David Bruce's FWD DBT-4 Sport Model Prototype blog and image gallery. Posts from January 2013 to February 2017.
Our second FWD prototype, the "Orange trike" was completed in February 2012 and we rode that throughout 2012 to test changes made in the suspension and steering yoke. To see the Orange trike in action watch some of our ride videos! During 2012 we committed funds, time and resources for a totally new design and commissioned machined parts and materials for the new layout.
So that being said, we published the first pictures of the first DBT4 prototype: (January 2013)
Goals of the new layout were to: reduce welds by approx 50 percent, simplify the design by reducing bolt on assemblies and hardware, cleanup the aesthetic appearance and make it look less "busy", reduce horizontally placed components and place them inline, simplify the steering unit, allow the use of large cogs and triple cranks, make the seat more adjustable front and back and have a variable recline position, make the joining flange available for purchase so that customers can customize their trikes by creating their own rear sections that bolt into the FWD front unit, increase the ground clearance, allow conversion to direct steering handles with purchase of handle units from other trike companies and oh yeah, reduce the weight by 5 pounds or more!
Front profile: I concentrated on reducing the number and size of horizontal parts in the slipstream compared to the original prototypes. Recumbent trikes suffer from aero drag, so one of the goals was to place parts and hardware inline. This new design uses a "leading arm" suspension instead of the earlier "swing arm." The "swing arm" creates a lot of tire wear and is a major pain to adjust toe-in.
Steering detail: We are using the center joystick with u-joint we tested on the Orange trike. In fact, we tore down that trike and used most of the hardware. The seat went back to the Red trike. When I started drawing the new design, placement of the tie rods and pivot were very important, so we have a cleaner, simpler layout.
Elastomer suspension: After my very first trike I built, I said the next ones will have some sort of front suspension or damping. The leading arm pivots on two internal acetal bushings per side. The elastomers are used in a number of recumbent designs and are available in different firmness levels. The green ones are "hard" and resist the compression and the yellows are "soft" and are used to control rebound. It's important to adjust the preload on these before your first ride. The pivots are welded to align with the desired castor and can be adjusted for more or less castor. We strived to buy off the shelf parts and hardware if possible, obviously some things are custom made due to the FWD concept.
But lets be clear here, this is designed to smooth out the ride a little and is not designed for off road or severe road hazards, the travel is very small. Is it worth it? Time will tell. (Note: update on the FWD suspension, I have spent some time on a rigid Catrike 700 and can tell you the elastomer suspension is definitely working to reduce bumps and smooth out the ride, it's very noticeable!! Edit 07/06/13)
Driveline detail: The heart of the FWD trike! The front frame houses the custom made differential. This diff is the one I used all last year and shows minimal wear on the internals. The diff can be adjusted side to side a little to help with chainline position. Two large bearings slide into the frame mounted shell. The inboard "CV" shells are custom made for the half shafts.
Something new, is the half shaft material. The Orange trike used store bought chrome plated steel shafts which started to rust and pitted from the sweat dripping down off the legs, so we bought some titanium! (the cost to fix and refinished the chrome was more than the titanium rods) Titanium has this aura of being super hard to machine, and really it turned better than stainless on my home lathe and is super corrosion resistant and lighter, I knocked off 2 ounces from each shaft alone. Drilling it however, is very difficult! Mainly because it's hard to keep cool.
Gearing details: An issue with the prototypes was the spacing for the derailleur cage. There was no room for a long cage derailleur so triple cranks and large cogs couldn't be used. Which any long time recumbent rider would scream "WHAT?" The derailleur mount and clamp are adjustable for best fit. Long cages should not be a problem as I drew all the parts in place using a Dura Ace long cage derailleur.
Gear mount: The gearing shown is an 8 speed and the shifter clamp can be adjusted inward and outward to optimize chain and derailleur spacing for 7,8,9 and more speeds. There is a machined post the part clamps to and is welded to the front frame.
