R/C Tech Forums

Go Back   R/C Tech Forums > General Forums > Electric On-Road

Reply
 
Thread Tools Search this Thread
Old 11-05-2008, 05:19 PM   #361
Tech Elite
 
Join Date: Aug 2002
Location: Houston, Texas
Posts: 3,777
Trader Rating: 27 (100%+)
Send a message via AIM to John Stranahan
Default

Dual A-arm Front Suspension Wide Pan
I cut a second cross plate for the front dual A-arm suspension to correct, wheelbase, Servo linkage angle, shock clearance, and caster. Here are a couple more pics. There is great clearance for the steering links now. They are perpendicular to the chassis now. I won't have to Dremmel any red to get shock clearance. I improved my procedure at the little drill press to achieve better hole location. I'll mention this as this graphite is difficult to drill a straight hole that is located where you started the drill point. I used a small $60 drill press at the highest speed.

I used a fat center drill. The shaft is 3/8 inch then tapers to a short 1/4 inch long .114 drill. It has a countersink built in, but I have the wrong angle on it so I use a 6 blade 82 degree counter sink which does nice work. Even the center punch does not like to go in straight. I layed the project out with a compass and ruler which is all the accuracy you will need (and all the accuracy you are going to get without a highspeed CNC router). I center punched with a starrett automatic punch. Locate the hole by lowering the fat center drill into your punch mark. Clamp the work. Drill, then start the countersink if it needs one. Without moving the work, change the bit to the countersink bit. Countersink until it looks as wide as the screw head. When you are finished drop a screw in the hole and then recountersink until the head is flush with the work. You can do this last procedure after removing the tape or sticker drawing from the graphite. This plate came out better than the last. You always find some little thing that can be improved. If I were making it again I would move the lower A-arm mounts about 1/16 inch back to have a wider range of casters available.
Note there are more accurate ways to layout and drill a project on metal. The drilling wander is such a problem on graphite and fiberglass, that it makes the method I used good enough. Those hourglass standoff, because they have a hardcoat do not drill straight either. You need to drill both ends toward the middle and then tap #8 x 32 from one end only.

If anyone would like dimensions I can put some on the drawing. It's only a few hour project including drawing it up.

A CRC based, low, dampened, dual A-arm front suspension suitable for 1/10 pan. The center to center distance between the large #8 holes on my Pantoura chassis was 3.0 inches.
I dont plan to use this front end on the oval, although it is very good indeed there.

Last pic: Front suspension ready for a test. It only needs some caster spacers. Roll center came out good. Low. Upper arms can be shimmed up on the inner pivot to lower roll center. Lower arms can be deshimmed to raise the inner pivot to raise the roll center.
Attached Thumbnails
CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-front-suspension-crc-based-006.jpg   CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-front-suspension-crc-based-007.jpg   CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-crc-based-front-suspension-schematic.jpg   CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-front-suspension-crc-based-finished-002.jpg  

Last edited by John Stranahan; 11-13-2008 at 11:56 PM.
John Stranahan is offline   Reply With Quote
Old 11-07-2008, 03:54 PM   #362
Tech Elite
 
Join Date: Aug 2002
Location: Houston, Texas
Posts: 3,777
Trader Rating: 27 (100%+)
Send a message via AIM to John Stranahan
Default

There were 120 views since my last post. Thanks. there is one new pic and some new red text up above. The dual A-arm suspension is ready for a test.


CRC based ruggedized strut front suspension
Long arm suspension
I received a few more parts which allowed me to assemble the finished version of this suspension which I showed previously. I have added CRC part #3277, $14.99. This allows the use of uncut upper A-arm and plastic rod end.

There is a geometry change with this addition. Mostly it changes it to what CRC calls the long arm suspension. The upper arm is longer than the prostrut upper arm. It is equivalent in length to the Associated suspension. This makes a slight change to the camber curve which some people including some team drivers prefer. It is a tuning option for this suspension as well as the Prostrut suspension which accomplishes the same task with the 3277 Graphite brace and long upper pivot balls. There is also a small change in roll center as the inner hinge pivot is moved up the height of the little graphite plate. The roll center is lowered slightly on a road car. The plate requires you to remove and sand the center brace out of the part for 1/10 scale use.

