BT clutch release, analysis & functional history 36-84:

BT clutch release

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Re: BT clutch release, analysis & functional history 36-84:

#31

Post by RUBONE »

The extended tips on the pushrods did not end in '38. they existed all through the Panhead era.

Most aftermarket bearings do not have the factory style crimped on retainer with the oiling divots pressed in.
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Re: BT clutch release, analysis & functional history 36-84:

#32

Post by RooDog »

And I always thought these over-designed bearings were bullet proof, and lasted forever.....
Shows how little I know.....
....RooDog....
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Re: BT clutch release, analysis & functional history 36-84:

#33

Post by nifty »

Thanks Rubone
Do you know when the extension was deleted?
When extension deleted, did the part number change?
In modern times the pushrods with extension don't appear to be advertised as being for Pans.
I have a sample short pushrod with just the short parallel nub and then the taper seat for -39 bearing, does that mean it is modified or an incorrectly made repop?
Nifty
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Re: BT clutch release, analysis & functional history 36-84:

#34

Post by nifty »

Partial re-write

36-37 used 2446-36 Clutch Push Rod which has a distinctive, reduced OD extension tip at bearing end, but short or non existant centralizer nub and no clip groove, no taper seat, 2446-36 pushrod is approx 13-1/4” plus extension tip; tip supports ID of outer race of 2448-36 Clutch Release Bearing which is the smallest bearing used 36-38, apparently fragile, see Shop Dope 174 etc ; 2149-36 Slinger, oil, is a sheetmetal butterfly/2 blade propeller installed between 2143-31 starter clutch(31-38) & mainshaft nut (2149-36 propellor solidly mounted to mainshaft is possibly H-D’s most effective oil slinger); 2436-36 release finger, is slotted (presumably finger slot also engages/self centralizes with protruding pushrod extension tip?).-36 finger differs from later fingers by being narrower to suit corresponding narrow opening of -36 cover. Also 37337-36 Clutch Hub Nut Seal, cork, 36-58? Provides rotational drive to pushrod, cork “grip” on pushrod constitutes torque-limiting drive device for pushrod. The current AM repair kit pictured is in fact to 1938 specifications with bigger -38 bearing and -38 pushrod. There are also current production -36 style AM pushrods with Shovel style clip groove to convert early BT to 75up Shovel type Torrington release bearing.

Shop Dope 174, Mar 28 1938, MoCo recall notice for dealers to install new type BT release bearings and pushrods to 1938 model year bikes sold & unsold ; also recalled spare parts stocks of previous -36 bearings and pushrods. The new 2446-38 pushrod similar to 2446-36, but new 2446-38 pushrod has its .295” OD pilot nub extended to .250” long, pilot centralizes large ID end of new bearing, pushrod also has new taper seat which corresponds to new 2448-38 larger bearing copper plated for identification, also new was the pushrod groove for ball race retainer spring ring #2458-38 (wire clip) which when installed grips the ID of inner race of -38 bearing.
Courtesy of Speeding Big twin
Courtesy of Speeding Big twin
Shop Dope 174.jpg (215.11 KiB) Viewed 606 times
2458-38 (later 37312-38) ball race retainer spring ring (wire clip) 38-44?
2446-38 pushrod, has new .295” OD pilot nub extended to .250” long, also new groove for ball race retainer spring ring #2458-38 (wire clip) which when installed lightly grips the ID of inner race of -38 bearing. 2446-38 also has extension approx .250” OD x .350” long. 2446-38 pushrod approx 13-1/4” OAL (plus .350” extension tip); tapered shoulder of new pushrod corresponds to taper seat of new 2448-38 release bearing.

NOTE: The 1938 .295” x .250” pilot nub and taper seat pushrod details remained right through 1974, somewhere along the way, both the extension and the groove were deleted.

2448-38 release bearing, has pilot ID bearing, 1.154" OD x .523" thick, same bearing as early 45”)

