Low and Wide Big Tire from Scratch

[LowandWide]

Hi everyone,

I recently received a welder for Christmas, and was thinking of a project to build. I had a go cart as a kid, and loved it, and thought about building one of those, but we have ATVs and i kinda wanted something on two wheels.

After looking through quite a few build logs I stumbled onto Jeep2003's build log of a bike he made from an old swingset! I thought it was awesome. I now had a direction to go.

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I have been practicing with my welder just welding together random things I have laying around. (BTW - my welder is a Hobart Handler 125 wire feed welder with optional gas) I don't have gas yet, so I am using flux core wire. I have been very happy with the results, although I would like to eventually get the gas add-on kit and gas, but for now will just be using the flux-core.

I knew I was going to need a pipe bender, so I picked up one last thursday at Northern Tool (My Toy Store). On Thursday I also placed my order for the steel at the local metal supply place (which is not too local at 40 minutes away).

I tried out the bender on some 1" schedule 40 pipe that I had picked up and I was disappointed with the way the pipe would kink off on a 90 degree bend. I had read that packing the pipe with sand would help reduce this, and I watched a you tube video where the guy just duct taped the ends.

Friday I picked up my order at the metal supply place and this is what I got:

42 feet Schedule 40 3/4" pipe
4 feet Schedule 40 1" pipe
4 feet Schedule 40 1 1/4" pipe
4 feet Schedule 40 1 1/2" pipe
4 feet Schedule 40 1 3/4" pipe
4 feet 5/8" rod
4 feet 3/4" rod
4' x 6" x 1/4" plate
18" x 48" x 11ga sheet
Total was $157

I plan to build the majority out of 3/4" sch 40. Keep in mind that pipe is measured by the inside diameter so the pipe is actyally just over 1" OD.

I already had some 4" x 4' x 1/4" plate

I immediately set forth with bending the front forks when I got home Friday. I taped the end of one of a length of pipe, filled it to the top with sand and tapped it on the ground (concrete). The sand settled down and compacted. I topped it off with sand and tapped it again. After a couple more timed I taped the top with duct tape (3 layers).

Bending went much better and I got great results. Yes packing each pipe is a pain, but it is really worth it.

I wanted to keep the bike as low as practical, so I wanted to build the forks first. That way I could keep the body as low as I could make the steering neck.

I bent two pipes at 90 degrees, cut the 90 in the middle and spun the pipe around and welded it to make an "S" for the front forks.

I heated the bottom ends of the forks (after cutting to length) and used a hammer and anvil to flatten them out.

Next I cut the bottom tree out of the 4" wide 1/4" plate.

And welded it to the tubes. I calculated how wide I wanted the space for the front wheel, and cut a block of wood at that width. This is where I learned that jigs are good (as you will see later).

 

[LowandWide]

I got a lot more done this weekend, and will post more soon.

 

[gbabins1]

Welcome fellow Floridian. Looking good so far. :thumbsup:

 

[LowandWide]

Next I bent two lengths of pipe with a 90 on the end and bent the other end on less of an angle. I'm not sure what the angle was, as I just bent it till the two tubes met up near where the neck will be.

To back up for a minute, I had searched everywhere for the right wheel hub, but could not find what I wanted, so I plan to attempt to build my own hubs. I really would like to use a 3/4" axle, due to the width of the wheels, so I purchased two sizes of bearings. One size is 1 3/8 OD x 3/4 ID and the other is 1 5/8 OD x 3/4 IN. I purchased a few sizes of schedule 40 pipe and hope to be able to get one of the bearings to match up. Once I know which bearing I want to use I will order some more of them.

Next I made a jig to hold the front folks the correct distance from the ground, and at the right angle (24 - 25 degrees.)

Then i cut 2x4s to the correct length to hold the top of the frame up off the gorund. this allowed me to grind the frame top to make a good fit with the neck.

 

[LowandWide]

Welcome fellow Floridian. Looking good so far. :thumbsup:

Thanks! Building a bike = much more fun than fighting Florida traffic in mid-January!

 

[LowandWide]

Next I tacked the top of the frame to the neck. Just now as I post this I am realizing may have screwed up on my bearing size calculations, and I may need to replace this neck tube, but we'll see.

That's basically what I got done through the end of Saturday. I got a lot more done today, but its getting late and i'm going to bed. I'll post more tomorrow.