The machined delrin steering blocks are a 1/12 scale part. They should work the same as the associated part as far as ackerman goes if you can slide that servo a bit farther forward to get steering links perpendicular to the chassis. If you cannot use the Associated part which has another set of holes and longer arms.

That is a really nice looking and very rugged front suspension. I repeat the parts list here for convenience.

Optional CRC Ruggedized Front End (lighter or stronger parts in parenthesis)

1 CRC 1244 Upper Pivot, Upper A-arm Pivot 2.50
1 CRC 1251 Steering Block Front End, Traling Axle 1.99
(1 CRC 4277 Machined Delrin Steering Blocks, Trailing Axle 12.99)
1 CRC 1235 Steel Trailing Axles, 1/8 inch diameter 4.99
(1 CRC 4115 Trailing Titanium Stub Axle 14.99)
1 CRC 3246 Low Profile Plastic Pivot Balls 4.99
1 CRC 1252 Steel 6 x 32 front turnbuckle for Upper A-arm 4.99
(1 CRC 4274 Titanium 6 x 32 front Turnbuckle for Upper A-arm 5.99)
(CRC 3277 Cross Brace, Graphite, to eliminate cutting upper arms $15)
2 Associated 8425 King Pin Shim (10) 1.45 2.90
1 Losi A6088 1/8 x 1.246 inch TiN coated Hinge Pins for long Pan
Car Kingpin $5.95
(or Lunsford 3066 XXXT-MFT Hinge Pin Set Titanium 24)
4 Avid RC Flanged 1/8 x 5/16 bearings for 1/8 axle Front Wheels 1.00 4.00
(4 CRC 12481 Flanged 1/8 x 5/16 bearings for 1/8 axle Front Wheels $3.49 13.96)

Subtotal minimum aproximately $32, Maximum with all titanium and Delrin $107
Attached Thumbnails
CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-front-suspension-battle-axe-finished-001.jpg  

Last edited by John Stranahan; 11-07-2008 at 07:10 PM.
John Stranahan is offline   Reply With Quote
Old 11-08-2008, 01:43 AM   #363
Moderator
 
Pro ten Holland's Avatar
 
Join Date: May 2003
Location: Druten/Holland (Europe)
Posts: 1,677
Trader Rating: 1 (100%+)
Default

Quote:
Originally Posted by John Stranahan View Post

There is a geometry change with this addition. Mostly it changes it to what CRC calls the long arm suspension. The upper arm is longer than the prostrut upper arm. It is equivalent in length to the Associated suspension.
This geometry issue is why I changed back from the CRC pro-strut to the Asso front end.
The Asso front end gave me less steering on corner entry (which scrubs less speed) and gives less mid-corner understeer. The car also became more predictable on corner exit.

I have tried several caster setting and springs on the CRC front end, but the car immediately felt better with Asso front end.

As far as I can see, the Asso front end was originally deigned for 10thscale use and then adepted for 12th scale cars (the 12th scale version has shorter king pins and springs, but the lower arm are too tall to run small 12th scale tires without modification).
The CRC front end seems to be designed with 12th scale in mind. The short upper arm geometry seems to work best on narrower cars. (12th cale and 200mm).

Most drivers that use the CRC front end on their wide Pro10s here use the long suspension arm upgrade or that reason.
Pro ten Holland is offline   Reply With Quote
Old 11-13-2008, 06:30 PM   #364
Tech Elite
 
Join Date: Aug 2002
Location: Houston, Texas
Posts: 3,777
Trader Rating: 27 (100%+)
Send a message via AIM to John Stranahan
Default

Pro-ten--Thanks for the front end report. I guess I'll go with long arm suspension first.

There seemed to be high interest by a couple of fellows over at Hobby talk and by private message after our test and tune session with the Custom Works Aggressor Slider. The gist of the concerns can be summarized as follows.

How dare I: (this should precede each phrase)
Use a $10.00 wing and mount instead of the less effective $50.00 oval wing and mount.
Take off right rear wheel offset and right rear steer from a car at my track when it was working fine at the sellers track.
convert a road car to oval.
use a velodrome car on a flat track.
Push the oval envelope with a custom car.
Use left rear steer at anytime.
Report progress of the prototype “Sidewinder” car on the Web.