2436-38 Clutch Release Finger, one year only, no details known. Presumably width and slot similar to -39, probably less inside corner clearance so won’t work with -39 bearing unless ground for clearance?
2463-36 Push Rod Adjusting Screw, sometimes damaged when -36 bearing & pushrod failed
Shop Dope 179, Oct 18 1938, MoCo announced another new upgraded release bearing, part number 2448-38 unchanged, but new version cadmium plated for identification.
Courtesy of Speeding Big twin
Courtesy of Speeding Big twin
Shop Dope 179.jpg (225.46 KiB) Viewed 606 times
Shop Dope 187, Mar 15 1939, MoCo further modifications to 1938 & earlier cadmium plated 2448-38 release bearing, new version now has a 1/16” hole drilled, supposedly purely for easier identification. Again part number did not change.
Image Repop 38 pushrod, bearing & slinger kit, will fit back to 36.
Courtesy of Speeding Big twin
Courtesy of Speeding Big twin
Shop Dope 187.jpg (246.69 KiB) Viewed 606 times
Shop Dope 191 & 191A, Apr 28 1939, MoCo announced new cut-price $5 kit to retrofit new 1939 clutch release parts to 1938 models, kit includes 2126-38 cover , -39 release bearing, -39 finger, -38 finger shaft, -39 starter clutch, -39 deflector & -39 lockwasher, -38 Pushrod also offered for extra 60c to replace -36 pushrod when kit retro fitted to 1936 & 1937 models.
Courtesy of Speeding Big twin
Courtesy of Speeding Big twin
Shop Dope 191.jpg (235.18 KiB) Viewed 606 times
Courtesy of Speeding Big twin
Courtesy of Speeding Big twin
Shop Dope 191A.jpg (251.9 KiB) Viewed 606 times
Courtesy of Speeding Big twin
Courtesy of Speeding Big twin
Shop Dope 191A continued.jpg (110.81 KiB) Viewed 606 times
2436-36, 36-37 finger note how finger area is taller/wider than pivot area, the narrow pivot section corresponds with narrow opening in -36 cover. 2436-36 finger will not work with -39 bearing (insufficient clearance at inside corner)
Used with -36 cover & -36 finger shaft
Used with -36 cover & -36 finger shaft
2436-36 36-37 finger b.jpg (20.38 KiB) Viewed 601 times
39-64 used 37285-38 (previously 2446-38) pushrod; 39up used new 37310-39 (previously 2448-39) conical release bearing which contains many more & larger balls, and its increased OD does double duty as new oil slinger (propeller deleted). Also the pushrod was driven/rotated by 37337-36 Clutch Hub Nut Seal, cork 36-58? And later 12014 Clutch Hub Nut Seal, proper rubber lip seal 60?-84, seal “grip” on pushrod constitutes torque-limiting drive device for pushrod, also new for 39 was 33381-39 (later 33381-39T) starter clutch (kickstart ratchet on outer end of mainshaft) which incorporates a captive spring-loaded pin (later changed to ball) to provide rotational drive directly to corresponding groove in inner race of -39 release bearing, apparent intent was that if some other force acted on bearing, the ball would be pushed into starter clutch and thus starter clutch could spin harmlessly inside bearing (spring, ball and corresponding groove in inner race of -39 bearing form a torque-limiting drive device, however, I suspect the ball & spring were a work-around/afterthought to spin relatively heavy inner race with mainshaft and thus prevent pushrod & inner race wear from pushrod trying to suddenly accelerate inner race up to mainshaft speed whenever clutch released); there was also a new 37070-39 (previously 2436-39) release finger, slotted, approx 1/4” wide slot, the upper & lower faces of this finger also do double duty by engaging cut-away outer race of -39 bearing to prevent its rotation (finger slot also engages ¼” OD x .350” long extension of -38 & -41 pushrods). Also new for 1939 was.33429-39 DEFLECTOR, 0IL, mainshaft starter gear oil deflector/scraper 39-E79 all models with kickstart (piece of bent tin with dimple for countersunk screw, anti-rotation tab of 33429-39 is at front. Deflector catches & re-directs some of the oil flung off mainshaft starter gear and rotating slinger which 39-74 is the tin cover of -39 bearing, and 75-79 is the 37228-75 daisy wheel slinger on pushrod. Deflector catches flung oil and re-directs drip stream of oil primarily to bush of starter gear and also to -39 finger and -39 clutch release bearing, and to 37312-75 Torrington wafer bearing). And in so doing, also deflects/reduces oil which would otherwise be flung at release shaft upper bush, thus minimizing oil leak from top of release bush.
DEFLECTOR MUST HAVE SOME CLEARANCE TO OD OF -39 RELEASE BEARING or -75 slinger.
NARROW SLOT 37070-39 FINGER ONLY FOR -39 CONICAL BEARING; 37070-39 FINGER MUST NOT BE USED WITH CLIP TYPE TORRINGTON NEEDLE ROLLER THRUST BEARING.

