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Experimental Can-Am frame X-1 (updated)


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#1 JimF

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Posted 13 April 2015 - 03:30 PM

Here is the first test mule for something I've been thinking about for a bit. I'm calling this experimental because I'm completely unsure as to whether there's much merit in it or not. What I mean is that if I took a current standard build (saaaay.... multi-rail .047") and varied it from 4-5-6 rails per side or changed the wheelbase or guidelead... that's no great experiment. I know that the variations will work, just a question of what track and what conditions. But with this... I just don't know.

 

So... what is it and why?

 

What...

  • The what is almost a full perimeter design with main rails and forks that can be changed.
  • Handmade .032" nose with an R-Geo bracket and bracket brace.
  • Tuning forks are fixed in front and are .047"
  • This is version 1.2 with a single frame rail of .055".
  • Version 1.1 had single frame rails of .047". I just changed this today after initial testing yesterday.
  • Rear brass tabs are for weight placement and to spread the frame rails.

Why...

  • Inspired by Rick's "Toronto" F1, this is an experiment with a softer flexing frame.
  • Weight placement... There is very little weight in the mid-section of this frame.
  • Most weight is concentrated at front and rear corners (mostly rear)

Variability...

  • After initial testing, I dropped out the two original (.047") main rails and replaced with .055".
  • This was very easy to do and didn't disrupt anything else.
  • The forward half of the forks (currently) .047" could also be easily be replaced with .055".
  • I could also replace them with fork rails in tubes without disrupting the rest of the chassis.

So... I'll clean this up and then testing will continue.

 

c2d72226-98ae-4242-a5b0-5d5f14b5c0cb_zps

 

287cad0c-cd4d-45ac-8e04-9d72436c47c8_zps


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#2 Pablo

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Posted 13 April 2015 - 03:58 PM

I could look at that for an hour.  :heart: Obviously lots of thinking going on as usual.

 

Glad you are back in the groove, Jim F.


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#3 brnursebmt

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Posted 13 April 2015 - 04:48 PM

Wow!


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#4 Gator Bob

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Posted 13 April 2015 - 05:17 PM

Super nice, Jim!

Bet it will work great.

 

Is the bite bar soldered to the outer hinged pan rails?


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#5 JimF

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Posted 13 April 2015 - 06:18 PM

Bob:

 

Yes, the bite bar is soldered to the outer pans. The pan hinges are .055" in 3/32" tubing so the movement is both fore and aft and a little bit 3D. However, not really tippy pans in the normal interpretation.


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#6 Tim Neja

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Posted 13 April 2015 - 06:35 PM

Very interesting!! Fun trying different stuff!! Love your testing and explanations!! :)


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#7 chaparrAL

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Posted 13 April 2015 - 08:09 PM

I like it!  :good:


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#8 robbovius

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Posted 14 April 2015 - 05:53 AM

That's pretty neat.

 

So, the idea of this frame is to allow the front and rear axles to twist relative to each other, and control the twist by the stiffness of the single outer rails and the central rails of the fork?



#9 Tex

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Posted 14 April 2015 - 06:52 AM

Always enjoy seeing your designs... the wheels are turning.

 

Being somewhat "softer", is this meant to be run on a flat track? Just guessing, but I think a not-too-moderate side hit will bend the perimeter rail... not being critical, just feedback.

 

Look forward to a race report on it.


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#10 SlowBeas

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Posted 14 April 2015 - 10:07 AM

Like Bob, I'm curious about the soldered outer (pan) rails. I've soldered pans to the bite bar in the past and found that it severely limits the ability of the pans to move independently of one another.
 
I'll be interested in your report.
 
As always, your craftsmanship is truly a work of art, and I really enjoy reading about your successes and stealing... I mean "leveraging"... your ideas.
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#11 Jairus

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Posted 14 April 2015 - 10:14 AM

Wow, lots of variables to test... like moving the rear pan hinge to the fork to see if that improves handling. 

I love the look of that motor bracket.

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#12 JimF

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Posted 14 April 2015 - 11:15 AM

Thanks for all the comments, guys. The flex is a major compnent of this design but also the corner weighting is possibly as important as well.
 

So, the idea of this frame is to allow the front and rear axles to twist relative to each other, and control the twist by the stiffness of the single outer rails and the central rails of the fork?

 
Yes. Those are the only structural components and they can be changed relatively easily. The general idea came from Rick B via the "Toronto" F1. His take was that many F1 frames are built stiffer than they need to be. The general effect of the greater twist flex is more cornering speed but without the critical nature of high bite designs. It works on the "Toronto" we'll see about this.
 

Being somewhat "softer", is this meant to be run on a flat track? Just guessing, but I think a not-too-moderate side hit will bend the perimeter rail... not being critical, just feedback.

 
Actually, this is meant as a speedway car rather than flat track although almost all of our King, Hillclimb, etc., tracks are relatively flat. On the relative fragility... yes, it might. I built an F1 with this general idea (soft flex) well before the Toronto and it worked great winning easily its first time out. However, in practice for another race, I folded it up pretty badly with one big hit caused by controller weirdness. The hope is that the elasticity of the rail will cause it spring back rather than take a set but that remains to be seen.
 

Like Bob, I'm curious about the soldered outer (pan) rails. I've soldered pans to the bite bar in the past and found that it severely limits the ability of the pans to move independently of one another.

 
These pans work like a shaker rather than a more conventional hinge. The bite bar is .039" and there is enough flex in it that the pans are somewhat independent. One of the planned variables is to switch this bar out for an .032" and an .047" to see if there any notable difference.
 

Wow, lots of variables to test... like moving the rear pan hinge to the fork to see if that improves handling. I love the look of that motor bracket.

 
Hmmmmm... hadn't thought of that. I don't know if Rick still offers that bracket or not. It has been chopped a bit from stock form but the cut-down bracket face is the way it comes.


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#13 old & gray

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Posted 14 April 2015 - 01:51 PM

Hmmmmm... hadn't thought of that. I don't know if Rick still offers that bracket or not. It has been chopped a bit from stock form but the cut-down bracket face is the way it comes.

 
Rick still lists it on his website, and PCH lists it as "RGEO PRO 1" Brass Motor Bracket - .050 - RGEO-350".


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#14 Gator Bob

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Posted 14 April 2015 - 02:57 PM

but I think a not-too-moderate side hit will bend the perimeter rail...

 
A side hit impact will be absorbed by the bite bar with the 'dog leg' in the hinge arm forcing the pan rails to go up on impact. 
 

Like Bob, I'm curious about the soldered outer (pan) rails. I've soldered pans to the bite bar in the past and found that it severely limits the ability of the pans to move independently of one another.

 
I have a flat track 4" chassis that has three .032 'bite bars' soldered to the pans... no bar boxes... and you would be surprised how much 3D movement there is. The pans will still move F to R independently and the 'thin' bar flexes and the pans still have hinge 'action'.  
 
If you solder a 'thick' bite bar to the pans it limits all movement to the size of the 'boxes' or tubes the bar and/or hinge tube runs through. It then becomes a 'shaker'.
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#15 JimF

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Posted 15 April 2015 - 01:24 AM

Here is a closer look at the bite bar setup. This currently has the .039" bar in a 3/32" square tube. Bottom pic shows the ready to test setup at 93.6 grams all up. I may get it on track as early as tomorrow (Wednesday).
 
27f08926-97d8-48c2-a327-791a0c892059_zps
 
614eeb44-20ea-4562-9f53-40663e680255_zps
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#16 Eddie Fleming

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Posted 15 April 2015 - 04:38 PM

Chassis looks super. I am looking forward to a report on its performance.

 

What brand is that Lola body?


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#17 Dominator

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Posted 15 April 2015 - 05:29 PM

Another sweet build, Jim.


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#18 JimF

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Posted 15 April 2015 - 06:52 PM

Chassis looks super. I am looking forward to a report on it's performance.

 

What brand is that Lola body?

 

Tested it today in less than optimal conditions. After a tweak, results were very positive.

 

The body is an O/S 407-L.


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#19 JimF

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Posted 15 April 2015 - 08:19 PM

Can-Am X-1 track test

 

I tested the new frame today at Fast Track Hobbies in Rocklin, CA. The track was their 165' "Purple Angel" which is a unique test venue. This is a very fast track but almost all the turns are interconnected. Thus, the car stays at high cornering speeds but changes direction almost continually. Lightweight and/or high bite cars usually do not too work well here because despite the speeds, the design favors somewhat heavier cars that can roll from one direction to the other.

 

Track conditions today were not perfect. The bite was off and so personal best times were not in the cards today. I also did a lot of motor, tire, body testing today with this new car. I know how to go fast on this track and so the target was set by my historically best car to date here. This is a six-rail .047" at about 106 grams. Today, that car ran a best of 5.02 with a good motor on board. The car was consistent but fairly loose regardless of tire tuning (best with this car in good conditions is about 4.86)

 

The new car was set up as shown above and started with JK 8703 slightly narrowed.

  • Right from the first, the new car exhibited horrendous wheel hop. Basically, I couldn't get it off the line at all.
  • I couldn't get the car under 5.40 and the bouncing/grinding was making me cringe.
  • Slight wheel hop is not unknown with tuning fork designs but this was like a bent axle or blown bearing.
  • I checked all the basics (axle, bent wheel, bad bearing, broken solder joint, etc... all good)
  • I suspected two things. (1) needed a flex limiter, (2) too much flex in the rear chord of the motor box.

Soooo...

 

First, I applied a flex limiter in the usual place (blue arrow)... absolutely no change at all.

  • So then, I applied some reinforcement to the rear chord of the forks (red arrows)... MAGIC!!!
  • The two "L" shaped braces are .055" soldered to the bracket face and full soldered along the rear chord.
  • From this point on... this was the fastest car in the box on this day.
  • Same setup that was running 5.40 was suddenly running 5.05.
  • The handling (even at 93.6 gr.) was so good, that I couldn't believe how hard I could drive it.

I continued to test, first going through four new Retro Hawks... the best one ran a 4.98, worst was a 5.10.

Eventually, I put in one of my best F7s and got into the low 4.9s (4.92 best)

I tested the three bodies that I use most commonly (shown below) but no difference that I could quantify.

I tried my usual litany of tires but with the slidey conditions, the only thing that was decent was full width JK 8703.

 

Soooo...

 

I'm not sure what to do next because there wasn't anything I put my finger on to fix. I guess the next step is to try it with the forks in tubes and also to test on different tracks and conditions.

 

Or... maybe just build another one...  :shok:

 

0767280f-7020-484e-81f5-354e0a772b31_zps

 

d17ae257-4413-4e76-bfb3-ccf5d6fbb6eb_zps


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#20 Dominator

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Posted 15 April 2015 - 10:06 PM

What about trying .063" on the perimeter or running a limiter from the fork to the perimeter rail like you did on the Toronto?


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#21 JimF

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Posted 15 April 2015 - 11:01 PM

Good thinking, Dom. I could try both of those things and either might work.
 
I think the issue here was not too much twist overall but too much vertical flex in the motor box. The rear chords of the forks are .047" and they had a lot of vertical flex forward of the junction with the bracket The thicker perimeter rail would stiffen the torsion but the motor box is so isolated from the rest of the frame that I don't (think) it would have the right effect on the vertical flex. The first laps I did with the car were with .047" perimeter rails. There was some of the chatter and bounce but not much and it was a different track/different day. Switching to the .055" perimeter for this version didn't make any difference.The single limiter that I soldered at the crux of the forks stiffened the torsion but didn't do much of anything with the vertical flex. The add on "L" braces definitely stiffened that area and stopped the problem cold. The "V" limiter might do it where the single wire bit at the crux didn't.
 
I have a race this weekend so I'm going to let it go for now. Then... I think the next step will be forks in tube and see what happens.


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#22 Gator Bob

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Posted 15 April 2015 - 11:02 PM

Just a guess ...

 

If the forks go in a floating tube or box (unsoldered) the hop may come back.

 

How much space is between the bite bar and the fork rails? They may have been 'bouncing' off each other if the clearance is small and the 'torque wrap' of the motor box rails.

