Straight axel rail rider

[BSAdadGriffindork]

I’m also curious to see where the flying wedge COG ends up being and if I’ll need to mess with the weights much... Do you think I should aim for 1/2”? 3/4"?

It has been a long time since we built a wedge, but IIRC I suspect it will be nearly impossible to acheive a CoM placement that is 1/2" ahead of the rear axle, if the rear axle is put back as far as possible (< 3/4" from the rear of the block). In fact, 3/4" CoM may even be a generous assumption with the Flying Wedge design (because the bolts put extra mass far ahead of the rear axle, and lead is being used). I didn't see anywhere about what CoM to expect with the design...

A car becomes more unstable as the CoM is placed further aft. It seems that the Flying Wedge has screws with adjustable weights (nuts and washers) underneath as a means to partly control CoM placement, and hence, stability. But because you are building a rail-rider, IMO the stability aspect is already addressed. So, there may be no need to complicate your wedge design with a movable weighting system; there's not much mass in a #8 steel nut relative to lead (Pb) or tungsten (W) anyway.

I’m not sure if it’s because i used round tungsten weights or because i took a little more out in the middle than his plans but the first time I put it on my CoG stand it was a 1/2” and i then rearranged to move it just ahead of 1/2”. I didn’t use the screw design either. It’s pretty much just the shape of the flying wedge but hollowed out 1/8 on the top, sides and around the weights.

Should I use my last blank to remake it with a COG that’s closer to .75” or 1.0”? Or think 1/2” is good?

[BSAdadGriffindork]

BSAdadGriffindork,

Please know that I was just playing around with testing this idea on the topic..
To see if it was even possible to flip a pinewood pro jig top side of the block and drill a axle hole in a wedge design on 3 dreg toe and 2.5 positive camber.

The images I share show it is possible to drill with the pinewood pro jig flipped at just above the axle slot at a 1/4'' thick.

( However please take caution on what the opposite wheel.. lifted wheel side is doing in the images as I'm just testing this idea for my self on the topic.)

It also shows that one needs to account for a lifted axle hole ..
As just cutting the block at 1/4'' thick at the axle slot left no room in the block to lift the opposite axle hole higher for a lifted wheel.

Just by cutting the block at a 1/4'' thick at the axle slot.. and testing.. it was just to get low enough to flip the jig and drill a hole just above the axle slot.

I do hope that my testing images are helpful for the topic and for idea of flipping the pinewood pro jig drilling top side of the block
and for the problems one can encounter in doing so... if wanting to run the car on 3 wheels.

If one could get the flipped pinewood pro jig to drill the hole at 2.5 positive camber... lower into the axle slot and to a height of 1/8'' off the bottom of the wedge block .
Plus also leave room in the block for a lifted wheel axle hole then Id say the idea of flipping the jig top side of the block.. would be doable.

Thank you,

It worked well enough on this wedge angle. I placed the steering wheel in alignment with the back wheels but as you mentioned, that didn’t leave much room for the raised wheel. I ended up just moving the raised wheel back a little bit which got it off the ground. Hopefully the front wheels not being aligned won’t cause any issues

I did accidentally expose the bottom of my rear axles when sanding though! Hopefully covering it up with a mix of putty and wood glue will do the trick. Fingers crossed.

[FatSebastian]

It’s pretty much just the shape of the flying wedge but hollowed out 1/8 on the top, sides and around the weights.

Ah! Okay, so you are racing a hollowed-out rail-riding wedge weighted with tungsten (whereas the Flying Wedge is a straight-running, lead-weighted wedge with a system of nuts and washers underneath to tune the weight and balance).

Should I use my last blank to remake it with a COG that’s closer to .75” or 1.0”? Or think 1/2” is good?

Others with better or more recent experience may have different opinions, but IMO 1/2" is quite aggressive and will be risky without the ability to tune and test on a track of identical make up. If you have never raced on your unit's track before (and it sounds like this may be your first race), then rail riding at 3/4" or more should still provide comfortable performance without risking loss of control on a well-assembled Aluminum track. If an old wooden track, then maybe 7/8".

Perhaps someone else can chime in with a different perspective...

[BSAdadGriffindork]

It’s pretty much just the shape of the flying wedge but hollowed out 1/8 on the top, sides and around the weights.

Ah! Okay, so you are racing a hollowed-out rail-riding wedge weighted with tungsten (whereas the Flying Wedge is a straight-running, lead-weighted wedge with a system of nuts and washers underneath to tune the weight and balance).

Should I use my last blank to remake it with a COG that’s closer to .75” or 1.0”? Or think 1/2” is good?

