Rubber mount softail
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- NewB
- Posts: 5
- Joined: Mon Jun 04, 2012 3:47 pm
- SELF INTRODUCTION: Enthusiast who has built motorcycles for 40 years, and is a great proponent of this original website! Two years ago I built a rubber mounted softail that has not failed. There have been many failures with these due to the poor design (extremely high forces) of the rear shock travel. Motor/trans mounting dimensions came from this website, and I couldn't have done it w/o CH Forum input.
Rubber mount softail
Rubber mount Evo softail in a Paughco Twin Cam frame (no center downtube). I just wrote up a long complete description but lost it when I went to preview it, and found out that I couldn't go back to add more pics without losing everything (lacking serious PC abilities!). If you are interested I will talk more about it. For the present I will just post it, and can explain later if anyone is interested. I have 5000 miles on it currently.
- Attachments
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- Cradle dimensions
- Rbr Mnt Cradle small.jpg (253.11 KiB) Viewed 7826 times
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- Front Motor Mount
- Front motor mnt.jpg (218.19 KiB) Viewed 7826 times
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- RH view cradle
- Cradle RH view.jpg (95.03 KiB) Viewed 7826 times
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- LH view cradle
- Cradle LH view.jpg (96.84 KiB) Viewed 7826 times
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- Cradle & TC frame
- Cradle & TC frame.jpg (101.23 KiB) Viewed 7826 times
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- Death Valley
- DthVly2 small.jpg (91.26 KiB) Viewed 7826 times
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- Contributor
- Posts: 804
- Joined: Wed Oct 26, 2011 10:43 pm
- SELF INTRODUCTION: I was on the last board as bonustoolkit. I have changed that to my given name.
I started a project build there " File and Fit." I paln to continue that when I go back home in Dec. 2011. I first joined the board when Gary W had it in the year 2005. That was the time I really gained an interest in building chops. I have a long way to go, compared to some here.
Re: Rubber mount softail
I am interested. Thanks for posting.
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- NewB
- Posts: 5
- Joined: Mon Jun 04, 2012 3:47 pm
- SELF INTRODUCTION: Enthusiast who has built motorcycles for 40 years, and is a great proponent of this original website! Two years ago I built a rubber mounted softail that has not failed. There have been many failures with these due to the poor design (extremely high forces) of the rear shock travel. Motor/trans mounting dimensions came from this website, and I couldn't have done it w/o CH Forum input.
Re: Rubber mount softail
One of the main challenges in building this was due to the relativley poor rear suspension design that a softail has. Because the rear shocks are located underneath the eng/trans, the attachment point for the shocks to the swing arm is very close to the pivot point of the swing arm, something like 8" or 9" (23cm). On a "normal" rear suspension, that distance might be on the order of two feet (61cm). Because of this, the shock springs must be much more stiff (higher spring constant), on the order of three times greater than "normal" rear shocks (for the same amount of return force). The downside of this, is that those high spring forces will be applied the rubber mount system. This is the primary reason that other rubber mount softails out there have had difficulties with their life cycle (failed). The two stiff rear springs will just eventually mash the rubber in one direction, failing it in the worst case, or minimizing it's effectiveness in the best case. My rear bushings are polyuerathane with a DUR A rating of 70 (too high for my liking). They were sourced from automotive, and were designed to be used on the leaf springs for an older model Ford Mustang. I did not modify the size of the holes in the frame where the swing arm pivot axle goes through, so there is 1/16" inch clearance that allows for poly bushing movement, and acts as a maximum allowed bushing displacement. (The stock swing arm setup has some steel bushing that passes through the frame.) See crosssection. More, later, thx for responding!
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- NewB
- Posts: 5
- Joined: Mon Jun 04, 2012 3:47 pm
- SELF INTRODUCTION: Enthusiast who has built motorcycles for 40 years, and is a great proponent of this original website! Two years ago I built a rubber mounted softail that has not failed. There have been many failures with these due to the poor design (extremely high forces) of the rear shock travel. Motor/trans mounting dimensions came from this website, and I couldn't have done it w/o CH Forum input.
Re: Rubber mount softail
Nore pics
- Attachments
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- Front motor mount uses Dyna bushing
- Rbr Mnt front small.jpg (241.61 KiB) Viewed 7799 times
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- Crossection w/ stock on left and modified on RHS
- Rbr Mnt section view small.jpg (251.15 KiB) Viewed 7799 times