Motor mounts don’t accept 8mm shaft pinions?

[Diem Turner]

I’m getting really, really frustrated with this crap. I have a TP 4070 with an 8mm shaft going into a build. Guess what? The motor plate bore is (again) too small to accept Saga 8mm Mod-1 pinions. Of which I have a very nice selection. The shoulder of the gear barely fits in the motor plate, and when you factor in the grub screws? Nope. They rub on the bore. And no, thanks for the suggestion, but the shaft on the TP isn’t long enough to flip the pinion. So now I’m going out to my shop in the unheated barn nestled in the quite picturesque yet frozen, arctic tundra to fire up my drill press and machine the bore out of YET ANOTHER ”big motor” motor mount. I’m getting sick of this. The “big motor” plates from all brands I’ve used to date (PPS, the Arrma “option” big motor plate for stock mounts, and now the Iron Man “big can” mount) do indeed accommodate the bolt spacing of the bigger motors but apparently in no way account for the fact that the bigger motors might actually have a bigger shaft. I’ve successfully deleted so many expletives in this post…
WTF.

Let me begin by stating, unequivocally, that it is not my intent to on your myopic motor plate machining meanderings (you thought I was going to follow this with a BUT dot dot dot, didn't you? You know what that makes you? An absolutely correct observer of reality so at this point I extend my congratulations) BUT...
I don't understand what the problem is here. I mean, from a linguistic and contextual point of view, I understand the issue you're describing. As someone mentioned, spools can help circumvent this particular problem as some are designed so that you can position the spur gear anywhere on the shaft of the spool (so long as it remains between the motor mount and diff/spool support...going beyond those boundaries will present an all new slate of issues that I'll spare you all the indignity of watching me delve into at length, in verbose & autistic detail...) but even this is not necessary. This is a brief video of my 100% stock PPS grub lock motor mount where I have intentionally lowered (or slid sideways depending on your current orientation in relation to the axis of the motor as you read this) the pinion as far as it will go.

There's a cheap and easy solution to this problem (which I [sort of] never had because I got these before I ever got my PPS or Rotolock motor mounts because they're just better in every conceivable way...I say sort of because I did have this issue but it was with the stock Arrma motor plate that comes in the 6S BLX platform vehicles which wasn't intended for large motors so I found myself, much as you describe, widening the opening of the motor mount with a stepped drill to accomodate a protruding grub on a pinion gear).

Torx grubs are infinitely better than hex grubs. They're so worth the swap. Moreover, these are 5x5mm which makes them the perfect length for 8mm pinions as they barely protrude a half mm when snugged down. Should you be in a particularly tight squeeze, that half mm can easily be removed with a file or grinder leaving plenty o' meat to plunge your favorite Torx® bit into.

So in closing...save yourself the anguish, stop committing machinual assault on your motor plates and discover the joy and pleasure that affixing a Torx® grubbed pinion and/or spool/spur gear can bring to your life. I know what it has done for mine.

FG Grub screw with Torx M5x5mm - 15pcs. (part nr.: 6930/05)

6,50 €

 

[joshjosh]

Let me begin by stating, unequivocally, that it is not my intent to on your myopic motor plate machining meanderings (you thought I was going to follow this with a BUT dot dot dot, didn't you? You know what that makes you? An absolutely correct observer of reality so at this point I extend my congratulations) BUT...
I don't understand what the problem is here. I mean, from a linguistic and contextual point of view, I understand the issue you're describing. As someone mentioned, spools can help circumvent this particular problem as some are designed so that you can position the spur gear anywhere on the shaft of the spool (so long as it remains between the motor mount and diff/spool support...going beyond those boundaries will present an all new slate of issues that I'll spare you all the indignity of watching me delve into at length, in verbose & autistic detail...) but even this is not necessary. This is a brief video of my 100% stock PPS grub lock motor mount where I have intentionally lowered (or slid sideways depending on your current orientation in relation to the axis of the motor as you read this) the pinion as far as it will go.

There's a cheap and easy solution to this problem (which I [sort of] never had because I got these before I ever got my PPS or Rotolock motor mounts because they're just better in every conceivable way...I say sort of because I did have this issue but it was with the stock Arrma motor plate that comes in the 6S BLX platform vehicles which wasn't intended for large motors so I found myself, much as you describe, widening the opening of the motor mount with a stepped drill to accomodate a protruding grub on a pinion gear).

