Homebuilt Recumbent Idea & Input Needed

Discussion in 'Motorized Recumbents' started by Wheres my dog, Aug 31, 2010.

  1. Wheres my dog

    Wheres my dog New Member

    Hello All,

    First let me say I live in a state with no laws regarding an MB, so I believe there would be no issues here. And this would be more of a learning experience that would hold value more then the outcome of it.

    This would not be a daily road bike, more so for longer trips in the country, rather then inside the town travel.

    Onhand already I have a DAX Titan 49cc engine as well as a BMP friction drive kit.

    Thinking of building a somewhat simple recumbent style MB. I am thinking of a single 20" or 26" wheel in the read which will be driven by the 49cc and friction drive kit. The front would be two 20" or 26" wheels mounted on a solid axle held in place by pillow block bearings perhaps.

    The main frame would be a sizable aluminum tube or steel tube. The rear drive wheel would be an adaptation of a simple front fork of a bocycle also containing a disc brake, and as a backup, a v brake as well.

    Not even sure I would have any pedals per say, may just pegs for the feet, or a crank that leads chain to a freewheel sprocket under the seat hidden for the looks of pedal power.

    Steering would be by two hand levers mounted on the side of the seat, and cable would be ran to the front wheels near the bearings which would be mounted on top of a separate piece of steel plating which would "float" on top of a ball bearing which would allow for turning above the main frame.

    Searching the web now, but if you can visualize the bearing I need for the front end to work, could you point me to a website maybe?

    Here is a link to the front wheels I would use...


    Any thoughts on this first take at building?

    All input is appreciated...

  2. srdavo

    srdavo Active Member

  3. Wheres my dog

    Wheres my dog New Member

    Been to that site many a time and got my inspiration from there....
  4. SimpleSimon

    SimpleSimon Active Member

    Visualizing your proposed steering system, I want to ask: Why?

    It seems to be unduly complicated, and fraught with technical issues. Kingpins and a drop axle T frame with an extension boom footrest/crank seems a better solution, overall. Also, with a tadpole recumbent (which is what you are describing) you need front brakes - under braking weight and load shift forward. A rear brake only will almost certainly result in rear wheel lock ups and LOOOOOOONG stopping distances.

    A very straightforward hard-tail tadpole using a 1.5 inch square tube main spar and drop center axle beam is dead simple to build, and it lets you get seat height down lower, improving your CoG for cornering.

    If you'd like I'd be glad to design one for you.
  5. Wheres my dog

    Wheres my dog New Member

    I would appreciate that greatly if you would be kind enough to show me a design or two as this is my first attempt!

    Any help is greatly appreciated sir!
  6. SimpleSimon

    SimpleSimon Active Member

    No problem. I'll post a couple of views of one this evening.
  7. SimpleSimon

    SimpleSimon Active Member

    Here ya go

    Attached are two views of a basic T type drop center axle design. Since you indicated that you intend to use a reversed straight front fork for your rear wheel support, I have not drawn that in, as I'd need a bit more info before I'd do so.

    A basic tadpole is as simple as it can get - as drawn it is a 48.5" long wheelbase, and a 32" width.

    Attached Files:

  8. Wheres my dog

    Wheres my dog New Member

    Last edited: Sep 10, 2010
  9. SimpleSimon

    SimpleSimon Active Member

    Sure, but I have some advice. I have ridden a Triton Pro X, and while it corners well for a delta trike, the fact is that a direct drive single speed front wheel is a real bear to pedal.

    I know from your other thread that you are contemplating an MB, running under power and seldom if ever pedaled, but I'd like to suggest that Murphy absolutely loves pranks, and having to ride one home several miles with a dead engine would get really old really fast.

    Also, how do you propose to power it? What type engine, what type drive? Other considerations are - what size wheels do you want? Since on a recumbent it is the X-seam measurement that is of primary concern for seat/crank separation, how tall are you? What is your X-seam length?
    Last edited: Sep 10, 2010
  10. Wheres my dog

    Wheres my dog New Member


    At my first ever attempt at a recumbent, I was just trying for the easiest approach at doing it. I have already built several successful types of MB's over the years.

    I would consider a single wheel drive in the back to be able to make it a multispeed recumbent.

    I would like to go with 26" wheels if I could. I would go with either my BMP kit or my GEBE setup powered by my EHO35.

    Top speed is not my concern, I am very happy with the low 20mph range and a little extra power for pulling.

    I am a tall one at 6' 2" . . . but would like to stay with a more compact, shorter wheelbase design if possible!
  11. SimpleSimon

    SimpleSimon Active Member


    How about pedal power via differential effect to both rear wheels, with the GEBE running inboard of the right rear wheel? Gives you engine power on just the right wheel, but if pedaling power to both through a "poor man's differential" utilizing a multi-speed hub as a jackshaft?

    That's pretty straightforward to design, even though it probably sounds complex. Put the seat as low and far back as reasonably possible, and I can get the wheelbase down around 4 feet, with width being about 30 inches.

    If that sounds good, let me know.
  12. Wheres my dog

    Wheres my dog New Member


    I would like to know more about that design...

    If you could share some designs and or thoughts?

    How would I go about making a poor mans differential?
  13. SimpleSimon

    SimpleSimon Active Member

    "Poor man's differential" is my label for a system I developed to produce a differential effect for trikes, without paying the insane prices that the very few manufacturers of bicycle differentials charge.