Brake mounts and Bearing Holder: This area is where I really wanted to change things up from the prototypes! The Avid BB7's are not made in a 'mirror' configuration so one has to be "upside down" and as I like things to be symmetrical I came up with this. The caliper placement has been machined for the international standard mount and uses a 160mm rotor. The top mounting hole can be used to mount accessory posts and posts designed to be used for a direct steer modification. Due to space requirements a 160mm is the only rotor size possible. Edit 06/21/2014
The outboard bearings are inch size with a custom .5 inch diameter chromed steel axle. The axle has a machined keyway for a common size round dowel pin so you can get them at a hardware store if you lose one. The drive coupler fits into a Bitek hub and is locked in with the brake rotor bolts. There are 2 bearings with a spacing gap between them. The bearings are in a sleeve assembly and fitted into the mount. The entire brake unit is welded on to the steering caps which have a single 8mm bolt locking them onto the threaded steerer tube. Standard 1" threaded headsets are used. This frame is using Interloc Racing Design Headsets.
Front Frame details: The current top tube is 2 inch diameter with a 1.5 inch lower tube to add support and doubles as guard for the derailleur cage. Later frames will have a one piece bent lower tube and possible changes in tube diameters. The water bottle bosses are cone shape and welded to the top tube with the front derailleur cable guides built in with stainless steel threaded inserts.
Front Frame details: Race gearing is 53/39 with a 12-23 8 speed cassette. A 68mm wide threaded bottom bracket sleeve is welded into an over size tube. The derailleur mast is 1.25" diameter and has an accessory post option. The chain will not hit the bottle cage. The top tube can be cut longer for taller riders and rear derailleur position can be adjusted to clear big feet. The plan is to make two sizes of front frames as the weld jig can be adjusted. (The front frame and related items might change in the future to reduce drag and weight. Edit 06/21/2014)
(The rear frame design is evolving as we get more road time on the trike, as well. The early frames bent at the middle where the weld was for the simple seat mount, so we had to change the wall thickness and made a clamp on seat fixture. Early in 2013 this was the issue that led to the simple single tube with offset rear wheel that went to the HPV races in February 2013.)
Note on gearing: The diff adds width and the short chain does not allow "cross chaining" which is supposed to be a No-No anyway! Extreme angles on the gearing and chain causes premature wear.
Jan 15th 2013: Did some more tests, put new tires on, and trying to get used to the new seat position and gearing. Early rides showed a extra effort to pedal despite the ceramic bearings through out the driveline. We've been testing with various seat positions and angles and still can't find out what is wrong.
Early Feb 2013: Finally starting to dial in the resistance issue and have it traced to two things: Some play in the bearing sleeves as they fit inside the new brake mounts allowing some unwanted negative camber resulting in the brake rotors binding. The clue here was finally smelling some pads. But no noise or squealing typical of brake rub. Without any load on the wheel assemblies the wheels spin free.
Stupid on my part as I had to lock down the sleeves on the Orange trike as well, but the designed in lock screw placement is evidently ineffective. I didn't want to make it very difficult to get the sleeves out and in on the prototype. Production frames will have the sleeves lock-tighted as well. But still can't seem to get on top of the gear. Changed to a 52 chainring and was riding when the fiberglass seat shell cracked. So we'll have another thing to fix!
Feb 15th 2013: After having some issues with driveline and ergonomics I created a test frame to lower the crank height and raise the seat a little. We are also testing a simple clamp on seat mount. Of course I'm out of time now and been been spending more time building than riding as my schedule is two months behind. (November 2012 the trike was to be completed, December 2012 to dial in and ride like hell in January and February for the 2013 Florida HPV Challenge!)
Quick and dirty test frame: A single cantilever 2" diameter tube with an offset rear wheel and disc brake mount. The quickest thing I could make with using scrap material lying around that would work for the changes I want to test. The HPV race rules requires two independent braking systems so if tech inspection said I needed a brake I would be ready. I made this frame 3 degrees lower, so that when the wheel was added the crank height would pivot lower. However the quick fix of a seat mount is not the desired height yet and will have modify it some more.
Still looks weird, might look better with more refined seat mounts, that would be another change as I don't want a production frame welded in the seat back support area as this frame is. Not sure what the general public thinks about offset rear wheels. Custom fender and rack mount for sure...
I want to look at some different rear frame configurations, as I'm pretty set on the front frame layout with perhaps tweaking angles and tube diameters. Plus I need to use the stuff I already spent money on! We'll see, I need to put miles on!