View attachment 349544

Torx grubs are infinitely better than hex grubs. They're so worth the swap. Moreover, these are 5x5mm which makes them the perfect length for 8mm pinions as they barely protrude a half mm when snugged down. Should you be in a particularly tight squeeze, that half mm can easily be removed with a file or grinder leaving plenty o' meat to plunge your favorite Torx® bit into.
View attachment 349545View attachment 349546

So in closing...save yourself the anguish, stop committing machinual assault on your motor plates and discover the joy and pleasure that affixing a Torx® grubbed pinion and/or spool/spur gear can bring to your life. I know what it has done for mine.

FG Grub screw with Torx M5x5mm - 15pcs. (part nr.: 6930/05)

6,50 €

It is a valid solution if you’re running a spool. Great for a speed runner, but not great for handling if you aren’t driving in a straight line. The pinion physically doesn’t fit the hole. Grub screw or not.

 

[Diem Turner]

It is a valid solution if you’re running a spool. Great for a speed runner, but not great for handling if you aren’t driving in a straight line. The pinion physically doesn’t fit the hole. Grub screw or not.View attachment 349547

This should be a valid solution if you're running a diff too (which I've tried as well and I don't have any issues with gear mesh or that my gears fit inside the recess of my motor plate as I exclusively use 8mm pinions). And yes, it 100% does fit neatly inside the motor plate (at the very least on the PPS and Rotolock motor mounts, which are the only two I can verify because I own one of each). That's why I recorded and uploaded the video for a brief illustration of that it does actually work without the need for modification. I understand that spools aren't ideal for every use case and that where they shine is speed running and at the drag strip but, the spool wasn't the crux of my argument or suggestion (although I do happen to know that Dan is looking to do some speed running which is why I included a spool as a possible solution to the problem but seeing as they're not exactly cheap in comparison to a handful of grub screws, the grub screws are the focus of what I was talking about and why they're the only part that I list specifically with a price and part number).

I took a few more pics in the event that it wasn't as obvious to see in the video as I may have thought. Here you can see that the grub screw of the pinion gear is 1/4-1/3 of its diameter below the flat of the motor plate. So the shoulder of the pinion must be inside the motor plate. I realize that black on really dark steel doesn't make for the best contrast but I marked the motor plate's flat plane on the shoulder of the pinion with it installed and then tried to get at least one good pic where you can see how much of the shoulder is below the surface. I tried to get a pic of the motor plate and (I hope) that the recess is about as deep as the mark on my pinion would suggest.

Scorched's Rotolock also accommodates the broad shoulder of an 8mm pinion without any clearance issues. To be clear, I'm not saying that because this works on these two mounts that it, therefore, should work on every other motor plate. I'm only addressing Scorched's Rotolock (which I don't believe Dan has had a chance to try out yet) and PPS since Dan specifically mentioned them in the OP.

I hope the pictures help to more clearly illustrate that 8mm pinions fit inside PPS motor plates without the need for any modification, as was the intent of my original response.

 

[Dan B.]

Let me begin by stating, unequivocally, that it is not my intent to on your myopic motor plate machining meanderings (you thought I was going to follow this with a BUT dot dot dot, didn't you? You know what that makes you? An absolutely correct observer of reality so at this point I extend my congratulations) BUT...
I don't understand what the problem is here. I mean, from a linguistic and contextual point of view, I understand the issue you're describing. As someone mentioned, spools can help circumvent this particular problem as some are designed so that you can position the spur gear anywhere on the shaft of the spool (so long as it remains between the motor mount and diff/spool support...going beyond those boundaries will present an all new slate of issues that I'll spare you all the indignity of watching me delve into at length, in verbose & autistic detail...) but even this is not necessary. This is a brief video of my 100% stock PPS grub lock motor mount where I have intentionally lowered (or slid sideways depending on your current orientation in relation to the axis of the motor as you read this) the pinion as far as it will go.

