Briggs build without welding...

[twowheeledfox]

Hi everyone. I have a nice vintage Briggs 3hp that I would really like to use for a build for various reasons (reliability is very important, I rebuilt the motor myself, it's relatively small, etc).

Here's the problem: I don't have a welder, or access to one. Most of the DIY-type builds I've seen involve welding something or another, which I'd really like to avoid because of how much of a hassle it is to get a welder to do a small job like that out here.

What I would be able to do is get a large frame which would comfortabley fit the motor, and buy any bolts/plates needed for a clean no-weld mount, etc.

Anyone tried this? Let me know, thanks

 

[wayne z]

I think that a build like that could easily be done. Just hafta think and research what others have done.
Bolted joints and gusseted joints are more reliable and predictable as far as failure mode and strength.
That's why there's not a lot of welded joints in aircraft construction.
A welded joint, especialy aluminum, is very rigid and tends tends to propegate cracks from stress or vibration. Cracks are hard to see and a joint can fail all at once .

Bolted joints give a little let off stress and tend to wallow holes or bend bolts to give you plenty notice before they fail.
By studying bolt shear strength and tensile strength, and material strength, It.s easy to estimate the strength needed for any particular joint.

Here's a pic of my experimental plane, built from aluminum with all bolted construction.

 

[twowheeledfox]

Thanks for the reply. I was thinking something along those lines with regard to strength and reliability, I'd just never seen any members here do a weld-less Briggs build.

As far as attaching it to the frame, I was thinking of attaching the motor at two points:

1- the top. I would use a piece of bent plate steel or angle iron bolted to the head of the motor and attached at the frame end to a U-bolt/plate arrangment which secures the assembly to the downtube. The piece of iron/steel would be bent at the appropriate angle to the frame.

2- the bottom. Use the four standard mounting holes on the bottom of the motor, connected to some kind of metal plate which is than U-bolted to the frame on the downtube and seat-tube.

I forgot to ask, is it okay to tilt the motor about 15-20 degrees? I'd have a far wider range of frames to pick from if I could just tilt it a little.

Finally, if I manage to get the thing in the frame, there's the issue of the drive system- first, the shaft can't stick out too far, and second, I need to find a way to mount a belt hoop or sprocket on a wheel without welding. Than comes drive system and clutch, etc.

I want it to be simple and reliable, so I was thinking of direct belt drive with a tension clutch. It seems to be the simplest since it involves no transmission or clutch and the "tensioner" or pulley can be mounted in different places on the frame. However, I don't know what to use for a tensioner, where to mount it or what to use to control it (lever? handlebar lever? etc).

Sorry for the long-windedness and thanks for you help.

That plane is amazing, by the way- looks factory-built

 

[wayne z]

Everything you mentioned has been done and posted about here at these forums.
Go back and research posts in the Boardtrack, 4 stroke, and DIY forums, and experiment with the search feature at the top of this page. Tremendous valuable info here, about 26,000 members now.

 

[MEASURE TWICE]

The first motor bike I built had no welds.

The Briggs 3hp was mounted at 3 points. The first two points only used the two left side mount holes on the engine by the crankshaft. This meant that no jack shaft was necessary, except at slow speed you could notice the weight on the right side.

Also it had the bolts go right through holes drilled in the bottom tube. I know you could make clamp so not as to weaken the frame, but it worked.

The third was connected to the top bar. It was with a metal cable that went on with
u-bolts clamp to the top tube and then a piece of metal that used a head bolt to go through it. Note: best not to loosen just the one bolt.

I used the criss cross sequence and loosened all to take the one out to make the connection. Tightening also with a sequence to not warp and crack the head.

There was no clutch just a washing machine pulley attached to the rear wheel with v-belt drive.

Lots of fun riding it in the woods. See what others have done, no problem asking questions…OK!

Measure Twice

 

[lowracer]

I did a no-weld 2.5hp Lifan rack.
Check out the link
http://motorbicycling.com/f36/felt-like-good-time-swap-engines-27109.html
-Lowracer-

 

[Dirt Road Cowboy]

BGF sells the mounting bracket on ebay:
bicycle Motorized ENGINE adjust 4-stroke mount plate | eBay

and the complete kit on his website:
4 - cycle 49cc MOTOR bicycle Motorized GAS ENGINE KIT

There are probably others out there too.

 

[Dirt Road Cowboy]

Double Post.

 

[livesteamfan]

I know this is an older thread and no one probably looks at it anymore, but my bike currently uses a Briggs engine and I have not welded anything on it. Before the 3.5hp Briggs, the same mount was holding a 5.5hp Honda GX160. I'm currently building another bike using the same idea, but going around the downtube and seatpost with u-bolts instead of drilling right through them, this way it can be transferred between bikes easier or removed if I want to sell the bike by itself or do something to it. But also, being I can't weld, I went with the simplicity of a single speed, no jackshaft belt drive. My current build will use a brake lever belt tensioner instead of a pedal one so I can still pedal the bike around.