Originally Posted by RAL (Post 6442524)

I know at our local carpet track these are your options for "stock" all combo's are looked at as equal. Don't know if it really is. I'm sure the gurus on here can tell you. I'm curious as well as to how they match up.

27t 4cell
17.5 4cell
13.5 1s lipo

Originally Posted by kn7671 (Post 6437526)

Just better! :lol:

Originally Posted by GasGod (Post 6442988)

I really wanna see saddle pack lipos--any backyard "engeniering"been done .
like on some helio packs wired in parallel to get the Mah up?

Originally Posted by ammdrew (Post 6446191)

13.5 3.7v does the same laptimes as 13.5 4 cell. So no it is not equal to 17.5 4 cell....

Originally Posted by ammdrew (Post 6446191)

13.5 3.7v does the same laptimes as 13.5 4 cell. So no it is not equal to 17.5 4 cell....QUOTE]

Testing here showed that with the same gearing a 1s / 13.5 was VERY close to the same as a 4-cell / 17.5. But when we started gearing the 1s / 13.5 up to where it was optimized it was significantly faster than the 4-cell / 17.5 is.

I know the W. Washington guys (Bodine, DuTemple, et al) have decided that 1s / 13.5 and 4-cell 13.5 run together acceptably well. The Fantasy World Summer Sizzler (25th Annual!!) allowed either of these specs and the main proved to be a duel between Mike with a 4-cell car vs. Brian with a 1s car. Bodine made a small mistake early and spent 6 minutes running several seconds behind but the gap was pretty much the same throughout. With 1 minute to go the 4-cell car began to slow noticeably (geared pretty aggressively to keep ahead of the BodineMachine) to near full dump at the end where he won by a second or so. Had the race been even one more lap (heck...one more corner) and Brian would have had him.

Originally Posted by AdrianM (Post 4094783)

Please copy and paste this into MS Word so you have saved locally:)

Building a Diff

I use plain chrome steel diff balls from BMI, IRS, anyone...they are all the same high grade 1/8" ball bearings.

I like to use Schumacher U1301 silicon diff grease or Associated silicon diff grease, the thick type in a plastic cup not the stealth grease in a squeeze tube. Stealth grease is too thin and gets flung out too easy.

The diff balls I buy come in a 100 pack for ~$8. I open the pack over a clean paper tower and dump them out. All diff balls have a coating of oil on them to protect them while they sit on a shelf. I use motor spray carefull to wet them and then roll them on the paper towel to dry them. I then dump them all into the cup of diff grease. I keep them there untill I use them.

When I build a diff I sand both sides of the diff rings with 600 grit wet-dry sandpaper lubricated with a little motor spray untill I see an even finish across the face of the rings. I then clean the rings with motor spray and dry them on a clean paper tower.

Be sure to clean your finger tips with motor spray before touching the diff balls or rings. If you get any bearing oil or traction compound on them from your fingers it will contaminate the diff and mess it up.

I then pluck the diff balls out of the diff grease cup with a small clean flat blade screwdriver and put them in the spur gear. They will carry all the diff grease they need with them. You do not need to put more on the rings. I put a ball in all 12 holes in the outer circle. The inner circle of holes is for the no longer used small diameter "Stealth" diff rings.

Assemble the diff normally but tighten it slowly until you just start to get diff action. If you overtighten it you can dimple the rings and flat spot the balls. Tighten it and check the gear for slipping. As soon as the gear starts to get hard to slip stop.

Mount some tires on the axle. Hold one tire and the gear locked and force the opposide side to turn a few turns. Repeat with the other side. This is called cutting the diff. Cutting the diff smooths out any imperfections in the rings and balls by burnishing them. The diff may have loosened a little from cutting it so readjust it so the gear is very hard to slip (this is tighter than the previous step).

Install a motor and put the car up so the wheel are not touching the table. Run it at meduim throttle and alternatly touch one tire then the other untill it just stops then let go. This will heat up and fling out excess diff grease as well as breaking in the diff. Do this a couple times per side.

Re adjust the diff a final time so it wil not slip and you are done. The diff should be glass smooth. It should spin very freely as if it were really loose but the diff gear should be almost impossible to slip.

If the diff is gritty with new rings and balls replace the outer right side hub bearing.

If the diff is slipping you have some petroleum oil contamination in the diff. Take everything apart and start over after cleaing everything with motor spray.

Originally Posted by Scottrik (Post 6446629)

Testing here showed that with the same gearing a 1s / 13.5 was VERY close to the same as a 4-cell / 17.5. But when we started gearing the 1s / 13.5 up to where it was optimized it was significantly faster than the 4-cell / 17.5 is.

I know the W. Washington guys (Bodine, DuTemple, et al) have decided that 1s / 13.5 and 4-cell 13.5 run together acceptably well. The Fantasy World Summer Sizzler (25th Annual!!) allowed either of these specs and the main proved to be a duel between Mike with a 4-cell car vs. Brian with a 1s car. Bodine made a small mistake early and spent 6 minutes running several seconds behind but the gap was pretty much the same throughout. With 1 minute to go the 4-cell car began to slow noticeably (geared pretty aggressively to keep ahead of the BodineMachine) to near full dump at the end where he won by a second or so. Had the race been even one more lap (heck...one more corner) and Brian would have had him.

Originally Posted by Slapmaster6000 (Post 6451320)

I would like to point out this was on asphalt out doors on a 80x 120'ish medium turn type track. Take this scenario to a 40x90 carpet track and I feel that you will see the 4 cell car has a .2ths advantage. Moral to the story is; even with weight allowances, I don't think that you will achieve a true evenness between 4 cell & 1S.

I can say that for those that are holding onto their 4 cells..... let 'em go! The 1S pack is the brushless motor of batteries. It's true that we are giving up on the best cells that we have had since the Sanyo 2000's, but get over it. You will be happier for it.

Brian

Originally Posted by mkdut (Post 6451351)

Anytime I can pick up 2 tenths on you I am happy. Makes for some pretty equal racing.