Four on the floor rail rider thoughts

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doct1010
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Re: Four on the floor rail rider thoughts

Post by doct1010 »

*5 J's* wrote:.... Hmm- let me think out loud - what if I drill x amount of toe-in then bend an axle for y amount of camber. Then I can roll the axle slightly to tweak. I would still be adjusting in two planes simultaneously, but would it be an order of magnitude less.....
One of the "quirks" of the bent axle method we found confounding. You are always adjusting in two planes. Your idea, I think would further confound. With the predetermined toe built in AND a bent axle you have the additional variable of x degrees to consinder and as you state are still adjusting in two planes.

I like the idea of building in the toe angle, we did this for rear wheel cant. What if you drilled for cant and shim for toe with that nice, clean, shiny, straight axle?
Last edited by doct1010 on Fri Feb 26, 2010 11:46 am, edited 1 time in total.
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Re: Four on the floor rail rider thoughts

Post by quadad »

The talk in this thread about negative camber on the FDW for a 4-down RR presents me the image of a car whose NDFW is riding the rail with the DFW driving away from the rail. Is that what is being talked about here ?
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Re: Four on the floor rail rider thoughts

Post by *5 J's* »

The talk in this thread about negative camber on the FDW for a 4-down RR presents me the image of a car whose NDFW is riding the rail with the DFW driving away from the rail. Is that what is being talked about here ?
Well I guess all options are on the table - but I believe Randy at Max-V showed a decrease in speed if the NDFW rides the rail with the DFW driving away from the rail. ((Rail Rider study in Volume 8 Issue 4 of his newsletter) I think we'll stick with using the DFW to steer into the rail. I like the other concepts but will wait for feedback from real world application.

The variables that I looking at now is finding the proper negative camber in the rears - the proper toe and camber on the front wheels - and also looking at the best method to get the needed camber or toe - drilling/shimming/bending. I understand the proper toe and camber will depend on the individual car and track - but I am looking at how and how I will know when I have these set/aligned correctly on our car. As far as how they will react on the track - I will have to wait and see as we have a VERY old wooden track - the best I can do at home is my 8 foot piece of MDF board.

For the RANGE of negative camber, considering my rules requiring all four wheels to be flat on the track, I can use just enough negative camber to keep the wheel on the axle head - up to the point just before the wheel starts riding on edge. (Not sure the required axle angle is for this camber range).

For the RANGE of toe - It sounds like I want enough toe to drive drift say 2" over 4'. I have seen posts using anywhere from 0.5" to 3.5" over 4'. It seems the smoother the track the less drift needed. Given our old wooden track I made need more towards the 3" over 4'. Now how much toe do I need do get this and what does that equate to for an axle angle. Above Stan proposes 0.4° toe in on DFW, then about 0.2° toe-out on the other? (Again, I'm not sure the required axle angle is for this camber range. I had calculated and axle angle of 2.29° and 1.89° respectively, but Stan points out that this may not be a good calculation)
Last edited by *5 J's* on Fri Feb 26, 2010 7:09 am, edited 1 time in total.
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sporty
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Re: Four on the floor rail rider thoughts

Post by sporty »

I have posted this before. I did not read through all the posts.


4 wheel , RR.


Rear wheels, either canted or not, depending on your rules.


The dom front wheel, no cant or if allowed slight cant, but not to much. Toe in the wheel, either by bent axle or drilled angle axle whole.

Non Dom wheel. no cant or cant, depending on the rules, on what you are allowed to do.

But you want the wheel toed out a little. the fourth wheel even if slightly touching, effects the RR car.

It can cause it to push the RR dom wheel off the rail.

So A slight toe out, is what you want. not allot ! This will also help keep that wheel to the axle head, versus the car body.

On a alignment board, its going to look just like the 3 wheel RR cars. meaning you're drift and how the car does on the alignment board is going to be the same as a 3 wheel RR car.

People i know are looking for a good set of numbers, the problem is. Every track is different , every builder is different.

The standard 3 to 3 1/2 drift at 4 feet is just that the standard number out there. This does a RR, but it may not yield the fastest times.

I have heard of 1/2 to 1 3/4 drift at 4 feet on a super nice track. Then also keep in mind, that you're weight placement and wheel location also is going to factor in.

How much of a drift you will need !


Yes, track tested and proved and timed runs.


I helped 5 families use this process, all won there ranking in there pack and are all headed to council.


The three families I helped last year, all placed 1st thru 3rd last year at council, this included the runner up field.


Not that i like to get into this result and that result. Just I seen testing and info is really what people want to know, that this method works.


I certainly would not recommend, using the non dom wheel to push into the rail ! or have the dom front wheel toe out and pull the car into the rail on the other side of the car.

I have played with this for giggles, and it was not something I seen good results with. But perhaps someone has done it with good results. Just not me.

