Help me with a slipperential & mount for my savage please.
 

Ok... Hi everyone:wink:

I have a savage flux.. Here is my build with some pics and vids
http://www.rc-monster.com/forum/showthread.php?t=26750

Anyway i have been having serious tranny issues with gears stripping etc... I feel the tranny is the weak point in the savage drive train. If i can eliminate these gears, not only will i save weight but less can go wrong regarding gears.

This is where the slipperential comes into play... i obviously know where to get one from so i am not worried about that... but mounting is another thing.

I have seen some people make mounts for their savages but i am not capable of that as i do not have the machinery...

So i am going to have to work out a way of using existing parts and making them work with my savage.

The first thing i am looking for is a slipperential/motor mount... I found a few which look very nice but i am not sure if they are being produced, home built or what ever really.....

This one below is my favourite and i would love to get my hands on this... I believe mike makes them? but i am not entirely sure... but whoever does is an artist :mdr:

http://lh4.google.com/ssspconcepts/R...0/IMG_2071.JPG

There is a pic below (terrible i know :whistle:) of where i would fit this mount.
I was thinking of running 3 support braces between the TVPs(twin vertical plates) along the bottom, centre of the chassis.
I can then bolt the centre diff mounting plate to the braces (points in red) using the exiting holes in the mounting plate and have it facing the way shown (Motor in green).

http://i878.photobucket.com/albums/a...87/001edit.jpg

This should work quite well dont you think? i would have to get new drive shafts made up, but i dont think that would be a problem...

Now i am curious to know whether i will still be able to utilise some form of mechanical braking as i dont like motor brakes???? How do truggys use mechanical brakes when using brushless motors? Could someone enlighten me here...:whistle:

Also just to inform people... i am using the neu1520 motor... it is quite heavy but i am mostly worried that in a crash, that the motor will rip off from this style of mount?:diablo: Has anyone experienced this before? Or should it be strong enough?:neutral:

Thank you very much in advance...

I have never worked with diffs or slipperentials as savages have rubbish transmissions.... so your help and knowledge on what you think would work best would be very appreciated.

Josh

Well I know that the "Universal Center Diff Mount" that is in the RCM store does not allow the use of the Slipperential.

oh really? so what diff would you recommend as the "strongest" most reliable diff to be used with this particular mount...

And could you recommend anyother mounts that would work with the slipperential?

Thank you for the heads up

On the contrary, the universal CD mount is in fact compatible with the 46t and 58t mod.8 Slipperential diff. :)

Thanks for chiming in mike...
Are you going to be getting the universal mount back in any time soon???
Also i am trying to use this speed calculator, and i am wondering if my results below look correct?

Differential Ratio: 3.2222222222222223
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 58 (58t mod.8 Slipperential diff.)
Pinion Tooth Count: 14
Total Voltage: 22.2
Motor KV: 1600 - Neu 1520
Tire Diameter (inches): 5.5
Tire Ballooning (inches): 0.5
Motor Current Draw: 0
Motor Coil Resistance: 0
Spur/Pinion Ratio: 4.14 : 1
Total Ratio: 13.34921 : 1
Tire Circumference (inches): 20.42 inches (518.68 mm)
Rollout: 1.53:1
Total Motor Speed: 35520 RPM
Vehicle Speed: 51.45 mph (82.65 km/h)
Effective KV Value: 1600


I am currently geared for 53mph with my savage tranny, and i am running 110degrees on motor and esc, 90-100 on the lipos. I am hoping to run 9s eventually just for road runs.

Anyway back to the main topic & bottom line is that the slipperential does work with the universal mount.

My question, does the universal mount come with the base plate shown in the picture above? It would make it much easier for me to mount the diff if i have that plate to bolt to the braces.

Mike, do you know anyone who has tested your slipperntial on 9s+ set-ups? and how i dont mean to be rude, but how confident are you about your mounting securing the motor to it? I personally believe that the motor would strip away from the mount on a hard landing considering the weight of the 1520?

Thanks

Great thread, this is exactly what I am thinking about doing with my Savage. I'm using the FLM Savage Flux XL tvp's on mine. Nice wheels Jay, I think using the universal CD mount and slipperential would be perfect for this truck.

So Mike, how about a universal CD mount and mount plate made to fit the Savage tranny mount holes already in the tvp's? That would be perfect, consider it sold, along with a slipperential.

I see, I was referring to this thread, but didn't read far enough past the first post: http://www.rc-monster.com/forum/showthread.php?t=25940

So it will work, but the mount will need some modding of the top plate.

ahem...

http://i152.photobucket.com/albums/s...tormountv2.jpg
http://i152.photobucket.com/albums/s...gerenderv2.jpg
http://i152.photobucket.com/albums/s...nt2ndangle.jpg

oooooooweeeeeee brushless boy... what is that you are mocking up? Looks pretty good... Uses the standard mounting points... And it looks very robust too!!!

Just one little thing... According to your drawings, if i am correct regarding the motor... You have to fit the motor first then fit the pinion? as the pinion cant fit through the hole already fitted to the motor shaft? Or am i looking at it wrong?

Looks like it will fit with the appropriate shimming, which shouldnt be too much of a problem... But maybe mike will take this into account when machining the next batch of mounts?


Mike please chime in, as i think quite a few of us savage owners would definitely throw out stock trannys away as they are a huge weak point in our drive train, and if this idea was more easy to implement, im sure everyone would do it (people with fluxs do get bored of the wheelies)

Thanks a lot

Thanks, another member here asked for the same thing.. Slipperential mount for a savage.

You have to put the pinion on after the motor, its an easy thing to do, or i could tweak the design so you dont have to:whistle: shoot me a pm if your interested

Looks nice Bb16.

you have pm bb16...

Anyway back to this in regards to the mechanical brakes...
Lots of truggys use centre diffs, but how would they utilise mechanical brakes?

I dont see the point to making the pinion slip through the motor mount, its a single set screw< 2.0mm driver, and it takes less than a second to do. Plus You would need a huge hole to fit anything over like a 13t pinion

i guess there is easy enough access directly from above...

So can i expect to receive one next week :) haha jk

But on a serious note... when are you thinking about making some mock ups?

There is nothing above the motor mount to block your access...

And Im going to talk to mike to see if he can run a few of them

when you say run? do you mean test? or machine?
I would be happy to test it with a larger motor and as a brushless forward facing mount idea...

machine them

Mothman Here has first dibs, your second:yes:

lol ok... second is fine :) how long do you think the whole process will take. Im not rushing its just i need to know whether its worth me temporarily rebuilding my tranny and hoping it lasts more than 10 runs :)

rebuild your trans...

I call third dibs, very nice design.

Why thank you kind sir

Looks pretty good Ben. I was working on a mount for a Sav for a while, but gave up when Mike was coming out w/ the universal mount, and finding that designing in CAD is a pita. Mike makes it look a lot easier than it is.

Unfortunately the universal mount has been OOS for a couple months and no updates on an ETA.

The only issue putting in a CD in a sav the the limitations onf gear ratio, especially if you want to use the bulletproof diffs. They are a low gear ratio (3.22 iirc) so if you want to go a CD and run big tires etc, you need to come up with quite a reduction in the CD/pinion. Even an extreme 10/50 ratio only gets 16.1:1. I wouldn't bother running 0.8mod gears either.

Perhaps Mike is working on something to go with the Savage 5B kit he's developing. Ditching the tranny would be nice. Mech brakes are easy to do as well, but honestly I'd stick w/ motor brakes for simplicity and lack of brake fade.

ok finsster how would i maintain mech brakes if i wanted to keep them?

You are also talking abuot gearing which is important regarding space between the tvps etc...
Do you think a 58/14 gear combo work/fit? (that would bring me to around 53mph, i think)
What gearing do people usually use when gearing for 50 using a cd?

The mount you choose needs to have the 3mm tapped holes to mount the brake pads. The brake disks just slide over the diff output shaft. Lastly you need to have some sort of brake cam. Usually this is in the CD top plate. Kinda tricky with the motor mount there. The mount I was trying to design would have this on the side.
Lastly you have to figure out where to mount the brake servo, and tie that to the thr via a y-cable or a 3 chan radio.

=> Major pita to run mech brakes with a motor over diff type mount. Motor brakes is far simpler and prolly more effective.

As far as gearing goes, just figure out what final drive ratio you have now or what others are using in your app, and work the math back from there. If the diffs are 3.22, and you want a FDR of 14:1, divide 14/3.22. (4.35) That's your spur to pinion ratio. Then pick out a set of gears that is close and is reasonable for your app. In that ex, a 46/11 gearing would be close and a 46 spur is widely available. For a slipperential, the 50T spur is your best bet imo.

Note that the larger the spur, the farther below the TVPs the spur will hang, or you will have to raise the mount and run sharper angles on the driveshafts. Conversely, a v. small pinion will wear more quickly. Have to find a balance

Thanks for the help finnster, i hope i can run mech brakes, if and when i find an appropriate mount, i will look into the brakes. I just want a decent motor and diff mount.

I am a little worried about choosing the wrong spur gear which will have difficulties fitting. I may need some pics of the slipperential with the 58t spur on and see if it will work in a savage and has enough clearance.

Plus i am hoping it is quick and easy to change the spur on the slipperential as i will want to run a plastic spur vs a metal one so my pinion doesnt experience wear....

So just to go back to the original topic... does the product in the rc monster store come with the base plate shown in this picture?

http://lh4.google.com/ssspconcepts/R...0/IMG_2071.JPG

Im hoping to do this mod within the next month or so... unless BB16 has his in production by then i most likely will have to go with this universal mount, and it would help if the plate was included...

MIke is reviewing the design for my slipperential mount

BB16 thanks for the update... please keep me updated. Way to keen on getting this going.

Rodger dodger... I got bored during english class today... started making random things...
http://i152.photobucket.com/albums/s...10/1515can.jpg

that can looks quite kl... should use it on a motor...

Have you made any revisions to the savage slipperential/motor mount?

BB16 i dont know why, but i am having so many bad thoughts that on a bad landing, the motor would rip from the motor mount as its only held on via 2 screws (2 small screws). Would there be any other way of mounting some form of plate under the motor and attatching it to the motor and mount in some way which still maintains flexibility?

Jahay,
fear not the stregth of m3 screws - each metric m3 threaded screw has a tensile stregth in excess of 165000 psi. This equates to hundreds of pounds of force when tightened and is more than sufficient for the task at hand. :)

@ Jahay: Everyone mounts the motors like that, and I haven't heard of any damages. I've had bad enough landings on my truggy the chassis flexed and bent up far enough to slap the rear of the motor, yet no damage to the motor mount. (did sever a servo wire running underneath tho.)

I would also strongly recc using the steel mod1 spurs. Not only are you looking at easily stripping plastic (vs steel) the smaller pitch will make it even weaker. The spur is $27, yet the pinion is $10. Replacing a pinion every now and then is much cheaper than the spur, plus nothing ruins your day like stripping a spur, and then sitting waiting for the new one to ship.

The CD mount is back in stock and I just ordered one. I was planning to mount it on an FLM skidplate, but the ext one I wanted is OOS.

I cant tell from the pix on the skid plate tho how clean it will be. On the RCM site, the pix of the FLM skid show little relief machine work. OTOH, some pix on FLMs site show quite a bit of machining. I'm assuming the FLM pix are more recent revs of the part, so not sure how this will effect it.


Lastly, does anyone have any ideas on dogbones? Even if I kept the rear stocker, the f would have to have a longer one.

Thank for restoring my confidence in this method of motor mounting mike!

Thanks finnster for the info. I will prob just run the steel spur then...

I didnt like the idea of mounting the CD to my skid plate and as i am not using an FLM Chassis it would make it difficult anyway. I would probably mount the motor in a similar way but mount it to the TVPs via braces or attatch the cd mount to a plate and attatch the plate to the braces.

Has anyone got any pictures of what the universal mount looks like from underneath and where the screw holes are located?

Finnster GCM were going to make my custom dogbones for me. Im quite happy with the ones they use with their DB-17 xxl conversion and they have held up without any signs of distortion so far. Here is their site.... http://gcmachine.ca/index.php/fabrication/index

Instrustions
 

Mike's RCM universal diff mount comes with a paper template that you can use to make the four holes for mounting it in the chassis or whatever plate you use in your configuration. His design provides you with 4 = M3 screws that screw into the bottom of the mount to hold it in place. For personal reasons I tapped mine out to M4 to use 4mm screws for my project. I love overkill when it comes to strength. The kit is quite simple and easy to set up and even modify if you need to. All-in-all it is a great setup and it is perfect in resolving tranny issues by elliminating the tranny all together. I have mine setup with an HPI lightning hardened diff with an RCM savage aluminum cup with a 44t steel spur and it is very smooth.

All you need are the FLM or HPI 74mm cross braces that go across the TVPs. You could mount it directly to the braces (which I may do) altho atm I am leaning towards mounting on a skid plate that is attached to such braces and bolted directly into the TVPs. I have some electronics and a rear steering servo I want to protect from rocks and sticks. Plus I'm thinking it would give a bit of flexibility in mounting location.
Either way requires a bit of modding, but Savs are really easy to mod w/ the TVP structure. Just a 4mm hole thru each TVP and you can install a brace wherever there is space.

Thanks for the heads up on the custom bones.

@ Jerry, thx for the tip on the bottom mounting screws. I may tap mine out to 4mm too. Last thing I want to do is shear or strip a 3mm screw (had enough of these when I had an emaxx....)

I was considering doing that finnster with the braces but it if i can find another way of mounting it i would be happier.

I know this is a silly question, but i have never tried tapping my own holes. I know this would definitely benefit the mount and prevent any stripping. What specific tools would i need to do it?

All you need is a properly sized drill bit and a hand tap (and the tap wrench to hold it.) You first drill out the hole to the approx size, then run a hand tap down the hole which cuts the threads. Basically looks like a threaded drill bit.

You can get taps all over the place, but small metrics are not so common. I get mine from McMaster Carr, but I'm sure Harbor Freight or any other decent hardware dealer has them. M4x0.7mm and M3x.5mm are the most common sizes in RCs. Invaluable tools to have IMO.

Interesting idea about mounting the CD sideways. I wonder if it would fit inside TVPs tho.. Only 74mm clearance. You would not want to tap the thru hole, just the mount the screws are going into.

Simple
 

Here is a link to one of the cheapest sets I have seen. I have one of these plus a few others. 3mm and smaller taps are easy to break, so I have spare taps just in case. You can find larger and better tap sets, but this is a good starter set.


http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXE224

All you have to do is drill the hole with the matching drill bit according to the size of tap, then tap the hole out with a threading tool. Use a piece of scrap to practice on and make sure you can do it farely well before trying it on your exspensive toy. It's really not difficult at all once you know what you are doing. Keep the drill straight and level to make a good hole to work with. When you use the tap the standard method is to move forward 1 turn and back off 1/2 turn repeating this all the way through until you reach the desired deapth. This will help to keep the hole clean and keep the tap from gauling and getting jammed in the hole, or even breaking off in the hole.

thanks for the links and explanations, sounds pretty simple.....

Finnster - i was considering using another style of mount used on truggys which mount on its side, but this cause a few too many problems.
- It just wouldnt fit inbetween the tvps properly
- The CD would be way out of line with the diff axles

But i did like the idea of LCG.... This universal mount will be fine though.