20 inch full suspension street build (now with twin motors)

Hey Guys,

Here is my latest build. The Motoped is still moving forward. But, I wanted to try out the new frame jig. So, I decided to start on a build I began planning over the summer.

For the last 2 years I have been watching eBay for a decent downhill frame for a low cost. This is an Intense frame built for Haro. It was in rough shape, dented, and slightly bent. So, I got it for a song. The damage means nothing to me because I am only using the suspension. Even if the suspension is bent, I can repair that with my TIG and my jig.

This build is basically an extensive upgrade to my Cannondale Hooligan. The Hooligan was built as a "Quickie" build. I have about 10 hours in that build, total. So, it was limited to what could be accomplished in a short period of time. This build will use all the components from my Hooligan.

What changes are being made to the bike beyond the new frame with rear suspension?

---The wheelbase is increasing 2 and 1/4 inches from the Hooligan's 41 inches to 43.25 inches. This is being done to increase stability at speed (45mph) and reduce wheelie tendency.
---The battery capacity is increasing from 25 ah (12S) to 40ah. That looks to be the most I can fit in this relatively small frame without taking extreme measures.
---The head tube is replaceable and the front ride height is adjustable 1/2 inch vertically. There are a number of reasons I have decided to go in this direction with the head tube. More on that later.......
---The rear suspension travel is being reduced from 8 inches to around 4.5 inches (this is a road bike after all) using a shorter travel shock I had laying around the shop.
---The bottom bracket is raised 1.4 inches to provide crank clearance with some suspension squat.

The box is 6016 and is 1/8 inch thick. I wanted the frame to be as strong as possible and I needed some thickness to tap threads into. It measures 6 inches wide. This was the widest that was practical and aesthetic. It will have removable G10 side covers. It will most likely be flat black with some subtle white lettering.

This bike will be setup with a 5 turn 3220 with delta/wye switching. Gearing is 26mph in wye and 45 in delta.

The Hooligan already handles very well. It should be improved tremendously. The weight will better distributed and, with only 25ah, it is too light. The added 15ah of battery capacity will increase stability by adding weight. Also, the bike is really too wheelie prone right now. The new suspended bike should be much more controllable. This is a good thing because this bike is being built to accept two 3220s when I get bored with it as it is.

I hope to have the box done this weekend. I will be out of town for 5 days over Christmas, though. So, the build will stall for a while at that point.

Matt

5 minutes with the plasma cutter........

Adjustable head tube mounted to frame jig at the exact angle the Hooligan used, but moved forward to increase the wheelbase.

Top and back plate plasma cut and tacked in place.

I am not sure if I will be able to get any more work done today or if the rest of the box will have to wait. We shall see....... :wink:

Matt

I got the bottom of the box section done and the box to frame (rear suspension mount point) junctions welded. I will post pictures tomorrow.

It looks like I will have room for 50ah inside. I do not have that much lipo on-hand, though. But, I will have plenty of room for controller, relay, delta/wye board, etc.

Matt

That jig looks like it works awesome. And wow you are fast. Nice.

I plan on extensive bracing inside the box at the rear to support the suspension loads transmitted to the box. This will slightly reduce the interior space in favor of drastic strength increase.

Thoughts?

Matt

Wow Matt, that's an awesome jig...your craftsman's skills increases day by day as your equipment....that's cool.
Nice find on that frame....
So the 8 screws will fix the front block to the frame plate? That's what I would be more careful with....(edit) internal brackets was exactly what I was thinking about to suggest!!!
Perhaps consider to extend some of those brackets till the front plate bores for the 8 screws?

Anyway I don't expect you would make that bike as is for production, I'm sure that's simply a good platform to test and than go to next awesome steps soon :wink:

This bike is just for my own use.

The clamps that hold the head tube are recessed into slots milled into the front of the plate. So, the screws do not take side to side loads. The clamps transmit the load to the front plate (6mm thick plate) directly by way of the recesses they are set into.

Matt

Beautiful work so far Matt. Subscribed.....

I have a lot of welding done. The front plate that the head tube bolts to is 1/4 inch thick while the rest of the box is 1/8 inch thick. It is a bit heavy (for aluminum), but, stupidly strong. Also, the front plate is welded inside and outside. It should be way overkill STRONG. I also braced the swing arm inside to reduce flex. As a road bike, I want it to be stiffer than a dirt bike would be.

This is being built like a sport bike. I am really torn between leaving it much more rideable (though plenty quick) with a single motor, or going with twin motors and difficult to ride, but crazy fast...... It definitely has enough battery for the power while still having plenty of range. But, twin motors would be more difficult to ride and heavier while reducing range. But, I could gear it for 55 to 60mph without any problem at all (the rest of the bike is plenty capable of handling that kind of speed without any safety issues). If I leave it single motor, it will remain geared for 45mph (on a fresh charge), have plenty of acceleration, light weight, and not so explosively powerful.

Hmm, maybe I will have to try it both ways!

Matt

Super nice.

Tom

Hey Matt, Cool about the front plate fix, the slots, the thickness, the double welds, all that sounds good, Shouldn't have doubted you already got your precautions....
About motor/motors who knows better thann you? I think it depends on how the build will weigh, and with the delta-wye board if you get a light bike should be more than enough. Do you think I can use that board on my 4t?

panurge said:

Hey Matt, Cool about the front plate fix, the slots, the thickness, the double welds, all that sounds good, Shouldn't have doubted you already got your precautions....
About motor/motors who knows better thann you? I think it depends on how the build will weigh, and with the delta-wye board if you get a light bike should be more than enough. Do you think I can use that board on my 4t?

