Jon Hall's TRX850 FF (2008)

This is a sad saga of what nearly was and what might have been. This is an FF built by Jon Hall, based on Yamaha's TRX850 twin. Monty Billington sent me this old photo in 2020 and Michael Moore dug up some information from Dominic Lowe, from the time the photo was taken, back in 2008.
Dominic had written:
"Jon Hall had a long discussion with us when we had a look at the TRX. The actual donor bike is worth noting, as although it shares an engine with the TDM, the TRX has a tubular trellis frame and not a welded pressed steel frame, hence the TRX frame is easier to modify. I think Jon's major disappointment with the project was the very limited lock available with his own design of Hossack front end. It might not be clear in Monty's pictures, but the lower mounting points for the front suspension units clash with the fork at around 15 degrees of lock to one side (or to the other side).
You can also see where Jon has added about 6 to 8 inches into the chassis behind the gearbox and ahead of the swingarm for the fuel tank. There is no corresponding reduction in swingarm length because it's the standard item.
I know it's very easy to criticise and pick fault with other people's work and this is not meant to be negatively critical. However, as I see it, the issues that would need to be ironed out on Jon's TRX are:
1. The airbox intrudes into the rider's lap area. I suggest this could be addressed by mounting the engine lower and canting it further forward (making best use of the DRY-SUMP engine design).
2. The original mono-shock rear suspension limits the reduction in seat height. I suggest that a twin-shock rear suspension would allow the seat to be lowered – the limit is the upper chain run.
3. The steering lock is very limited. This requires a redesign of the lower wishbone and maybe some other parts too. In principle, the Hossack FFE will work, but as I have found with my own design, there are a lot of potential clashes.
Jon put a lot of time and effort into the project (I've seen the build file), but is (or was) in senior management of a large engineering concern, so I expect his free time is somewhat limited. I don't think the TRX had seen any use apart from a couple of test runs since Jon built it and I doubt it could be quickly and easily modified to make it properly usable on the road." Dominic Lowe
Jan Nelder recalls that he also visited Jon Hall with the Lowe brothers at the time, and that it was somewhere near Chippenham, in Wiltshire.
Tragically, it seems this project never proceeded any further than what you can see here. PNB

Jon Hall's TRX850 FF (2008)

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front end

If he is willing to sell it, it should make a good basis for FF with a re-engineered Hossack FFE. Can’t see the airbox as a problem from photo. Crank is already at near axle level, and I think seat height is fine.

Good example

This is a good example of the problems associated with "cut'n shut" conversions of motorised bicycles, mentioned in a piece ("Books") on this site covering basic parameters - "Invariably, at some stage in the process, constructors will consider how much easier much of it would be if starting from scratch."

Modern motorised bicycles are tightly integrated designs and casual modification of something as central as seat location is very rarely simple. The Tmax/Cmax conversion is the only one I've encountered that could be described as easy. All that needs is footboxes, a seatback and a new fuel tank. And yet only three have been done as far as I know. It's clear that most people underestimate the task, even people with engineering backgrounds. This particular example also highlights the importance of an initial design process to avoid issues like the lock limitation found here. Obviously a good seat back though!

It might be thought tragic that the project was not completed, although Mr. Hall has done better than most and it's probable that time pressure, rather than technical difficulty stopped further work. However I think the real tradgety is the failure of the world's motorised bicycle manufactueres to do this work themselves. One might imagine that making comfortable, safe and efficient powered two wheelers is their reason for existance. Perhaps if they stopped whining about their loss of market share and thought about their ridiculous products they might see this.

Jon.Hall's picture

TRX850FF - filling in some blanks part 2

Hi all - hilariously I just posted a comment - but accidentally on the "FF machines - scooters" page. D'oh!
If you're interested and can navigate there, I've filled in a bit about the TRX850FF.

To continue...just as I was facing the thought of shortening the wheelbase and finding a way to create bodywork to cover the unlovely plumbing and bracketry (and achieve one real requirement, keeping the drag and weather off), Monty advertised his V50FF for sale. One of the two V50 Phasars, converted by Royce to "mini-Voyager" style. Partially dismantled and in need of some finishing bits and pieces - but real centre hub steering, full and effective bright yellow bodywork, and tight wheelbase. No brainer. Monty apparently found the cockpit too tight; luckily for me my long back (see above) that meant I could never fit in a Quasar, is offset by short legs!, so with a bit of work all was good. The front bodywork went on easily and was quick to remove and replace, all round a nice job.

The V50FF was great to ride, stable, good handling and steering, and great fun. Gentle weave after about 85mph but that's nearly flat out anyway for a Guzzi 500 even with fairings. I took it to Beaulieu 2008 (there's a picture on Monty's website). Some time later I sold it to Rob Ring who modified it again slightly, and last I heard Eddie McDonnell had it (completing a circle as he had the other V50 Phasar).

The TRX850FF was stripped for all the saleable Yamaha components, all that remains as a memento to all the disc cutting, grinding, welding sizzle and smoke (sorry neighbours) is the top wishbone with its expensive low stiction spherical joints....

Still waiting for that commercially-produced compact FF that I can ride just in everyday clothes and a helmet....and buy from Fowlers like any other bike...