    Here is how it works: a differential is just a system to allow two separate wheels on a common axle to turn at different rates, which can be achieved in various ways. I took a solid axle trike conversion rear end, and sawed the axle in half in the center. Then I had the axle ends dressed and a keyway milled in the inboard end of each half axle (plus a matching keyway on the outboard end of the left half axle). Each half axle then received a freewheel capable sprocket on the inboard end, and a keyed mounting flange on each outboard end.

    The two sprockets were set up so that they transmitted power when rotated in the forward direction, turning the half axles. If the half axle was turning faster on one side than the other (which they will, in turns), then only the slower turning half axle was receiving power. I did that by taking a Shimano three-speed hub, and two identical dérailleur cassette sprockets which I modified with a Dremel tool so that they could be mounted to the spoke flanges of the hub. The hub with sprockets was mounted as a "mid-drive" in the original rear triangle dropouts, and two chain loops connected each hub output sprocket to a half axle sprocket.

    Power came to the hub from a jackshaft that brought the power and pedal loops together just forward of the mid-drive hub (an HT engine was mounted just behind the seat post in the modified rear triangle of the bike). The two powered sprockets on that jackshaft were also freewheel capable, so I didn't end up wiith spinning pedals under power. I used a pull starter to start the engine.

    Most delta trikes are powered only at one wheel. I do not care for that - it causes problems in cornering and in straight line tracking. Which is why I developed the system described above.
    Last edited by a moderator: Dec 18, 2015
  14. Wheres my dog

    Wheres my dog New Member


    I appreciate all the thoughts and input and drawings so far... very respectful of you to help me like this!

    Attached, is more or less of a design I would like to go with, if possible!

    I like to stay on the simple side as much as I can... and have the GEBE set up on the rear wheel, hopefully being 26" in height!

    Any further thoughts on the attached picture in terms of design?


    Attached Files:

  15. SimpleSimon

    SimpleSimon Active Member


    That's about as simple a tadpole as they get.
  16. SimpleSimon

    SimpleSimon Active Member

    Wmd? I've been drawing sketches, but what I run into is dimension issues. You indicated that you want the design as simple, and as short a wheelbase as you can reasonably get. The recumbent you posted a pic of is an elegantly simple design, but it also appears to be based on three 16" (maybe 18") wheels. When you go to a 26" rear wheel, that effectively shortens your available frame rail length for basing the rest of the design off of. With a 48.5" WB length, and a 26" WB width, you end up with a main rail of insufficient length to allow for pedaling well.

    With recumbents, it is not your inseam that controls crank distance, rather it is your X-seam. The X-seam is measured by sitting on the floor with your back square against a wall or table leg, then measure the distance from the intersection of that vertical surface to the base of your heel, with your leg flat and toes pointed straight up. You said you are 6' 2" tall - most guys in that height range have an X-seam around 40 inches long.

    A 40 inch X-seam won't fit inside the wheelbase, as the cranks are shown to be on the pictured tadpole. Realistically, just about the bare minimum that would fit in would be 60-62" WB length. With that length, you'd be well advised to go to a 30" or 32" WB width.

    Now, a crank forward design is very doable in a 4 ft WB length.

    It would help if you'd give me some idea of the type seat you want to use, and an X-seam length you'll need.

    Attached is a pic of a crank forward on an extension boom type of frame.

    Attached Files:

  17. Turtle Tedd

    Turtle Tedd Member

    SS..you da man when it comes to these tadpole trikes....off topic here , but how is yours coming?
    Last edited: Sep 15, 2010
  18. SimpleSimon

    SimpleSimon Active Member

    Pretty slowly, right now. My right foot is giving me fits - the open wound on my heel is at exactly the point of highest pressure in walking, standing, even sitting down. Consequently, it is NOT healing well.

    My Dr. put me in a "pressure cast" yesterday, and I will be getting a new cast every 3-4 days until this thing heals up. Which nearly immobilizes me - the cast is deliberately made with a "rocker" sole, to discourage walking or standing. So, I cannot stand at my workbench to do any metal cutting right now.

    I took delivery of two cast resin 5 spoke 20" wheels yesterday - a guy I deal with had them and offered to send them to me for the cost of shipping ($9.50). They are NOT set up for any sort of brakes, so I spent today designing an insert that uses a 5 lug 1" long pin set to hold and space out a disc brake disc. They have heavy duty 1/2" axle centers with two sets of ball bearings, so ought to be fairly durable. I intend to use those for the front, at least to begin with.

    I am having a Shimano three speed rear hub drilled for 12 gauge spokes, which will then be laced into a 26" heavy duty steel rim I have. The GEBE ring will mount to that, with the engine behind the seat on a cantilevered shelf off the rear suspension frame. The belt will run horizontally, rather than vertically. I'm considering making a modified drive mount so that I can switch between drive sprockets while underway.
  19. vegaspaddy

    vegaspaddy Member

    HANG IN THERE SS.... i can only guess how fustrating been laid up is but, the longer you can rest the quicker that foot will heal !!!!!!!!!!

    sorry for been off topic...
  20. Sadly in 2007 Recumbent Cyclist News shut it's doors...:icon_cry:
    Fortunately I downloaded their home built issue. It's a 625K PDF Doc. I'm on Dial-up (no other choice...really) but I will try to attach it. It is a very good issue with lots of good (interesting) ideas. OK this is not going to work. Maybe if I parse it up into several sections it might work.

    Attached Files: