Sav XL conversion options..6 or 8S?

[mothman]

Originally Posted by Finnster

Heavy is ok as I want a big bruiser of a truck, and I'm not the jumping buildings type. Nor looking to set landspeed records.
But yes, I really really want a CD. I had been working on a mount end of last year, but its a pain and expensive to do. Got halfway thru it. I wanted it to mount in at least one set of tranny holes and have motor forward. Later decided just to mount on a skid plate like a traditional diff.
Lately I saw the (G?) maxx CD mount that mike made. I would really like something like that w. his slipdiff. I've got time to put this together, so I'll wait on those. the tekno mount is a simple mount for now and to see how it performs. If need be I'll step upto the 80mm 1100kv if needed.

What is the amp draw on that thing btw?

That is one sweet mount. But I prefer the motor to be at the center. Anyway, I believe that number of people might be interested in the mount and maybe you can start a thread about this mount. And when you have enough people, I bet the price must be much lower. You can ask Mike to machine this.

[Finnster]

Originally Posted by mothman

That is one sweet mount. But I prefer the motor to be at the center. Anyway, I believe that number of people might be interested in the mount and maybe you can start a thread about this mount. And when you have enough people, I bet the price must be much lower. You can ask Mike to machine this.

Oh thanks, its still in pretty rough stages still. I made a number of diff designs, but only the one was much advanced.
CAD is freaking hard lol. After playing with it I can really see just how great Mike's work is.

IDK if I would actually had emachine do the work, I was just using the proggy to play w/ over the Xmas break. It works well for simple things, but I was having a hard time doing others, like putting bolt holes on the side. The only way to do it economically would be have a large # of pieces made. 1 or 10 is not much of a price diff.

I would def want to prototype something 1st, I highly doubt it would be right on the 1st try, and I don't want to make some POS like the Kershaw DD kit.
I had thought of giving up on it as the Kershaw kit was supposed to come out soon and the Flux just got announced when I was doing it. I figured it would be a mostly moot point then, but seeing the weaknesses in both the designs, there is def some room in there for a good mount.

I did angle the motor on purpose as the width between the chassis is fairly narrow (74mm) and there is not enough room to fit a motor like a Neu and the spur gear if they lay flat, plus it puts the driveshaft at a hard angle and the spur have would to end up sticking out the side. I calced an angle that would lay the most flat and off to one side, but be flexible enough for a variety of gearing options. What its rly designed to do is have the motor going fwd, leaving back open for batts, and space on the side for the str servo. God knows just how it all would end up fitting together w/o some prototyping 1st. Unless you've got access to cheap machining, its an expensive process

[Finnster]

BTW.. I had a 2Y on 8s w/ the MGM before in my Revo, was really nice and was always stone cold. Always wanted to do the 10S, but only ever got one run of 12S A123. It was pretty bonkers.

FLydma.com still has some 5S 2500 30C packs FS, $50ea. I have 2s and 4S of these for my .5, these are great batts at great prices. Def check it out.

[Finnster]

That reminds me... One bad thing about doing the CD conv is that you lose the tranny reduction ratio. I have 2.89 Cen diffs now, and I couldn't really find a ratio that would work. I would have to use other diffs.

Originally Posted by Finnster

BTW.. I had a 2Y on 8s w/ the MGM before in my Revo, was really nice and was always stone cold. Always wanted to do the 10S, but only ever got one run of 12S A123. It was pretty bonkers.

FLydma.com still has some 5S 2500 30C packs FS, $50ea. I have 2s and 4S of these for my .5, these are great batts at great prices. Def check it out.

thanks for the heads up on the 5s packs, though they are too fat for my battery tray...I did end up buying a couple from True Rc that were 138x43x25, I did but one 5s 2500 pac from Mike ...thats all he had...the price Diversity had though was GREAT...I ll never beat that price!!

my tray measures 165mm x 52mm

[mothman]

Originally Posted by Finnster

I did angle the motor on purpose as the width between the chassis is fairly narrow (74mm) and there is not enough room to fit a motor like a Neu and the spur gear if they lay flat, plus it puts the driveshaft at a hard angle and the spur have would to end up sticking out the side. I calced an angle that would lay the most flat and off to one side, but be flexible enough for a variety of gearing options. What its rly designed to do is have the motor going fwd, leaving back open for batts, and space on the side for the str servo. God knows just how it all would end up fitting together w/o some prototyping 1st. Unless you've got access to cheap machining, its an expensive process

Yeah it is too narrow to fit the motor if the mount lay flat on the side of CD. Plus, the drive shaft will have to be positioned at a certain angle which will cause inefficiency and stress to the drive train. What I meant by motor at the center was the motor is positioned right on top of the center diff.