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Re: Four on the floor rail rider thoughts

Post by *5 J's* »

Thanks Sporty - yes I had read this post and scrounged a wealth of info out of it. I certainly understand each car will need to be tweaked and it depends on the track. But I think we should be able to bound the range - as well as talk through what variables affect what. I think right now toe is my biggest question, and I have a good range of drift to shoot for. Thinking out loud... where do we tweak to... 2" of drift or 3 1/2" of drift... hmmm.... Our Pack uses a REAL old wooden track but District uses a nice long shiny aluminum track.

By the way last year my son's car was aligned neutral and won the Pack and finished 9th at District - I think the top cars may have been RR's as they were extremely quiet. Last year I did the rough cutting - he (as a TIger) did the sanding, wheel prep, and axle prep - I did the painting (he couldn't handle the fumes) - he did the assembly - I did the alignment. This year I have purchased a scroll saw so he can do the rough cut as well. I hope to get him excited about the alignment phase this year.
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Re: Four on the floor rail rider thoughts

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*5 J's* wrote: Thinking out loud... where do we tweak to... 2" of drift or 3 1/2" of drift... hmmm.... Our Pack uses a REAL old wooden track but District uses a nice long shiny aluminum track.
In general, rough track more toe. We always started with a base line of 2" in 4',(as per warp, actually he recommended a bit more) worked well for us. We tuned for a very good Piantedosi wood. District race was a 48' aluminium, same set up worked well due to poor track condition with terrible joints due to hasty assembly. Had it been extremely smooth and fast maybe we back off a bit. IMO, the key to the toe angle is just enough to hold rail on rough track if you get bumped, however not too much to scrub time amd cause wheel climb. Also keep in mind the car will react very different at speed!
I think the top cars may have been RR's as they were extremely quiet.
...and probably had exceptional wheel/axle prep and alignment.
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Re: Four on the floor rail rider thoughts

Post by *5 J's* »

...and probably had exceptional wheel/axle prep and alignment.
Agreed - but I feel we had real good wheel/axle prep and alignment as well - but the fastest cars were just that much quiter than my sons.
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Re: Four on the floor rail rider thoughts

Post by doct1010 »

Were your wheels canted? Three touching? Could you tell if others did the same?
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Re: Four on the floor rail rider thoughts

Post by Stan Pope »

*5 J's* wrote: For the RANGE of toe - It sounds like I want enough toe to drive drift say 2" over 4'. I have seen posts using anywhere from 0.5" to 3.5" over 4'. It seems the smoother the track the less drift needed. Given our old wooden track I made need more towards the 3" over 4'. Now how much toe do I need do get this and what does that equate to for an axle angle.
Working from http://www.stanpope.net/driftcomp.htm, I compute 0.43 degrees needed for drift of 2" in 4' of travel or 0.60 degrees needed for 2" drift in the 41" of travel that you can accomplish on a 48" (4') board. I'm not sure which you are specifying.

If camber is introduced to the dominant front axle, the weight of the nose will keep the wheel toe angle very close to the axle toe angle until the wheel reaches the rail. The drift test has no rail to deflect the wheel, so that deflection should not be considered in evaluating the drift test results!
*5 J's* wrote:Above Stan proposes 0.4° toe in on DFW, then about 0.2° toe-out on the other? (Again, I'm not sure the required axle angle is for this camber range. I had calculated and axle angle of 2.29° and 1.89° respectively, but Stan points out that this may not be a good calculation)
I don't recall saying anything about toe-out on the offside front wheel. Nor do I feel qualified to say much about "4 wheels touching" setup.
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Re: Four on the floor rail rider thoughts

Post by *5 J's* »

Maybe if 0.4 degre toe in on RR, then about 0.2 degr toe-out on the other?
This is the sentence I was referring to, but I now see that was a question rather than a statement. My apologies.
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Re: Four on the floor rail rider thoughts

Post by Stan Pope »

Not a problem ... I was afraid that senility was creeping up on me faster than I realized! :)

The toe angle computation takes the curved path into consideration. However, you may find that your car has exactly the specified toe angle, but the path curvature is vastly different. One common reason is that the car is being steered by something other than its front wheel, namely by the rear wheels! If the rear wheels are toed or their frictions are unbalanced, they will mess with the path. In addition, experiments here definitely show that the concept of "dominant rear wheel" is a reality. Put toe in on both rear wheels and you can change the path by moving the CM left or right!
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Re: Four on the floor rail rider thoughts

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In our new pack they have the "four wheels touching" rule and I am going with all of Sporty's great info regarding this. ie) Toe in with the DFW and then a slight toe out for the NDFW. One thing I have not been able to locate is his suggestion for the cant of the front wheels specifically the NDFW. I can only assume he uses a positive cant for the DFW but what about the NDFW? In my head I assumed that it would most likely be a negative cant for the NDFW with the slight toe out but in some pictures from another thread http://www.derbytalk.com/viewtopic.php? ... oor#p73578it appears that a winning car with the 4-touching rule used a positive cant for both front wheels. Does this make it easier to keep both fronts touching because I have read that some people have had problems with accidentally raising a wheel once they begin fiddling with the toe of the front wheels. :scratching:
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Re: Four on the floor rail rider thoughts

Post by Speedster »

This actually happened to me this year. I build and tune a 3 wheel rail rider. The very last thing I do is face that 4th wheel. I used a straight nail this year for the 4th wheel. I try to adjust it down to the point where it hangs on the axle but it will roll. Our inspectors take the cars in their hand and roll the cars with the weight of their arm on the car. They do not set the car by itself and push the car. I (accidentally) adjusted the nail at one point the weight of my arm allowed the 4th wheel to roll but when the car was not touched I could spin the 4th wheel which gave me a 3 wheel rail rider. I glued the 4th axle and when dry the car still acted the same way. I have not tried to duplicate this.

Nelvis, Sporty used a Negative Cant on the NDFW. This keeps the bottom of the wheel as far away from the guide strip as possible. Yes, when you deal with a bent axle on the NDFW some people (ME) have a very difficult time not affecting the DFW. I have found tuning the car on my 30' Best track as a 3 wheel rail rider and then bringing the NDFW down straight has little affect on the speed, even if the wheel rolls. If you spread the slot a tiny bit at the NDFW you can angle the axle to give the wheel Negative camber while bringing the wheel down. This will cause the wheel to migrate to the axle head. Slots are actually an advantage in this case. I drill a hole through the car near the pointed end of the axle on the NDFW. When I have the wheel in position I use a very small screw to push on the top of the axle. This gives it Negative camber. When the glue is dry I remove the screw and put glue down the hole. I cover the hole with a decal.
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Re: Four on the floor rail rider thoughts

Post by Nelvis »

Thank you for the response Speedster! I guess that maybe I should have clarified a couple things. Due to a coping saw incident (100% my fault) the entire front half of the car is very thin. So as per Sporty's info I was hoping to do everything with simply a collection of bent axels. I don't know if I have enough wood to do some of the things you describe such as drilling near the axel tip and using a screw etc. My plan was to go ahead and get the rears set with negative cant and neutral toe. Then with straight axels determine which front wheel wants to naturally be the dominant. From there I would get an axel with a minor bend and get the positive cant and toe-in on that DFW. Now here's where I am picturing problems. By putting that positive cant on the DFW am I not in effect further jacking up that dominant front side? Perhaps I'm wrong but I am picturing a positive cant with a bent nail as further raising that side of the car. So now (again imagining) I have a lot of air under my NDFW to overcome. When I then put a negative cant on the NDFW how will I get it to touch. I was assuming that a negative cant with a bent axel would in effect slightly raise that wheel even further off the track.

So if any of this makes any sense so far, my next thought was that perhaps I should instead (with straight front axels) determine the naturally dominant front wheel. Then with a positive cant force the NDFW to become the DFW. Now theoretically I would have much less air under my other wheel to deal with. Alternatively as I mentioned in my previous post why not just put positive cant on both fronts like the guy did in that other thread. If its properly rail riding and I have enough clearance for the guide strip then what are the disadvantages of going this route?

Sorry for the rambling post (I'm more of a visual learner) but hopefully someone will understand what I'm trying to say.



Lastly Speedster here are some of the things that I am confused about in your method:
Speedster wrote: Nelvis, Sporty used a Negative Cant on the NDFW. This keeps the bottom of the wheel as far away from the guide strip as possible. Yes, when you deal with a bent axle on the NDFW some people (ME) have a very difficult time not affecting the DFW. I have found tuning the car on my 30' Best track as a 3 wheel rail rider and then bringing the NDFW down straight has little affect on the speed, even if the wheel rolls. If you spread the slot a tiny bit at the NDFW you can angle the axle to give the wheel Negative camber while bringing the wheel down. This will cause the wheel to migrate to the axle head. Slots are actually an advantage in this case. I drill a hole through the car near the pointed end of the axle on the NDFW. When I have the wheel in position I use a very small screw to push on the top of the axle. This gives it Negative camber. When the glue is dry I remove the screw and put glue down the hole. I cover the hole with a decal.
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Re: Four on the floor rail rider thoughts

Post by Speedster »

I understand exactly what you said because we built a car exactly like that our 1st year. It gave me fits. I now leave a bit more wood in the front so I can make the screw work. If you put Negative cant on the NDFW you will lower that wheel but it will probably end up having excessive toe-out and look ridiculous. That's why I gave that system up. If you have Positive cant on both front wheels you will also have toe-in. They will be fighting each other all the way down the track and riding the rail. As you adjust for your top speed you might put a lot of weight on what was originally your DFW or lift it off the ground completely. With the NDFW with Negative cant, rolling straight, the wheel rides out to the axle head and stays there. To some extent, the NDFW will be helping the DFW instead of fighting it and it will be easier to accomplish the set-up. If you have access to a track, try your set-up. Once you have your times raise the wheel off the ground and run it again, maybe even re-tuning the car. This wouldn't be a perfect comparison but maybe somewhat close. I would be interested in hearing the results.
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