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Old 08-27-2013, 06:41 AM   #106
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Thanks for the info, Rick. Do you know what the material is on the ball diff axles? Were the threads ground perhaps? Also, how did they locate the drive washer disk, it appears to be a press fit...
Ned - not sure on the material , I know we were playing with S-7 but for production I'd suspect O-1 or A-2 (not my stong suit) think the threads were machined in before heat treat , and the thrust washer carrier is pressed against a small shoulder - the outer portion is 5/16" while the axle is 8mm or .315".

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Old 08-27-2013, 07:42 AM   #107
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I agree 1/10 scale would be a reasonable alternative to get some gas on-road going and also the idea of using a smaller motor. My first modded RC300 a couple of years ago used a Losi .20 small block, I got the engine and pipe for $50.00 on eBay. I think new the engine is around $150. Also to my thinking 4.7 to 5.12 is a bit low on gearing. I was thinking closer to 5.5 to 5.8. But if you specify a gear ratio range, it would be the same for all. Gonna do some figuring on gear ratios...

I have a set-up using an OS .18 with 32p gears that I never put into a car. It could be used in a 235mm 1/10 or an 1/8th scale "lightweight".

Guess I'm starting to get motivated again!
Getting higher numeric ratios would require smaller pinions, which means the clutch bell would no longer be an off-the-shelf item. However, I have toyed with the idea of using a two-speed clutch bell (threaded to accept gears, but not using the intended gears) and inserting a standard 32p pinion into the ID of the bell and securing with a screw into the existing hole in the pinion. That means the bell would need a hole or slot cut into it for the screw to go through, which is again an easy job with a Dremel cutoff wheel.

The 2-speed bell also accepts a wider variety of clutch shoes (with springs!) that the standard bell won't. Here is the 2-speed bell:

http://www3.towerhobbies.com/cgi-bin...?&I=LXBMC3&P=7

and here is the standard single-speed, 14T bell:

http://www3.towerhobbies.com/cgi-bin...?&I=LXVP66&P=7

The 1/10 scale 235mm car does have a lot of things going for it, the first of which is we don't have to make the differential! The rest of the design would be much simpler, also. Plus there are several nice bodies available. I think it's important to make these look different from 1/10 sedans and the 200mm HPI-ish stuff to generate interest and make a casual observer ask "What's THAT?!" (hopefully in a positive tone).

On the other hand, America is the land of "Bigger Is Better". A large (but lightweight and reasonably powered) 1/8 scale car undeniably has a certain "WOW" factor to it. It could still be raced on small parking lot tracks, and would probably be very easy to drive, and quite rugged, too.
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Old 08-27-2013, 09:00 AM   #108
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Ned - not sure on the material , I know we were playing with S-7 but for production I'd suspect O-1 or A-2 (not my stong suit) think the threads were machined in before heat treat , and the thrust washer carrier is pressed against a small shoulder - the outer portion is 5/16" while the axle is 8mm or .315".

Rick
I kinda suspected that would be the process. Not really one for a DYI'eer!

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Old 08-27-2013, 09:08 AM   #109
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Default Clutch Bells/Pinions

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Getting higher numeric ratios would require smaller pinions, which means the clutch bell would no longer be an off-the-shelf item. However, I have toyed with the idea of using a two-speed clutch bell (threaded to accept gears, but not using the intended gears) and inserting a standard 32p pinion into the ID of the bell and securing with a screw into the existing hole in the pinion. That means the bell would need a hole or slot cut into it for the screw to go through, which is again an easy job with a Dremel cutoff wheel.

The 2-speed bell also accepts a wider variety of clutch shoes (with springs!) that the standard bell won't. Here is the 2-speed bell:

http://www3.towerhobbies.com/cgi-bin...?&I=LXBMC3&P=7

and here is the standard single-speed, 14T bell:

http://www3.towerhobbies.com/cgi-bin...?&I=LXVP66&P=7

The 1/10 scale 235mm car does have a lot of things going for it, the first of which is we don't have to make the differential! The rest of the design would be much simpler, also. Plus there are several nice bodies available. I think it's important to make these look different from 1/10 sedans and the 200mm HPI-ish stuff to generate interest and make a casual observer ask "What's THAT?!" (hopefully in a positive tone).

