DIY Trike/Velomobile Design

Recumbents and all feet forward machines

DIY Trike/Velomobile Design

Postby AndrewBurns » Fri Jul 27, 2012 6:11 am

Hey all, I'm totally new to the whole bent thing (never owned or ridden one) but I think the idea is kinda cool and would love to give a velomobile a go, I just don't think they're practical enough to warrant buying one.

That doesn't mean I can't have a look at designing and building one though...

I've never built a bike frame either but I've got some composites experience and I'm keen to give it a shot. I started last night by measuring myself up and reading a bit about rider location, crank location etc. I've had an attempt at placing my dummy rider in a position I think might work however I don't have any experience actually riding a recumbent so if you could critique the position in the picture that would be great. The oval represents the clearance needed around the cranks. I'm thinking the cranks might be a little too high as the clearance above the tip of the toe at the top of the stroke is pretty much level with the riders face so the fairing might restrict visibility.

Image
Image
AndrewBurns
 
Posts: 996
Joined: Sun Oct 09, 2011 1:36 pm

by BNA » Fri Jul 27, 2012 10:30 am

BNA
 

Re: DIY Trike/Velomobile Design

Postby Poiter » Fri Jul 27, 2012 10:30 am

Nice one.
The cranks do look a little high in that the fairing will need to curve over that high pont and then start dropping to the nose.
You could use that position on an open recumbent and it would be pretty aero.
Laid back seat doesn't always turn out best in a faired vehicle
That position looks similar to my Roto Velo layout although the BB is lower.

Some good ideas for you here: http://www.recumbents.com/wisil/wianeck ... efault.htm
User avatar
Poiter
 
Posts: 243
Joined: Wed Mar 26, 2008 6:18 pm
Location: Canberra

Re: DIY Trike/Velomobile Design

Postby AndrewBurns » Fri Jul 27, 2012 8:35 pm

Thanks for the link, very interesting. I've updated the design with a lower angle to the BB (from 10 degrees to 5 degrees) and a more upright seat position (from 50 degrees to 55 degrees). I also added approximate wheel locations, a 26" wheel at the rear and two 20" wheels at the front (all with 1.1" tyres), wheelbase is approximately 1m at this point and distance between the front wheels is 680mm.

Side view
Image

Front view
Image

Perspective view
Image

I was planning on double wishbone front suspension but I don't think that I can without making the front track a lot larger, there's really not much room between the wheels and my legs to fit it in! How important is suspension in these things? I might be able to fit some very limited suspension in depending on the arrangement of the hubs, brakes and steering assemblies.

In terms of steering I was considering using standard head tubes, headsets and steerer tubes as kingpin assemblies, I'm sure I've seen this done before, any comments about this? I'm also looking for sources of things like hubs capable of running with stub axles and other recumbent specific things so if people have suppliers I'd love to hear about them. I'm looking around for dimensions for various parts to include in my model but unfortunately not many bicycle manufacturers supply dimensioned drawings or 3D models compared to industrial equipment suppliers...
Image
AndrewBurns
 
Posts: 996
Joined: Sun Oct 09, 2011 1:36 pm

Re: DIY Trike/Velomobile Design

Postby Recycler » Fri Jul 27, 2012 8:48 pm

AndrewBurns G,day. About your steering, read up about Ackerman Steering Geometry. Yes you can parts of old frames. Good Luck ! Bob.
Recycler
 
Posts: 178
Joined: Sat Dec 22, 2007 10:32 am
Location: Woolgoolga NSW

Re: DIY Trike/Velomobile Design

Postby Phil » Fri Jul 27, 2012 9:40 pm

1.1" or 28mm tyres and no suspension - thats my trike. Well depends on your roads - if its smooth you will be fine otherwise I hop you don't have any fillings.

Seriously I ride my Carbon Highracer with 23mm tyres for the extra comfort over the trike, on chipseal roads with the trike I get shaken so much my eyes can barely focus.

