Growing up my dad was way above the curve in technology. We spemnt many nights in our shop developing new ways to make parts better/lighter. He wanted to give us an edge. Here is my sister's 1985 JMC. Just as it was last raced. I believe it to be the most advanced bike in BMX history. It could still be taken out on the track today. To begin with, ser #M8501 1985 JMC JR Mini Special frame and forks. (Jim Melton really knew how to build them.) The wheels: Araya 20s 20x1 1/8 rims-double butted spokes, aluminum nipples, Shimano cassette hubs (these were taken apart, insides bored out, new sealed bearings & aluminum axels added), IRC Road Lite EX Tires. Custom made BB w/ sealed bearings & Aluminum axels. Custom made cranks w/intregrated pedal shafts made for Hare Pedals & 52t sprocket attached to an Italian Hollow pin chain makes to bike go forward. Nylon headset and custom Aluminum 3 bolt stem hold the Powerlite handlebars w/ Grab-on grips to the forks. KK Plastic lever and adjusable AR brakes stop the bike. The Uni Seat is held in place by a custom Clamp. This bike weighs 9#15oz and won the NBL Grands w/ my sister aboard. I am the proud owner of it now and will be taking it to shows whenever I can.
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What do you think? Thanks again. Tommy

S W E E T ! ! ! ! ! !

very cool! you don't see as much custom made stuff these days as you did in the eightys. thank you for sharing

That truely is a work of art and great piece of "mini" tech history. It is very cool that you still have it.

That being said, may I ask a few questions? If your dad was shaving ounces, why use a 52t front sproket? I would assume he has his reasons, maybe somethig to do with attaching it to the cranks. And with the large front sprocket (extra ounces) he had to use a larger freewheel (extra ounces). Just curious.

The chain links definitely look different, straight on the inside and concave on the outside, but I am not seeing the 'hollow pins'. Am I just not seeing correctly?

I have no desire to 'pick apart' your dads build. It is awsome. Just wondering about some details.

About the sprocket. There were a lot of tests done- it seemed that the chain rolled better on a larger gear. The gears were the same weight as most any of the smaller ones with the way that they were drilled out, no exter weight there. I'll have to look at the chain- it may have been replaced by me before the pic.

Yes, the early pic is with another chain I had put on it. Heres the right pic.
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very nice do u have a lil one that can put it back on the dirt

Again, not challenging you by any means. That was what I figured you meant by the hollow pin chain. I also believe you about there not being much difference in weight chain ring sizes.

My thought process is from a father BITD that had a son who rode a bike that size. He was my saving grace as he was constantly helping me with repairs on my sidehack after a hard day at Corona. I believe he was an engineer by trade so he had a different way of seeing things.

He made a statement once that has stuck with me to this day. I don't know why, I do not know how true it is or if it can be proven. Maybe someone here with an engineering background can shed some light on it.

He told me, "by using small gears, front and back, you are also using less chain, and the less chain you use the more torque you get to the rear wheel faster."

I understand what he said but I have no clue how true it is. Anybody out there have any insight on this?

That is one of the coolest bikes I have ever seen. Tons of out-of-the-box thinking.


Thanks for sharing.

+1
Jim Kav

That is friggin' awesome!!!!!!

that's a killer bike tommy!
mike

it is true, but for a younger rider with very little torque. the larger gears allow the chain to flow better around the gears which make the same gear ratio feel easier to pedal.

awesome bike. he could have saved more weight with a straight laced front wheel instead of 3 cross.

Thanks Steve. Physics and engineenering are a mystery to me.

Great photos, you can see your dad spent a lot of time thinking how to build a better machine with your sister in mind. I think it says a lot about how important it was to him to prepare for the races and to help you guys have a great time on race day. That is really way over the top though, very cool to see, thanks.

Mike

That is the trickest bike I have ever seen.
May I ask is your Dad around? Sitting down & shooting the stuff with a guy like that would be priceless.

b.

Can anyone tell me more about the AR brakes? It looks like the alignment is adjusted with a cam. Very cool. I never saw anything like those BITD.

Dad just passed away, kind of the reason I'm sharring his Science projects now. And yes, most of the people around here really loved talking with him. Always trying to help the riders/ parents get better.
Those brakes were taken off a ten speed, super light and easily adjustable.
Thanks for all the nice comments. Tommy

Tommy, thank you so much for sharing. That bike is not only a cool piece of engineering, but an amazing piece of BMX history. On top of that, as you've alluded, it is a family heirloom and I am sure it brings back great memories.

Not only the larger front gear and rear gear, but far more links in the chain would increase the weight no?

Added wieght yes, but well worth it for the little guys. My dad's tests proved that w/ the lower power riders, not having the chain bend so tightly around the smaller gears, they could go the same distance more easily. There is a point where horsepower overtakes this, but its up around 70lbs of leg pressure. Teenagers start getting to this point, but they're not ridding Minies. My dad really paid more attention to the little guys. My gears on my bikes were the usual 44-16. I'm 7 years older than my sister and did not benefit from the larger gears. Countless number of hours spent in the shop testing every detail. Take those cranks, no ridr over 70lbs is going to be able to ride them. But they work for the little guys. Kelly was National #1 on this bike. SCIENCE

Sweet bike for sure, and the modifications are unreal. Love it ...