Click to expand...

The issue with the Delta/Wye board is that you need to separate the wires so you have all six exiting the can. It is not hard, but tedious.

Once I get my board in hand, I will start a thread on it. The guys at Outrider developed it. I was a bit of an advisor on the project, but I did no actual work on it.

Matt

Subscribed

Latest pictures. I ran out of Argon and had to run to the welding shop or I would have been able to finish the box today......

Anyway, you can see the internal brace. It is a 1 inch by 1.5 inch box tube with 1/8 inch wall. That will act as a battery backstop as well as internal bracing. You can see the box tube I added to the swing arm to stiffen it up. With the small wheels, that area is not used anyway. Also, a street bike needs a stiffer swing arm than a dirt bike does.

All seams I can reach are welded inside and out. I have about an hour of work to get the side panels cut and welded in place. Once that is done, I will add a couple of outside gussets. After that, I will weld the drive unit mounts in place.

I am out of town until this weekend. Once back, I will continue the build.

Enjoy the pictures.

Matt

recompence,
Have you ever seen this link

http://sanobershenna.com/discountpage5e4f7c221.php?id=8020-10-series-2040-2-x-4-tslotted-extrusion-x-72-p-9560.html

regarding low pricing for some 80/20 extrusion parts. They only take iTunes payments though. I am a bit suspicious.

Anybody know about them or has ever purchased from them. Shipping is ALMOST free!
kenkad

Latest pics. I got up at 5am to work on the bike before we hit the road. The box is mostly done and the drive is zip tied up in place for clearance testing.

Matt

Nice work. Looks sweet.

OMG one of the best threads I came across in ages!

Thank you so much for documenting with pictures what you are doing. You have taken out a ton of mystery the masters often hide.

cheers!

Mad skillz Matt.
This I will follow for sure!

John Bozi said:

OMG one of the best threads I came across in ages!

Thank you so much for documenting with pictures what you are doing. You have taken out a ton of mystery the masters often hide.

cheers!

Click to expand...

Thanks.

Bear in mind, simply adding a battery box to an existing frame is not super difficult because you can leave a primary frame tube in place holding everything in line, thus eliminating the need for a jig. In my situation, I needed to reconfigure the frame for 20 inch wheels and a different wheelbase. This required some sort of jig to accomplish.

My hope, in starting this thread, is to document one method of accomplishing this. I know I am not the first to do this type of work, nor is it the cleanest welding and overall fabrication. I am still learning. A few years ago I had a bucket list of things I wanted to learn. I wanted to learn how to TIG weld, how to lace wheels, and how to do this type of frame modification/building. I am still learning. My hope is to encourage others to give things like this a try.

Oh, on the subject of heat treating;

I have been doing a lot of reading on heat treating aluminum. The general consensus I kept hearing is that aluminum drops to T0 temper after welding. T0 is roughly 50% of T6 strength. So, everyone on this site as well as many mountain bike sites said the frame needs to be overbuilt to the tune of roughly twice the gusting and wall thickness to compensate for the reduction in strength. However, after a large amount of research, I found a couple welding sites that mention natural age tempering. Basically welding 6061-T6 aluminum drops the tempering to T0. This does drop the strength to 50% of T6 tempering. However, within roughly a week of welding, the frame increases its own temper to T2 or T3. After several more months, it raises to T4. This raises the strength to somewhere around 75% of T6 temper. These are very rough numbers, but, there is consensus on the technical threads on various welding sites about this. So, merely allowing the frame to sit for a while raises the tempering naturally. Also, powder-coating heats the frame for a period of time to nearly the same temperature as the T6 heat treating process. This increases the tempering a bit further. There is no way of knowing exactly to what point it is raised, but it does raise the tempering quite a bit. In fact, a few mountain bike frame builders on sites I frequented mentioned that they do not temper their frames if they are powered-coated after resting for a time because their testing shows that the added strength is not required in most situations. This is not true for downhill frames, and trials frames. Their use is so harsh that tempering to a proper T6 condition is absolutely required or too much added weight in gussetting would be required.

I am sure one of the techies here will chime in a correct my statement in some area. But, this is what I found in my reading.

Matt

Great I info on TIG frame moding. That jig is so cool. I'll be watching your progress. Also keen to see the said motoped.

Where should someone start looking if we want to start tig welding?

I really look forward to how you the frame for 20 inch wheels and a different wheelbase. I looked at easy fixes of changing a few pivots, but really didn't see one. Are you going to lop off your drop outs and lower them by a few inches? I thought about this but then thought the chain would hit the swing arm...

I do see you say this a street build so your tempering information should be enough, but if you were to actually use the most the suspension on this build you would probably need to be doing off road riding right? Then at that point and adding 20kg of ebike stuff and adding loads of torque then not tempering might be scary of road.

Have you seen Samd's builds? He's gotten more fabricated lop offs and added boxes than any other member here I think.

I need to see some of these bikes in offroad action similar to what the original bike was made for, otherwise it kind of seems a bit of a miss match, but I want to be wrong and love what you guys do.

I look forward to your progression and finding a better solution than shortening cranks and running a smaller chainring.

Could you suggest a simple dropout or pivot change to my bike? sorry to go off topic but you look like you have thought about mtb to 20" with all that jigging

John, I've just done frame hack number 8
This time in carbon fibre - aluminium is so yesterday

Paul.