Really hope that Mike can start working on that CD mount for the emaxx. With this mount, the CD can be easily fitted on the Savage. But even then, my guess the mount would still cost around $60-$70.

[pb4ugo]

Originally Posted by Finnster

That reminds me... One bad thing about doing the CD conv is that you lose the tranny reduction ratio. I have 2.89 Cen diffs now, and I couldn't really find a ratio that would work. I would have to use other diffs.

A 51t Ofna diff just about perfectly matched the 2nd gear in a Savage with the stock diffs. You could use the larger Ofna spur or on the "norm" 1/8th diffs you could use one of the large spurs like from the CRT.

[mothman]

Originally Posted by Finnster

I did angle the motor on purpose as the width between the chassis is fairly narrow (74mm) and there is not enough room to fit a motor like a Neu and the spur gear if they lay flat, plus it puts the driveshaft at a hard angle and the spur have would to end up sticking out the side. I calced an angle that would lay the most flat and off to one side, but be flexible enough for a variety of gearing options. What its rly designed to do is have the motor going fwd, leaving back open for batts, and space on the side for the str servo. God knows just how it all would end up fitting together w/o some prototyping 1st. Unless you've got access to cheap machining, its an expensive process

Yeah it is too narrow to fit the motor if the mount lay flat on the side of CD. Plus, the drive shaft will have to be positioned at a certain angle which will cause inefficiency and stress to the drive train. What I meant by motor at the center was the motor is positioned right on top of the center diff.

Really hope that Mike can start working on that CD mount for the emaxx. With this mount, the CD can be easily fitted on the Savage. But even then, my guess the mount would still cost around $60-$70.

[Finnster]

I thought about putting the motor right on top, and its an easier thing to design, but I decided to make it offset so that the CoG was a bit lower from dropping the motor a couple cm, and also to keep the motor on one side to save room for the steering servo and maybe radio mount on one side opposite of the motor.

Neu motors are 44mm(?) in diameter, so at worst it only leaves 30mm of extra space between the TVPs. Obviously you are going to loose the oem radio box if the motor goes fwd, so I had planned on using an FLM radio tray plate, and removing material that would interefere (or making my own.)

This plate does sit somewhat high, and it incorporates the uppermounts for the str servo rack. The lower and more offset you can get the motor, the more room it leaves for the plate. I think if you managed to get the motor level w/ the CD, the motor would fit under plate, as that is not possible, if I have to raise the motor some, then perhaps I would only have to trim away 25-30mm from the plate. That leaves quite a bit of room for a str servo, and even a radio box, or even esc, if you could tuck the servo underneath the plate. I attached a really crappy drawing illustrating what I mean.

If you plant the motor right above the CD, you loose almost all this space, the motor sits high, and/or you have to sit the CD well to the side and have drivelines at unhappy angles.

Lastly, I know you can get pretty big spurs, but, big spurs take up lots more of the limited space between the plates, and more importantly, the stick out far underneath the CD. The CD will already sit quite a bit higher than the F/R diff outputs, so the bigger the spur, the higher it needs to sit to not have the spur hanging it nuts out the bottom of the truck. Ideally a very small spur would be used so the CD could be mounted low and at more optimum angles for the drivelines, and make up the FDR by low gearing in the diffs, say 4.2s or whatever as in truggy diffs.

For may particular intent, I think I need a 15-17:1 FDR, which is next to impossible w. Cen 2.89s and a CD. At worst take it upto about stock ratios on the diffs, and use Mike's 50T spur on the slipperential w/ 10T pinion. Better yet would be 4.2 or so diffs, Mike's 46T and a 11T+ pinion.

[pb4ugo]

Originally Posted by Finnster

I thought about putting the motor right on top, and its an easier thing to design, but I decided to make it offset so that the CoG was a bit lower from dropping the motor a couple cm, and also to keep the motor on one side to save room for the steering servo and maybe radio mount on one side opposite of the motor.

Neu motors are 44mm(?) in diameter, so at worst it only leaves 30mm of extra space between the TVPs. Obviously you are going to loose the oem radio box if the motor goes fwd, so I had planned on using an FLM radio tray plate, and removing material that would interefere (or making my own.)