Apparently at unknown time late in Panhead era, (apparently way later than the -41 part number implies) the -38 pushrod was deleted and replaced by 37285-41 Clutch Push Rod, which is sans the previous ¼” OD x .350” long extension, and sans the groove for wire clip. -41 pushrod used to end 64, works with -39 bearing, 2126-38 cover etc back to 36.

Nifty
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Re: BT clutch release, analysis & functional history 36-84:

#35

Post by Raytag »

nifty wrote: Sat Nov 13, 2021 9:55 am BT Transmission Mainshaft Bushings.

All years, proper “fit” of clutch pushrod to both ends of transmission mainshaft, is an essential part of clutch release mechanism.
BEWARE some AM mainshafts sold requiring at least one bushing, but bushing not included in sale and no instruction to install a bushing before shaft used.

If pushrod loose/wobbles in either end of mainshaft, have a close look:

Sloppy pushrod at clutch end means the pushrod is supported/centralized only by the pushrod seal in clutch nut, seal secondary function is to drive/rotate pushrod, seal won’t last long if it is also trying to support/centralize the pushrod. When seal gets loose with -39 release bearing, mainshaft & pushrod rotate at different speeds which induces wear at interface of pushrod to bearing. When seal gets loose with Torrington wafer release bearing, the slinger stops slinging oil and all moving parts inside cover suffer.

Sloppy pushrod at kick end means release bearing is not held central, creates lost axial pushrod motion (pushrod forced sideways by finger), clutch plate separation reduced. Operational contact between release bearing and release finger is “off”, which reduces life of both; more likely for Torrington type clip to be displaced by contact with finger.
Some folk insist that when using -39 release bearing. pushrod bush only needed at clutch end. Their belief is that bearing fits nicely over the starter clutch and it supports pushrod. Others opine that when seal is present in clutch nut, no bush required at clutch end. IMO go with close fitting bushes both ends.

37436-36 BUSHING, Transmission mainshaft end, approx .375” x .435” x .500” long. (for clutch pushrod, sometimes just one end or both ends of mainshaft, some bronze, some steel, 36 to Early 80 – El, UL, FL, FX, FLH, FLH•80, Classic
Eastern A-37436-36, steel, from Vital V-Twin Cycles $1.55 ea
Eastern A-37436-36 steel from J&P 620-485; J&P Warehouse 1073971; $2.99 ea
V-Twin number 17-9830 steel, advertised as Eastern, from Dennis Kirk $4.39 ea
IMO fitted clearance .002” both ends, after straightened & polished pushrod lapped to bushes.

Andrews mainshafts come with pre-sized bronze bushes both ends, last one I bought I measured and found clearance to new pushrod to be .005” clutch end .003” kick end.

Pushrod must not bind in mainshaft as clutch arm moves (release finger “tips” travel through an arc against release bearing, similar to rocker arm pad to valve tip ).

Due to seal at clutch nut, pushrod should not spin in mainshaft, but when clutch operated, pushrod is always moving in and out. During assembly, work some moly grease into mainshaft.

More starter clutch data
2143-31 Starter Clutch BT 31-38, 2 keyways; has no captive ball & spring (used V models & 36-38 BT with small release bearing)

Nifty
No they don`t.
One bushing at the clutch side.
None at the starter side

Andrews=208500 (OEM=35040-50) at starter end. ID = .419.
PR = .374
The old MS (2-key slot for starter clutch) ID = .394

Before ordering I looked up at Andrews but they don`t mention them bushings at all.

Ray
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Re: BT clutch release, analysis & functional history 36-84:

#36

Post by nifty »

Raytag
Thank You for taking the time to comment

Unfortunately I didn't take photos of Andrews mainshaft ends when I measured my stated clearances.
Extract from build sheet with shaft in question:
"Mainshaft -70, RENEWED, ANDREWS
Mainshaft run-out, spec .zero - 003” : AS INSTALLED NIL
Mainshaft wear tolerance.0005”, replace shaft if worn .001”) AS INSTALLED NIL
Mainshaft actual diameter at high gear bush area AS INSTALLED NEW ANDREWS SHAFT 0.999”
Mainshaft actual diameter at 3rd gear AS INSTALLED NEW ANDREWS SHAFT 1.1605”
Mainshaft ID clearance to clutch pushrod AS INSTALLED, NEW PUSHROD IN NEW ANDREWS SHAFT clutch end .005” - kick end .003”, bronze bushed both ends."

