Charlie Chops’ StreetFox Tadpole Trike – ride report

Boy, time flies when you’re having fun. I had the bike out after my last post about a week ago it, but while I did maintenance on the roadster so that I can start driving it soon.

I got back to the StreetFox yesterday. I re-did the bars as they were too low and limited my turning radius quite a bit. I cut them off a couple inches out from the stem and re-oriented them similar to the direct steering bars on a Terra Trike. I bought a couple Mirro mirrors from the local bike shop and tried them first in the bar ends but had to move my head too far to glance at them, so I made a 3″ long post out of some more handlebar stock and positioned them close to the end of the brake levers. They look around my big self quite well, so that’s where they will stay.

I hadn’t done a very good job on the first fitting of the Avid BB7 discs but I managed to get them sorted and cut out all the drag. They work fantastic. I like then so well I believe I will retrofit them to my Giant suspension bike when I rebuild it sometime this summer. It’s a 2002 that just rolled 5,000 miles and the gearing, chain, brakes and cables are due for rehab.

So, I got the StreetFox out yesterday and road it a few miles. I’m surprised how heavy it is—around 50 pounds is my guess. I have a 300 limit scale in the shop. I weighed me at 251 and then stepped on it with the bike in my arms and it went TILT. Not much more I can do for that problem, but there is still a chunk of main rail to come off in front of the bottom bracket (BB) and a few more lightening holes I can place here and there.

Pedal effort seems high, however the cranks are 5mm shorter than what I’m used to. The gearing is way off also. With it I hardly ever go up on the big ring unless I’ve got a really huge downhill. On the StreetFox I had to get a couple – three gears into that ring to feel about right. That’s something I will remedy when I find appropriate upgrades.

When I first rode it a week or so back I had a lot of pedal cadence front end wobble which may have been caused to some degree by the mal-adjusted front brakes. Seems better now. The BB assembly is slightly out of square so that the derailleur sits crooked. The idler pulleys can come in closer to the main rail – easy fix. The seat does need a buttocks pad, but otherwise works as I envisioned. The bolsters keep me well contained and I can corner it quite sharply even at 12/13 mph.

Overall, I’m quite pleased with how it turned out. It’ll probably never be done as I continually make running changes in the hot rods. The wheelbase ended up at 45-1/2″. I could have squeezed maybe another inch – inch and a half out of that by moving the upright for the dropout back more. Another way to save a little more space might be use a seat post with the elastomer in it in place of the shock/spring. I’d like to get a suspension SF down to a 40″ wheelbase. This bike is nearly done, but I will build another with higher grade parts secured first, then match drop out width as required for the wheel, etc. Next winter’s project.

StreetFox Recumbent Tadpole Trike DIY Plan – AtomicZombie

Plans, tutorials, videos and more

The StreetFox Recumbent Trike is a fast and comfortable version of the classic “tadpole” style trike (two wheels in the front), which includes rear suspension, three wheel braking, and 26 inch rear wheel for optimal gear range. The StreetFox looks and handles as good as any commercially produced trike, and can be completely made using commonly available and inexpensive bicycle components and some square tubing. Not one single machined part is needed. The StreetFox has an adjustable bottom bracket so it can fit riders of most heights, from 5 feet to well over 6 feet tall. Due to the rugged construction and use of sturdy 14 mm axle, 48 spoke front wheels, the StreetFox can easily accommodate riders over 250 pounds.

Because this project only requires a basic welder, an angle grinder and a hand drill, the StreetFox can be built by anyone with the desire to put a little effort into this rewarding hobby. Because of the simple mono tube main frame, the StreetFox is highly customizable, allowing the builder to alter the plan to suit his or her own needs, or simply to try new ideas. The most complex part of the trike is obviously the steering, but the StreetFox uses commonly available and “bullet proof” BMX wheels and hubs, so you don’t need to source hard-to-find, expensive front wheel parts. All three wheels have standard bicycle brakes and cables as well, so you can find most of your parts by salvaging old bicycles or at most bicycle stores.

Every step of the build is detailed in high resolution photos, with clear instructions on how to calculate critical angles and lengths based on the parts you have on hand. The final product is a very sleek looking tadpole style trike that looks professionally built and rides like a dream. Enjoying the scenery on a comfortable recumbent trike is like sitting in your favorite chair, but you can always put your ankle to the pedals and get the wind in your hair because the StreetFox is as fast as it is comfortable.

Plans, tutorials, videos and more

Take a look at our Builder’s Gallery to see other StreetFox examples, including many creative modifications to the plan. Our international builders community ranges from students to retired engineers, but they all have one thing in common – the desire to build their own stuff!