There's a cheap and easy solution to this problem (which I [sort of] never had because I got these before I ever got my PPS or Rotolock motor mounts because they're just better in every conceivable way...I say sort of because I did have this issue but it was with the stock Arrma motor plate that comes in the 6S BLX platform vehicles which wasn't intended for large motors so I found myself, much as you describe, widening the opening of the motor mount with a stepped drill to accomodate a protruding grub on a pinion gear).

View attachment 349544

Torx grubs are infinitely better than hex grubs. They're so worth the swap. Moreover, these are 5x5mm which makes them the perfect length for 8mm pinions as they barely protrude a half mm when snugged down. Should you be in a particularly tight squeeze, that half mm can easily be removed with a file or grinder leaving plenty o' meat to plunge your favorite Torx® bit into.
View attachment 349545View attachment 349546

So in closing...save yourself the anguish, stop committing machinual assault on your motor plates and discover the joy and pleasure that affixing a Torx® grubbed pinion and/or spool/spur gear can bring to your life. I know what it has done for mine.

FG Grub screw with Torx M5x5mm - 15pcs. (part nr.: 6930/05)

6,50 €

I should clear one thing up. The PPS mount I referenced in the OP was the old V1, not the new grub lock style, and I know he now states specifically that bigger motors fit those, so maybe there is an accommodation for an 8mm shaft pinion.
I went with the “big motor” Ironman RC mount (love the side loading spool mount!) at your recommendation, Mr Turner, since my previously ordered PPS mount hadn’t come yet and the Ironman was only two days away from my greedy, impatient hands. It also fails to accommodate an 8mm pinion, so I just sucked it up and ordered a titanium spool for it so I could move the spur wherever I wanted to, as I was sick of boring motor plates at this point and my fun tank was full. Of course, that was problem solved and what I should have done in the first place, but I was still in the fantasy land of keeping this to a KISS budget build. We all know how that worked out…
I will say that in your pictures the grub screw wasn’t protruding any less than mine, I think. I didn’t mic the grub screws from Saga, but they barely protruded at all and still made contact with the bore of the plate. Another 0.5mm less would have done it I think. I did mill down the grub screw to fit at one point and when test fitting it was ok, but I stripped it while removing it because there wasn’t enough meat left on the hex. I was very glad I didn’t have thread lock on it yet! I’ll check out those Torx grubs you referenced, I’d like to have some on hand. Thanks for the info!

 

[Diem Turner]

I should clear one thing up. The PPS mount I referenced in the OP was the old V1, not the new grub lock style, and I know he now states specifically that bigger motors fit those, so maybe there is an accommodation for an 8mm shaft pinion.
I went with the “big motor” Ironman RC mount (love the side loading spool mount!) at your recommendation, Mr Turner, since my previously ordered PPS mount hadn’t come yet and the Ironman was only two days away from my greedy, impatient hands. It also fails to accommodate an 8mm pinion, so I just sucked it up and ordered a titanium spool for it so I could move the spur wherever I wanted to, as I was sick of boring motor plates at this point and my fun tank was full. Of course, that was problem solved and what I should have done in the first place, but I was still in the fantasy land of keeping this to a KISS budget build. We all know how that worked out…
I will say that in your pictures the grub screw wasn’t protruding any less than mine, I think. I didn’t mic the grub screws from Saga, but they barely protruded at all and still made contact with the bore of the plate. Another 0.5mm less would have done it I think. I did mill down the grub screw to fit at one point and when test fitting it was ok, but I stripped it while removing it because there wasn’t enough meat left on the hex. I was very glad I didn’t have thread lock on it yet! I’ll check out those Torx grubs you referenced, I’d like to have some on hand. Thanks for the info!

Always a pleasure! And HELL YEAH! I was your 14000th reaction score point! Bloody hell man, whorra time to be alive! Can this day get any better? This calls for hookers n blow.

 

[joshjosh]

This should be a valid solution if you're running a diff too (which I've tried as well and I don't have any issues with gear mesh or that my gears fit inside the recess of my motor plate as I exclusively use 8mm pinions). And yes, it 100% does fit neatly inside the motor plate (at the very least on the PPS and Rotolock motor mounts, which are the only two I can verify because I own one of each). That's why I recorded and uploaded the video for a brief illustration of that it does actually work without the need for modification. I understand that spools aren't ideal for every use case and that where they shine is speed running and at the drag strip but, the spool wasn't the crux of my argument or suggestion (although I do happen to know that Dan is looking to do some speed running which is why I included a spool as a possible solution to the problem but seeing as they're not exactly cheap in comparison to a handful of grub screws, the grub screws are the focus of what I was talking about and why they're the only part that I list specifically with a price and part number).