 

It's very cool the two short 'L' rails calmed the car that much. WTG, Jim.

 

Thinner .032" bar? maybe...


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#23 slotcarone

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Posted 15 April 2015 - 11:11 PM

Jim,

 

I had a similar experience with a F1 Retro chassis. Horrendous hop and chatter and it was cured by adding to pieces exactly like you did. Now very smoothe!!


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#24 JimF

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Posted 15 April 2015 - 11:15 PM

If the forks go in a floating tube or box (unsoldered) the hop may come back.


Yeah... it might for sure although then it would be a torque wrap which I don't (think) is what's going on here.
 

How much space is between the bite bar and the fork rails? They may have been 'bouncing' off each other if the clearance is small and the 'torque wrap' of the motor box rails.


There is about .015" between the bar and the rails. As it is here... the forward leg of the forks can touch the bar in extreme twist. However, when I put the limiter in place it was just aft of the bar and in that configuration, the forward legs couldn't touch the bar because the twist was so much less.
 

It's very cool the two short 'L' rails calmed the car that much.

Thinner .032" bar? maybe...

 
Yeah... I had one cut and ready to drop in but when the miraculous "cure" happened, I forgot to try it.


Jim Fowler

#25 JimF

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Posted 15 April 2015 - 11:20 PM

Jim I had a similar experience with a F1 retro chassis. Horrendous hop and chatter and it was cured by adding to pieces exactly like you did. Now very smoothe!!

 

You know... I was thinking about this concept a while back and actually put a tiny version into an F1 that I wrote up last year sometime (a Toronto I think). In that case, it didn't seem to do much and I sorta dropped the idea. Now, it makes me think that it was the right idea but just not enough of it.


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#26 Michael Rigsby

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Posted 16 April 2015 - 05:01 AM

This is actually a very good design. I built one very, very similar playing around one weekend, but ended up using .062" outer perimeter wire after finding the .047" too soft for our Hillclimb. I used an R-Geo bracket in the back with no crossplate, and the outer pans were all .047" wire. All brass was .032" except the motor bracket. A very fast chassis and very easy to tune. Probably the only tuning fork I ever built that really worked on a Hillclimb, which are the predominant tracks down here.

 

Of course, my builds are nowhere near as neat as Jim's, as his are works of art in cleanliness.

 

This would make a good basic kit to put into the hands of novice builders as it's not that hard to build, and wire sizes can be changed for track tuning quite quickly (hint, hint).


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#27 A. J. Hoyt

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Posted 20 April 2015 - 11:48 AM

Jim,

 

I had a similar "chatter" character in what became my "go to" chassis design three years ago. I cut a vertical slot for some .025" wire to mount flush (or slightly below) into the face of the motor bracket such that the wire, after being soldered in, gets sandwiched between the motor mounting face and the bracket (trapped so it can't go anywhere or even flex to weaken or fail the solder joint).

 

This wire went "up" and then had a 120 degree bend that took it to the mainrail, another 30 degree bend so that I had a land about 1/2 inch long to solder it to the mainrail ahead of the but along side the motor. This was quite a bit lighter than the .055" wire "L" you show but seems absolutely stiff in gusseting up that cantilever zone from the motor bracket to the mainrail.

 

Like yours, the chatter went away but, much more importantly, the chassis ALL really hook up off the corners allowing me to just glide the car into the corner and punch it out very early. Extremely forgiving and very fast for every lap because it is not driven as a straight, then a turn, then a straight - it just strings the whole lap together as a smooth "rhythm" kind of driving. Just as important, when pushed, it will allow you to step up your laps to chase someone down!

 

Also interesting is that it did not seem to change the twist stiffness from front axle to rear axle at all - just stiffens up the longitudinal flex where it needs it. Actually, I think it changes the "resonant" frequency of the rear axle torque "wrap up", kind of like traction bars on a leaf spring 1:1 car. If the stiffness of this area matches the torque/bite, it seems to get on a "resonance", the source of the chatter.

 

I really like your outside the box thinking and watch your threads with great interest. Not enough people experimenting out there with new things that are completely within the spirit and letter that the rules allow, in my opinion. Glad to see you are and that you choose to take time to share with well thought out and written articles with nice, clear pictures.

