Heisler Universals & Shafts Design
Nelson Riedel, Nelson@NelsonsLocomotive.com
/2005, last updated 09/29/2009


This page describes the design of the model universals and drive shafts.  The initial plan was to make the Us and the cross using the investment casting process.  That didn't work out so it was then decided to fabricate the cross from brass rod stock and the Us from cast iron flat stock.    This page was updated in the fall of 2009 to reflect those changes.   The universal have now been fabricated and look good.

The Cass foreman had told me end caps with grease fitting had been added to the Cass 6 universals to improve lubrication.  The following couple photos show the end caps and pin retention bolts.   

This shows the end cap on one side of a  female slip joint that mates with the square end of the drive shaft.   The end caps (one on each side) are held to the U by six screws.  That is a grease nipple in the center of the end cap
This is one of the pins which joins the two halves of the U joint pictured above.   The bolts hold the pin in the center cross. (The other pin has a notch cut in the side  This pin holds the second pin in place via the notch.) 

The groves in the side of the pin are lubrication (grease) channels.  


This close-up photo of a center cross shows the holes for the bolts that retain the pin.
This is the end or one of the Us on MRSR91.  Note that there is no end cover.  The  pin is held in place by a retaining clip.  There is a second clip on the other end of the pin.  The other pin is held in place by this pin via the notch half way through the side of the other pin to let this pin pass by but prevent the other pin from slipping out.. 

I didn't notice any way to lubricate the pins on this universal.  Maybe they are lubricated only when assembled.  That is maybe why the folks at Cass modified their Us.

I plan to use the retaining ring scheme to  avoid making all the caps and drilling screw holes, etc. 

Lubrication will be provided via a channel drilled in each end of each pin that mates with a small cross drilled hole that comes out the side of the pin near the center of the bearing.       

The plan is to pretty much scale the shafts and universals.  As a starting point the following decisions were made about the shafts and Us:  

  • Shaft Diameter will be 9/16"

  • Shaft slip joint will have a 5/8" square cross-section.

  • Round U will accept a 1" length of 5/8" diameter shaft.

  • Square U slip joint length will accept a 1.5" length of shaft

  • Cross pins will be 3/8" diameter.


Bearing:  A standard flanged sleeve bearing will be used in the ends of the Universal Us.  

Universal Cross-HM303: The Universal Cross will be made from two pieces of 3/4" brass rod silver soldered together.  A 3/4 diameter partial circle hole must be cut in the side of one of the rods and the other rod slide into the hole and silver soldered in place.  The holes through the center of the rods  will be drilled/bored undersize and then reamed to the exact size.

The 6-32 hole is for a set screw to keep the HM300 pin from rotating (the HM 301 pin has a notch and can't rotate).

The photo on right shows a fabricated universal cross. 

Universal Round Shaft U - HM304:

The round shaft U will be machined from a single piece rectangular cast iron stock.


This is a fabricated round shaft U. 
Universal Square Shaft U-HM305:

This U will also be machined from cast iron rectangular bar stock.  

The challenge will be to make the square hole.        

This is a fabricated square shaft U. 
Universal Pins: The pins will be made from 3/8" diameter mild steel rods.  The shorter pin is retained by the other pin via the notch.  The longer pin is held in place by .029" wide external retaining rings (standard hardware for 3/8" diameter shaft) 

The 3/16" holes in the ends and 1/16" cross holes are for lubrication.  The 3/16" holes will be fitted with the oil hole covers described below.


Oil Hole Cover:  These oil hole covers will be used in the ends of the universal pins.  They are available from McMaster-Carr.  Part #1214K1 has  A=3/16", B=1/4" and C=9/32".  The catalog says: These low-profile covers have a self-closing ball valve. When you're ready to fill, the pressure of your oil container easily depresses the ball.   Friend Dave Johnson uses this type cover on his Ten Wheeler for grease nipples.  He uses a grease gun with a tapered nose fitting --- works great.   The drive-in covers are zinc-plated steel.

Drive Shafts: The drive shafts are made from 5/8" mild steel square stock. The end that oes in the round U is turned 5/8" diameter.  The middle part is turned 9/16" diameter.  A key slot will be milled in the round end to mate with the slot broached in the Universal U.   The lengths vary from about 7" for the shaft to in the front truck to about 15" for the shaft to the middle truck.   The exact length of the shafts will be determined after all other variables have been  fixed.
Assembled Universal:  The universal can be assembled with one square U and one round U as shown on the right or with two round Us.  Each three truck Heisler has three Square-Round Universals and three Round-Round Universals.   

Photo above shows a completed U joint.    

Drawings and a Parts List for the Gears & Shafts may be downloaded from the Drawings and Parts List pages.   The Universal Construction page(s) will explain how the these parts were machined.  

Heisler Project
NLW Home