I took a few more pics in the event that it wasn't as obvious to see in the video as I may have thought. Here you can see that the grub screw of the pinion gear is 1/4-1/3 of its diameter below the flat of the motor plate. So the shoulder of the pinion must be inside the motor plate. I realize that black on really dark steel doesn't make for the best contrast but I marked the motor plate's flat plane on the shoulder of the pinion with it installed and then tried to get at least one good pic where you can see how much of the shoulder is below the surface. I tried to get a pic of the motor plate and (I hope) that the recess is about as deep as the mark on my pinion would suggest.

Scorched's Rotolock also accommodates the broad shoulder of an 8mm pinion without any clearance issues. To be clear, I'm not saying that because this works on these two mounts that it, therefore, should work on every other motor plate. I'm only addressing Scorched's Rotolock (which I don't believe Dan has had a chance to try out yet) and PPS since Dan specifically mentioned them in the OP.

I hope the pictures help to more clearly illustrate that 8mm pinions fit inside PPS motor plates without the need for any modification, as was the intent of my original response.
View attachment 349564View attachment 349565View attachment 349566View attachment 349567

It looks like your pinion would stick too far out to properly line up with a diff, no? The only reason your PPS partially works with that 8MM pinion is because you’re using the 25mm motor mount holes. Most 8MM shaft motors will be the 30MM hole, and the pinion doesn’t come close to working on those.

I had not looked into the Torx ones, I may give those a go. eBay has cheap flat bottom gr5 TI m5x5 grub screw I use that don’t hit. Had great luck with those. The Torx grub screws don’t look like they have nearly the bite surface, though, and they’re double the weight of the TI. Not that .22 grams each is going to make or break anything, but I’ll take every advantage I can get, especially when it comes to driveline rotational mass.

TI grub

Torx grub

I especially like how they measure a little short

 

[Diem Turner]

It looks like your pinion would stick too far out to properly line up with a diff, no? The only reason your PPS partially works with that 8MM pinion is because you’re using the 25mm motor mount holes. Most 8MM shaft motors will be the 30MM hole, and the pinion doesn’t come close to working on those.

I had not looked into the Torx ones, I may give those a go. eBay has cheap flat bottom gr5 TI m5x5 grub screw I use that don’t hit. Had great luck with those. The Torx grub screws don’t look like they have nearly the bite surface, though, and they’re double the weight of the TI. Not that .22 grams each is going to make or break anything, but I’ll take every advantage I can get, especially when it comes to driveline rotational mass.

TI grub
View attachment 349608

Torx grub
View attachment 349607

I especially like how they measure a little short
View attachment 349612

That's a fair point that I hadn't considered. Guess it's time to extract the 1721 and bolt in the 5680 to see what's what.

While I share your sentiments regarding rotational mass as I can observe my spool rolling back when it comes to the end of a spin, caused solely by the offset of mass on the spool of that tiny piece of metal we call a grub (just for giggles, I've glued a second grub opposite the pinion grub to act as a balancing counter weight, I try to remind myself from time to time, "As accurate as necessary but not as accurate as possible". I do think we're plumbing the depths of the law of diminishing returns and agree that fractional grams is not where we are going to make meaningful improvements (I'm not saying you're wrong to do it the way you do it, quite the opposite).

That is funny indeed. But, if you think about it, those six one hundredths of a mm are so small as to make no appreciable difference. It might not even make a difference at 100 grub screws or even a thousand but...how much material have they pocketed after a million grub screws are produced? What about a billion? It's probably not going to be tons (though it can be frightening sometimes how quickly numbers explode when you're counting billions of whatever). but probably a good bit more than we think. That's some sneaky micro-burglaring, gotta admit.

 

[joshjosh]

That's a fair point that I hadn't considered. Guess it's time to extract the 1721 and bolt in the 5680 to see what's what.

While I share your sentiments regarding rotational mass as I can observe my spool rolling back when it comes to the end of a spin, caused solely by the offset of mass on the spool of that tiny piece of metal we call a grub (just for giggles, I've glued a second grub opposite the pinion grub to act as a balancing counter weight, I try to remind myself from time to time, "As accurate as necessary but not as accurate as possible". I do think we're plumbing the depths of the law of diminishing returns and agree that fractional grams is not where we are going to make meaningful improvements (I'm not saying you're wrong to do it the way you do it, quite the opposite).

That is funny indeed. But, if you think about it, those six one hundredths of a mm are so small as to make no appreciable difference. It might not even make a difference at 100 grub screws or even a thousand but...how much material have they pocketed after a million grub screws are produced? What about a billion? It's probably not going to be tons (though it can be frightening sometimes how quickly numbers explode when you're counting billions of whatever). but probably a good bit more than we think. That's some sneaky micro-burglaring, gotta admit.

Haha, hadn’t thought of it that way! It looks like it’s shorter from being ground flat.

 

[joshjosh]

Haha, hadn’t thought of it that way! It looks like it’s shorter from being ground flat.
View attachment 349621

These look to be the same size that I got with my PP shaft kit, they are 12.9 grade, flat, and cheap. With these I’m able to put a grub screw in pinion on even the non-flat spot of the shaft. I’m finally able to run dual grubs!
M5x4 grub screw

M5x4 is sank down in there

M5x4.9 barely sticks out

 

[RCSid]

View attachment 349564

You don't have any issues with uneven gear wear with the Spur/Pinion running offset like that?

 

[Diem Turner]

You don't have any issues with uneven gear wear with the Spur/Pinion running offset like that?

I would if I ran them like that. I only slid the pinion over to demonstrate that the PPS motor plate would happily accommodate the shoulder of an 8mm pinion. While true, it only hold true for motors with the 25mm bolt pattern which centers the motor on the plate. Large can 30mm...not so much.

I’m getting really, really frustrated with this crap. I have a TP 4070 with an 8mm shaft going into a build. Guess what? The motor plate bore is (again) too small to accept Saga 8mm Mod-1 pinions. Of which I have a very nice selection. The shoulder of the gear barely fits in the motor plate, and when you factor in the grub screws? Nope. They rub on the bore. And no, thanks for the suggestion, but the shaft on the TP isn’t long enough to flip the pinion. So now I’m going out to my shop in the unheated barn nestled in the quite picturesque yet frozen, arctic tundra to fire up my drill press and machine the bore out of YET ANOTHER ”big motor” motor mount. I’m getting sick of this. The “big motor” plates from all brands I’ve used to date (PPS, the Arrma “option” big motor plate for stock mounts, and now the Iron Man “big can” mount) do indeed accommodate the bolt spacing of the bigger motors but apparently in no way account for the fact that the bigger motors might actually have a bigger shaft. I’ve successfully deleted so many expletives in this post…
WTF.

I have to revise my initial reply. Or, at the very least, add a caveat. They work fine with 8mm pinions...provided that it's a motor with a 25mm bolt pattern (I have several 40-50mm can motors with an 8mm shaft). When I bolted up a 5680 with a 30mm bolt pattern, it obviously offsets the motor shaft and so, you're right to b!tch about the motor plate. Since I've been running a spool this problem was just never an issue as Joe Diaz spools allow you complete freedom to position the spur wherever you like (as I said, as long as it's between the motor mount and diff support...I won't go into all that nonsense again).

 

[joshjosh]

Looks like it might work with a Limitless V2 mount! This is awesome, because I’d love to put a center differential in my Limitless sometimes. It just drives a lot better around a track with diff’s. I don’t currently have a diff, about to hit up JRC. I don’t want to give away all my secrets, but currently a 76-77 TTC seems to be exactly perfect. Will verify once I gear down for bashing.

 

[RCSid]

Looks like it might work with a Limitless V2 mount! This is awesome, because I’d love to put a center differential in my Limitless sometimes. It just drives a lot better around a track with diff’s. I don’t currently have a diff, about to hit up JRC. I don’t want to give away all my secrets, but currently a 76-77 TTC seems to be exactly perfect. Will verify once I gear down for bashing.View attachment 349701

Def report back. that's my interest, running the center diff. I had reached out to PPS & RamJam and they both said that taking out more material would compromise the mesh screw stability.... RamJam said that he's coming out with a line of Spur/Pinion gears soon and that he may look into a line of "slimmer" spur gears to solve that problem so it can lock down and line up with a center diff.

