Welded on a front motor mount

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k.mah

New Member
Nov 22, 2012
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oceanside,ca
Had a spare engine lying around and a spare beach cruiser so decided to build another mb. My original problem was that the down tube was oversized. I know how to mount on these type of tubes, but just got a welder and wanted to fab something. Also swapped the stock bolt studs with bolts going into the motor itself. I basically copied the mount sold on gasbike.net (http://www.gasbike.net/alum-bike-frame-gt-2-a.html)

Took a total of about 45 minutes to cut, shape and weld the piece in place. I used an angle grinder and the welder.



I went over all the welds to reinforce them after the pic was taken, and am VERY confident that the frame will break well before the mount (take a look at those horrible welds on the frame....eek!)

As for:
chain clearance, perfect
How solid is it, rock solid
Air filter/Throttle cable clearance....BARELY enough room. If i was to do it over again i would make it about half as long.
 
2door

2door

Moderator
Staff member
Sep 15, 2008
16,302
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63
Littleton, Colorado
Absolutely the best option is a welded mount. You did good, k. mah. I like the simplicity.
Did you use the rear mount to the seat tube? I'm pleased to see no rubber too:)
Thanks for sharing and show us a picture after it's painted.

Tom
 
K

k.mah

New Member
Nov 22, 2012
173
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0
oceanside,ca
Thank you! I've been avoiding rubber mounting after reading about isolating all the vibrations, just made sense. I did use the seat tube with the stock mount. I think I may just clearcoat it, although it won't blend perfectly, I love that raw look!
 
racie35

racie35

Active Member
Nov 17, 2012
1,702
5
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usa
cars and trucks have engines mounted in rubber......whats the deal with solid on a bike?
 
2door

2door

Moderator
Staff member
Sep 15, 2008
16,302
175
63
Littleton, Colorado
racie35 said:
cars and trucks have engines mounted in rubber......whats the deal with solid on a bike?
Click to expand...
Cars, trucks, motorcycles and outboards are mounted in a rubber sandwich style of mount. No metal to metal contact. When people try to insert rubber or some resilient material in a bicycle engine mount they do not isolate the mounting fasteners from the vibrations. That allows the vibes to be transfered directly to the fasteners and the mounts resulting in failure of one or both. You can not eleminate the vibrations produced from the engine but using rubber in the mounts simply transfers them to places that can't take it.

There have been pages of discussion here on the pros and cons of rubber mounts. Use the search feature and you'll see that all of the experienced builders agree; mount the engine as solid to the bike frame as possible and live with the vibes.

Tom
 
BikeBerryKelci

BikeBerryKelci

New Member
Oct 25, 2012
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brea
2door said:
Cars, trucks, motorcycles and outboards are mounted in a rubber sandwich style of mount. No metal to metal contact. When people try to insert rubber or some resilient material in a bicycle engine mount they do not isolate the mounting fasteners from the vibrations. That allows the vibes to be transfered directly to the fasteners and the mounts resulting in failure of one or both. You can not eleminate the vibrations produced from the engine but using rubber in the mounts simply transfers them to places that can't take it.

There have been pages of discussion here on the pros and cons of rubber mounts. Use the search feature and you'll see that all of the experienced builders agree; mount the engine as solid to the bike frame as possible and live with the vibes.

Tom
Click to expand...

Great advice! very detailed.
 
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