Feb 23-24th 2013: Just like in the TV shows I was working on this thing the day before the event and finally resolved an issue at 3pm. I didn't even put a mile on the new configuration! So I went to the Florida Challenge Races at the Brian Piccolo Park. At first I was sort of worried about the trike as it's first major outing would be time trials, sprints, sharp cornering and the high banks of a velodrome!
I shot some video of the weekend and that is posted on youtube and also on our "Ride Videos" page. Racing is fun and provides great feedback on the trike's performance. I was 4th in the trike class 200m sprint on the outdoor track at 28.32 mph with no sprint training. The goal was to do over 30mph but build issues and lack of road miles prevented that...next year! The velodrome events showed some other issues...like suspension creates a negative effect on the 30 degree banking!
March 2nd 2013: I took the new trike to the 9th Catrike Rally and put a few decals on it! It's real if it has a decal! As usual, a lot of interest! I rode in the front bunch and talked to Catrike folks and others during the ride, I might even be on video with Kim's Bicycle Trail Review video. I'm not sure but maybe the ceramic bearings are breaking in as this thing seems to get faster each ride. Wheel to wheel with Mark's tricked out Catrike 700 coasting down some of the downhills on the West Orange Trail.
March 23rd 2013: I took the DBT4 to the 2013 Withlacoochee "Clean Air Ride" and did we get wet! It had rained about two or three days and we got soaked in less than a mile into the 60 mile ride. Normally the pro photographers get good shots, I just didn't like this shot of me looking in the low mirror. ( Edit-There are accessories now to raise the mirror above the wheel)
May 7th 2013: I took some time off away from building in March as I was going nonstop for a few months just to get the DBT4 on the road! I've had some new pieces being machined: a new upper tube clamp for the seat, beefier steering tube caps with more surface area for welding and new rear dropouts for a conventional rear frame assy. I still need to get or rent a tubing bender so I can start work on the rear frame assy's.
There is still a huge amount of work to do on each frame as it's all custom on the driveline, not sure of what color will be offered, the first few frames I'll leave unpainted and see what the first customer wants it to be. (edit: First Two Trikes will have a special black and white paint theme)
June 24th 2013: I'm sorry I haven't updated recently, I've had some personal issues, nothing catastrophic however. I injured my back at the gym Memorial Day weekend doing situps, actually getting off the machine I twisted wrong and tore a lower disc and twisted my pelvic. It's was severely painful a couple of weeks ago and I've been seeing the chiropractor and doing lite exercise. Today I finished the titanium half shafts which are a pain to machine up with lots of machining steps:
Titanium was used mainly for corrosion resistance as the shaft is directly under the legs where sweat drips down. The earlier chromed steel shafts on the Orange trike starting rusting and pitting the chrome. These titanium shafts sure look pretty!
Nov 02nd 2013: We've been busy working and having like a zillion things to do that have nothing to do with the FWD Trike! But we did post 3 videos showing some detail on the Blue prototype trike:
Check our ride video link above to see selected videos or use FWD Trike or David Bruce for youtube keywords and see all the trike videos. We just got our tubing bender and hopefully in a few days we can start practicing bends for the rear frames. We did some black anodizing and powdercoated the steering knuckles and some other parts.
Nov 23rd 2013 The manual tube bender is mounted and I had some "fun" trying to bend some stuff! This thing is big and takes up a lot of space for the handle. We bent some 1.25" tubing for the new rear frame wheel stays. The main 2" tube has been fighting us, but we did got 3 tubes bent so the next fabrication phase will begin! I made a tubing holder to notch the rear stays and look forward to doing the final fit and jigging so we can hit the welder.
I got the rotary table set up and will work on the end caps and touching up parts to match the tubing diameter as this new batch of tubing is a little over sized at .015 and I like my parts especially clamps to have a precise fit. Bought 2 new liteweight Halo front hubs and having them laced up (to be used as rear wheels) for the first two trikes with their special introduction paint scheme. These Halo hubs are super nice and approx 100 grams lighter than the Shimano hubs.
Dec 14th 2013 I went to the welder and we did three new rear frame sections. The lower rear tube is 2 inch diameter and bent to approx 20 degrees with 1.25 inch rear stays. I must say the bent tubes adds to the professional look. The cable guide will be for the optional rear brake.