 

[joshjosh]

Def report back. that's my interest, running the center diff. I had reached out to PPS & RamJam and they both said that taking out more material would compromise the mesh screw stability.... RamJam said that he's coming out with a line of Spur/Pinion gears soon and that he may look into a line of "slimmer" spur gears to solve that problem so it can lock down and line up with a center diff.

It pulled one from a truck in build, it works like a champ.

 

[joshjosh]

I should clear one thing up. The PPS mount I referenced in the OP was the old V1, not the new grub lock style, and I know he now states specifically that bigger motors fit those, so maybe there is an accommodation for an 8mm shaft pinion.
I went with the “big motor” Ironman RC mount (love the side loading spool mount!) at your recommendation, Mr Turner, since my previously ordered PPS mount hadn’t come yet and the Ironman was only two days away from my greedy, impatient hands. It also fails to accommodate an 8mm pinion, so I just sucked it up and ordered a titanium spool for it so I could move the spur wherever I wanted to, as I was sick of boring motor plates at this point and my fun tank was full. Of course, that was problem solved and what I should have done in the first place, but I was still in the fantasy land of keeping this to a KISS budget build. We all know how that worked out…
I will say that in your pictures the grub screw wasn’t protruding any less than mine, I think. I didn’t mic the grub screws from Saga, but they barely protruded at all and still made contact with the bore of the plate. Another 0.5mm less would have done it I think. I did mill down the grub screw to fit at one point and when test fitting it was ok, but I stripped it while removing it because there wasn’t enough meat left on the hex. I was very glad I didn’t have thread lock on it yet! I’ll check out those Torx grubs you referenced, I’d like to have some on hand. Thanks for the info!

Had a chance to test the motor mount?

 

[Dan B.]

Had a chance to test the motor mount?

I never really had to because I just bit the bullet and got a center spool so I could move the spur where I needed it to be.
However, I’m doing another build right now so I can check it out on this one. I’ll be using a new gen PPS motor mount, and I’m not sure of the motor yet but it should have an 8 mm shaft. I’ll check it out.

 

[joshjosh]

I never really had to because I just bit the bullet and got a center spool so I could move the spur where I needed it to be.
However, I’m doing another build right now so I can check it out on this one. I’ll be using a new gen PPS motor mount, and I’m not sure of the motor yet but it should have an 8 mm shaft. I’ll check it out.

Haven’t seen a new gen, can it fit a 8mm pinion gear?

 

[Dan B.]

Haven’t seen a new gen, can it fit a 8mm pinion gear?

What I meant by “new gen” was the current grublock mounts he’s been making for awhile now. The other one I used had been on my shelf for a few years and was one of the first styles he did, before the current grub lock mounts.
I’ll see about the pinion situation. At the end of the day, I guess it would really only matter if you wanted a center diff or were using the factory Arrma Lim spools. I do have a street basher I’ll be rebuilding soon that I definitely want a center diff in, but I think that will end up running a Castle 1650, and those just have a 5mm shaft. And jeez man, after the last few builds getting various TP motors with 8mm shafts, that 6mm looks so small to me! I’m like, can this thing really take it?

 

[joshjosh]

What I meant by “new gen” was the current grublock mounts he’s been making for awhile now. The other one I used had been on my shelf for a few years and was one of the first styles he did, before the current grub lock mounts.
I’ll see about the pinion situation. At the end of the day, I guess it would really only matter if you wanted a center diff or were using the factory Arrma Lim spools. I do have a street basher I’ll be rebuilding soon that I definitely want a center diff in, but I think that will end up running a Castle 1650, and those just have a 5mm shaft. And jeez man, after the last few builds getting various TP motors with 8mm shafts, that 6mm looks so small to me! I’m like, can this thing really take it?

Agreed, that 8mm shaft looks massive sitting next to its little brother!
I like the old design myself. I almost never use the grub screw on the new mount, but there was a dedicated 30mm slide for the old gen. The new gen tried to double them up in the same mount, and IMO, failed at the execution.