A string of insults followed including insults of our track that they have never visited and then a dual at 20 paces was suggested. The only helpful suggestion was that we square up difficult cars and add a little left rear wheel positive offset at our track. Interestingly that is exactly what we did to the Custom Works Aggressor Slider

Since there was such heightened interest in the Custom Works test and tune, I proceed with the following Test and Tune Session. Also in the heat of battle I may have forgotten to mention that the last full size vehicle for consumers that I remember that is hinged in the middle (articulates in bump) is the Connestoga Horse Drawn Wagon from the 1800's. As I was accused of bringing F1 tech to oval, maybe just a tiny bit more tech is in order.



Woods Racing X15 200 mm Oval Pan Car

This car is interesting in that it uses a T-plate, but not in the typical sense. See Photo Two. There are two pivot balls along the length of the chassis. The tweak screws (being redundant with the side springs) are not used. Note that there are also three pivot balls on the leading edge of the pod. The springing of the T-plate is avoided completely in bump and the task taken over by the center spring. This is interesting in that this may be the precursor to the center pivot link car design as one might look at all this and say why do we need a T-plate at all when all the functions are taken over by the 3 shock setup and pivots.

The first thing I did was squared up the car. The right rear is at 103 mm for unknown reasons. It appears that although the pod is slightly offset left on the T-plate that it is not a typical offset pod car as when it is squared up there is considerable space between the pod and the left wheel. The pod is quite narrow though which may be fooling me a little. The right hand hub is the same length as my 190 mm Pantoura.

Anyway I have put in a little left rear wheel positive offset as this has proved helpful for everyone that has tried it at our track.

In looking at the front wheels, they are placed at the moment symmetrically about the cars center line, but the width at the front is only 190 m. There is a position to move the right front wheels out 10 mm. (Hmmm this is going to give me some left rear steer if I try it.)

Second task was to free up all those pivots. With all shocks removed the motions were gummy. I took them apart; the pivot balls were shiny and smooth, so I just cleaned the sockets with charcoal lighter fluid and put them back together. The friction of the back pivot balls is carefully fine tuned with the 4-40 locktnuts. Too tight and they freeze up.
Trailranger should get a kick out of this car as he suggested something similar at the back end of the T-plate.



Last pic shows the LiPo adaptor I added. This way I can use two strips of tape on the pack sideways. If needed, the traditional long wrap can be used as well for an important race or series. That pod top plate fit the brushless motor really well.

John
Attached Thumbnails
CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-woods-racing-x15-001.jpg   CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-woods-racing-x15-003.jpg   CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-woods-racing-x15-006.jpg   CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-woods-racing-x15-lipo-holdown-002.jpg  

Last edited by John Stranahan; 11-14-2008 at 11:51 AM.
John Stranahan is offline   Reply With Quote
Old 11-13-2008, 11:50 PM   #365
Tech Elite
 
Join Date: Aug 2002
Location: Houston, Texas
Posts: 3,777
Trader Rating: 27 (100%+)
Send a message via AIM to John Stranahan
Default

Woods Racing X15 Oval Car

The electronics install went well. I placed the speed control on a .25 inch tall polypropylene plastic block to clear the T-plate. It fit nice like that. Ballast will probably be required so the extra weight of the block is not a problem. I probably will put ballast behind the battery where newer cars put the speed control. Maybe a small test tomorrow. I plan a full set of runs or a race on Sunday.


CRC based Dual A-arm suspension
I had a good long session trying to tune in this suspension. I had problems. I traced the problem to insufficient clearance with the wheels at full lock. The suspesion would ride ontop of the steering link and more or less become rigid. Steering was poor.
I relocated the servo a little farther back and extended the steering arms one hole to give the links more clearance. A very short test today showed my steering was back. Now another session to tune it up. I'll post a new pic later. I also added a tubular brace between the lower A-arm mounts to make them more rigid in controlling caster. I beefed up the A-arms with a triangular wedge to extend the A all the way out.

John
Attached Thumbnails
CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-woods-racing-x15-electronics-install.jpg  
John Stranahan is offline   Reply With Quote
Old 11-15-2008, 04:57 PM   #366
Tech Elite
 
Join Date: Aug 2002
Location: Houston, Texas
Posts: 3,777
Trader Rating: 27 (100%+)
Send a message via AIM to John Stranahan
Default

I'm giving this a post to itself because its tricky

Front Wheel Offset & Rear Steer

A lot of chassis these days are coming with the ability to offset the front wheels in fairly small increments. Some of the newer models can offset either wheel out or in in small increments. This is one thing that is happening when you try an asymetrical offset; that is one front wheel is farther from center than the other.

First lets say that the rear axle points in the direction of its forward thrust. In other words it points to the center front on a square symmetrical car. In the photo imagine the right hand wheel in the left set of holes. In this position the car is 190 mm wide at the front. Each wheel is half that distance from center or 95 mm. The center is clearly that center body post. The rear axle points directly at that center post.
Now one of the changes I made to the car before my tuning session was that I made the car long (for mod, to keep the front wheels down) and moved that right front wheel out the allowed 10 mm to the next set of holes. This moves the center of the front of the car to the right by 5 mm. In other words a spot 5 mm right of the center post is now 100mm from each front wheel.
The rear axle is still pointing at the center body post. It points to the left of center now. It is giving me left rear steer. How much. Well its arc tan 5/270 or 1 degree where 5 is the distance the center of the car moved and 270 is the wheel base and arc tan is inv tan on most calculators.

I don't have a choice of right rear steer on this chassis.

I am beginning to think some differences in our tuning is the power plant in the car. I say this because I was invited to a dual with stock motors. The battery was not mentioned. One of our 4 cell 13.5 cars was able to drive at full throttle all the way around the track under some conditions. Naturally you are not going to have corner exit issues as the car has been near full throttle for the whole turn. We are running 13.5 LiPo now or six cell equivalent.

The point of this post is just to show that when you offset just one front wheel you are throwing in some rear steer. I do wonder why this world champion's company only offers left rear steer. Maybe its because it is six cell and could have had more power.

polite comments welcome.

track report to come

John
Attached Thumbnails
CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-woods-racing-x15-front-end.jpg  

Last edited by John Stranahan; 11-15-2008 at 05:51 PM.
John Stranahan is offline   Reply With Quote
Old 11-15-2008, 05:21 PM   #367
Tech Elite
 
Join Date: Aug 2002
Location: Houston, Texas
Posts: 3,777
Trader Rating: 27 (100%+)
Send a message via AIM to John Stranahan
Default

Woods Racing X15 First Test and Tune Session
Well this is not the first time around this track in a similar car. I had Rick's early model Battle Axe early in the thread. Since this Woods car is really a center pivot car without side links it should have tuned up pretty similarly.

This is what I did for an initial setup.
The car was extremely light. I needed 4 ounces of ballast to make it 43 ounces. I put a machined brass weight as far left and back as possible as this helps with corner exit issues and reduces the tension needed from the right rear shock collar.

I liked about 12 ounces of left downtweak on the battle axe. I put the rear of the car on the scales and used the right rear spring to put a 12 ounce excess on the left rear. I only moved the collar slightly. I call this adding left downtweak.

I made the front wide to 200 mm or gave the right front 10 mm positive offset. (This is subtle code for adding 1 degree left rear steer. See the post above)

I had #5 red springs on the battle axe. I thought I should try green 6#, but had none in stock. I left it with red and it drove well. I got in some greens now, so I started with those on the Woods Racing X15.

I went car level. Pod with 2 mm droop when held in the air. About 5 mm ride height.

I tried a popular set of front tires. GRP pink left front and GRP Purple right front.

I suspected I would still like XXPink/Purple rears so I started this set on both rears.

I chose a long wheelbase because it helps hold the front end down in mod. I suspect front end lift is responsible for our corner exit loops.

I had 3 mm positive offset already at the right. The most I could give the left and still fit the body well was 7 mm. That gives me 4 mm extra of left positive offset compared to the right. Rear width is 210 mm now.

Center spring was supple and had medium oil. That's what I prefer.

Side springs were on the stiff side and had very viscous oil. I left them alone. These last two items affect handling but not to the extend of those that precede them.

Test Session
Well the car was very good. I could drive it well. I could give it good throttle on the straights. I was reaching my full throttle points. The car was a little bit bouncy over the bumps in the front.

I had no red springs as they went to New York with Ricks Battle Axe. I put on 4 # whites from Windtunnel. Now I had a bit too much steering traction which was evidenced by more rear drift. Jimmy gave me some reds and that was perfect again.

Now I did some tire test.
I put on a pink left rear. This is what I noticed. I had to roll on throttle a little slower as I was getting occasional wheel spin. I put the XXPink back on the left rear and the problem went away. Now it could be in fact that the xxpink/ purple spin also but when they do the car does not dart around as the traction is even on both sides so your car is not upset.

