Mondo Shock

[rev106]

I have for a while, wanted to build a 26 mono shock type bmx bike. The first Coaster Brake Challenge this year will be a 9 mile down hill run so I figured this would be the impetus for me to go ahead and get it done before the 4th of July, the date of the first heat. The pic is just inspiration, the build will take it's own course for sure. I will try and make the whole bike only using what I have laying around. I will qualify that by saying I have close to 150 crates full of bike parts and nearly a complete frame building/machine shop at my disposal so that makes the criteria not really much of a challenge but hey, we'll see! I want to make it look like it was from that era, paint? Not sure. The main thing was the shock, I thought I had one somewhere and was lucky to find it quickly after work today and get the front triangle mocked up in the fixture.

Making the head tube, this saw never cuts straight....

Master tube set for my give-away cruiser so I don't have to keep figuring out the miter.

Using some .065 4130 it is rusting away anyway, may as well make this beast weigh as much as an e-bike.

The critical lynch pin to the whole project....

Pre honing out the seat tube to fir a 7/8 post. ....

getting the head tube 90 degrees....

Cutting the notch for the seat tube in the mill..

MACHINE TOOLS ARE WONDERFUL!!!!!

About and hour in....looking like a bike...

 

[Funkme]

Baaa haaa, all those machine tools, damn boy I would have a field day... love the ole mono shocks...

 

[MattiThundrrr]

This is ohhh soooo verrry EXCITINGGGGGG!

 

[rev106]

made some more progress. got to use my fancy new tube bender to make a looptail rear end! I needed an excuse to make use it. got the loop mocked up and the lower linkage, and the frame tacked in place. More to come.

Had enough time to get the shock in place...

 

[OddJob]

Wow! Just checked in to see what was up, you are moving at the speed of power tools!

Diggin' the cantilever stays to the mono-shock set up. I can't remember, will this frame fit 26" wheel / tires or smaller?

 

[MattiThundrrr]

I'm hoping it's 26". For the culture

 

[rev106]

Wow! Just checked in to see what was up, you are moving at the speed of power tools!

Diggin' the cantilever stays to the mono-shock set up. I can't remember, will this frame fit 26" wheel / tires or smaller?

, 26 wheels for sure, 20" bmx are cool and all but they take forever to get anywhere.

 

[rev106]

Got it mostly tacked good, I will be taking it out ofthe fixture to check chain ring clearance and finish welding in the next few days. I need to build some wheels too. Coaster Brake of course.

 

[ifitsfreeitsforme]

oh, juicy. Can't wait to see more.

 

[kingfish254]

That frame jig is awesome!!!!
Love the looptail!!!

 

[rev106]

Made some more progress.

Borrowed a wheel to check crank and wheel clearance. I moved the lower swing arm structs inside the frame to make room for the chain ring.

Cranks clear both sides. I will need to box up the swing arm in the fixture next.

Borrowed a wheel

and make a brake bridge while the frame is back in the fixture to insure function. I need to build some wheels so I can put a load on the bike and see how far the shock will compress.

Borrowed a wheel, I need to re-pack the hub anyway.

Nerd alert!!!!!

 

[MattiThundrrr]

Some people's parts pile...
This whole thing is making me giddy

 

[arty dave]

 

[rev106]

Got some of the swing arm assembly boxed in, some tacked in place. I figure I'll need to make about 60 more frames before my welding becomes consistent, right now some passes are good and others not so much. All part of the reason I'm doing this is to become a better welder/frame builder. Each time, it does get a littler easier and faster. Moved the swing arm lowers in to clear the chain ring.

Fork was one I made to do a study on how to make them, I gave the rest away and this one is a little off but it will fit in with the theme of the build just fine. Twin drop outs so I can change the way the bike rides.

Nerd alert on the cranks! I've been hoarding BMX parts since when you could get a whole Mongoose motomag bike for 10 bucks. A long time ago for sure! I figure I have enough stuff left to build a few ore cruisers and by then I doubt I'll want more no want to pay the crazy prices for this stuff.

Going to go with a Schwinn headset because it was what I found first.

 

[rev106]

Got my wheels built up tonight. Has a NOS Shimano high flange coaster but shell only, found the guts at my shop luckily. High flange out front, rattle can flat back and some old cruiser knobbies for traction, it is coming along!!!

 

[BartRidesEternal]

Sweeeeeet!
I like the colour on the rims.

Does the hingy part of the rear stays get bronze/steel/plastic bushing for 'wear' purposes?

 

[rev106]

Sweeeeeet!
I like the colour on the rims.

Does the hingy part of the rear stays get bronze/steel/plastic bushing for 'wear' purposes?

I have a few washers in there, we'll see how it holds up, I can make changes if need be.

 

[rev106]

Goal is to have it rideable for our Tuesday BMX ride, it will be a good shake down run. Been at it for a few hours now in the am, I have a bit more to do before it is ready. Fork steer tube was too short so I extended it. I have done this many times and I like to use a MIG welder and fill the gap with weld to make it strong. I use a donor stem as an insert and while the weld holds that insert can fail as I found out the hard way! Had to finish honing out the seat tube so I could put a seat on it and test the boing factor, looks like I have about 2 inches of travel! It works! Had to use the WRIST BREAKER 5000 to hone it out, I hate that thing, is has picked me up off the floor and wacked me aroud more than once! Still have to finish welding it up and I want to reinforce the rear triangle and the shock support. I changed my design a bit to I can take the rear triangle off the bike completely. Stem and bars need to be dealt with too. Frame has some serious rake which is good becasue I am building it to do a serious downhil bomb so it should be pretty stable as long as the rear end has no lateral movement, so far it feels stiff. You can see the sharpie mark I made to test how far the rear end travels so I don't have any collision with both halves of the frame.

 

[rev106]

Got the extra strut in the frame and corrected some off kilter brackets so rear end is in alignment with the front. Stem is next + finish welding and gussets.

 

[rev106]

2 pm, and I took it up and down my street. Rear end still needs some tweaking and the shock is way to weak to hold my weight. I have another shock I will have to mod the frame a bit I think but in the end it will be better. Used some motocross bars that add 37 pounds to the weight of the bike. I think I thrashed on it pretty hard to get to this point so I'll work on it some more later. Enjoy.