Stubby lipo
 

is any one running in the uk with a stubby lipo if so how do they compare to the stick and saddle layouts

Dan Greenwood has just installed a Vampire one recently and can run it through the middle or across the back if he needs to. I am sure he will post soon, maybe with some pictures too (looks really good)

Yes I run a stubby across the back of mine, it does look very tidy and works well. It means you can run a standard chassis without all the dremelling needed for saddles.

I've kept the same 65/35 weight distribution as used with other layouts, but it centralises the weight and lowers the CoG, so in theory you get more grip, more responsiveness and less grip-roll. And it gives you the option to run the car a lot lighter with the same WD. I haven't actually tried this yet (still at about 1720g overall as I have a lot of ballast), but I think it will be a good idea indoors where there are no bumps.

Had my best result of the winter on Sunday using this layout at Kiddi :thumbsup:.

Why would a stubby LiPo lead to a lower CoG? :)

The stubby is about 100g lighter than saddles/stick. If you put that 100g back on using dense ballast flat on the chassis, the CoG drops.

Also, with a bit of dremelling the stubby sits a few mm lower in the chassis than a normal stick pack (as the chassis curves up at the edges), so there's a gain there too. This can also be done with saddles, but requires a bit more dremelling.

Stubby packs are (often) higher than conventional size packs, and thus result in a higher CoG. The idea of using the shorter packs is not to add extra weight under them, and ending up with an all-round lighter car.

Picture of mine attached.

Briefly, comparing to the T lipo setup I was running before with 5400 saddles, the stubby pack mounted forward (the pack is shorter than the gap so need a piece of foam or similair to mount front or back), the balance is within 0.1% further forward that the T setup and back (not side to side) it's 0.2% further back. It's 80g lighter overall like for like.

First run will be this weekend at Off Road Wars.

Oh forgot to add, to do this I've obviously removed the section of the vertical bracing to allow the stick through however I've also removed the nimh cell seperator bracings just under the middle which allows the cells to be mounted a few mm lower (as referred to above). However I had already done this on the T setup also so my test is like for like in this regard the 5400 cells and the stubby pack are the same height i.e. just under max legal limit for height.

thanks :thumbsup::thumbsup:
i think i will give this a try:):)

I'm not suggesting putting the ballast under the Lipo, that would raise the CoG. If the ballast and Lipo are both flat on the chassis the CoG calculations are:

Stubby Lipo (200g and 25mm high) = 200g x 12.5mm = 2500gmm
Lead ballast (100g, 3mm high) = 100g * 1.5mm = 150gmm
CoG position = ( 2500 + 150 ) / 300g = 8.8mm

If a standard Lipo is 300g and 23mm high, its CoG is 11.5mm (half its height).

So the (stubby with ballast) has a 2.7mm lower CoG than the (big lipo without ballast). The trick is finding somewhere to put the ballast, but because the pack is so small there's plenty of spare space on the chassis.

And you also have the option of not running the ballast and having a nice light car for smooth indoor tracks. Win win :).

Dan, I don't know if that car is fast, but it sure looks great! You do nice work!

Sorry but i forgot to ask can i do this with a saddle chassis:blush:

:thumbsup:

Thanks Chazz.

Leelar, you can but be aware there is already some of the internal bracing removed for the saddle setup. I tired this out on a saddle chassis but the car you see above has been built onto a new standard plastic chassis so it has full height bracings to the sides of the stubby lipo

Forget the lipo. Can we get some detail on your rear camber link set up?! :confused:

They are nothing special, Dan is just using the prototype "tower forward" rear shock tower that bring it further forward, shocks mounted on the rear and camber pick up points are on the tower. They are in the same positions as we normally run though just mounted on the tower instead of the rear bulkhead.

You're got good eyes :D

Darren has it covered, there are hole positions for E speed high, low and one in the middle :)

My primary reason for liking it is moving the rear wing forward which I beleive makes the car jump better though having only used it indoors so far at BWOC I can't say I've thoroughly tested this tower, I did run a home made mod all last year outdoors though but this proto tower is MUCH nicer.

Hassle Paul to bring it into production when the X Factory router has some spare capacity! :D

Looks very nice, moving the wing over the axle sounds like a worthwile improvement. Are any mods needed to the bulkhead to mount the tower in this position? Making the tower itself shouldn't be difficult.

Yes all new bulkhead will be needed, somthing we are working on/playing with right now.......

We have been working on tower forward for about a year, and have run into one problem which, so far, we have not been able to solve: Moving the ball stud is a long, tedious process. Ball studs screwed into CF need to go all the way through with a nut on the back, and there are too many things are in the way blocking access. To move a ball stud you've got to remove the tower, and it does not bolt on from the back with 4 EZ screws as the standard tower does.

It's a difficult problem, and, as Dan implies, we must find time to work on it, time we just don't have ATM. We have an idea as to the answer, but haven't had a chance to spend the time (and money) to see if it will work.

Chas,why not make the adjustment a "slot",with a washer under the ballstud and a washer under the nut on the other side it will clamp up ok,no need to strip anything down then to make adjustments.......slacken off and slide!!!

Sounds too much like a recipe for a disaster to be honest, if it comes loose your camber will move all over the place and if it is on a slide how will you ever know that both sides are in "exactly" the same location....

If anything comes loose it can be a disaster!!To get them the same,measure them.....

Chippy, this is like everything else. We are going to do it right or we won't do it. We take care that our cars are top-level racing machines yet easy to work on, and we'll keep both principles here.

Have faith, we will get it right, and when we do you'll love it.

Taking the "slot" idea a bit further,a series of recesses on the nut side the same depth and radius as the washer would give a more positive location and no worries about getting them in the same position each side,to adjust,slacken the nut a couple of turns,release the washer and select your revised location and re tighten.A simple suggestion sometimes helps trigger another line of thought sometimes when your trying to solve a snag!!!:thumbsup:Cheers for now.

How about something old fashioned.... a spanner ;) for the front side of the tower and a nut driver for the rear side. Or an open ended ballend with a custom ballstud, if you added some material on the front side of the ball you could slot it, drill a hole in it, insert an allen key vertically, hey presto.

There are other issues too. The wing and its mounts must come off to move a shock position. The wing mounts, which screw in from the front, are hard to get at when they are forward.

We very much appreciate all your input. Unlike many R/C companies, we thrive on input from The Family. No N.I.H. with us. We have implemented many changes over the years that were suggested by The Family. Each of the suggestions above will be carefully investigated, at least by producing some C.A.D. if not actual parts.

In this case, it's not easy to come up with something that works well, is good to work on, and can be produced in quantity at a reasonable price. That's four criteria, each of which often is in conflict with the others. When we stopped working on tower forward we had made and tried several different versions of it and none met all four criteria, especially the EZ to work on one.

The performance difference is not great, if there is any at all. If you think about it, moving the wing forward takes away its leverage, making it less effective. Paul did this in fact to minimize the wing on large high speed outdoor tracks, but moving the wing forward in the normal mounts and trimming the Gurney accomplishes 99% of that. Paul says the primary advantage is that, in his opinion, the car looks better. I disagree.

We have the SCX - 60CF to do, and the X - 7. How much time should a two-man company invest in a project the delays the two big things, is proving difficult to do, and does not produce much benefit? I hope everyone out there is willing to continue winning races with the tower in the standard position so we can have a ballistic 4WD in your hands later this year.

N.I.H. = Not Invented Here

/me tips his hat to the xfactory guru's :cool:

So my car was great this weekend, I must admit not initially but that was just far to much front tyre, by the final it was great. I'm keeping mine set like this for the foreseeable future.

Please can you post setup?

Just wanted to write in on the tower-forward topic. The brief history is this: Last year around this time Chris Cristo, a team driver here in the states, drilled holes behind the camberlink in his rear bulkhead, slimmed down the 'legs' of the stock tower, and mounted it on the front of the bulkhead. I think Greenwood modded his similarly shortly there-after. I saw their work and said, "Hey, I can put a camberlink in the tower, cut off the whole front of the bulkhead." So that's what I did last summer. As Chipy96 suggested the ballstuds are located in slots - more figure 8-style with definite mounting spots, like many 1/8th gas cars use.

The ballstud goes through with a small nut on the back; clearance is tight if you're running one of the stock-width holes instead of the E-Speed locations. The reason we haven't made this available is it's a royal pain to change ballstud locations though - I have to take out the trans, bulkhead, and then take off the rear tower to do it right. It also complicates removing the rear shocks more than I'd like. I have a better way to do it in my head, but haven't had the time to draw it up and make the parts to test it. The idea was suggested to me by Dan Couglietta - make the camberlink a separate plate that bolts to the shocktower, perhaps using the wing mount holes. Look for it soon though - now that the SCX-60CF is pretty much shipping, I can focus back on 4wd and a few side projects.

....

AntH,

Will try to do it tonight though it's nothing unusual. If I forget please reply to this thread or PM me to remind me

Hi Dan

Any update on the setup yet

As I expected I totally forgot and now I've read this again in work I may well forget again (but will try not to tonight).

Dan grows older...

Out of interest, what is the weight of the vampire short lipo?

EFRA list says 212/228 g, measured 217.5 g

This discussion happened on RCTech, so I'll post it here to see what you guys think. Family Member Martin B. came up with this idea:

The X - 6 motor is deliberately in the car off-center, 0.030" (approx) to the right so the rotating mass of the rotor is centered in the car. This has a number of advantages, which we like. Several guys have tried moving the motor into the center by putting spacers between the trans and motor plate, but most have found this doesn't help.

Martin posits that, when installing a shorty pack across the rear it should be mounted 0.030" to the left. This helps to equalize the R-L weight of the heavy stuff in the rear while keeping the advantage of the centered rotor.

Finally had time at home to write up setup. Nothing that unusual here though (stubby aside) heavier damping that normal for high grip, no rear roll bar which I suspect will stay off for the time being when using the stubby.

Was happy on the day with only a Trishbits front bulkhead for weight, car was really good though.