I can perhaps understand early OE shafts having loose pushrod fit at KS end, on account of close fit of -39 bearing to -39 Starter Clutch (as outlined in above Shop Dope ie instruction to polish for running fit)
But in modern times, it is my experience that many -39 bearings are quite loose on -39 Starter Clutch, to my mind the pushrod, piloted to heavy -39 bearing shouldn't flail around unsupported, so I feel pushrod & bearing should be centralised somewhere, thus I do it at the source with mainshaft bushes, as, again in my experience, so do Andrews. (at least sometimes)

It is interesting that in your experience starter end of Andrews mainshaft has loose fit to pushrod.

Likewise I do not feel that the wafer/Torrington bearing and daisy wheel slinger should be allowed to flail about due to unsupported pushrod, to my mind this would guarantee the clip hitting inside of finger slot and loss of clip.

Raytag, I'm not saying you are wrong, nor am I currently accepting that I am wrong.

What I am trying to achieve with this thread is establish the best way to set up the release mechanism for best function and long life of components, regardless of OE "correct", or AM "as sold".

Nifty
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Re: BT clutch release, analysis & functional history 36-84:

#37

Post by nifty »

NOTE Re 2458-38 (later 37312-38) ball race retainer spring ring (wire clip) 38-44?
At east one OE Parts Book indicates use of wire clip until 1944.
However, the clip only engages with the small -38 bearing, if clip used with -39 bearing, clip is completely clear of both races.
If using -39 bearing, the clip, if present, prevents removal of pushrod from clutch end of mainshaft and so a swivel end -41 clutch hub puller must be used, or KS cover removed and pushrod extracted (or custom sleeve over pushrod used with non-swivel end puller)
With -39 bearing, best to not use/remove clip, that way there is no chance of clip coming up against end of mainshaft.
Nifty
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Re: BT clutch release, analysis & functional history 36-84:

#38

Post by Raytag »

All good Nifty.
I am with you reg the needed bushings on both sides and simply highlighting what I have currently in front of me on the work bench

Perhaps Andrews saves on the right hand bushing with regard to the "support thru the release finger" ?
I`m ordering that bushing but I guess I will end up making one myself.

BTW: Thanks for your effort!

Ray
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Re: BT clutch release, analysis & functional history 36-84:

#39

Post by nifty »

Raytag wrote: Sun Nov 21, 2021 9:03 am Perhaps Andrews saves on the right hand bushing with regard to the "support thru the release finger" ?
Ray
Thanks Ray
Perhaps that Is Andrews thinking, but its a big ask for first, a perfectly height centralised finger and second, the aforesaid centralised finger does not restrain the pushrod fore & aft.

I'm still working on the how to check & re-centralise finger chapter, watch this space!
Then of course there is the "other" contents of the cover, again another work in progress.
Nifty
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Re: BT clutch release, analysis & functional history 36-84:

#40

Post by nifty »

Cast fingers
Some AM 37070-39B fingers appear to be investment/lost-wax cast, slot width slightly tapered, but still min .416” wide at ends of radius. Cast fingers are more rounded than sintered fingers, but don’t exhibit machining tool marks except where “runner-gate” (molten metal inlet) removed. Cast fingers exhibit a “part line” where wax master/temporary pattern was molded in cheap plastic or plaster dies. Many individual wax parts are assembled to a wax “tree”. Wax “tree” is multiple dipped in refractory ceramic slurry to create temporary mold. Wax is melted/burned out, leaving ceramic “shell” tree mold for steel, or whatever pourable metal. Multiple parts per pour, when cooled, ceramic tree mold broken/abrasive blasted away, only separating from tree and runner/gate trimming required for multiple finished parts. This final trimming is the only machining. Investment cast finger should be stronger than sintered, almost as good as machined from bar stock. Sample finger “as cast” female square for shaft is .505”, which will be looser than I would prefer on a typical .495” male square of shaft. One day, when I need a new finger, I might not be able to get a solid steel finger and be forced to run this “loose square” cast finger, if I am, because I care, I will also smooth working radius with oil-stone before use.
The last solid steel finger I measured had a .503” female square hole.

The AM -36 finger in previous photo also appears to be investment cast
Nifty
Attachments
wax mold part line b rsz.JPG
wax mold part line b rsz.JPG (146.61 KiB) Viewed 525 times
trimmed end opposite slot has machine tool marks but pic was out of focus
trimmed end opposite slot has machine tool marks but pic was out of focus
wax mold part line a rsz.JPG (147.27 KiB) Viewed 525 times
would work ok as is, would work better if smoothed a little
would work ok as is, would work better if smoothed a little
cast release finger working radius rsz.JPG (175.18 KiB) Viewed 525 times
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