That implies a distance of 35 + 4 + 4 = 43mm or 1.69” between infeed and outfeed wires. With a steering angle of 5 degrees, 43mm is enough to allow the guide magnet to shift 3.8mm (0.15”) left for left hand l/c or the same right for right hand l/c.


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 4 posts ] 

All times are UTC


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB® Forum Software © phpBB Group