Some detail pics of the rear frame with the end cap and upper seat clamp tube. The drop out spacing has custom fit spacers for the Halo Hubs or other hubs and will use a standard 135mm quick release skewer. The tanges on the dropouts will be used to mount a subframe that will hold a fender and the all important neck rest for the lower seat reclines:
On the blue trike ready for some rides:
Close up of the end cap prototype and seat clamp area. The subframe will fit in between the seat height adjusters and be clamped in.
Jan 05th 2014 For the upcoming HPV race event I switched over the center steering to try out direct steering and added the rear subframe. The first editions will have the subframe bolt on the provide a place to mount a head rest and fender, like the short KMX MudGuard. We'll be tweaking the height and position of the subframe a little. The prototype subframe is using scrap parts I had laying around.
Left side of the subframe: it bolts onto the rear dropout and the front has fittings that mate with the seat clamp mount and is clamped together to add some support for the rear stays and provide a location to mount a headrest. The curvature space can be used to place bags, I'm using some frame bags for a DF bike. Once I get the subframe position right, we might just weld them on.
Have to modify the rear mount on the brake side to clear the caliper!
Feb 10th 2014 Well the big race weekend has come and gone! I am freaking tired! I took the new rear frame design and put some new ideas to handle the track to the test. Results are in and...so-so. A different group of racers showed up and man they are fast on their trikes. I set some new personal best mph averages but still not in race shape. But the biggest thing was the trike felt sluggish and just would not turn easy on Saturday's road race.
Best finish was 3rd in the standing start outdoor sprint at 26.95mph into a stiff headwind, the winner's speed was 30.5mph. I had done 25.6mph on my test sprints into a headwind near home and 27 mph something with a tail/cross wind. Now the wheel sizes are different so the gear inches are different as well so I cant say my trike is way slower, because my high gear is 86 inch and the 700 is 114 inch.
That's why you see huge chainrings on bikes with small wheels.
On the velodrome side of things is where I really wanted to see some improvement. Last year the suspension and the offset rear wheel wanted to roll the trike off the banking so it was hard to control and I lost a lost of drive traction as the right wheel was lifting and spinning. So after Saturdays racing, I changed the right side elastomer damper to the "soft" yellow one. The idea for the soft elastomer was allow the trike to compress more into the banking side. Changing that also changed the rightside castor and naturally made the trike turn to the left. Not only did that work very well, the handling on the 200 meter short track was way better. Maybe the green "hard" elastomers are too stiff, I haven't tested the "medium" red ones. It's hard to dial in a velodrome event when you have don't access to the track.
Too bad we don't have a local race series every few weeks, I can guarantee fitness would improve!
March 01 2014 After February's race I got sick from some company I had over and it was really rough on me for March's Catrike Rally, it was their 10th Rally so I had to go coughing and hacking. It seemed like I was sick for a month!
April 15 2014 I've been really lazy lately, something I ate maybe... I haven't been riding too much, been trying to workout angles for the rear subframe for the DBT4 and also working on a race specific FWD trike using existing parts and stuff lying around. The race trike will be an aero test bed and hopefully a test bed for power watt readings to compare between trike platforms.
Pictures of the new subframe prototype before welding:
The subframe will do a few things: one, it will add support to the rear wheel stays. Two, the upper plate has a cross tube to mount a cool looking KMX mudguard/fender. Three, a couple of water bottle mounts with spacers. Four, the upper plate can be used to mount different brands of head/neck rests with additional accessories or mounting posts. The smaller holes are the same size for all the other accessory posts designed for the trike. (edit: The rod end design is flawed and has to be redone)
These first ones will be bolted on and clamped together using the rear seat adjustable sliders. Later frames might have these curving tubes welded on. I plan to extend the rear seat stays another inch to refine the angle and aesthetics. The newer front frames are a little longer so the seat will be forward more and allow some more clearance.
May 15th 2014 I got the newly welded subframe mounted with extra water bottle and KMX Mudguard fender and flashy light. I haven't mounted a head/neck rest yet. Something that has taken me a while to recognize is the fiberglass seat is molded differently and really needs a neck rest. The little post that the light is on, can be inserted into the small holes and used to mount the head rest. All I have to do is machine up different lengths for different things.
June 15th 2014 I've been doing a lot of little things for the race trike and pushing to get the rear frame ready for welding. The hard part will be the miter angles for the front frame's crosstubes using aero profile tubing. The front section will be different for the race trike.
The photo below is from a recent Cocoa River ride. Brevard County doesn't have any MUP or trail systems and this scenic ride is almost like a MUP on the weekends. Too many stops and the occasional policeman yelling at cyclists to obey the stop signs however! Additionally, the residents complain about all the walkers, runners and cyclists. I'm sure the village businesses love us! Money trumps residents!!
Good news however, as Gov Scott has approved the funding for the Florida Coast to Coast Trail connector and we'll have a trailhead in Titusville! I'm sure Titusville will love the additional income.
July 4th Weekend I've been starting to ride more and man it's hot out! I took a few days off to extend my weekend and got a lot of stuff done. The rear frame for the race trike is pretty much done except for paint. I got to work on a subframe for a frame bag to have on training rides.
I even got the first edition wheel covers on and fitted with a little trim work to do. I might buy some thinner ABS material and make the race covers. The .016 aluminum weighs about 5 oz each side. The first ABS ones were 8 oz each but that material was .062 thick. One you get the pattern, these don't take long to cut out and drill. With aluminum I can paint or maybe just polish. I want to put a bunch of decals on as well!
This single cantilever race rear frame is similar to last years test frame only a lot more refined! I have a flange for a 140-160 mm disc brake in case the race inspectors insist on another braking system.
July 27th 2014 Fresh from the welder as we did some of the front frame and the training support frame. The training support frame is to be used when training as there is a space for a frame bag and support tube to mount a cool KMX mudguard, flashy light and head rest. When the seat is on, the rear clamp sandwiches the support tube ( aerofoil tubing mount) and bolts to the titanium axle. This frame bag I believe came from nashbar. Still working on the right combo for the wheel covers.
October 04th 2014 Yes it's been a while since I posted anything, sorry about that. In August a bunch of stuff happened in all aspects of my life and we are slowing getting them sorted out. The welder took a new job and part of his training is going out of state so, I lost three weeks in August waiting for the welder to come back. And other little things to nag me. Anyway, fresh pictures from today:
November 2014 Race trike details and more pictures continued on the DBT4 Race Page...
February 09 2017 Yes it's been a while since I posted anything, I'm still here! Since the race trike was built I have not done much in design or fabrication. I am disappointed in the race trike in numerous ways and have been trying to fix it. My welder went AWOL so have not done anything new.
However one morning in October 2016 I was going through boxes of stuff and saw the samagaga diff unit I've had for a while. I looked at it in a fresh light and began to see ways I could modify it to use on next gen FWD frames. My custom diff has a lot of pieces and fabrication so costs a lot, but the sama diff is less than $90 and is robust. So I have been working on the modifications to the unit to fit bearings for an internal shell, and then the CV joints to custom fit the diff:
I think this will work out well and use existing drive shafts already made up. I commissioned the machine shop to make the main CV shell so I can get the next process started. The original prototype CVs are welded to the diff axles and then bolted together. This new CV design is machined to fit the samagaga splined axle then we'll braze it together. The end cap will be aluminum and bolt on. This will all be inside the freehub cassette body.
The samagaga diff will require a new frame shell as it's larger than my custom diff. The plan is to redo the front frame design at the same time to use less material and welds, but will have the same frame mounts so will work and fit on previous versions of the DBT4. The modular concept allows swapping of parts and design improvements.
I remade my frame jig and support stand while I was in this rebuilding mode! I'm also working on a new version of the rear frame support that will allow a head rest, rack and or fender and bolt on to the rear frame. I sort of built my self into a corner with the rear frame, and any new rear frames built might have a welded support to streamline the look. We'll see!
These prototype pieces are designed to use a seatpost rack setup.
Some additional specs for the Blue Trike (January 2013) * as shown:
* Production mule was setup for a racing meet in February and has some titanium bolts and ceramic hybrid bearings through out driveline and bottom bracket.
** Frame material has different tube diameters and wall thickness for different areas.
*** Ready to ride weight, with computer and mirror accessories. 4 pounds less than the Red trike.
Testing will reveal flaws, issues or things that need to be improved, deleted or modified. Oh and yes I have a name for the Trike and snazzy decals, but will only post that when the units are ready.
Design, material, specs and additional stuff subject to change! Very Likely!!
David Bruce, February 2017
Please contact Dave: email@example.com
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