 

Keep it in the slot,

 

AJ


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#28 JimF

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Posted 20 April 2015 - 01:09 PM

AJ... Thanks for the feedback. I wonder if you have a pic that you might share that shows your idea???

 

OK... the X-1 raced to a comfortable win in its first outing yesterday. I honestly didn't expect this light frame to be very good on a surface with varied bite and conditions... but it was really good. The biggest advantage seemed to be that it could gain one-three feet in the donut on the very dirty King at Eddie's Slot Car World. Even racing against young gun Justin Colvin (who I cheerfully admit is a better driver than I am) I could gain ground in cornering in these highly variable conditions.

 

The pic below shows the frame as it raced. Right below the the frame itself is a fork in tube setup ready to drop in. I didn't try it over the race weekend once it became evident that this was the car I was going to race. That will be the next step. I want to see what effect it will have to drop in the forks in tubes. Then, it may be time for the next version, incorporating what I've learned so far.

 

ce6c5d10-b5dc-4a20-8c5a-37127ad6764c_zps


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#29 Tex

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Posted 20 April 2015 - 01:24 PM

Very cool... love the development of the tuning fork.


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#30 JimF

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Posted 30 April 2015 - 12:37 AM

OK... some further testing today still at Fast Track Hobbies in Rocklin. Testing today was primarily about the tuning fork and determining the effect of the forward chords going into tubes. The track had been cleaned since my last test and the surface condition was much better than in the prior test. This time, I was running a JK 8713T slightly narrowed just as I raced it last on the King at Eddie's SCW in Vallejo. The results were even faster than the prior test here and still easy to drive fast with it. The F-7 motor had laid down a little in the race last week, yet I was still able to run comfortably in the 4.82 - 4.89 range. I got a few laps in the 4.7s which is as fast as I've ever gone on this track before... and this even with a modest motor.

 

Then, I tried the pre-fabbed forks in tubes setup as shown above in post #28. I just dropped out the fixed forks and dropped in the little setup as shown and went right back to the track. The car was still good but not quite as hooked up as before. Best times were in the 4.94-5.05 range. This is still good, but just not great like the previous test. I then tried some different tires looking for a little more bite and although some full width untreated tires 'felt' better, the times didn't show any improvement. 

 

I then tried this 95 gram car on the flat MTT with just a gear change. I kept the 9t pinion and went from a 27 to a 30t crown. Later, I went to an 8t pinion. Unfortunately this track was pretty dry and loose and I never got any good results. Of course, this weight is definitely too light for a flat track and for sure, most of my 100 (ish) gram cars were not much to write home about either. After some tires and then a sort of half-hearted attempt at some additions of weight, I left it for what it is, and went on to a bunch of other cars that I had to test on this day.

 

So.... so far, this car has been great on higher speed tracks at the 95 gram original build. I'd also say that it prefers a track with some bite on it but it still was good here at FTH on the Purple Angel when it was decidedly loose. As far as a flat track car, I don't have a great feel for that yet but I have any number of other cars that work great on flatsters so I'm not feeling pressured to make this a go or at least not at this weight. Next steps I think are to build up another one and then work one against the other and also try the general concept on a 4.5" stock car.

 

So far... this is the first car I'd reach for on any high speed track that we run on here in NorCal.


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Jim Fowler

#31 SlowBeas

SlowBeas

    Troublesome De-slotter

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Posted 30 April 2015 - 11:54 AM

I think I had the same experience as AJ, although I have no pics of it, either.

 

Basically, I bent a short "L." The shortest leg of the L was soldered to the face of the motor bracket, and the longer (maybe 1/2") piece was soldered up the inside of the main rail – in this case, of the tuning fork as it moves forward of the motor bracket.

 

I found this small reinforcement stopped all chatter and the made the chassis much more responsive for me.


Jim Beasley
South Carolina, USA

"Assuming either the Left Wing or the Right Wing gained control of the country, it would probably fly around in circles."
- Pat Paulsen, 1968
"I drive way too fast to worry about cholesterol."
- Steven Wright ca. 1983





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