Best Performance Spur Gear and Clutch Bell?

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xxz28xx

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What kind of Spur Gears and Clutch Bells do you guys use? I'm not too concerned about gear ratio's, but more about what brand of gears you guys are using. HPI, Hot Racing, Integy, Robinson Racing. I've been burning up spur gears lately and I have a feeling things are getting too hot since the teeth melt/strip within 5-10 minutes of on-road operation. I have yet to take off the CB and check my clutches. Things that you probably need to know in order to help me:

-2 year old Stock Savage 25, no modifications, only about 1-2 gallons of fuel ran thru it.
-Stock 49/15 Spur/CB gearing, have tried 52T Spur-no change.
-Happens under any conditions, even on warmup runs up/down my street.
-Tried multiple gear meshes, from paper thin to slightly sloppy, only change is where on the spur gear teeth gets melted, closer to top of tooth or closer to center of the gear.
-On my 8th Spur gear.
-Have tried different Slipper Clutch settings-no change.
-Engine plate or anything like that is not bent/cracked.
-Engine mounting bolts are locktited down.
-Had this problem before which made me hide the truck for a year.
-Engine was tuned to 250 degree range last time I had it running.

Any thoughts are welcome. I have a feeling I should find out why this is happening, rather than getting heavier duty gears, but it may be necessary...
 
I run the hpi 18 tooth cb and the old savage 25 spur. If it's melting theres a problem.
 
I'm not 100% sure on this but it could have to do with the gear ratio. Different gear ratios are used for different types of surfaces. It could be your gear mesh also. Even though you said you have the gear mesh set correctly, the motor may be at a slight angle and only part of the teeth are meshing. I've done that before but caught it before I ran the truck. Other than that, I'm really not sure, but somebody else here will chime in and help. Also, by the way, I'm running the Hpi steel spur and racing clutch bell.
 
yea i stripped 2 in 1 day and it was because my motor plate was cracked so the the engine would move around while i was driving and i ended up stripping 2 spur gear in like 10 mins.
 
oo ya srry i didnt even answer your question:duh::duh: i am running the hpi 49 tooth spur and a hpi 15 tooth cb.(i might switch to the 18 tooth tho)
 
I run an hpi 47/16 metal combo, the robinson imo is the best alternative because it is a solid piece...no screws to come loose. I would also check to see if something is binding to cause excessive strain on the designed weak link in the drivetrain system, such as a bearing worn out or broken in the diffs.
 
I don't think it has anything to do w/ your gear ratio. Have you checked your clutch shoes? they could be worn causing them to drag(your shoes and springs ) your springs could be worn out. replace your clutch shoes and springs and see if that helps . also take some sandpaper to the inside of the clutch bell and scuff it up. this will help the shoes grab better.
If this doesn't work ... make sure your slipper clutch isn't too loose and slipping allot., tighten it all the way down then back it off 1/4 to 1/2 turn. Hope you get your problem fixed bud.. Welcome to hpisf. and Keep us posted on what happens

OOOh you might wanna upgrade your clutch shoes to nova brand
 
First off, thanks for the welcome, and I am glad to be here. Second, you guys are amazingly fast to respond...

Here's a pick to get a better understanding of what's going on here:

IMG_1899.JPG


And to address some of the suggestions:
-The engine plate is not broken.
-If I look at the spur gear and clutch gear and kinda line them up I can see that they are flush, so the engine isn't cocked.
-Slipper clutch has been set to different strengths, from max tight to about 1/2 turn out.
-If I roll the car around, there is no abnormal noises coming from the drive train, nor any odd noises when I am driving it before the gear strips.
 
Hey xxz28xxx, Welcome to the site. bud.
After reading your latest post, I would try tighten the spur spring till it's fully compressed, but not over tightened.
This is not a cure for melting teeth, but can help in not contributing to the problem, in my opinion.

Before you do this, pull the spur gear off and check for any glazing on the slipper pads surface.
If you find any glazing, ruff it up some with 200 grit sandpaper and reinstall.
If the spring loses it's tension over time, so go ahead and tighten flush for now, until you can replace it.

If you hate slipper clutches as I do, you can ckeck out a thread called "DIRRECTDRIVE MY RIDE" in the "Hop Ups" section of this forum.
https://www.hpisavageforum.com/forums/showthread.php?t=2468

I can't say much on Integy except I want thier 20T CB. I know zip on any Hot Racing products.

I have been content with a modifide HPI spur set up and HPI CB's, but have a couple of Robinson Racing combo's in my parts bag.
The Robinson steel gears sets can be great for combatting the melted teeth problem but also add a certain amount of risk to the engines crankshaft and tranny parts.
Not to mention, the the combo itself. Thats the reason why my sets are still in thier still in thier original packaging.....lol.

The danger to damage is due to the un-forseen hard or bad landings we put our trucks through, on an average.
We can tweak the chassis or drift the engine's position ever so slightly just from normal air jumps.

It's not a matter of how, it's a matter of when.
A cracked motor plate is NOT your friend when running metal gears.

The savage is more vulnerable to chassis twists and motor plate breaks in my opinion.
It warrants special reinforcement measures, if your going to rely on metal gears in an off road competition rutine.

Take away the jump factor, I would be using the robinson combo right now.

As far as your melting "teeth issue" goes, I would guess that you might try giving extra attention to a propper mesh attempt.
Almost all gear combos work fine, but there are some that do not. No matter how good your mesh is.

There's a handy gear ratio/compatabillity chart floating around out here for a refference if you need some solid ratios.

If your running in thick grass or up hill climbs. try a lowering the gear ratio to reduce the accessive heat generated at the CB.
It's this heat thats almost always responsible for the melting teeth.

I know there are links here that have the propper mesh info with pics.
Those instructions can help with any questions on how to get the mesh position set propperly.

I hope this helpped, xxz28xxx.

Don't be afraid to ask more questions, ok?

======================== And keep us posted about your progress. Later, bud.==================================
 
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Yep I fully agree with SiteJester. I was having the same problem I blew 4 spurs in 2 days. My savageX is only 4 or 5 months old and I ran at least 2 gallons through the stock mill and didn't have a single problem with my spur gear. Then I put an Axial.32 in it and had about 3 or 4 tanks ran through it. Then the next time I bashed was half way through a tank (engine temp was fine) and the truck just locked up. Two teeth from the stock spur melted into two grooves on the clutch bell. I put in a new spur and started bashing again thinking no worries, as soon as I pulled the truck up to add more fuel it locked up again, so I quit bashing for the day. In the morning I went to LHS to get 2 new spur gears....put a new one on and was ready to rock and roll......wrong I didn't even have it warmed up yet and the darn thing melted another tooth into the clutch bell. At this point I was getting mad about the situation. I was thinking "its gotta be meshed wrong" so I put on another and final of the four spurs I went through to try again got it warmed up went through a 1/4 tank and guess what happened.........yep melted tooth.....AGAIN. So I got some Aluminum NOVA clutch shoes from SiteJester(hes da man) and put on a used spur from my box of junk and I almost have a half of gallon through it and no more melted spur gears. Right now I'm using stock 47t spur/15t CB but will be purchasing a Robinson Spur and CB. I have no experience with RR and it seem to be hit and miss with peoples opinion of them some like them some don't. Good luck bud hope you get it all ironed out. Check this link for Nova products.

https://www.hpisavageforum.com/forums/showthread.php?t=733
 
So I took off the CB and the shoes look fine, inside the CB the surface is pretty smooth. But the bearing for the CB came apart when I took it out. It still spins fine, but the pieces on either side of it can come off, normal? Also that brass bushing on the front is slightly worn, but I don't think that one makes much of a difference. I rechecked the engine plate and its definately not cracked or bent, all screws are loctited in tight. The slipper clutch was also tight. This is getting me pretty worked up... Here's some pics of the ordeal:
 
aaaaand more. it wont let me post 5 attachments at once so I had to split em up.
 
Can anyone find the links for HPI's spur gear/CB chart. I also believe there's a links for gear meshing vid. Hey SJ., do you remember where to find the links. I haven't been very good at posting links yet. Thanks anyone!!!
 