 

[LowandWide]

Sunday I bent some pipe for the bottom frame piece. I was hoping for a smaller angle, but its OK. I really like the rear angles of Jeeps bike with the way the rear upright sweeps to the front instead of just going straight up.

I decided that the best way to keep everything straight for welding was to create a better jig. I kept the part that holds the front handlebars, and extended it back on the ground, then built 2 platforms at about 6" off the ground, which will hold the bottom of the frame. I could then get a center line and position the bottom pieces the correct distance apart. The front is about 9" between the pipe, but the rear is 12 1/2" to account for the tire, sprocket, etc.

In order to determine where to bend the bottom pipes upwards, I needed something to act as a rear axle, si I used a piece of pipe and positioned it in the approximate location of where the rear axle will be. Then I bent the bottom pipes on a 90 degree angle (the max angle of my bender). If I had a nice fancy bender, I could have just bent it to what I wanted and been done with it, but instead I will need to use two bends to get an angle greater than 90 degrees.

Then I cut the bottom pipes off equal distance from the ground. I plan to weld on brackets that extend past the rear of the frame tube for mounting the axle, and those brackets will act as a brace for this weld, so I think it will be strong enough.

I then bent two more pieces of pipe at 90 degrees and set it up next to the frame to determine where I wanted to cut them so to make the sweep back to the frame.

Ok, so this is what I have done as of right now. I was ready to tack weld one side together, but I was getting tired, and did not want to rush it, si its just set in place. I have to cut the left side also.

I set the tire (I only bought one so far) in its approximate location. Its sitting on a 2 x 4 so it will actually be a little lower.

I really happy with it so far. What do ya think?

 

[Square_Chopper]

AWESOME! :thumbsup:

 

[LowandWide]

Ok, now that I am caught up posting on my progress, I thought I would share some of my ideas moving forward.

Jeep2003 is checking on his tire size so I can see if I should use the same drive ratio as him, or if I need a greater ratio. I'm thinking aiming for about 9:1, but really don't know yet. The big tires may need 10:1. Anyone have experience with this?

I would like to use a brake caliper that mounts and grabs onto the sprocket. My thought is that this will help keep the rear end as narrow as possible. Are these any good? Would I be better off with a band on the clutch?

I will probably use either the 212cc engine from Harbor Freight or the 208cc engine from Northern Tool. The one from Northern is a few bucks more, but it appears to be a little higher quality. They both get good reviews, so it may just come down to price when I am ready for it.

Here are some more specs that I would not mind some input on:
Chain: #40
Axles: 3/4" - I will make slots so they are adjustable on the rear axle. Where can I get the adjusters?

The hubs I hope to build. If they dont turn out ok then I will need to locate some. Bad Dog has some, but they seems to have some in a package, and are pretty pricy. I am going to cut 1/4" plate in 6" circles, drill the mounting holes for my hubs (4 on 4"), drill the center bore and weld the plate to whatever pipe best fits my bearings. I'll need to make a sprocket mounting plate also. I plan to build the hub so that the inside face of the sprocket is 3/4" away from the outside face of the tire. Hopefully that will give me enough room for the chain next to the tire.

I was going to just use some of the ball bearings for the neck, but there also may need to be something between the tree and the neck to make the turning easier. Maybe just a flat nylon washer?



I plan to use a jackshaft, but as I mentioned above have not decided what drive ratio to use.

I hope my bearings come today. I am looking forward to mocking up some axles and I have a lot of hesitation on building them myself. If they work it will save me a ton of $, which is a good thing.

 

[LowandWide]

AWESOME! :thumbsup:

Thanks. Where in So Florida are you? Do you Florida guys notice that you don't come across many old bikes down here? Seems they are all up north.

One of my other interests are old Apache Popup Campers, and they are pretty hard to find down here. Seem like tons of them up north though.

 

[LowandWide]

I calculated my top speed using this website.

Mini Bike Speed Calculator (MPH)

I could not find the max RPM for the HF engine, but the NT engine claims a max RPM of 3850.

That gives me the following numbers with a 22" tire:

10:1 25.198 mph
9:1 27.998 mph
8:1 31.498 mph

 

[Square_Chopper]

I'm down in West Palm and no, there definitely aren't many vintage bikes in Florida from what I've seen. There are some here but they're pretty few and far between. Just gotta be patient and watch craigslist like a hawk. All the really good stuff seems to be in Michigan and Cali.

 

[mopar70]

I noticed that you are butting pipe together. If you can put a slug (smaller pipe inside) it will make those areas much stronger and they will have a far less chance of braking.