I put on XXPink fronts on both sides (a change from pink left and purple right). My custom car likes this. This car did not and ceased to steer. I put the pink left and purple right fronts back on.

Nice session. The car looked quick. I'll have some competition tomorrow.


Inerter
This car came with a buddy in the form of a pile of parts in a box. I have it mostly assembled from spares. Jimmy helped me out by selling me some really nice shocks cheap. I plan to use this car as a test mule to test the inerter on a road car. I have no plans to use the inerter on the oval as the cars are not lacking rear traction at our lower speeds on the flat oval.
John
Attached Thumbnails
CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-woods-racing-x15-ballast.jpg  

Last edited by John Stranahan; 11-17-2008 at 10:43 AM.
John Stranahan is offline   Reply With Quote
Old 11-16-2008, 07:23 PM   #368
Tech Adept
 
Robertw321's Avatar
R/C Tech Charter Subscriber
 
Join Date: Aug 2002
Location: Parma, Ohio
Posts: 105
Trader Rating: 1 (100%+)
Default

John,

I think I see the misunderstanding in the rear steer discussion.

If I have read your posts right, your front and rear axles are still parallel and the center lines of the axles are offset from the centerline of the chassis. I know my Woods car does not have what we would call a rear steer option.

In what oval racers call rear steer, the rear axle is not parallel to the front with the left side wheelbase being slightly shorter than the right.

What you are using we just call offset. We use it, both right and left, all the time.

I think simple terminology differences are causing the confusion.
__________________
Bob Williams
Robertw321 is offline   Reply With Quote
Old 11-16-2008, 08:26 PM   #369
Tech Elite
 
Join Date: Aug 2002
Location: Houston, Texas
Posts: 3,777
Trader Rating: 27 (100%+)
Send a message via AIM to John Stranahan
Default

Bob- I agree that on my Woods car I have just used offset. I moved the right front out 10 mm. On my custom car the 3-link "sidewinder" the axles are not parallel there is definitely left rear steer. Also on my custom car there is left rear positive offset. On the custom works Agressor slider as received, the axles were not parallel there was definitely right rear steer and right rear positive offset. I believe, I have used each term rear steer and rear wheel offset properly and they are used the same as you describe.

Now the Woods car. Even if all I did was give it 10mm positive right front wheel offset, the results are equivalent to 1 degree left rear steer, even though I have not touched the rear. I can put the car on the setup board and measure this angle. An explanation is in a post above. No doubt Nascar teams are tinkering with this front offset to get some yaw in the car as the rules at the rear have been tightened and yaw (or crabbing) has been found to be beneficial.

Pic shows axle at angle to the car center line causing left rear steer. The controversy is that some people believe that left rear steer should never be used. Some others believe you should never tinker with an assembled oval car as delivered new or used.


John
Attached Thumbnails
CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-lipo-13.5-resized.jpg  

Last edited by John Stranahan; 11-27-2008 at 11:45 PM.
John Stranahan is offline   Reply With Quote
Old 11-16-2008, 08:47 PM   #370
Tech Elite
 
Join Date: Aug 2002
Location: Houston, Texas
Posts: 3,777
Trader Rating: 27 (100%+)
Send a message via AIM to John Stranahan
Default

Woods Racing X15

Note there is a prototype Woods car on Ebay for $503.

I had good luck With the Woods car. The only change I made was to ride height. I was rubbing the right rear corner of the chassis. Turn in was excellent. Cornering speed good. Manners on the Straight were outstanding. I could rocket out perfectly straight, make my diamond raceline with ease on the near side. Corner speed is slightly lower than the 3-link "sidewinder", but that was known ahead of time. I could make rapid progress on the other cars that showed. The only thing I touched up was to reset left downtweak to 12 ounces after the first session. This helped eliminate completely just a tiny bit of corner exit problems.

Custom Works Slider
JG had the custom Works car really flying today. He made a couple more changes. We took out a spacer from under the front of the T-plate that could be used for a high center pivot. He also installed an aftermarket Finish Line med steel T-plate replacing what looked like a light black fiberglass T-plate. These two changes got him completely under control. We were only close before.

We are having some problems with the sliding parts of the car (battery tray, front bumper) sliding in an accident and disabling or causing poor driving afterword. I suggested steel screws could be made tighter.

Inerter (inertia device)
We discussed the Application of an inerter to a center shock RC ROAD car previously. The purpose of the device is to better tune the suspension so that it responds to bumps in a better way. It keeps the tire contact pressure more even. The more even the pressure with which the tire touches the ground, the more traction there will be. The goal is to pick up a few MPH on a bumpy straight of a big off-road track. And also just to gain knowlege of what the device is. LiPo 3.5.
Well, here is the device installed. It is a servo with out power or electronics or brushes. Basically a geared mass (the inertia). The suspension feels reallly interesting. It has some "inertia to it" if you bend the pod down it coasts a little bit and then returns. That is the goal. The ratio and leverage may be in a zone of usefulness when I feel it with my fingers. Now this is a road car. The reason it is, is that it will be driven on a road course. The weight will be evenly balanced left and right. Yes it was originally an oval chassis. There is less difference than some people think.

last pic: Woods Prototype oval car. This is not a velodrome car from the appearance of the battery location. The front end is similar to a 1978 bronco solid axle front end with radius rods extending back from the axle.

John
Attached Thumbnails
CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-inerter001.jpg   CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-inerter-installed-001.jpg   CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-inerter-installed-002.jpg   CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-woods-prototype.jpg  

Last edited by John Stranahan; 11-17-2008 at 10:47 AM.
John Stranahan is offline   Reply With Quote
Old 11-17-2008, 10:07 AM   #371
Tech Master
 
pejota's Avatar
 
Join Date: Apr 2008
Location: Vero Beach, FL
Posts: 1,022
Trader Rating: 12 (100%+)
Default

As always, lots of great reading. I always feel smarter after reading your posts, John.

That Prototype looks interesting, but how much does it weigh? Holy smokes there are a lot of parts on that thing.
pejota is offline   Reply With Quote
Old 11-17-2008, 10:41 AM   #372
Tech Elite
 
Join Date: Aug 2002
Location: Houston, Texas
Posts: 3,777
Trader Rating: 27 (100%+)
Send a message via AIM to John Stranahan
Default

Pejota-Thanks. I think it would come in at legal weight with six cell. I had to add 4 ounces of Ballast to my Woods Car. I don't know why with all that attention to the front end, that it is not dual A-arms. A dampened floating beam front axle is probably a step above our strut suspension, though, by about 50 years. It would make a great high speed run car.

After putting the inerter equiped car on the bench and pushing on it, I think it maybe has too much gear in the inerter. It is like a center shock with very viscous oil. First thing I will do is reduce the oil viscosity in the center shock. Next maybe a gear change.

john
John Stranahan is offline   Reply With Quote
Old 11-18-2008, 12:47 AM   #373
Tech Elite
 
Join Date: Aug 2002
Location: Houston, Texas
Posts: 3,777
Trader Rating: 27 (100%+)
Send a message via AIM to John Stranahan
Default

World GT Road Car, Test Mule
Well this is my World GT car. Not quite to specs. There is a little more motor and battery on board. LiPo, Novak 3.5 R. In spite of this tuning will be similar. First off I checked the side to side weight. The right side with the inerter installed is 1.5 ounces heavy. Total weight is 42 ounces. I may add 1 ounce of ballast to the left side. I will do this with a slightly heavier LiPo battery with more capacity.

This is really a test mule to test two recent devices. Speeds will reach about 50 mph on the straight. This type of speed usually sends a pan car airborne on my track unless you take drastic measures like dampening the front end with shocks. I have not done so on this test mule. Instead I installed a full width diffuser, shown in photo two, similar to the one I tested and liked on my Wide Pan car.

Secondly there is that new device on board tied to the rear suspension. This is an inerter (inertia device) That acts a little like a shock but better in that you can tune the frequency of the suspension movement by changing the leverage or mass of the armature that is spinning. There is no power or electronics in the device it is strictly mechanical and thus on my approved list as well as F1's approved list which does not allow computerized suspension movement control. I put thin fluid in the shock and the suspension now works in a very interesting fashion. It slows down the suspension movements and exagerates the ends of the movement. Good performance will be evidenced by faster speed on the straight. Typical pan car get up to 47-49 mph. 47 for a T-plate car, 49 for a center pivot side link car. Speed is limited by rear suspension bouncing over the bumps. The 3-link rear improves this to 53 mph. I will see if this device helps. It is somewhat hard to tune the mass and gears, but I was able to extend the lever arm to good effect. It feels like it might do some good or at least be very different. The width of this car at the front wheels is only 190 mm as this is the only symmetrical position for the front wheels. The chassis is a Woods Racing Oval car very similar to the one I ran on Sunday.

