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How To: Excelsior rear hub Cushion Sprocket

May 19, 2010

IMG_3318These rebuild projects are never just one simple thing.  While getting into the X brakes, I knew that a few other items needed attention in the rear hub.  The first thing was the drive sprocket

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Excelsior Cushion Sprocket

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Excelsior offered a Cushion Sprocket, which used coil springs to dampen out the vibrations that the motor transmitted through the drive train.  Remember that this was about 10 years before crankshaft shock absorbers became common.  While belt drive bikes had a smooth feel due to the belts absorbing vibrations, the chain drive bikes were less comfortable…

 

 

X’s solution was to let the sprocket float between two plates that were locked to the rear axle.  The sprocket was free to rotate relative to the axle, but while rotating it would compress 6 springs.  This would take up some of the shock, then the springs would push the sprocket to rotate it back into its relaxed position.  Of course, this happened many times per minute as the power pulses were delivered from the pistons, through the chain, to the sprocket.

The springs in my X were tired and broken.  Square section springs are available from tooling shops, as used for die presses.  I bought a set of springs from MSC that had a spring rate that seemed to approximate the old ones.  Fitting them was a simple plug and play ordeal.

IMG_3322IMG_3324 

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The MSC part number is #07660590 The link is here.ramond springs

 

With the brakes and Cushion Sprocket sorted, once again I had to fire up the lathe to make some new shafts and nuts.  That crack in the hollow tube axle worried me, but it wasn’t under much stress due to the solid axle that runs inside it.  But I made up a new part from 4140 chrome moly anyway.  Straightforward lathe work, and a quick session on the mill to cut the groove on the end for the lock washer.  Then a large hex nut and a special round nut with grooves, as shown in earlier posts.   Please do yourself a favor, if you have these types of nuts on your old bike, don’t use a hammer and screwdriver to tighten/loosen them!  It will work ok for a few times, but eventually the nut will be destroyed.  And the next owner of the bike will curse your name….

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I popped it all back in the bike, and it did fine on the ride from Atascadero to Creston and back.  Now to start carving a wooden brake for that Premier…

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5 Comments leave one →
  1. Paul Louis Venne permalink
    August 22, 2010 10:46 pm

    Pete, Wow again. I am wondering when the cushion sprocket came out. I don’t remember it being stock on the Series 16 bike. Your bike must be velvet smooth. Charle Carter who has done many Excelsiors says they shift like a buttery dream. Really? I’ll have to be gentle since I sold the extra cushion sprocket I had to Benjamin Binns in Australia. He is doing a 1918. I think they were standard by then. If I can get your email I will send you some pics of my project. It has an earlier clutch throw out arm. Thanks, Paul Venne vennepaul at gmail.com

    • Pete Young permalink*
      August 23, 2010 12:48 pm

      Hi Paul. My bike is an X Series 17, which seems to have been made for the 1916 calendar year. (maybe made in late 15 or early 16?). Jerry Capa and Charlie Carter both recommended that I install a Cushion Sprocket, since it makes the bike ride smoother. So I bought a good one form Jerry about 6 years ago. I still have the original plain sprocket in the small pile of ‘extra’ parts. The Cushion Hubs was introduced on the later bikes, I think in 17 or 18, I’ll have to check my old advertisements to see exactly when. The bike does ride smooth, and was much better on yesterday’s ride after I fitted some nice long ball-end grips from Matt Smith up in Oregon. There is still some engine vibration, but it is manageable.

      I’ll email you offline.
      Pete

  2. November 4, 2014 9:52 am

    God forgive my lathe envy.

  3. November 4, 2014 9:54 am

    Was the engine vibe a hint of things to come? How is the rebuild coming? I’ve seen rods more than once now I think on Ebay.

    • November 4, 2014 10:00 am

      I don’t think so, but maybe? Finishing the Ariel rebuild this month, and the Excelsior is next up on the workbench. It doesn’t need much now, but the center hole in the mainshaft is off center by .002″, so i’ve been unable to align the flywheels & crankpin. I have an idea of how to do it though…

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