 

[LowandWide]

I noticed that you are butting pipe together. If you can put a slug (smaller pipe inside) it will make those areas much stronger and they will have a far less chance of braking.

That’s an excellent idea that I had not thought of. The only places I have a butt is in the neck where the “S” are and in the rear when the two bends come together. I think the front will be strong enough since the majority of the weight will be on the lower tree, which is ¼” steel. In the back I plan to weld a ¼” flange for mounting the rear axle. This will span the two pieces and hopefully tie everything together.

I’ll keep that advise in the back of my mind though, because I am sure eventually I’ll have a butt joint that needs strengthening. (already thinking what my next project should be)

 

[jeep2003]

looks amazing! I measured my tires theyre about 19 1/4" with no weight on it. i suspect it slouches 3/4 or so when im on it. Thats another thing to consider. it rolls alot easier when theres more pressure in these fat tires so you can have a taller ratio if you run them inflated. Im about 160lbs. I cant run much pressure in mine or itll hit the tank and fork. My calculations ended up a bit different after i got them mounted ya know. I didnt count the gear ratio tonight it was getting too dark. Ill try again tomorrow.
Thats what i do put a slug in between the pipes before you weld it. also helps line them up better too. Im running flux core in my welder right now. I got a 20lb roll of it for 10$ cant beat that:laugh: though i am switching from argon mix back to straight co2 when i go back to solid wire because its cheaper.
You said you heated the bottom of your fork legs to flatten them out so im guessing you have that ability. I was thinking at the rear end where you can only get 90 degree bends you can heat them and bend them the rest of the way by hand. that would probrobly work fine if you just bend it a little per inch. just dont wannna go too far in one spot or it will distort.
I think your hubs will turn out fine. a little bit of runout on these big mushy tires isnt the end of the world. Disk brake on the sprocket probrobly isnt what you want here. you need pretty good clearance between the tire and the sprocket and a good size sprocket to git between the chain. usually it gets to be too small when your running a jackshaft. maby you can fit it though.. :thumbsup:

 

[Clayon]

Great looking build, you do nice work. I remember seeing jeeps big tire bike and thought about building one, glad to see you did. :thumbsup:

 

[LowandWide]

I didnt count the gear ratio tonight it was getting too dark. Ill try again tomorrow.

No problem. These hubs are going to take forever to cut out anyway.

You said you heated the bottom of your fork legs to flatten them out so im guessing you have that ability. I was thinking at the rear end where you can only get 90 degree bends you can heat them and bend them the rest of the way by hand. that would probrobly work fine if you just bend it a little per inch. just dont wannna go too far in one spot or it will distort.

I had not thought of that. While I did heat the forks to flaten, it was a pain and if I had to do it again I would weld a bracket in instead. If I had a shop press, that would have been ideal. Oh well, if I had a CNC Cutter I would be done by now, but then whats the point? I'm ranting now.

Disk brake on the sprocket probrobly isnt what you want here. you need pretty good clearance between the tire and the sprocket and a good size sprocket to git between the chain. usually it gets to be too small when your running a jackshaft. maby you can fit it though.. :thumbsup:

I sure would be open to suggestions. Disk or band brake on the jackshaft or clutch? Once I have the hubs welded up and tire on I will have a better idea of how much room I will have in the back.

 

[LowandWide]

Great looking build, you do nice work. I remember seeing jeeps big tire bike and thought about building one, glad to see you did. :thumbsup:

Thanks. This is my first welding and bending project. I have studied it to death on the net. Watched tons of videos on welding, etc.

I did end up making one side about 1/2" longer than the other side.:shrug: I can make up for the difference in the rear bracket. I think it will be ok.

 

[Moedog07]

I am enjoying the build, looks great. I want to build a fat tire bike in a bad way but that will have to wait. I am knee deep in redoing my Warrior. Maybe the warrior will need a companion...

Any ideas on the seat yet?

 

[jeep2003]

well its probrobly straighter than mine anyway. i havnt ever made a jig always just build by eye :laugh: you know even factory built bikes the frames tend to be kinda out of square. my super bronc for example. its obvious at the head tube its a good 1/4" to 3/8" off from side to side. :shrug: As for the brake you really cant go wrong with a band on the clutch from my experience. they always work the best for me. they stop reliably and dont get wet. you can put the band on the jackshaft too but youll have to make your own drum. disk on the jackshaft could work too but it depends how big of a disk and what kind of caliper.