This plate does sit somewhat high, and it incorporates the uppermounts for the str servo rack. The lower and more offset you can get the motor, the more room it leaves for the plate. I think if you managed to get the motor level w/ the CD, the motor would fit under plate, as that is not possible, if I have to raise the motor some, then perhaps I would only have to trim away 25-30mm from the plate. That leaves quite a bit of room for a str servo, and even a radio box, or even esc, if you could tuck the servo underneath the plate. I attached a really crappy drawing illustrating what I mean.

If you plant the motor right above the CD, you loose almost all this space, the motor sits high, and/or you have to sit the CD well to the side and have drivelines at unhappy angles.

Lastly, I know you can get pretty big spurs, but, big spurs take up lots more of the limited space between the plates, and more importantly, the stick out far underneath the CD. The CD will already sit quite a bit higher than the F/R diff outputs, so the bigger the spur, the higher it needs to sit to not have the spur hanging it nuts out the bottom of the truck. Ideally a very small spur would be used so the CD could be mounted low and at more optimum angles for the drivelines, and make up the FDR by low gearing in the diffs, say 4.2s or whatever as in truggy diffs.

For may particular intent, I think I need a 15-17:1 FDR, which is next to impossible w. Cen 2.89s and a CD. At worst take it upto about stock ratios on the diffs, and use Mike's 50T spur on the slipperential w/ 10T pinion. Better yet would be 4.2 or so diffs, Mike's 46T and a 11T+ pinion.

That's why I centered the diff and offset a slipper shaft on my conversion. Brings the motor down to below the top of the tvp and maintains good driveline angles, also allows for more gear reduction. If you're custom machining anyways, may be the way to go.

[MetalMan]

Finnster, I like that Savage layout a lot... Should allow both batteries to sit inside the FLM extended low CG TVPs as well. Only thing is, I wouldn't incorporate the servo mounts into the upper deck as I am using the FLM servo mounts which IMO would be a simpler option.

Have you considered designing a CD mount similar to what I have on my Savage? This is just about the strongest way to do it (from what I have found), because it incorporates the motor and center diff into the chassis, which also strengthens the chassis. The skidplate method is definitely easier, but the attachment points for the skidplate are few and far between, and you will lose some chassis strength as well.

Last point, if you go with a Slipperential, I can pretty much guarantee you won't have any issues with the Flux diffs. This means you could go back to the original diff ratio and use the 46t gear.

[Finnster]

@ p4: Do you have a pic of your setup to show what you mean? I'm taking it you made basically a 1spd tranny? (sort of like the kershaw DD unit, but hopefully less craptacular lol) An idler gear would def help getting the ratio down a bit, lend flexbility to the geometry, but its a bit more complicated unit to get together and beyond was I was thinking of doing.

MM:
It is a better design. My first designs were to have the motor mount directly attach to the tranny mount holes, but I was having problems calculating exactly where those holes were. I actually went so far as to buy a used geometry textbook that was @ the library for $0.50 lol. I could measure all the lengths between the holes easy enuf w. a caliper, but what I was having a hard time determining was the angles between the holes. Its a pita to calc angles when you don't have a 90* angle, and its been forever since i've done geometry. I know there was something simple I was missing.

Ie, are the upper and lower holes directly underneath ea other and perpendicular to the ground, as well as parallel top line to bottom line? IOW, could you draw a big 90 between 3 sets of holes. It didn't seem like you could, but I really need to go back and look. I know the rear upper tranny mount is not perp to the lower mount, and I couldn't verify the front one.

The tranny mount is somewhat asymetrical, and I wouldn't want to assume they do run perp, then to create a mount and find out its pitched forward or backwards one way or the other. Also, What I was considering was reducing the number of mounts that need to be machined and designed. if the motor mount could be made in a dimension the same as a popular plastic mount (say a losi 8) then only one mount would need to be made, then use the plastic part for other side. Its a bit cheaty, but I didn't want to draw a whole other mount and worry about the geometry issues.

If I had a CNC or even a drill press to hand machine parts that would be one thing, but trying to draw up a CAD file on a cheap freeware SW, then send it to someone to build, then get it back to see I fragged up a measurement and it doesn't fit sucks.

Lastly, I wasn't sure this would leave enough room in back for batts as the tranny was pretty well centered. I would hope to move it up some, and maybe where I could use an OEM driveshaft. Less custom stuff to drive price and headaches higher.