The way a diffuser works is this. Laminar flow (smooth flow) enters below bumper and passes a short flat section to keep it smooth. Then the diffuser curves away from the pavement. This expands the air and creates a vacuum under the front. As a side effect there is some motor cooling air above the chassis now.

Tuning the World GT car
I have taken some steps that are well described earlier in the thread.

I checked and will equalize side to side weight.


I removed bumpsteer
I put spacers under the ballstuds on the steering arms. This was to remove bumpsteer. Push the wheel up through its suspension travel, it should not steer left or right by itself. The servo has two sets of holes. This servo mount actually lets you slide the servo up and down. Find a set of adjustments to eliminate the bump steer. That angled servo makes this possible.

I have reset Ackerman
Your steering links should exted perpendicular to the chassis. I moved the servo forward to accomplish this with the front wheels set at long wheel base position. I discussed ackerman earlier in the thread.

I set toe in to zero

The car has Wolfe White 4# Front Springs. They probably will be too soft for the sweeper.

I set camber to about -1.5

I used soft side springs and light (30 weight) side oil to maximize rear cornering grip. The center spring is too light, but combined with the inerter it is hard to bottom the car. I run chassis level. Ride height 6 mm. 2 mm pod droop when held in the air. Trim or adjust shock ball cups to get this last result right.

I squared the car to the nearest 1mm by using my setup board and adding thin and thick washers to the left rear inside the hub on the axle.

Gear will eventually be 90/12 48 pitch.

I installed un-cut CRC spec tires. These tires in trued form worked great on the wide pan.

pic #1 Front full width Diffuser. This is a piece of the HPI wing under the red tape.

pic #2 World GT car is in Nascar road race colors. Now that looks different than your typical touring car.

Pic # 3 Wiring and install came out very good and neat.

A reader gave this type of wing a nice name by PM. He called it a COT wing as he was advising I change it to an oval wing on the oval. I personally don't see that I have any different demands of the wing on this road course than I do on the oval. I have the same demands and the COT wing tested faster for me on the oval. It has to be the big one from J-Concepts though #0110. This one is slightly smaller. It looks a helluvalot more Nascar like. Especially Jimmys black one.

John
Attached Thumbnails
CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-test-mule-inerter-front-diffuser-005.jpg   CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-test-mule-inerter-front-diffuser-006.jpg   CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks-test-mule-inerter-front-diffuser.jpg  

Last edited by John Stranahan; 11-24-2008 at 11:34 PM.
John Stranahan is offline   Reply With Quote
Old 11-18-2008, 12:28 PM   #374
Tech Fanatic
 
JGLracing's Avatar
 
Join Date: Dec 2007
Posts: 876
Trader Rating: 23 (96%+)
Default woods car

thats a nice looking car .....john is she ready to run
JGLracing is offline   Reply With Quote
Old 11-18-2008, 12:38 PM   #375
Tech Elite
 
Join Date: Aug 2002
Location: Houston, Texas
Posts: 3,777
Trader Rating: 27 (100%+)
Send a message via AIM to John Stranahan
Default

Thanks. Ready to go. Tomorrow afternoon test. I have a reference to your black wing up above. I am getting the link just now from your new paint pic.

John
John Stranahan is offline   Reply With Quote
Reply

Similar Threads
Thread Thread Starter Forum Replies Last Post
CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks John Stranahan Oval, Larger Scales and More 0 05-25-2008 11:48 AM
Electric 10th scale sell-off (T4 team, Sphere, Transponder, LiPo, Brushless...) floatch R/C Items: For Sale/Trade 27 03-14-2008 04:37 AM
Battle Brushless Sensorless Mamba Max : Trinity N80 VS CM 36 moumerico Electric Off-Road 3 04-12-2007 03:18 PM
Battle of the EPs (On or Off Road)! marzin Singapore R/C Racers 4 09-22-2005 09:27 PM



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off



All times are GMT -7. It is currently 09:27 PM.


We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
Powered By: vBulletin v3.9.2.1
Privacy Policy | Terms of Use | Advertise Content © 2001-2011 RCTech.net