Same roads on Baalzamons ICE FS trike - barely notice the bumps.
Image
User avatar
Phil
 
Posts: 466
Joined: Tue Jan 25, 2011 11:07 pm
Location: Perth, WA

Re: DIY Trike/Velomobile Design

Postby AndrewBurns » Sun Jul 29, 2012 4:02 pm

Ok so I'm trying to design in double wishbone suspension (I've seen a few designs that use wishbone and a few that use sliding kingpins, the wishbone designs seem more mechanically sound to me). It is very difficult however to avoid the rider's legs. The designs that I've found do two things:

- Lay the rider back a bit more, allowing the rider to move forward relative to the wheels but keeping the CG around the middle, this places the suspension arms in the pocket under the knees.
- Sweep the suspension arms forward, allowing the pivots and shocks (bulky things) to be in the pocket under the knees/thighs while the front wheels are further forward.

The problem with laying the rider back is reducing visibility and possibly putting the legs at a less efficient angle (unless the BB is raised) and the problem with sweeping the suspension arms forward is that vertical loadings on the wheels will induce a strong twisting moment in the suspension arms. I think that both of these problems can be overcome but require some careful design work.
Image
AndrewBurns
 
Posts: 996
Joined: Sun Oct 09, 2011 1:36 pm

Re: DIY Trike/Velomobile Design

Postby GraemeK » Sun Jul 29, 2012 4:18 pm

Hi Andrew -have a look at the Atomis Zombie site.
http://www.atomiczombie.com/
Although the info is aimed at end users with limited technical experience it offers a lot of good ideas.
The plans are useful for dimensions and the guy who runs the site has come up with simple solutions to most the difficult design problems and recumbent specific part supply issues -- Should be a lot of help to you.

Graeme
GraemeK
 
Posts: 211
Joined: Tue Dec 29, 2009 3:49 pm

Re: DIY Trike/Velomobile Design

Postby John Lewis » Sun Jul 29, 2012 8:05 pm

GraemeK wrote:Hi Andrew -have a look at the Atomis Zombie site.
http://www.atomiczombie.com/
Although the info is aimed at end users with limited technical experience it offers a lot of good ideas.
The plans are useful for dimensions and the guy who runs the site has come up with simple solutions to most the difficult design problems and recumbent specific part supply issues -- Should be a lot of help to you.

Graeme


I'll second that. I have built a number of the AZ designs. The trikes can all be used as a starting point in your designs. StreetFox, Tomahawk and DeltaWolf to name a few. You may even find some examples of velos in the the Gallery.
More info here.

Ricky Horwitz Thunderbolt.

http://www.ihpva.org/Projects/Practical ... index.html

Also google Ricky horwitz design primer. Its a PDF.

To round off here are Tim Smith from Devonports projects.

http://www.ihpva.org/projects/tstrike/home.htm

All trikes but handy info.

There was a corro velo on instructibles recently. It may be of interest.

http://www.instructables.com/id/Facet-V1-Velomobile/

You could Google for Lee Wakefield Velomobile He had a very nice Coroplast one and there are images on line.

This is made with woodstrips like a canoe. There are some images of a wooden Quest built this way too.


http://texasrecumbents.wordpress.com/20 ... e-love-em/

Googling wooden quest velomobile brings up quite a few hits.

I hope some of these links will help you in you endeavours. (I was giong to say quest) :D

John
John Lewis
 
Posts: 1209
Joined: Tue Oct 02, 2007 7:12 pm
Location: Albany. 400km South of Perth

Re: DIY Trike/Velomobile Design

Postby Poiter » Mon Jul 30, 2012 8:31 am

Can you rotate the cranks and leg in the drawing?
Be interesting to see where the knee comes up to at full height.
Was messing around with this on a bike I want to fully fair and even with a low BB the knee rotates up quite high approaching my sight line.
User avatar
Poiter
 
Posts: 243
Joined: Wed Mar 26, 2008 6:18 pm
Location: Canberra

Re: DIY Trike/Velomobile Design

Postby AndrewBurns » Mon Jul 30, 2012 1:49 pm

Thanks for all the links and advice. I'll have a go at rotating the legs in the drawing to get the maximum knee height tonight, keep in mind though that the dummy is dimensioned on my measurements and I have relatively short legs compared to my torso.

Considering using some "Burner RCP" oil damped spring shocks on the front wheels, I got a quote from the manufacturer in Asia of $170 USD each. 48mm stroke, think the stock spring rate is 750 pounds/inch, I'll have to see if I can arrange the front-end geometry to work with these numbers. I'm also considering building the frame from pre-made carbon tubes direct from China, once I have the frame design more dialed in I'll put out some RFQ's to see if I can get a price worth going for. Assuming I can get tubes of the right dimensions at the right price it would be a lot faster and easier than me making them, I just have to finish and join them.