All of Atomic Zombie Extreme Machines plans are downloadable PDF format. Multiple discounts, free tutorials, videos, gallery, newsletters, blog and more:

Plans, tutorials, videos and more

Meet AZ krew members and bike builders –

We introduce you to some of our novice and guru bike builders:

Dragonwood recumbent bike

Atomic Zombie bike builder David Moeller's handmade wooden recumbent trike

Read all about it here:

Sick chopper from Estonia – builders gallery


Atomic Zombie June newsletter online

It’s our largest Atomic Zombie newsletter ever, jam-packed with tons of informative stuff, features, pictures and build blogs, including:

• Viking Tandem Trike – NEW Atomic Zombie bike builders DIY project
• Teen’s Warrior Trike video
• Meet AZ Krew members
• Bike Builders Tips
• Builders Gallery
• Dragon DeltaWolf
• Builder Feedback
• Powder Coat Painting
• Recumbents Rule!
• High Rollin’ Dutchman Recumbent
• FAQs
• Vigilante Chopper
• DIY Kick Bike
• and more!

Thanks to all of our contributors. Contact KoolKat through the AZ builders forum if you’d like to submit something for future newsletters.

Viking Recumbent Tandem Trike test ride video

We took a brief video of Brad testing the Viking Recumbent Tandem Trike this evening. Even though there are only a few tack welds in some places, he ended up taking for a boot without any problems.

How’d it handle? Watch the video and find out!

Viking Recumbent Tandem Trike – test ride success

We are rolling:

High Rollin’ Dutchman Recumbent Bike – builders forum

Below you see a fellow bike-hacker (actually he’s building a big electric carrier bike) modeling on the HR to show the lack of knee/handlebar clearance.

Wouter shows there’s no room for the legs

No other option than to cut the goose neck!

This is my HR in its current state. I made the gooseneck extra long (since it easier to make it shorter than longer afterward).

There is plenty enough room now for the knees. The steering is a bit less nice than before though. The longer goose neck adds extra tiller of course and it also flexes a little..

Besides these details it is an absolute blast to ride! It is fast, comfortable and the view is great. And I’m very glad the HR is high enough for people to see you, even cars when you’re next to them. I also found out that you DO can see quite a lot behind you by turning the neck and looking over the shoulder. Still thinking about mirrors though. Today I also took some detours over grass, gravel, or curbs for the fun and to overtake people. The bike handles it fine!

I asked the guy from the recumbent shop/factory in this town if he could hook me up with some extra long brake and shifter cables and he said he could. Then I will FINALLY install it, do the final adjustments and tidying and then.. paint!


UK recumbent lowracer

See the pictures:

Viking tandem trike build update –

The next step in the Viking Tandem Trike build is the two front booms that will extend outwards front the front of the frame to hold the two front wheels and steering hardware. The steering geometry and front end are always the most complex and finicky part of a tadpole trike, and I have done my best to make this one as easy to build as possible by using only one angle in the front frame design.

The head tubes are set at 90 degrees and the center-point steering is automatically set by the angle of the two boom tubes, so this takes some of the difficult work away from building the front end. I won’t lie to ya though – it’s still a lot more work than watching TV!

One single V formed by the two front booms creates the center-point steering angles as well as sets the exact height for the front of the frame. This geometry also allows room for under seat steering as well as a place for the chain to pass without getting overly complex with more than one idler pulley. Some tadpole trikes are a horrific mess under the seat due to overly complex chain lines and steering hardware, and I am doing my best to avoid this.

I cannot live with “good enough”, so it took most of a day to cut, weld, cut, and re-weld all sorts of different steering bits in order to get the Ackerman steering geometry to track perfectly through the entire range of motion. Since the inside wheel in a turn has to carve a tighter circle, the steering geometry must account for this or one wheel will scrub in a turn, causing excess friction and tire wear.

Claims that this is a “feature” designed to slow the trike down in corners is just not my style, so I hacked away at the positioning of the steering rods and control arms until the trike made a prefect turn at all angles. I have learned that this process can only be done by trial and error although there are mathematical guides that can get somewhat close some of the time.

After five attempts at various steering setups, I came up with the perfect placement of control arm and connecting rod. A simple jig made of a bit of wood and a screw was made that would make it easy to set the control arms up for welding. Although the Viking shares a lot of the front design with our Warrior Tadpole Trike, it’s amazing how much different the steering geometry had to be in order to eliminate all wheel scrub during tight turns.

Under seat steering is not hard to create once all of the angles and control arm positions are known. Some of the other concerns I dealt with when creating the steering system were the position of the chain as it passes by the control rods as well as the clearance for handlebars. If a chain line is an afterthought, there will probably be more than one idler pulley necessary and as many as three if the design is really messy. More pulleys, means more power loss and points for failure. I am still aiming for a single idler, although I will not claim success until the chain is installed tomorrow!

To test the ergonomics of the under seat steering system and styles for handlebars, I drop on my basic plywood base seat and try out different lengths and heights for the handlebars. The Viking handlebars will be typical as compared to most tandem trikes, with plenty of room for the levers and shifters. The stoker will also have under seat handlebars, although they will be in a fixed position.

Today, I will try to get the transmission installed if I have the chance to spend another day in the AtomicZombie Garage. I am estimating that there is still three full days of work left in this project before I get to crack the top of the first can of bright red spray paint, and we are eager to hit the road and see how The Viking will handle.

Possibly an initial test ride later today!

Read the Viking tandem trike project blog: