Low trike design advice needed

[Bobbo1260]

Hi,

Im new here and am hoping any bike/trike builders here can advise me.
I am adapting my traditional upright trike with an e-bike kit to a lower version for better stability.
I need to run a single length of preferably steel box section 1 metre long horizontally and then cut and MIG weld a 400mm length of of the same section vertically to weld to the existing headset tube to form the frame.
My question is what height, width and gauge of steel would be advisable, I was thinking along the lines of 60mm x 40mm x 2.5mm, to aid the mounting of a go kart seat and adjustable distance crank set..

Thanks in advance.

Bob.

 

[AndyBike]

Three wheels+Stability.
Words not often heard together

Seriously though. What are your design shape influences ?

 

[Bobbo1260]

Hi Andy,
You are spot on there . Even with some stabilisers I fitted trikes are still dodgy across unavoidable inclines, such as the entrances to peoples drives. I notice in the states your footpaths are nice and wide so the crossover isn’t as steep as on the UK’s 6ft wide footpaths.
To show my idea I have included a couple of pictures. My intention is that the seat/chair height of my design would be half the height of my current sear height, thus lower centre of gravity.

 

[lenny]

 

[saneagle]

Hi Andy,
You are spot on there . Even with some stabilisers I fitted trikes are still dodgy across unavoidable inclines, such as the entrances to peoples drives. I notice in the states your footpaths are nice and wide so the crossover isn’t as steep as on the UK’s 6ft wide footpaths.
To show my idea I have included a couple of pictures. My intention is that the seat/chair height of my design would be half the height of my current sear height, thus lower centre of gravity.

View attachment 57601View attachment 57602

It would be a lot easier to respond the wheels to 20" rims as long as you have enough pedal clearance from the ground, and mount the battery under the basket.

 

[Bobbo1260]

I did consider fitting smaller wheels as that would work with the pedals but the centre of gravity would only by lowered by 3 inches. When you look at the more stable versions of trikes such as tomcat, recumbents and trikes used by the disabled in marathons they all have a lower centre of gravity via a longer frame with the pedals moved forward to provide a decent out stretch of one’s legs when pedalling.
The cost of these are over £2000 plus, especially when having pedal assist.
I already have the main components so adapting what I have seems economical.
The Sinclar C5 went to the extreme though and was too low for traffic to see them, plus battery efficiency wasn’t that good back then.

 

[saneagle]

I did consider fitting smaller wheels as that would work with the pedals but the centre of gravity would only by lowered by 3 inches. When you look at the more stable versions of trikes such as tomcat, recumbents and trikes used by the disabled in marathons they all have a lower centre of gravity via a longer frame with the pedals moved forward to provide a decent out stretch of one’s legs when pedalling.
The cost of these are over £2000 plus, especially when having pedal assist.
I already have the main components so adapting what I have seems economical.
The Sinclar C5 went to the extreme though and was too low for traffic to see them, plus battery efficiency wasn’t that good back then.

One here for £200.

KMX Kobra Recumbent Trike | eBay

<p>KMX recumbent trike for racing or for disability riding. Adult size or large child, this is in need of some updating I.e a service would benefit and certainly for someone who is familiar with working on bikes. Good tyres but gears and brakes need some attention. Happy viewing </p>

www.ebay.co.uk

 

[lenny]

 

[lenny]

 

[guerney]

How robust are KMX Cobras? I forced myself to not put in a bid, because I'd read about KMX frames breaking, failed axles, and of course they've gone out of businesss. Looked at the bidding history sometime afterwards, a familiar winning pattern - huge bid right at the end with seconds to spare, with the winner relying on incremental auto bidding (the winner hadn't put in a bid previously for this item, unlike the other competitors), allowing no time for the others to respond.

 

[AndyBike]

Can you sort some sort of rear suspension. Independent would improve handling.

I meant to say - are you building this yourself, as in welding tubing, or will it be more of a conversion ?

 

[lenny]

Windcheetah recumbent bike front and rear fairings Mike Burrows | in Walton on Thames, Surrey | Gumtree

Windcheetah (speedy) Recumbent trike designed/built by Mike Burrows (of Lotus and Giant TCR & MCR fame) 700c carbon Massi tri-spoke rear wheel Carbon front and rear carbon fairings (white) - will need new velcro fixing. Carbon bucket seats 20" front wheels with cove

www.gumtree.com

 

[Bobbo1260]

I’m basically removing the complete rear axle assembly and bolting a length of box section to it in place of the existing frame. The front will then be angled upwards by mig welding and then welded to the front head set of a doner bike. Doner bike crank will be bolted on as will a 2nd hand go kart seat so then be adjusted.
A structural engineer has since told me that 40mm x 80mm x 2mm steel box section would sufficient and considering the doner head set is 3 mm thick I’m gonna have a go at welding it myself.

 

[Bobbo1260]

One here for £200.

KMX Kobra Recumbent Trike | eBay

<p>KMX recumbent trike for racing or for disability riding. Adult size or large child, this is in need of some updating I.e a service would benefit and certainly for someone who is familiar with working on bikes. Good tyres but gears and brakes need some attention. Happy viewing </p>

www.ebay.co.uk

I final decided on 40 x 80 x 2mm rectangular steel tube. Sourced a doner small bike to use the front wheel and forks only to find that bike frames are now made from chromoly which needs skill hound mine to weld to mild steel.
My solution is to weld a steel tube to the steel frame member that has an internaL diameter that is 1/2 millimetre greater than the head set tubes external diameter. After welding the two steels together I can slide the chromoly tube inside the steel tube smeared with JB two part metal adhesive. Having used J B weld weld before I’m confident it will have sufficient grip to secure the two given the surface areas.