Anybody know about these hubs: http://www.ebay.com/itm/ws/eBayISAPI.dl ... 1097157887

They don't seem particularly expensive and I have a dimensioned drawing for them which is a plus, mate them to a 20" rim and I'd have some good front wheels I'm thinking.
Image
AndrewBurns
 
Posts: 996
Joined: Sun Oct 09, 2011 1:36 pm

Re: DIY Trike/Velomobile Design

Postby Poiter » Tue Jul 31, 2012 8:49 am

You could buy wheels already built up from TriSled http://www.trisled.com.au/shop/shopdisplayproducts.asp?id=14&cat=Wheels
The bearing they use have a conical inner race on the outside bearing and the conical head axle bolts up flush.
Th e-bay ones would need a protruding bolt or nut.
Looks like a lot of meat behind the rotor mount on the Ebay ones too.

Somewhere I have a picture of wishbone front set up.
One of our OzHPV guys, Lloyd, at Albury has that sort of front suspension on a self built trike.

Poit
Last edited by Poiter on Tue Jul 31, 2012 7:26 pm, edited 1 time in total.
User avatar
Poiter
 
Posts: 243
Joined: Wed Mar 26, 2008 6:18 pm
Location: Canberra

Re: DIY Trike/Velomobile Design

Postby Joeblake » Tue Jul 31, 2012 10:30 am

Have you considered moving the suspension to the seat? I've got three Greenspeeds, all with mesh seats around an open metal frame with shock cord through eyes in the mesh. It's quite comfortable, and the cord only needs replacing every 2 or 3 years.

Image


Image

Joe
To acquire immunity to eloquence is of the utmost importance to the citizens of a democracy
Bertrand Russell
Many people feel their lifestyle has a high price, but they're quite cool with that .. as long as somebody ELSE pays the price.
Joeblake
 
Posts: 12961
Joined: Fri Oct 17, 2008 9:04 pm
Location: Lesmurdie WA

Re: DIY Trike/Velomobile Design

Postby Poiter » Thu Aug 02, 2012 8:01 am

Suspension on a VM is so much more than just having a comfy mesh seat Joe.
User avatar
Poiter
 
Posts: 243
Joined: Wed Mar 26, 2008 6:18 pm
Location: Canberra

Re: DIY Trike/Velomobile Design

Postby Joeblake » Thu Aug 02, 2012 10:19 am

Quite true, but while I've never ridden a VM, I've also never found any problems with handling on either of my (unsprung) trikes. Perhaps any such problems on a VM may be linked to the lack of ability for the rider lean hard into a corner to keep the wheels ground-bound.

Image

Although even suspension doesn't always help. :lol:

Image



Joe
To acquire immunity to eloquence is of the utmost importance to the citizens of a democracy
Bertrand Russell
Many people feel their lifestyle has a high price, but they're quite cool with that .. as long as somebody ELSE pays the price.
Joeblake
 
Posts: 12961
Joined: Fri Oct 17, 2008 9:04 pm
Location: Lesmurdie WA

Re: DIY Trike/Velomobile Design

Postby Roinik » Thu Aug 02, 2012 6:27 pm

I'm amazed that Paul hasn't been on yet. According to some, the most important part of the suspension cushioning is toward the back of the VM, either the seat or the rear wheel. Paul will also mention that you need more camber on your front wheels for a bit more stability when cornering in a VM. As for the legs, there is always the option of doing some moulding like the WAW or the Milan for the knees and feet. That gives better frontal profile and better vision if it proves to be an issue. The question that you haven't answered is whether this is destined to be for track, leisure or for touring. Each application has variations on wheel size, GVM, whether you want to install pedal assist and how much luggage space you want.

Ian
You don't need the best kit, you just need the best attitude.
Roinik
 
Posts: 142
Joined: Thu Jul 12, 2012 10:39 pm
Location: Adelaide

Re: DIY Trike/Velomobile Design

Postby AndrewBurns » Thu Aug 02, 2012 8:48 pm

Ian, Is there any rule of thumb for the amount of camber to add to the front wheels? I'm just designing this for fun right now but if I did get to actually building it I would primarily use it for recreational rides and possibly the occasional commute or longer ride. In terms of luggage I'd be happy to be able to fit a rack and panniers over the rear wheel or maybe I could add in a compartment but I don't need all that much. I'd be aiming for minimum weight for better up-hill performance (lots of hills around Sydney).

I've attached some more pics of the changes I've made to the design. Reclined the rider slightly and shifted forward over the front wheels a bit to give more clearance under the legs for suspension and steering components. Added in bicycle head tubes for kingpins and MTB rear shocks in approximately the correct location. Current suspension layout would give a maximum vertical travel of about 60mm, spring rate at the wheels is about 10.7kg/mm, so full compression takes ~643kg. That's clearly a lot but I'm not sure I can get the shocks with weaker springs, I'll have to look into it.

Oh and I played with rotating the legs, no pics but at maximum height the knees come up to about the dashed line running from around neck high, remember that I have short legs compared to my torso.

Image

Image
Image
AndrewBurns
 
Posts: 996
Joined: Sun Oct 09, 2011 1:36 pm

Re: DIY Trike/Velomobile Design

Postby AndrewBurns » Thu Aug 02, 2012 8:51 pm

Oh and the Trisled site linked to doesn't mention it but what are the details of those Rotovelo front wheels? Are they 16" or 20", axle diameter? Disk brakes?
Image
AndrewBurns
 
Posts: 996
Joined: Sun Oct 09, 2011 1:36 pm

Re: DIY Trike/Velomobile Design

Postby Roinik » Fri Aug 03, 2012 12:47 am

Andrew,

Paul should be able to give some more details on the Mango. A normal car has 0-2 degrees positive camber. I suspect that 5-8 degrees is suitable for a stable VM. The Roto has 20" all round. There are several versions with 26" rear wheels but the comments are always around the lack of luggage space. I did see a link on the Living with a Velomobile thread regarding front end setup. Have a troll through that thread and see what you can dig up. The Mango and some others have light weight macpherson strut front ends from The Netherlands that seem to work well for the monocoque construction they use.

There are a couple of online discussions regarding wind tunnel simulations as well that might be useful when you get to designing the faring. If you are looking at a frame with a faring design then lighten the frame where possible and look at some ultralight (aircraft) design principals for the shell (i.e. ribs and lightweight exterior). 20 - 25kg for the entire setup is possible if you're willing to sacrifice a few creature comforts and have a trike base. There are also a couple of pedal assist companies like Bionix (wheel hub) and another one in the states (chain to BB) that can help with the hills and are all legal with the 200W assist limit.

Ian
You don't need the best kit, you just need the best attitude.
Roinik
 
Posts: 142
Joined: Thu Jul 12, 2012 10:39 pm
Location: Adelaide

Re: DIY Trike/Velomobile Design

Postby Phil » Fri Aug 03, 2012 10:03 am

[quote="Roinik']
A normal car has 0-2 degrees positive camber. I suspect that 5-8 degrees is suitable for a stable VM.
[/quote]


Definately negative camber on any of the cars I have owned. 0.5-1 degree for the road. 2-3 degrees on the track typically..

Eyeballing my Vortex it appears to be running around 5 degrees. Depending on your front suspension you will lose camber angle as the suspension is compressed which will affect your steering, but at velo/trike speeds you would not think it being too large to adapt to.
Image
User avatar
Phil
 
Posts: 466
Joined: Tue Jan 25, 2011 11:07 pm
Location: Perth, WA

Re: DIY Trike/Velomobile Design

Postby Poiter » Fri Aug 03, 2012 11:09 am

AndrewBurns wrote:Oh and the Trisled site linked to doesn't mention it but what are the details of those Rotovelo front wheels? Are they 16" or 20", axle diameter? Disk brakes?


RotoVelo has disk brake 406 wheels.
No rotors or calipers of course.
Axle is a 10mm tapered head bolt into a threaded mount on king pin.

In the Roto Velo with no suspension I have no problem with fast tight cornering.
The problem is keeping the tyres in contact with the ground on rough paths with tree routes on corners.
But being a tadpole it just slides and hops a bit.
User avatar
Poiter
 
Posts: 243
Joined: Wed Mar 26, 2008 6:18 pm
Location: Canberra

Re: DIY Trike/Velomobile Design

Postby Poiter » Fri Aug 03, 2012 11:22 am

Andrew's new Drawing.