On the other hand, America is the land of "Bigger Is Better". A large (but lightweight and reasonably powered) 1/8 scale car undeniably has a certain "WOW" factor to it. It could still be raced on small parking lot tracks, and would probably be very easy to drive, and quite rugged, too.
Understand exactly! The 235 mm car I have has a clutch bell that uses standard 32p pinions, set screwed into it. Slick solution. I started to duplicate it to fit on Assoc. GT clutch parts, but hating to machine steel, I made it from aluminum and ever messed that up! I think it might be beat to make a clutch bell assembly to accept good bearings and various pinions. Be especially good if 32p would work on the lightweight 1/8 scale car.
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Old 08-27-2013, 10:15 AM   #110
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Ned,
I'll have to look, but I wonder if Associated made screw on gears for their NTC3 two-speed clutch bells. I am pretty sure that I still have one in the garage. The flywheel and clutch were standard RC10GT fare. If using the screw-on bell (if it does exist) would allow for shimming the gear back-and-forth as needed on the bell for best gear mesh.

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Old 08-27-2013, 10:18 AM   #111
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Yep!! Here it is:
http://www3.towerhobbies.com/cgi-bin...P?I=LXBMC3&P=8
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Old 08-27-2013, 10:20 AM   #112
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and gears from 20t to 27t.
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Old 08-27-2013, 10:29 AM   #113
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and gears from 20t to 27t.
Unfortunately all of these will be far too big to get a useful ratio with direct drive. The bell is the one I was thinking of using (and previously linked to), but by inserting smaller pinions inside the bell ID.
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Old 08-27-2013, 05:37 PM   #114
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Hmm............screw-on adapter with a smaller shaft (5mm?) for more standard pinions? I'll have to dig my TRC/Composite Craft/RC10L nitro car out and take some pics of the clutch and pinion arrangement.
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Old 08-27-2013, 06:06 PM   #115
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Hmm............screw-on adapter with a smaller shaft (5mm?) for more standard pinions? I'll have to dig my TRC/Composite Craft/RC10L nitro car out and take some pics of the clutch and pinion arrangement.
The adapter could just clamp onto the OD of an existing pinion/bell combo uisng some set screws. Threaded would be pretty, but if we want to use a brake on the clutch bell, it would unscrew itself really quick!

Attaching a brake disk to the adapter would get around the problem, and would probably work better than having the brake pad contact the OD of the bell, at the expense of a more complicated braking mechanism.

I do have a concern with any of these ideas: how far can the pinion extend away from the engine before it creates problems with imbalance, mesh, and side loads?
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Old 08-27-2013, 06:54 PM   #116
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The adapter could just clamp onto the OD of an existing pinion/bell combo uisng some set screws. Threaded would be pretty, but if we want to use a brake on the clutch bell, it would unscrew itself really quick!

Attaching a brake disk to the adapter would get around the problem, and would probably work better than having the brake pad contact the OD of the bell, at the expense of a more complicated braking mechanism.

I do have a concern with any of these ideas: how far can the pinion extend away from the engine before it creates problems with imbalance, mesh, and side loads?
Howard,
If the band brake is on the clutch bell AND the adapter is secure (set screw/weld?) there should not be any problems. I wonder about the 5 times higher RPM the disk brake would see mounted on the engine...Disk on rear axle is best, imo.

Agree with your concerns on the clutch bell adapter ideas. Something that makes things worse is that, for me at least, one of my design criteria is that SG shaft engines should be used without removing any part of the crank. I believe the reasons for this are obvious.

Anyway the bearing support part of the SG shaft is great for being able to used larger/stronger bearings than the old Associated type adapters. On the other hand it forces the gear to be cantilevered further out away from the engine (as you point out, a potential problem). Another thing is the length will give additional leverage as the gears are forced apart under load. Is will likely be made worse using 32p gears. (All this is opinion, based on experience, not education!

Here are some pics of such an adapter I made a number of months ago as well as what I believe to be a TRC clutch. Notice that the TRC is shorter since it uses a cut off shaft.

Spec 1/8 Pan Car .21 no frill's racing-8lte-clutch-1.jpg

Spec 1/8 Pan Car .21 no frill's racing-8lte-clutch-2.jpg

Spec 1/8 Pan Car .21 no frill's racing-trc-clutch.jpg
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Old 08-27-2013, 08:06 PM   #117
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Howard,
If the band brake is on the clutch bell AND the adapter is secure (set screw/weld?) there should not be any problems. I wonder about the 5 times higher RPM the disk brake would see mounted on the engine...Disk on rear axle is best, imo.

