iblumberg

I recently got the Hara Edition and have been enjoying it as I learn to drive it. Initially, I built it using the spool. After some fun racing and practicing, the screws holding the bevel gear to the spool backed out resulting in the large and small bevel gears eating each other. In the process of rebuilding, I decided to install the oneway to try it out.

I have never driven a oneway. I race stock rubber on asphalt and during the rainy season, rubber on carpet. In this area, both inside and outside, the tracks tend to be fairly compact with lots of 90* and 180* medium to small radius turns.

Is the oneway worth using for these conditions? If so, what should I do to adjust my (sadly as yet minimal) driving style? I know that I have to avoid any heavy use of brakes, but what else?

Thanks,
Ira

Geetoo

iTrader: (1)

I tried adding kick up on my car using 2mm spacers on your pivot blocks in the front and rear. It had a big difference on turn in and transition. For short, your roll center is lower.

TadehI

A one way is only used for large and flowing tracks where there is minimal braking involved. It is not suitable for tracks which involve hard braking because it will make you slower. In this case you will be faster with either a spool or a differential in which case you can stop faster which alows you to drive harder (faster) into a corner before braking.

floodo1

this isnt entirely true.
with a spool the front tires are both braking, and doing a little initial turn in. therefore you need to slow down before the corner and slow down more (also because the tires are locked together and cannot spin independantly (as with a diff or oneway))
with a one-way you need to slow less for a corner because the front wheels arent doing any braking. the first half of the corner can be taken with more speed.

basically with a spool any slowing = less steering. whereas with a oneway any slowing = increased steering.

the reason why a oneway isnt usually run on a small tack is because usually the rear end cant keep up with the aggressive steering of the front end.

dont get me wrong sometimes a spool indeed will be faster. mainly tho the spool is for when one-ways are banned.

AngryAsian

iTrader: (4)

As far as i know, most of the guys at some of the smaller tracks around these parts run a one-way. (Victoria, Australia)

The advantage of a spool is a large amount of on-power steering and exit traction. You also have a car that can handle aggressive use of the brakes.

One-ways on the other hand need a smoother driving style but can carry more speed through a corner. Corner entry is made easier because you have more steering and the car rotates(Ie. turns) much nicer mid-turn. Exit traction isn't quite as good as a spool.

On a small track, you find that most cars can be driven with a one-way because you can bleed speed off through turning. Like floodo1 said, the one-way allows the outside front wheel to track extremely freely. This results in so much steering the rear of the car can find it hard to keep up.

In fact, the one-way allows both front wheels to turn faster than the rear(this is one of the main reasons why 4wd cars understeer and can cause drive-train stress. This is why the mitsubishi evo and WRX has a centre diff) and results in much more corner speed.

When in a turn, the car pivots on the inside rear wheel. Therefore, the ouside rear rotates faster, the inside front turns faster and the ouside front turns faster still. (This is due to a greater distance covered...)

The one-way allows this to happen and allows for much more front-end grip.

floodo1

further clarification: with spool both tires are locked together, therefore front power is split 50/50. with a oneway if the outside tire needs to spin faster it can, in which case the power will be transmitted to the inside tire. however if the outside tire does not need to spin faster then the split goes back to 50/50

google "traction circle". the reason that a one-way steers so much is that the front tires are alleviated of trying to decel the car, therefore all of their traction can be used for turning. with a spool or diff the tires are required to use some of their traction for braking, therefore they will have less than 100% ability to steer.

this is where knowing the track comes into play.
one way tracks usually dont have large speed changes. thats why people usually say larger more flowing tracks are for one ways. this makes sense because you will probably not need a lot of braking. by running the oneway you then gain the highest steering ability.

the type of track where a spool or diff comes into play is where you have high speed to very low speed sections. for example a u-turn at the end of a straight away. in this situation you need to be able to brake as much as possible so that you may continue your top speed for as long as possible. if you ran a one-way here you would have to slow down much much sooner.
naturally when you actually reach the corner you will be able to corner at higher speed with the oneway (due to increased steering) but you will already have lost more time under braking than you can gain in the corner.
furthermore from high speed to low speed the oneway often tends to oversteer due to the large weight transfer from front to rear. spring rates high enough to overcome this may have adverse effects elsewhere.

so the key is to look at the changes in speed not in the corner size. this is why a oneway can be HIGHLY succesful on even the smallest of tracks.

now someone needs to just come out with a one-way/lsd

hi-tech-redneck

iTrader: (1)

hey, xcat,u up? still looking for pro 4 bmi carpet set up for jr's ride,trying to put it together now,

tandman

iTrader: (7)

I thought that I would post my BMI Pro4 carpet setup for stock as it works really well.
Front suspension;
60wt. asc. oil, 2 hole piston, 30lb spring. 3rd hole in on tower, outer hole on arm. 0 degree front lower arm mount with one purple height spacer. One purple spacer under the f/r mount. 4 degree caster blocks, -1.5 camber.
Diff is tight. Black sway bar. 1.5mm spacer on the axle. Up travel 1.5mm.
2mm shim under the inner camber link.
Rear suspension;
40wt. asc oil, 2 hole pistons, 28 lb spring, outer hole on tower, middle hole on the arm. 2.5 toe in block with a purple spacer under the mounting blocks front and rear. No sway bar, 1.5mm axle spacer. Up travel 1mm. 1mm shim under the inner camber link.
This setup is very aggresive in the turns and you have to drive it hard to be fast. I only play with the up travel to dial it in when the traction comes up.

Essnowyt

tandman - Is that a foam or rubber tire set up?
If foam, what type and size?
If rubber what type of tire and insert? Is it a spec tire?
Snowy.

jim beam

Has anyone fitted 3800 cells to there pro4 ? if so, how much work is involved to fit them ?

Desolas

iTrader: (2)

I have. No issue. With the HPI chassis and an aftermarket one they fit just fine without any modification. I used a battery strap and they fit fine. I had beveled my battery slots a little large so the cells sat kind of low though, if yours are tight you may need to increase the bevel .. but I've got no problem going from GP3300's to IB3800's.

iblumberg

Same here.

I also use the battery strap. About the only issue I have is that my packs are a bit too wide to allow putting the foam on each of the posts that hold the battery strap. I can only put foam on one post. Both IB3800 and Elite 3600 cells fit fine in my Pro4 chassis. You do need to adjust the height of the battery strap a bit so that it just fits over the 3800 cells while still being low enough to hold the 3300 cells.

Ira

tandman

iTrader: (7)

The setup that I had posted is for foam tires. I start out with a 58.5mm and run them down to 56mm for club races. For lower traction I use Parma Magentas on the rear and cyan on the front. If the tracion is real high I will switch to the purple rear, plaid front combo to free up the car a bit.

floodo1

/yawn

Superfly1967

LOOSENING REAR DIFF QUESTON. We have 2 guys running the Pro 4 at our club, and both have had continual problems with the rear diff loosening up and needing to be replaced. I ran the Pro 4 when it first came out, and never had any problems with the rear diff. Is there some sort of defective part that needs to be replaced or what?

Has anyone else had problems with the rear diff. These cars were both new, ran for 2 heats, then diff going to crap.

Any info would be greatly appreciated.