Now it looks too high off the ground (COG) and you will have problems with cornering and lifting wheels or toppling over.

Pete
User avatar
Poiter
 
Posts: 243
Joined: Wed Mar 26, 2008 6:18 pm
Location: Canberra

Re: DIY Trike/Velomobile Design

Postby Baalzamon » Fri Aug 03, 2012 11:41 am

Poiter wrote:Andrew's new Drawing.

Now it looks too high off the ground (COG) and you will have problems with cornering and lifting wheels or toppling over.

Pete

Yep I'd be dropping that too, just have a look at the Mango's and quest to see how low they are to the ground
Masi Speciale CX 2008 - Brooks B17 special saddle, Garmin Edge 810
Image
Baalzamon
 
Posts: 4733
Joined: Mon Mar 12, 2007 1:23 pm
Location: Yangebup

Re: DIY Trike/Velomobile Design

Postby John Lewis » Fri Aug 03, 2012 7:59 pm

Camber and stuff.

I am referring to the angle of the wheels to vertical when I refer to camber.
The wheels on my mango are closer together at the top than the bottom. The angle, according to the clinometer on the phone, is about10 degrees from vertical.

I understand castor to be, for our purpose, the same as trail on a bike. The line where a vertical from the axle touches the ground is behind where the line through the pivot axes touches the ground.
The mango has a form of Mcpherson strut suspension.

John
John Lewis
 
Posts: 1209
Joined: Tue Oct 02, 2007 7:12 pm
Location: Albany. 400km South of Perth

Re: DIY Trike/Velomobile Design

Postby Roinik » Fri Aug 03, 2012 9:19 pm

John,

The easiest way to describe caster with double wishbone suspension is the angle imposed between the upper and lower ball joints in relation to vertical. Positive caster means the lower ball joint is further forward in relation to the upper ball joint. The more positive caster you give the wheel, the more it wants to travel straight. The down side of this is that it is harder to turn corners as you are always wanting to turn 'up-hill'. Negative caster is not as stable as positive caster and is generally avoided unless you want shopping trolley wheels. The same goes for Macpherson struts, however the camber is related to the strut angle Wishbone suspension can generally have more adjustment than the strut version.

Camber is, as you describe, the angle of the wheels to the vertical when looking edge on. Positive camber is when the distance between the tops of the wheels is greater than the distance between the bottoms of the wheels (thankyou). Conversely, the opposite is true for negative camber. Older vehicles used positive camber to help with ease of steering and running on unsealed roads with cross-ply tyres. Power assisted steering, radial tyres and asphalt meant that negative camber could be utilised to improve handling.

10 degrees on the Mango sounds about right for what I've read elsewhere.

Ian
You don't need the best kit, you just need the best attitude.
Roinik
 
Posts: 142
Joined: Thu Jul 12, 2012 10:39 pm
Location: Adelaide

Re: DIY Trike/Velomobile Design

Postby John Lewis » Sat Aug 04, 2012 3:10 pm

Thanks for the explanation Ian.

As I understand the camber on the Mango is aimed at giving a wider track for stability without making the body too wide. It in fact has a slight negative effect on speed as it creates more rolling resistance.

My mango seems to me to have insufficient caster. The back sits up and sinks with rider weight on the suspension. Of course the front settles too. With my light weight there is little caster and the velo seems to become unstable at higher speed. I was over two lanes at 50 kmh.

When Baalzamon rode it he had no problem in that regard. The mango sat well down with his extra weight and resulted in considerably more caster. He commented that the steering was still sensitive fairly though.

I may eventually go to the Risse air shock so that I can tailor the suspension.
As always the design is a series of trade offs.

John
John Lewis
 
Posts: 1209
Joined: Tue Oct 02, 2007 7:12 pm
Location: Albany. 400km South of Perth

Next

Return to Recumbents

Who is online

Users browsing this forum: No registered users



Popular Bike Shops
Wiggle Wiggle UK
Ground Effect Ground Effect NZ
Ebay Ebay AU
Chain Reaction Cycles CRC UK

“Bicycles BNA Twitter
“Bicycles BNA Facebook
“Google+ BNA Google+
“Bicycles BNA Newsletter

> FREE BNA Stickers