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Wow your clutch beel bearing are shot to $h!t, buy some new ones.
Bad bearings=More heat
More heat=Melted spur
 
I agree, FX. Also, if there's ever been fuel spills on or near the CB, the oils can coat the CB's parts surfaces and increase the heat factor by insulating the CB with baked on fuel residue.
 
ya think that one bearing can cause that much heat??? There haven't been any fuel spills in that area that I've ever noticed...I'm gonna get new bearings, scuff up the shoes and CB with sandpaper and give it another shot. Anything else I should try? What about that brass bushing on the front? That being out of shape has anything to do with it? It doesn't even seem to have that much of a purpose...
 
I would imagine the bearring going bad would be similar to the brass bushing going bad. I still use the brass bushing, myself.
Once the brass starts ovaling out of round, the alignment of the CB/Spur goes south.
Once this happens, the spur will take all the punishment until it starts to heat up out of alignment and melt at the contact of the CB teeth, as it will
and then strip out the intire spur.

All it takes for that to happen is one damaged tooth to start this process.
The fuel issue by it's self would probably not be the primary cause.

I noticed you have a 15T CB. Whats the spur gear T count?... If you can, I would reccommend going back to a standard CB/combo.
For now, at least. Like a 17T/47T or a 17T/49T. These combo's mesh well because their the most compatable compared to other odd combinations,
making it easier to mesh up.

I did mention the mess issue earlier, I believe. Maybe it's worth giving it some more consideration, is my guess. And the links too, as I mentioned.

Think of the mesh this way:
When you adjust the gear mesh, get the gears to come together snugly and then back it off a couple of hairs so the mesh can breath, so to speak.
Not air tight. You DO NOT not want any tightness, whats so ever.
Just 96-% tooth to tooth ingagement.
A good test for this is to hold the CB from movement while you move the Spur gear back and forth. Listen for a small ticking sound that indicates there's
a tiny amount of play. This is what you want.
Without that tick clearance sound, your likely going to be too tight in the mesh.

And double check this AFTER you tighten all the engine bolts.
This, along with replacing your bearring should do the trick.
That is assuming your using HPI clutch shoes.
The one's I saw in your pics almost looked too large for the CB.

======================================= Hope that helped, XXZ. And Good luck.=============================================
 
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the RPM's generated at the CB are so fast that any thing out of round are going to cause heat build up ( FRICTION )not a good thing so replace the bearings (both) and get a new brass bushing/Spacer.and try again. not to mention if your running your truck at WOT for long periods of time like all the way down your streetand back again................not good. IMO
 
xxz28xx said:
First off, thanks for the welcome, and I am glad to be here. Second, you guys are amazingly fast to respond...

Here's a pick to get a better understanding of what's going on here:

IMG_1899.JPG


And to address some of the suggestions:
-The engine plate is not broken.
-If I look at the spur gear and clutch gear and kinda line them up I can see that they are flush, so the engine isn't cocked.
-Slipper clutch has been set to different strengths, from max tight to about 1/2 turn out.
-If I roll the car around, there is no abnormal noises coming from the drive train, nor any odd noises when I am driving it before the gear strips.
Click to expand...
Now... judging from this pic, I would say that we have some alignment issues here.
And, it appears from the angle of your shot that the mesh is actually a little shallow, instead of being too tight...hmmm Can you get a front view of the spur?

Your going to have to remove it anyway, right?...
When you set the mesh, check and see if the CB gear is getting full coverage on the spurs width. It appears that your losing nearly 20% or more spur coverage here.
If you can't provide this adjustment room, then your going to want to shim out the CB the same thickness as the un-stripped section of the spur gear.

Does this make sence to you, my friend.
Your LHS should be able to help at that point when ordering these shims.
Other members here can also help in finding these shims.

It's just a basic spacing out to position deal and shouldn't be a big issue.
BUT.. Before you go to that trouble, get the other CB on there with the associated spur as I mentioned earlier. You might find that they line up propperly.

==================================================== Keep us posted, ok====================================================
 
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-I use the HPI 49T spur gear, which is the same count that the truck came with.
-I also am using the original clutches that the truck came with.
-The spur gear you see in the pic is from a slightly looser mesh, I started with the paper method and loosened it everytime I stripped a gear, thinking I may have done it too tight. No change. The wear patter that you see in the pic is the same no matter what the mesh is, when the mesh is tighter, the deeper the wear on the gear.
-I also went to the LHS and looked at a brand new Savage X and the gear mesh was snug and there was little or no play.
-This happens to the gear under any conditions. Some conditions I understand, like attempting to do donuts in loose gravel or a baseball field... But I notice that it happens whether I am running WOT up and down the street, or just warming it up in a grass field.
-I know what your saying about not covering the complete width of the spur, but the engine can't move any closer to the trans. What kind of shims can be used for the CB to bring it out a little bit? Anyone ever tried thin washers from a hardware store? Or do they usually have shims for this kinda application at a LHS?
-In my opinion, it definately seems like a heat issue rather than an mesh issue. If you really pay attention to the wear patter on the gear, especially on the part of the gear closer to the bottom of the pic, it is worn smooth. If these teeth were breaking, I would think that the teeth would not be smooth. Also, the plastic reminence of the teeth looks melted rather than chewed up. AND it happens whether I have the mesh set tight or loose. The pattern remains the same, just more towards the bottom of the tooth.
 
Use the 47T spur and the 17TCB. NEW...
Get the shims to fix the spur gear location issue.
Throw away the 15TCB.

It is posible that its over worn and has a wierd mesh issue. The truck shoud not need brakes to stay put at idol.

Dot not expect to warm up in grassy fields. Grass generates excessive heat and WILL quickly melt spur gears with continued use.

If you are running in a heat generating condition, drive out of it and don't stop the truck until the CB gets a chance to cool down.
Its when you stop, is how the CB melts the teeth quickly.
Follow the mesh instructions I layed out to the letter. Thats if you don't have better info. Do not run the truck until you address the shims issue.
Do not run the truck until you address the CB size and bearrings issue. Replace all the bearrings and use the brass bushing.

Make sure the CB spins free and un-restricted when you have the motor out of the truck.

Make sure idol is not too high. Again, Truck should be able to idol without movement or brakes.
If it doesn't stay stopped at idol, Try reducing the rpm's at the idol screw.
If that doesn't work, then replace the clutch shoe springs. They can get weak and drag.
 
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-I have the optional 18t spur gear that came with the truck, haven't used it yet. Should I try using that one? What spur gear should I try with it? Or should I go ahead and get a vented 17t CB and 47t spur?
-Truck idles fine, no need for brakes to keep it still.
-Engine was tuned to about 250* last time I had it, haven't checked it this time around. I haven't adjusted the carb so I assume it should be around the same.
-I will get bearings, the brass bushing, and shims for the CB before I retest.
-Grassy field I was thinking of in particular was mowed so the grass wasn't very tall, it was in a park.
-Come to think of it, the last time the gear melted was when I ran it down the street, slowed down almost to a stop and turned the truck around to head back up the street. As soon as I attempted to accel out of the turn, the gear melted.
 
Ok...xxz28xx, It looks like were on the right track to clearing this thing up for ya....

The 18T CB should be fine with a 49T spur, if your positive thier in good spape. Otherwise, I would do the 17/47 combo. It's up to you.

It's also good that your idol is not ingaging the CB.
Spacing the CB to align evenly to the spur and setting the mesh as I outlined in an earlier post is key to the efforts your making here.

When you have the CB shimmed and your ready to screw in the crankshaft bolt, that bolt should be tightened with some thread lock if posible.
At the same time, the CB should spin free on the bearrings that you've replaced. The brass bushing should be able to turn also with no tightness.

Just remember, set the mesh as I stated, with a positive fit. And yet, relaxed at the same time. Listen for that tiny "click" sound, I mentioned earlier.
And MAKE SURE you double check the mesh after you've tightened the engine bolts. It's very easy the get some unwanted movement as you tighten these bolts.

=================================================Good luck, my friend.========================================================
 
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I'll probably be messing with it this weekend, I'll let you guys know how it goes once I get it back together... Think I should get one of those HPI racing 17T CBs and a plastic 47T spur? Does anyone know if they really cut down the heat from the CB?
 
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