I'll have to go home and look at my notes from a while back and see what I knew.

[Finnster]

BTW, I do have a set of those FLM servo mounts as well. Those were an alt plan on mounting the str servo. Ideally underneath the plate, leaving the space on the plate open to mounting all the electronics.
I could mount the servo flat up against the bottom of the plate, or directly to the chassis. You could get it to work either way if you can find the space I think.



Hahaha... you see how complicated this got and why I decided to say F it and just keep the nitro running in there? I thought the KErshaw DD or Flux would solve things for me, as it turned out it didn't. Still lots of questions and a smelly nitro engine remain.....

[pb4ugo]

Originally Posted by Finnster

@ p4: Do you have a pic of your setup to show what you mean? I'm taking it you made basically a 1spd tranny? (sort of like the kershaw DD unit, but hopefully less craptacular lol) An idler gear would def help getting the ratio down a bit, lend flexbility to the geometry, but its a bit more complicated unit to get together and beyond was I was thinking of doing.

MM:
It is a better design. My first designs were to have the motor mount directly attach to the tranny mount holes, but I was having problems calculating exactly where those holes were. I actually went so far as to buy a used geometry textbook that was @ the library for $0.50 lol. I could measure all the lengths between the holes easy enuf w. a caliper, but what I was having a hard time determining was the angles between the holes. Its a pita to calc angles when you don't have a 90* angle, and its been forever since i've done geometry. I know there was something simple I was missing.

Ie, are the upper and lower holes directly underneath ea other and perpendicular to the ground, as well as parallel top line to bottom line? IOW, could you draw a big 90 between 3 sets of holes. It didn't seem like you could, but I really need to go back and look. I know the rear upper tranny mount is not perp to the lower mount, and I couldn't verify the front one.

The tranny mount is somewhat asymetrical, and I wouldn't want to assume they do run perp, then to create a mount and find out its pitched forward or backwards one way or the other. Also, What I was considering was reducing the number of mounts that need to be machined and designed. if the motor mount could be made in a dimension the same as a popular plastic mount (say a losi 8) then only one mount would need to be made, then use the plastic part for other side. Its a bit cheaty, but I didn't want to draw a whole other mount and worry about the geometry issues.

If I had a CNC or even a drill press to hand machine parts that would be one thing, but trying to draw up a CAD file on a cheap freeware SW, then send it to someone to build, then get it back to see I fragged up a measurement and it doesn't fit sucks.

Lastly, I wasn't sure this would leave enough room in back for batts as the tranny was pretty well centered. I would hope to move it up some, and maybe where I could use an OEM driveshaft. Less custom stuff to drive price and headaches higher.

I'll have to go home and look at my notes from a while back and see what I knew.

http://www.rc-monster.com/forum/showthread.php?t=19259

BTW, you are right about e-machineshop being hideously expensive. I ended up just getting the parts waterjet cut (hence the raw finish) and having a local machinist counterbore for the bearing recesses. If i were to ever be in a production situation like Mike, the machined finish would be important for sales, but for functionality it does nothing. If you want, I can submit any drawing you want to my waterjet place when I have other work for them (cheapest I've found). If you want any dimensions on what worked for me as well, just ask.

[MetalMan]

This is an older pic, but still pretty much the same (minus mechanical brakes):
http://img.photobucket.com/albums/v1...e/IMG_6071.jpg

The 1/8" thick pieces on the side are kinda like adapter plates, where they were not drawn up on a computer, but the holes in them were drilled using a TVP side as a template. Then other strategically placed holes were drilled with matching tapped holes in the CD/motor mounting pieces. Look at the top 2 button head screws in this pic (on either side of the velcro):
http://img.photobucket.com/albums/v1...e/IMG_8083.jpg
Those screws are just 2 of the ones holding the "adapter" plates to the chassis. Just to the left and down from the left-most of the 2 button head screws you can slightly see a countersunk 4mm screw, this is one of the ones attaching the CD/motor mount plates to the adapter plates. It's hard for me to explain it without adequate pictures, but the design is very simple. Manufacturing is very simple as well, provided you are able to drill 1/8" holes and tap them to 1/4" in 1/4" thick aluminum (with accuracy).

Thanks to your motor layout idea, I'm actually going to completely remake my CD/motor mount pieces so the motor can be positioned at the front and more to the left. Then there will just barely be enough room to fit my batteries inside the TVPs, and that will improve the handling of the truck a lot.