If its a 1985, then I belive you have a mini rather than a JR Mini.

The JR Mini was introduced in 1982 for Justin Roos and only about 54 were made.

The down tube on the JR mini is much thinner than the downtube on the mini.

Actually the bike is a 1-off built just for Kelly by Jim. My dad and Jim were pretty close. It was the first bike Jim built in 1985 and "he" called it a JR Mini. Thats why I used that name. But you can call it just a "Mini" if you want. Oh yah, the original invoice I have says "JR Mini" also.

Cool, a one off made Jim is very special, :-) Did he put the thinnner downtube on as in the original JR mini, or stick with the standard mini downtube on this build, love the family history that goes wioth the bike as well, very cool !!!!

About the bike: the tubes are thin walled and the demisions are a little differnt also. It was the 3rd and final JMC that Kelly rode. Came unpainted, I remember dad painting it and putting it in the furnace to harden the paint. Every part was created just for this bike. We had the time in the shop on the lathe making those parts fit. Learned a lot from those days about machining special parts. I still like building my own parts for those old bikes.

I myself am not a big fan of minis (I CANT RIDE IT), but this is by far one of THE coolest bikes I have seen on this site. Your dad must have been a very cool guy, and a freaking mad scientist on top of it. Thank you for sharing with us.

That's really cool stuff. Thanks for sharing.

How were the cranks made? I notice the front gear is a 52t, what was the rear cog?

Damn, you couldn't put a price on this gem even if you wanted to.

b.

That is without a doubt one of the most customized little rigs I have ever seen. What length are the crank arms? And hopefully I didn't miss it but what size rear gear are you running with the 52 up front?

wat cool thanks for sharing
dion
www.mbb-bikesbilliards.com

To answer some of the questions: the rear gear depended on the track, it was anything from a 22t to a 19t. The size cranks are 168mm made by taking an oval tube and putting it through a swedging machine under a lot of pressure and heat. Then it was heat treated after the bend was finished, the hole was then broched and another piece welded for the bb shaft to bolt through. We went through a lot of trials before we got them right. The rest was just easy machining and putting it all together. We had a great bike to start with which really helps when trying to build something that is as fast as it looks. JMC Minies rule.

Awesome scoot, better background story JD

WOW!

Tommy, you need to open up the vault and share more of Doc's creations. This one may be the most advanced, but you all need to see the stuff that Doc produced. Unreal.

Kelly had one amazing bike after another, and each had something slightly more advanced than the previous. Even Tommy's bikes had the input of Doc's science and engineering background. It is hall of fame material.

That's cool but just wait till I take the frame and fork I plan to create in the next few years and build to a complete bike. Then I'm gonna borrow old Doc Brown's DeLorean time machine and travel back to 1977. Then we'll see whose name is at the top of this thread

That is a sweet little machine. The concept of the gearing is rather novel in it's own right, regardless of what frame it was attached too.

All of Tommys' old rides are tricked out like this and he is still fast too......Allen Godfrey

Great bike, great story, great history!!!

Any pics of her riding it?

Pics and video of her winning the NBL Grands. JMCs had a reputition of breaking but that bike took a HARD crash over some doubles in the 1st moto. Still went on to win the rest of the days motos. I haven't got around to putting them on computer yet. Will share them later.

I remember seeing Kelly's amazing minis back in the day. I had no level the depth of modifications but it was crazy to me that a girl so little (she was tiny!) was riding a bike so light and amazingly trick. I am blown away just by the hub modifications you described. Pure genius.

Minute mark 5:15 look for #3 or the winner
http://www.youtube.com/user/oubmx2#p/c/9D3...A/0/lX_peuVKh9U

I remember Kelly racing in my brothers classes when there wern't enough girls to run or she would just race two classes. I do remeber her bikes being out of the ordinary and do also remember the strange gearing that your dad used to use. Did he use it on all her bikes? One of the fondest memories was hyour dad telling me how he was experimenting with different gasses in the tires to try to reduce weight. Kelly was still on sew-ups then.

Thanks Steve, Kelly was on the Orange bike that race. She was so little, but fast. I remember that race, too. Dad always had those large gears set up so well. He used to have kelly ride around pulling stuff behind her practice bike (we weren't allowed to ride our race bikes except on the track) to get that first straight pull. Complete domination was Kelly's goal.

It seems like the coolest technology went into minis as shown here and in other parts that made it to production. It blows my mind that that racer is under 10lbs. That is just CRAZY!

Thanks for sharing this one.

Hey Tommy, that bike sure brings back a lot of memories. Doc use to call me about his ideas for Kelly's bikes. Your Dad was a genius. I think I still have a couple of pictures of Kelly in my scrapbook. One of them is with all of her trophies. Thanks for sharing. Tell Kelly Vera and I say Hello!

Jim Melton

The honor of riding your bikes was ours, Jim. Dad really loved you and your company. Sharing these projects that dad created is a tribute to both of you. Tommy