Agree with your concerns on the clutch bell adapter ideas. Something that makes things worse is that, for me at least, one of my design criteria is that SG shaft engines should be used without removing any part of the crank. I believe the reasons for this are obvious.

Anyway the bearing support part of the SG shaft is great for being able to used larger/stronger bearings than the old Associated type adapters. On the other hand it forces the gear to be cantilevered further out away from the engine (as you point out, a potential problem). Another thing is the length will give additional leverage as the gears are forced apart under load. Is will likely be made worse using 32p gears. (All this is opinion, based on experience, not education!

Here are some pics of such an adapter I made a number of months ago as well as what I believe to be a TRC clutch. Notice that the TRC is shorter since it uses a cut off shaft.
That adapter is a thing of beauty! It's exactly what I envisioned, and you've already created it!

I'd love to use off-the-shelf clutch components, bells, and pinions, and your point of using the pilot shaft and larger bearings is valid. But since we then can't get a small enough pinion for a good ratio, maybe it's time to discuss the double-gear-reduction/jackshaft arrangement I mentioned earlier.

The good points of the jackshaft are that the gear pitches don't necessarily need to be the same for the clutch bell and the diff gear (although it's likely they will be 32p/mod.8 anyway); and it's a great place to put a brake disk or drum, away from the heat of the clutch and the oil from the front bearing.

The bad points are the extra parts and complication.

(The motor would be rotated 180 degrees, which looks different, but might be preferable for a can muffler. And it keeps the pit man from getting as dirty!)

So which is the lesser of two evils? The clutch bell/pinion adapter, or the jackshaft?
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Old 08-27-2013, 08:45 PM   #118
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That adapter is a thing of beauty! It's exactly what I envisioned, and you've already created it!

I'd love to use off-the-shelf clutch components, bells, and pinions, and your point of using the pilot shaft and larger bearings is valid. But since we then can't get a small enough pinion for a good ratio, maybe it's time to discuss the double-gear-reduction/jackshaft arrangement I mentioned earlier.

The good points of the jackshaft are that the gear pitches don't necessarily need to be the same for the clutch bell and the diff gear (although it's likely they will be 32p/mod.8 anyway); and it's a great place to put a brake disk or drum, away from the heat of the clutch and the oil from the front bearing.

The bad points are the extra parts and complication.

(The motor would be rotated 180 degrees, which looks different, but might be preferable for a can muffler. And it keeps the pit man from getting as dirty!)

So which is the lesser of two evils? The clutch bell/pinion adapter, or the jackshaft?
That's a good question! I think if you look at the competition on-road world, the current designs give us a pretty good answer. Unfortunately that is not the answer I want!

One more shot and "direct drive": How about a separate clutch bell and pinion? Some type of a drive dog connecting the bell to the pinion adapter which can be mounted on a separate bearing carrier...or maybe a copy of the old Delta set-up with the outboard bearing and a pinion with a shaft???

This a pic of the 11t pinion attached to a modified off-road type bell. The aluminum carrier holds two flanged bearings...

Spec 1/8 Pan Car .21 no frill's racing-img_20130827_224200_684%5B1%5D.jpg
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Old 08-27-2013, 10:21 PM   #119
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[QUOTE=howardcano;12488165]Getting higher numeric ratios would require smaller pinions, which means the clutch bell would no longer be an off-the-shelf item.
http://www.ebay.com/itm/270844596217...84.m1438.l2649
Howard...what about this 10 tooth bell with a 58 tooth spur?..I have old Associated 58 tooth spur gears (24 pitch) and they don't stick down below the bottom of the chassis like my 63's do.......which limits how short you can run the rears before they need replaced......one of my problems when I was trying to run my RC300 last year....donuts just cant be found.........
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Old 08-28-2013, 04:01 AM   #120
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Originally Posted by aarcobra View Post
That's a good question! I think if you look at the competition on-road world, the current designs give us a pretty good answer. Unfortunately that is not the answer I want!

One more shot and "direct drive": How about a separate clutch bell and pinion? Some type of a drive dog connecting the bell to the pinion adapter which can be mounted on a separate bearing carrier...or maybe a copy of the old Delta set-up with the outboard bearing and a pinion with a shaft???

This a pic of the 11t pinion attached to a modified off-road type bell. The aluminum carrier holds two flanged bearings...

Attachment 1105712
That's another very pretty way of doing it! But do you think it would be less complicated to just make a pillow block for a jackshaft? The shaft, gears, and bearings are all cheap and available.
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