Others with better or more recent experience may have different opinions, but IMO 1/2" is quite aggressive and will be risky without the ability to tune and test on a track of identical make up. If you have never raced on your unit's track before (and it sounds like this may be your first race), then rail riding at 3/4" or more should still provide comfortable performance without risking loss of control on a well-assembled Aluminum track. If an old wooden track, then maybe 7/8".

Perhaps someone else can chime in with a different perspective...

ok cool, I’ll try and shift some of my weights around and move the COG up some.

Does it matter how much actual weight is on the front wheel as long as the COG is in the correct place?

And it’s just my second year racing, did the same design last year but with straight wheels and did it all with just a drill and guide. Placed 2nd in my den.

Got the award for best looking car though! Haha

Borrowed a drill press and scroll saw this year, and bought that jig to alter the camber

I have one block left, with that said… what’s the best design for a strait axel rail rider? Some sort of wing?

[FatSebastian]

Does it matter how much actual weight is on the front wheel as long as the COG is in the correct place?

DFW loading, total wheelbase, and CoM placement are all interrelated through this equation. This entire discussion, and links therein, may be helpful. Also this.

[Loud2ns]

Does it matter how much actual weight is on the front wheel as long as the COG is in the correct place?

Checking the weight of the dfw is a bit more precise way to set up a car.
What kind of track is it? Do you get any test runs?

Sent from my SM-G991U using Tapatalk

[BSAdadGriffindork]

Does it matter how much actual weight is on the front wheel as long as the COG is in the correct place?

DFW loading, total wheelbase, and CoM placement are all interrelated through this equation. This entire discussion, and links therein, may be helpful. Also this.

I appreciate all y’all for all help! He placed 1st in his den, 3rd in his pack and 3rd in the city finals!! Looks like his best time was 3.0873 seconds and 203.73 mph on a beat up BestTrack

[Loud2ns]

Congrats, I hope you guys had a fun time through the whole build and race!

Sent from my SM-G991U using Tapatalk

[whodathunkit]

Congratulations, BSAdadGriffindork, and son.

[BSAdadGriffindork]

I'm curious if the jig could be flipped and used on the top side to get a positive 3 deg. I wonder if you shave some body off the dfw to get your inset if that would allow enough slop to rotate the jig to give a toe-in/steer of about 3 deg.

That is what I was thinking. If the jig was used from the top of the angled wedge instead of the flat bottom, I also think it would also induce a slight amount of toe in the correct direction, in addition to positive camber. (And I suspect not much toe angle is really needed for the flying wedge design because the CoM placement isn't terribly aggressive?)

You can get two generic wedges from a single block (maybe even two thin wedges and a plank) so you can experiment on the non-racing piece.

Btw, meant to say that you were correct about it creating enough of a toe-in angle. I think my first axle wasn’t straight or something on my first prototype because on my later builds, shimming it to create more toe-in ended up being too much.

Getting ready for our district build been considering dropping the extra $ on the turbo derby jig hybrid since it can create a correct angle for the Dfw a little more easily.

Also waiting to hear back from someone at the district to see if bent rails are actually allowed or not since they didn’t attach a graphic that said no modification of axles allowed like they usually do. Just said needs to be from the kit.

Recommend a good axle bender that’s not too pricey?

[whodathunkit]

Well if you’re going to drop $ on the turbo jig.
You might as well splurge on the $35.00 axle bending tool.

Some of the derbyworx axle bend tools run
around as high as $85.00 that iv seen on web sites.

Back in the day I just used a vise, Phillips screwdriver, and hammer
To tap and bend the axle.

[FatSebastian]

Back in the day I just used a vise, Phillips screwdriver, and hammer To tap and bend the axle.

I think you meant standard / slotted screwdriver? We have done that too… Definitely not too pricey!

[BSAdadGriffindork]

Well if you’re going to drop $ on the turbo jig.
You might as well splurge on the $35.00 axle bending tool.

Some of the derbyworx axle bend tools run
around as high as $85.00 that iv seen on web sites.

Back in the day I just used a vise, Phillips screwdriver, and hammer
To tap and bend the axle.

I may have to look into this old school technique. Wife isn’t thrilled about how quickly the $ from all the toys and tools are adding up. Haha

May have to save the derbyworx jigs for next year. Have a new drill press fence/table coming today and that just about got me murdered.

[whodathunkit]

Yeah, I hear you on that on..
I just got some of those turbo chucks in and my wife was after my hide faster than a Richard Petty pit stop!

I may ware the pants.. but she picks the color.
So I know what your saying.

[Vitamin K]

We still bend axles with a pair of pliers (I like linesman pliers) and a block of soft pine.